Damian Harty (Prodrive) Questions Forum
15 February 2003, 12:46 PM
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Damian - thanks, I don't feel so stupid for getting out of bed to type that question now!!! Did ATD come to you in a dream too? 
PS Three great questions and no drive in the ATD?!!!
PS Three great questions and no drive in the ATD?!!!
15 February 2003, 02:17 PM
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Damian thanks for the reply.
Gutted by your answer for the PS2 games question (from someone else), though not entirely surprised, I can't keep the dumbed down cars on the road but it certainly would be interesting to have played the game with the real settings.
In some of the other answers that you have given on this thread you mention cars from other manufacturers.
Is your sole speciality with the Impreza or do you get the chance to work on or evaluate different manufacturers vehicles in your role at Prodrive?
I know that Prodrive successfully raced the 550 Maranello Ferrari in varies GT series, does your expertise and crap driving get used is this type of project too.
Any interesting moments you would care to share during testing or development work at Prodrive.
Cheers
Nigel
Gutted by your answer for the PS2 games question (from someone else), though not entirely surprised, I can't keep the dumbed down cars on the road but it certainly would be interesting to have played the game with the real settings.
In some of the other answers that you have given on this thread you mention cars from other manufacturers.
Is your sole speciality with the Impreza or do you get the chance to work on or evaluate different manufacturers vehicles in your role at Prodrive?
I know that Prodrive successfully raced the 550 Maranello Ferrari in varies GT series, does your expertise and crap driving
get used is this type of project too.Any interesting moments you would care to share during testing or development work at Prodrive
.Cheers
Nigel
15 February 2003, 09:03 PM
#63
If ever there was a thread destined for the Scoobynet Hall of Fame ...
Much kudos to Damian and Simon for their efforts
1) Is there such a thing as "Prodrive geometry settings" for fast road/trackday usage ? The term seems to be bandied about frequently, both by third-party tuners and people on Scoobynet, but one is never sure there's a real basis to it, other than attaching Prodrive's name to it gives it more perceived gravitas.
2) Following on from 1), if you took a standard Impreza on its "optimal" geometry settings (by your earlier definition of good handling) and fitted new springs that lowered and stiffened the suspension, would you expect to have to alter the geometry setup from the previous values ? My thinking is that, if nothing else, the new springs have altered the vehicle's centre of gravity, which would have an affect on countless aspects of the suspension and the work it is there to do.
3) Why do your rally cars squeak so much ? Is it because you don't oil them properly 
or because you throw away all the bushes and use ball-joints wherever you can ?
Much kudos to Damian and Simon for their efforts
1) Is there such a thing as "Prodrive geometry settings" for fast road/trackday usage ? The term seems to be bandied about frequently, both by third-party tuners and people on Scoobynet, but one is never sure there's a real basis to it, other than attaching Prodrive's name to it gives it more perceived gravitas.
2) Following on from 1), if you took a standard Impreza on its "optimal" geometry settings (by your earlier definition of good handling) and fitted new springs that lowered and stiffened the suspension, would you expect to have to alter the geometry setup from the previous values ? My thinking is that, if nothing else, the new springs have altered the vehicle's centre of gravity, which would have an affect on countless aspects of the suspension and the work it is there to do.
3) Why do your rally cars squeak so much ?
Is it because you don't oil them properly or because you throw away all the bushes and use ball-joints wherever you can ?
16 February 2003, 09:27 AM
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Damian,
Many thanks for your feedback above, answering mine and other questions has validated my proposed STi7 improvement route of:
Whiteline ALK
Uprated rear ARB
Uprated droplinks and ARB bushes (rear)
Prodrive springs (when they show up!)
Hopefully this should improve the STi7 handling and sort out my wheelspin problem.
Cheers
Paul
[Edited by Paul N P - 2/16/2003 9:28:46 AM]
Many thanks for your feedback above, answering mine and other questions has validated my proposed STi7 improvement route of:
Whiteline ALK
Uprated rear ARB
Uprated droplinks and ARB bushes (rear)
Prodrive springs (when they show up!)
Hopefully this should improve the STi7 handling and sort out my wheelspin problem.
Cheers
Paul
[Edited by Paul N P - 2/16/2003 9:28:46 AM]
16 February 2003, 01:27 PM
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OK, some more answers on a Sunny Sunday when I should be out the driving the ATD car (I have it to do some road mileage/tyre wear evaluation)...
Damping Q: It is generally true that there is an "optimum" level of damping and that too much stops the wheels being able to follow the road, leading to a jumpy/skipping/pattering sensation in the car. One of the subtleties about dampers is that what is "just right" in one situation is too much or not enough in another. The dampers work at a variety of speeds - I mean the speed as measured along the damper rather than the speed of the car - and the damping settings are different at different speeds. What we do here at Prodrive is optimise the damper settings at all the different speeds for different effects. There is an excellent book by John Dixon called "The Shock Absorber Handbook", available on Amazon that describes this stuff really well. In terms of whether to make changes with dampers or roll bars, the key to vehicle dynamics is matching, so if you do all the turn-in with dampers then you get the effect you describe and if you do it all with anti-roll bars you get a sort of "turbo-lag" effect the steering, with an initial delay and then a catch-up as the car rolls - although it sounds like it would be OK, it feels dreadful to drive. For badly surfaced roads, too much roll bar is generally a bad thing because it leads to what we call "roll rock" - the feeling of being thrown from side to side, so for that reason too a balance between bars and dampers is good.
Geometry Q: What we're talking about here is what we call "static geometry" - toe-in/out and camber. Basically, static camber influences the way the car departs at the grip limit, with more negative camber giving more grip but also a more 'aggressive' departure. Basically, there is a best camber angle for the tyre to be presented at the grip limit; if the suspension gets stiffened then because the car rolls less the car needs less negative camber. Adjusting the camber difference front-to-rear gives a a difference in progression. It's quite a useful modifier to the vehicle but sadly not many vehicles have very readily adjustable camber. Camber also greatly influences tyre wear - "ideal" camber wears out the tyre uniformly, "too much" wears out the inside and "too little" wears out the outside. Beware though - "ideal" can give reasonably frisky behaviour at the limit. As a quick and dirty test, drive a bit of road you like in a style you like then pull up, hop out and lay your palm across the tyre from outside to in. The tyres will be working at about 50 degrees C or so, so they should be comfortably warm to the touch. If your camber is a long way off you can feel one edge of the tyre will be noticeably warmer than the other. If you repeat the same thing after a motorway drive you'll see whether or not it will lead to excess tyre wear on the inner shoulder. A lot of prototype vehicles we experiment with have adjustable camber but I'm not sure how easy it is on the road cars. Toe-in/out is altogether more adjustable and a powerful modifier on the way the vehicle behaves beneath the handling limit. Some toe-out at the front and toe-in at the rear promotes stability and the opposite promotes agility at the cost of stability. At the front, toe-in gives a great steering response but turns the steering feel all woolly and so spoils the car a bit. At the rear, the opposite is true. Personally I like the fronts out a little - about a quarter of a degree - and a touch of in on the rear, about the same amount. Note these are personal preferences to match my driving style, etc etc etc... and certainly aren't generically applicable to every car, or even every Scooby. In general, any toe setting other than parallel gives some heat in the tyres and hence accelerates tyre wear for road use.
Prodrive Handling Pack for 00 MY: Probably a bit too specific for me to comment on but it's likely that the Pro pack will feel firmer and more neutral and the Performance one will be a bit more rounded for everyday usage. Personally I choose daily comfort over absolute ability - but as I've already mentioned I am an old fart.
Adjustable Dampers Q: I have a general view that adjustable things usually means they are always wrong, whereas non-adjustable means they are right from time-to-time... But seriously, I mentioned earlier that the dampers work across a wide speed range. Adjustable units (in general) only affect a narrow portion of that range, typically the range in which you feel ride quality. For motorcycles, there are four-way adjustable dampers with low- and high-speed adjustability to try and address this but in reality it just confuses people. Adjustable dampers feel like you're making a big difference but that's because the ride gets hurt - they don't really change the handling all that much. In truth they can degrade it, particularly when turned up too high. I would definitely recommend non-adjustable dampers that have been well matched to the vehicle and target audience - the P1 is a good example of that philosophy carried through in practise.
ATD Drive Q: OK, you're right, I'm being mean not to consider an ATD drive on that basis. OK, providing no *even* better Q's come up then you're in...
Other Vehicles Q: I get to play in a fairly wide range of things in a wide variety of places. I don't ever drive circuit race cars (too specialised a technique) but more or less everything else I have a dabble with from time to time. I've certainly contributed to the 550 effort from a vehicle dynamics perspective and am currently contributing to the Ford Performance Vehicles V8 Falcon Touring Car in Australia.
Interesting Moments Q: One of the best of late was chasing a very well driven rear-drive *icon* around its home track and catching it despite a 50-60 bhp deficit in the ATD car. A great deal of hilarity ensued when we swapped cars and they found out how bad my driving really was, it made them even more impressed with the ATD car. The funniest thing was when we stopped I heard a noise from the back of the car and there was a student sitting very quietly in the back - it turned out he'd been there all along... Then there was the time a senior manager from, well, it doesn't matter where he was from, took me off our skid pan at 70 mph backwards. Oh, and the time I ate an apple in the ATD car while driving it in a power slide holding the steering wheel with my knee on a snow circle - I have logged data for that one but no video evidence of the apple. There was a witness in the car though... I also discovered that big drifts at 100 mph flat in fourth gear are greatly improved by Jimmi Hendrix on snow circles in Sweden. And the worst car? It has to be an MG-F - I've never known such a combination of dull and dangerous in the same car. Most disappointing car was a flash Aston - a lovely noise but otherwise unremarkable. Most improbable drive was being passenger while someone else was power sliding round a skid pan we were sharing with an enormous John Deere tractor. Those yellow wheels and agricultural tyres look very big when the steering wheel is in someone else's hands and you've told them not to lift-off...
Prodrive Geometry Q: Mike Wood has an encyclopaedic knowledge of settings for delivering good performance under different circumstances, so any Prodrive Geometry is probably Woody's. I usually like what he likes (we have quite similar driving styles on-road but he is much more flamboyant than me on track).
Ride Height/Geometry Q: Almost certainly the geometry will need modifying for a change in ride height, yes.
Squaky Rally Car Q: It's the anti-lag system making that squeaky noise. If you back a few years they never did, but now they do.
STi7 Upgrade Route Q: The only thing I'd add after that is to consider some damper upgrades - but only if you identify problematic behaviour. I think you're right, the selection you identify will give you a pleasing change in character and help address the wheelspin problem. Rear anti-roll bars help front end traction too, I didn't mention that because in my mind I'm always trying to separate traction and handling issues and if you were happy with the handling I didn't want to suggest something that would change it.
Damping Q: It is generally true that there is an "optimum" level of damping and that too much stops the wheels being able to follow the road, leading to a jumpy/skipping/pattering sensation in the car. One of the subtleties about dampers is that what is "just right" in one situation is too much or not enough in another. The dampers work at a variety of speeds - I mean the speed as measured along the damper rather than the speed of the car - and the damping settings are different at different speeds. What we do here at Prodrive is optimise the damper settings at all the different speeds for different effects. There is an excellent book by John Dixon called "The Shock Absorber Handbook", available on Amazon that describes this stuff really well. In terms of whether to make changes with dampers or roll bars, the key to vehicle dynamics is matching, so if you do all the turn-in with dampers then you get the effect you describe and if you do it all with anti-roll bars you get a sort of "turbo-lag" effect the steering, with an initial delay and then a catch-up as the car rolls - although it sounds like it would be OK, it feels dreadful to drive. For badly surfaced roads, too much roll bar is generally a bad thing because it leads to what we call "roll rock" - the feeling of being thrown from side to side, so for that reason too a balance between bars and dampers is good.
Geometry Q: What we're talking about here is what we call "static geometry" - toe-in/out and camber. Basically, static camber influences the way the car departs at the grip limit, with more negative camber giving more grip but also a more 'aggressive' departure. Basically, there is a best camber angle for the tyre to be presented at the grip limit; if the suspension gets stiffened then because the car rolls less the car needs less negative camber. Adjusting the camber difference front-to-rear gives a a difference in progression. It's quite a useful modifier to the vehicle but sadly not many vehicles have very readily adjustable camber. Camber also greatly influences tyre wear - "ideal" camber wears out the tyre uniformly, "too much" wears out the inside and "too little" wears out the outside. Beware though - "ideal" can give reasonably frisky behaviour at the limit. As a quick and dirty test, drive a bit of road you like in a style you like then pull up, hop out and lay your palm across the tyre from outside to in. The tyres will be working at about 50 degrees C or so, so they should be comfortably warm to the touch. If your camber is a long way off you can feel one edge of the tyre will be noticeably warmer than the other. If you repeat the same thing after a motorway drive you'll see whether or not it will lead to excess tyre wear on the inner shoulder. A lot of prototype vehicles we experiment with have adjustable camber but I'm not sure how easy it is on the road cars. Toe-in/out is altogether more adjustable and a powerful modifier on the way the vehicle behaves beneath the handling limit. Some toe-out at the front and toe-in at the rear promotes stability and the opposite promotes agility at the cost of stability. At the front, toe-in gives a great steering response but turns the steering feel all woolly and so spoils the car a bit. At the rear, the opposite is true. Personally I like the fronts out a little - about a quarter of a degree - and a touch of in on the rear, about the same amount. Note these are personal preferences to match my driving style, etc etc etc... and certainly aren't generically applicable to every car, or even every Scooby. In general, any toe setting other than parallel gives some heat in the tyres and hence accelerates tyre wear for road use.
Prodrive Handling Pack for 00 MY: Probably a bit too specific for me to comment on but it's likely that the Pro pack will feel firmer and more neutral and the Performance one will be a bit more rounded for everyday usage. Personally I choose daily comfort over absolute ability - but as I've already mentioned I am an old fart.
Adjustable Dampers Q: I have a general view that adjustable things usually means they are always wrong, whereas non-adjustable means they are right from time-to-time...
But seriously, I mentioned earlier that the dampers work across a wide speed range. Adjustable units (in general) only affect a narrow portion of that range, typically the range in which you feel ride quality. For motorcycles, there are four-way adjustable dampers with low- and high-speed adjustability to try and address this but in reality it just confuses people. Adjustable dampers feel like you're making a big difference but that's because the ride gets hurt - they don't really change the handling all that much. In truth they can degrade it, particularly when turned up too high. I would definitely recommend non-adjustable dampers that have been well matched to the vehicle and target audience - the P1 is a good example of that philosophy carried through in practise.ATD Drive Q: OK, you're right, I'm being mean not to consider an ATD drive on that basis. OK, providing no *even* better Q's come up then you're in...
Other Vehicles Q: I get to play in a fairly wide range of things in a wide variety of places. I don't ever drive circuit race cars (too specialised a technique) but more or less everything else I have a dabble with from time to time. I've certainly contributed to the 550 effort from a vehicle dynamics perspective and am currently contributing to the Ford Performance Vehicles V8 Falcon Touring Car in Australia.
Interesting Moments Q: One of the best of late was chasing a very well driven rear-drive *icon* around its home track and catching it despite a 50-60 bhp deficit in the ATD car. A great deal of hilarity ensued when we swapped cars and they found out how bad my driving really was, it made them even more impressed with the ATD car. The funniest thing was when we stopped I heard a noise from the back of the car and there was a student sitting very quietly in the back - it turned out he'd been there all along... Then there was the time a senior manager from, well, it doesn't matter where he was from, took me off our skid pan at 70 mph backwards. Oh, and the time I ate an apple in the ATD car while driving it in a power slide holding the steering wheel with my knee on a snow circle - I have logged data for that one but no video evidence of the apple. There was a witness in the car though... I also discovered that big drifts at 100 mph flat in fourth gear are greatly improved by Jimmi Hendrix on snow circles in Sweden. And the worst car? It has to be an MG-F - I've never known such a combination of dull and dangerous in the same car. Most disappointing car was a flash Aston - a lovely noise but otherwise unremarkable. Most improbable drive was being passenger while someone else was power sliding round a skid pan we were sharing with an enormous John Deere tractor. Those yellow wheels and agricultural tyres look very big when the steering wheel is in someone else's hands and you've told them not to lift-off...
Prodrive Geometry Q: Mike Wood has an encyclopaedic knowledge of settings for delivering good performance under different circumstances, so any Prodrive Geometry is probably Woody's. I usually like what he likes (we have quite similar driving styles on-road but he is much more flamboyant than me on track).
Ride Height/Geometry Q: Almost certainly the geometry will need modifying for a change in ride height, yes.
Squaky Rally Car Q: It's the anti-lag system making that squeaky noise. If you back a few years they never did, but now they do.
STi7 Upgrade Route Q: The only thing I'd add after that is to consider some damper upgrades - but only if you identify problematic behaviour. I think you're right, the selection you identify will give you a pleasing change in character and help address the wheelspin problem. Rear anti-roll bars help front end traction too, I didn't mention that because in my mind I'm always trying to separate traction and handling issues and if you were happy with the handling I didn't want to suggest something that would change it.
16 February 2003, 04:19 PM
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There is an excellent book by John Dixon called "The Shock Absorber Handbook", available on Amazon that describes this stuff really well.
16 February 2003, 07:22 PM
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Hi Damian
With the ATD system, do you apply more power to the outer wheels during cornering to reduce the radius of the turn ? If so, how do you retain yaw stability and ensure that the limit of adhesion is not breached due to the extra power transmitted by the already heavily loaded contact patch ?
I'm thinking specifically with regard to changing conditions / surfaces.
cheers
Andy
With the ATD system, do you apply more power to the outer wheels during cornering to reduce the radius of the turn ? If so, how do you retain yaw stability and ensure that the limit of adhesion is not breached due to the extra power transmitted by the already heavily loaded contact patch ?
I'm thinking specifically with regard to changing conditions / surfaces.
cheers
Andy
16 February 2003, 07:56 PM
#68
I know it's a few pages back now, but could i just add something about David's Wallis' question about the rear diff.
As he like many of us has found in the quest for silly power, the rear diff does tend to tramp a bit, but because the car has independant rear suspension this doesn't relate to true axle tramp with the rear wheels hoping away merrily (I have a lovely car for that in my parent's garage). This tramping is the torque build up twisting the diff on it's mounts and acts about the drivesaft axis.
By stiffening up the diff carrier bushes (both the two front 'A' frame bushes and the 2 bushes that the rear of the diff locates to the carrier) with poly bushes you do stop the diff moving around a fair bit, but you shift the problem back towards the engine. It has been suggested to me that I should replace the rear gearbox mount with a more solid rubber unit, a group N item which has more rubber and hence less 'give', and also replace the engine mounts with group N too.
Obviously combined with the 450lb sprung coil over front and 350lb rear set up my poor car will be evil on the road (it also has a full poly bushed suspension set up, solid drop links, piillow ball mounts, a complementary set of upper and lower strut braces front and rear) but it should be great on track
Excellent reading this thread, thanks for taking the time to post Damien (especially on you day off!)
As he like many of us has found in the quest for silly power, the rear diff does tend to tramp a bit, but because the car has independant rear suspension this doesn't relate to true axle tramp with the rear wheels hoping away merrily (I have a lovely car for that in my parent's garage). This tramping is the torque build up twisting the diff on it's mounts and acts about the drivesaft axis.
By stiffening up the diff carrier bushes (both the two front 'A' frame bushes and the 2 bushes that the rear of the diff locates to the carrier) with poly bushes you do stop the diff moving around a fair bit, but you shift the problem back towards the engine. It has been suggested to me that I should replace the rear gearbox mount with a more solid rubber unit, a group N item which has more rubber and hence less 'give', and also replace the engine mounts with group N too.
Obviously combined with the 450lb sprung coil over front and 350lb rear set up my poor car will be evil on the road (it also has a full poly bushed suspension set up, solid drop links, piillow ball mounts, a complementary set of upper and lower strut braces front and rear) but it should be great on track
Excellent reading this thread, thanks for taking the time to post Damien (especially on you day off!)
16 February 2003, 08:12 PM
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Damian - I'm going to pretend you didn't write that...things like that don't happen to me!
I can almost sense the Scoobynet technical gurus plotting better questions as we speak so I'll try not to get too excited!
Another question if you are still answering - what are the supposed advantages of a 6 speed gearbox? My friend has a modified sti7 but he compains that he is constantly changing gear to keep it 'on the boil'. I also hear a lot of people saying how much more 'driveable' a 300+ bhp WRX is compared with similar specced sti7 due to the 5 speed box on the wrx??? Is it just a case of FHI putting another tick in the sales brochure or does the 6spd really offer any advantages?
I can almost sense the Scoobynet technical gurus plotting better questions as we speak so I'll try not to get too excited!
Another question if you are still answering - what are the supposed advantages of a 6 speed gearbox? My friend has a modified sti7 but he compains that he is constantly changing gear to keep it 'on the boil'. I also hear a lot of people saying how much more 'driveable' a 300+ bhp WRX is compared with similar specced sti7 due to the 5 speed box on the wrx??? Is it just a case of FHI putting another tick in the sales brochure or does the 6spd really offer any advantages?
16 February 2003, 08:51 PM
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Damian
I am in the process of changing my stock STi Type R 16" wheels to 17" wheels with 215/40 r17 tyres - what are the optimum tyre pressures I should be running???
Many Thanks
I am in the process of changing my stock STi Type R 16" wheels to 17" wheels with 215/40 r17 tyres - what are the optimum tyre pressures I should be running???
Many Thanks
17 February 2003, 12:08 AM
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Damian -- Many thanks for your comments re the Prodrive handling pack here and on my other thread. Sorry, just one more question on this kit (I am seriously considering buying it but need some clarification and re-assurance from the "ultimate source of Prodrive suspension info").
You said that the Pro kit gives less "daily comfort" vs the Performance pack. BUT does it also give less "daily handling" (i.e. non-track, everyday road driving)???
Here's a review of the Pro kit by evo magazine in 1999 that has got me worried:
"The firmed up suspension (Prodrive Professional) is less successfull but then the RB5 (Stock suspension) is such a hard act to follow. The front is about 15 per cent stiffer, the rear 40 per cent, which has changed the character of the car. It has improved steering weight, feel and precision, especially at high speed, which was one of the few weakness of the RB5. The downside is that the ride is now over-firm on the sort of roads Imprezas normally shine on - those bumpy back-roads that get badly puddled when it rains."
Unfortunately neither kit is available for a test-drive from Subaru (on classic shape cars), so I have to rely on others' reviews and advice, and I would be grateful for yours.
Many thanks!
Andrei
You said that the Pro kit gives less "daily comfort" vs the Performance pack. BUT does it also give less "daily handling" (i.e. non-track, everyday road driving)???
Here's a review of the Pro kit by evo magazine in 1999 that has got me worried:
"The firmed up suspension (Prodrive Professional) is less successfull but then the RB5 (Stock suspension) is such a hard act to follow. The front is about 15 per cent stiffer, the rear 40 per cent, which has changed the character of the car. It has improved steering weight, feel and precision, especially at high speed, which was one of the few weakness of the RB5. The downside is that the ride is now over-firm on the sort of roads Imprezas normally shine on - those bumpy back-roads that get badly puddled when it rains."
Unfortunately neither kit is available for a test-drive from Subaru (on classic shape cars), so I have to rely on others' reviews and advice, and I would be grateful for yours.
Many thanks!
Andrei
17 February 2003, 12:39 AM
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Hallo
this is great reading!
What do you see happening with regards to handling control of cars in the next 10 years?
With the ATD system, it seems as tho new levels of car control are being developed. Perhaps we are in for a boom in the suspension / handling aspects of cars?
Could this get to a point where the car is clever enough to warn you if the grip levels are getting dangerous? Perhaps even taking over and calming the car down?
What about linking it up to a radar so that the car can take even more of control?
Or local authorities issuing 'safety settings' from the roadside?
I have a MY99 impreza, and am looking at updating the suspension.
Options are adjustable suspension or a prodrive suspension kit.
I drive a wide variety of roads in all conditions.
As its road driving, i may have to come off the throttle for tractors, sheep etc.
What should I look for in the suspension?
Would the impreza chasis respond well to a firming up of the suspension ala Prodrive Professional kit.
Or would it be best to keep the status quo?
I like the fluid feeling of the scooby over the b roads up here in scotland... the roads get very affected by the landscape / weather... but the car seems to be quite solid over them... not passing on the buck to my backside.
I would be looking for more of the same, and more confidance on corners on better roads.
keep up the great answers
this is great reading!
What do you see happening with regards to handling control of cars in the next 10 years?
With the ATD system, it seems as tho new levels of car control are being developed. Perhaps we are in for a boom in the suspension / handling aspects of cars?
Could this get to a point where the car is clever enough to warn you if the grip levels are getting dangerous? Perhaps even taking over and calming the car down?
What about linking it up to a radar so that the car can take even more of control?
Or local authorities issuing 'safety settings' from the roadside?
I have a MY99 impreza, and am looking at updating the suspension.
Options are adjustable suspension or a prodrive suspension kit.
I drive a wide variety of roads in all conditions.
As its road driving, i may have to come off the throttle for tractors, sheep etc.
What should I look for in the suspension?
Would the impreza chasis respond well to a firming up of the suspension ala Prodrive Professional kit.
Or would it be best to keep the status quo?
I like the fluid feeling of the scooby over the b roads up here in scotland... the roads get very affected by the landscape / weather... but the car seems to be quite solid over them... not passing on the buck to my backside.
I would be looking for more of the same, and more confidance on corners on better roads.
keep up the great answers
17 February 2003, 07:57 AM
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P1Fanatic,
Check out the following:
http://www.scoobynet.co.uk/bbs/threa...hreadid=167283
Cheers
Nigel
Check out the following:
http://www.scoobynet.co.uk/bbs/threa...hreadid=167283
Cheers
Nigel
17 February 2003, 01:41 PM
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Moderators / Simon, can we please 'lock' this thread to the top of the Suspension forum? This is one thread that all people looking to get the best out of their car should read!
17 February 2003, 07:18 PM
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ATD Q: I'm not at liberty to say how we do what we do - it's proprietary!
6 Speed Gearbox Q: Theoretically the more gears you have the more "optimum" your acceleration can be. However in the real world there comes a point when more gears means more messing about deciding which gear to use. I'm used to six gears on a bike but driving six-speed cars always seems to leave me in a bit of a muddle on the road. It's one of those things that is technically better but I'm not really sure it delivers anything for me except maybe a higher top gear for motorway cruising.
Tyre Pressure Q: Can't answer that, too specific! Whatever the tyre manufacturer tells you to run is a safe place to start.
Daily Handling Q: This is a bit difficult to answer since it depends what your day consists of. However, if you almost never do track days I think the Performance Pack is probably the one for you - it should deliver a noticeably more "sophisticated" ride. It's almost impossible to define what I mean by that but if you get it you will see what I mean; there is less sensation to do with the texture of the road while losing none of the information about the form of the road and the level of grip available, as well as good body control. There should also be useful improvements in your confidence in the car in a variety of circumstances.
Next Ten Years Q: I think that "passive" handling (i.e. without gadgets) is about as good as it is going to get now and the next leaps forward are going to be "active" in one form or another. Although there was a lot of fanfare about Active Suspension in reality it was a bit of an indirect way of going about things. I think there will be first an explosion of possible gadgets and then the market will home in on the ones it really wants. I'm betting on brake-based stability systems (already current), active steering with active toe adjustment, adaptive damping and active torque distribution. Tyre technology is moving on and yes, I can forsee the tyres themselves becoming "smarter" to tell the car when grip is reduced. However there is a problem that although they can tell you what the grip is *under* the tyre right now, they usually can't tell you what it's going to be - and normally that's where the problem is. So I can imagine a network whereby "smart" cars communicate their finding to a local "substation" and this in turn relays the information back to cars entering the region. Maybe there will be a technology that uses this information to limit what the car does, or maybe it will just be information for the driver to use or disregard, I don't know. Certainly though, if the information is like the current "Maximum Speed" signs on some bends it will be useless. At the bottom of the M69 there is a 270 degree cloverleaf signed at 30 mph and even my MkIV Cortina would do it an an indicated 80 mph... Radar-based "Intelligent Cruise Control" is already fitted to some luxury vehicles and may make its way down the market if people want it.
What to Look For in a Suspension Q: An ability to keep the wheels on the road over the roughest surfaces is important. Try some straight line full-throttle runs on what you regard as the roughest surface you'll drive hard over. If you get a noticeable amount of wheelspin when you wouldn't if the road was smooth, the suspension is probably a bit too firm, particularly if the wheelspin is a bit erratic and noses the car around or causes lots of steering wheel fight. On the other hand if the body is yumping, pitching and rolling such that the wheels run out of travel sometimes, it's too compliant for you. It's important to note this is a test that matches your car, your driving style and your driving environment and so I might draw different conclusions from it than you. That's one of the reasons we offer two different levels of suspension tune - one man's comfortable is another man's squashy.
6 Speed Gearbox Q: Theoretically the more gears you have the more "optimum" your acceleration can be. However in the real world there comes a point when more gears means more messing about deciding which gear to use. I'm used to six gears on a bike but driving six-speed cars always seems to leave me in a bit of a muddle on the road. It's one of those things that is technically better but I'm not really sure it delivers anything for me except maybe a higher top gear for motorway cruising.
Tyre Pressure Q: Can't answer that, too specific! Whatever the tyre manufacturer tells you to run is a safe place to start.
Daily Handling Q: This is a bit difficult to answer since it depends what your day consists of. However, if you almost never do track days I think the Performance Pack is probably the one for you - it should deliver a noticeably more "sophisticated" ride. It's almost impossible to define what I mean by that but if you get it you will see what I mean; there is less sensation to do with the texture of the road while losing none of the information about the form of the road and the level of grip available, as well as good body control. There should also be useful improvements in your confidence in the car in a variety of circumstances.
Next Ten Years Q: I think that "passive" handling (i.e. without gadgets) is about as good as it is going to get now and the next leaps forward are going to be "active" in one form or another. Although there was a lot of fanfare about Active Suspension in reality it was a bit of an indirect way of going about things. I think there will be first an explosion of possible gadgets and then the market will home in on the ones it really wants. I'm betting on brake-based stability systems (already current), active steering with active toe adjustment, adaptive damping and active torque distribution. Tyre technology is moving on and yes, I can forsee the tyres themselves becoming "smarter" to tell the car when grip is reduced. However there is a problem that although they can tell you what the grip is *under* the tyre right now, they usually can't tell you what it's going to be - and normally that's where the problem is. So I can imagine a network whereby "smart" cars communicate their finding to a local "substation" and this in turn relays the information back to cars entering the region. Maybe there will be a technology that uses this information to limit what the car does, or maybe it will just be information for the driver to use or disregard, I don't know. Certainly though, if the information is like the current "Maximum Speed" signs on some bends it will be useless. At the bottom of the M69 there is a 270 degree cloverleaf signed at 30 mph and even my MkIV Cortina would do it an an indicated 80 mph... Radar-based "Intelligent Cruise Control" is already fitted to some luxury vehicles and may make its way down the market if people want it.
What to Look For in a Suspension Q: An ability to keep the wheels on the road over the roughest surfaces is important. Try some straight line full-throttle runs on what you regard as the roughest surface you'll drive hard over. If you get a noticeable amount of wheelspin when you wouldn't if the road was smooth, the suspension is probably a bit too firm, particularly if the wheelspin is a bit erratic and noses the car around or causes lots of steering wheel fight. On the other hand if the body is yumping, pitching and rolling such that the wheels run out of travel sometimes, it's too compliant for you. It's important to note this is a test that matches your car, your driving style and your driving environment and so I might draw different conclusions from it than you. That's one of the reasons we offer two different levels of suspension tune - one man's comfortable is another man's squashy.
17 February 2003, 10:46 PM
#78
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Hi Damian,
Great reading,so heres some more questions
Cars are getting heavier(every new model release)which must effect vehicle dynamics.The new generation Impreza's seem to have put on more weight again.With so much technology in composite materials(motorsport) there seems to be very slow take up for production models.
Surely making a car lighter will make it handle better,stop,and accelerate better and reduce fuel consumption.
Are there any moves into this direction,or are we going to be driving around in 10 tonne cars in 10 years time? although with some nice gadgets.
Pete
Great reading,so heres some more questions
Cars are getting heavier(every new model release)which must effect vehicle dynamics.The new generation Impreza's seem to have put on more weight again.With so much technology in composite materials(motorsport) there seems to be very slow take up for production models.
Surely making a car lighter will make it handle better,stop,and accelerate better and reduce fuel consumption.
Are there any moves into this direction,or are we going to be driving around in 10 tonne cars in 10 years time? although with some nice gadgets.
Pete
18 February 2003, 08:53 AM
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Great thread - thanks Damian/Simon
A diff question - you mentioned previously the effect of the centre diff is most felt when sideways. Can a stronger viscous centre item assist in getting the car into this attitude under power?
I appreciate it's effect will depend a lot on other mods to the car - I'm running coil-overs with uprated front and rear ARB's/links/mounts with -2 degrees all round, parallel rear and 1 degree of total toe-in at the front along with a Quaife ATB front diff on a my00 Euro car.
On the road it's great and on track with slicks is also problem free. However, I often run on track with street tyres and have a large front end grip problem when I've over cooked the entry speed. Once the front is losing grip, more gas just makes the problem worse with the front running even wider. I'd like more gas to direct power to the rear wheels to at least balance the slide (to help correct my bad driving).
I recently fitted the uprated front ARB in an attempt to reduce the forces applied to front tyres on turn in, but haven't tried it on track yet. I'm concerned it will upset the balance I had before - when entry speed is correct the car digs in and seems to catapult itself out of the apex.
So, a long winded way of asking; would a stronger viscous unit 'react' quick enough to correct the axle speed differences. Or is it asking too much of a viscous solution? What would be the effect of a purely mechanical centre diff (similar to Quaife ATB) to handling?
Thanks
Richard
[Edited by dowser - 2/18/2003 9:49:29 AM]
A diff question - you mentioned previously the effect of the centre diff is most felt when sideways. Can a stronger viscous centre item assist in getting the car into this attitude under power?
I appreciate it's effect will depend a lot on other mods to the car - I'm running coil-overs with uprated front and rear ARB's/links/mounts with -2 degrees all round, parallel rear and 1 degree of total toe-in at the front along with a Quaife ATB front diff on a my00 Euro car.
On the road it's great and on track with slicks is also problem free. However, I often run on track with street tyres and have a large front end grip problem when I've over cooked the entry speed. Once the front is losing grip, more gas just makes the problem worse with the front running even wider. I'd like more gas to direct power to the rear wheels to at least balance the slide (to help correct my bad driving
).I recently fitted the uprated front ARB in an attempt to reduce the forces applied to front tyres on turn in, but haven't tried it on track yet. I'm concerned it will upset the balance I had before - when entry speed is correct the car digs in and seems to catapult itself out of the apex.
So, a long winded way of asking; would a stronger viscous unit 'react' quick enough to correct the axle speed differences. Or is it asking too much of a viscous solution? What would be the effect of a purely mechanical centre diff (similar to Quaife ATB) to handling?
Thanks
Richard
[Edited by dowser - 2/18/2003 9:49:29 AM]
18 February 2003, 06:50 PM
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Heavier Cars Q: Cars are indeed getting remorselessly heavier. It's one of the things that disappoints me. Composites in particular are not very robust in service and anything other than steel is quite expensive. Making a car lighter is indeed a very good thing - witness the performance of an Elise on its comparatively meagre power output. If you study a modern 1250 kg car, the weight breaks down roughly like this: Body structure: 300 kg, Engine & Transmission: 200 kg, Suspension incl wheels, brakes, steering etc: 250 kg, Other stuff that makes the car a nice place to be: 500 kg. Yup, that's half a ton of seats, sound insulation, carpets, trim panels, electric accessories, cup holders, dashboard, stereo, heater.... It shocks me too. So you can see if you went absolutely mad and halved the weight of the body structure, the car wouldn't get that much lighter. There's a lot of guff talked about how it's to do with modern crash legislation but the truth is the difference between a Mondeo and a Citroen BX amounts to another complete Body-in-White, or one-and-a-half spare engine & transmission assemblies - much more than the (roughly) 20% improvement in crash energy absorption warrants.
Centre Visco Q: Basically yes, the stiffer the visco the more responsive the car will be to attitude changes on the gas. I can't help thinking that an "uprated" (I presume bigger) front anti-roll bar will increase your understeer later in the turn; dampers are the thing to work with for front end "bite" as you turn in. However, I'm sure that by unloading the inside front wheel you will introduce some secondary effects too - maybe spinning up the inside front wheel will help push torque rearward in the driveline as you get back on the power, so it's a bit difficult to generalise about the effects on the vehicle. Mechanical diffs generally are "stronger" as I said before but they can feel a bit lumpy and discontinuous.
Wagon Torque Split Q: I'm afraid I have no idea. I think I'd be surprised if the driveline hardware was unique to the body style though, I would have expected them to all be the same but with different suspension settings.
Centre Visco Q: Basically yes, the stiffer the visco the more responsive the car will be to attitude changes on the gas. I can't help thinking that an "uprated" (I presume bigger) front anti-roll bar will increase your understeer later in the turn; dampers are the thing to work with for front end "bite" as you turn in. However, I'm sure that by unloading the inside front wheel you will introduce some secondary effects too - maybe spinning up the inside front wheel will help push torque rearward in the driveline as you get back on the power, so it's a bit difficult to generalise about the effects on the vehicle. Mechanical diffs generally are "stronger" as I said before but they can feel a bit lumpy and discontinuous.
Wagon Torque Split Q: I'm afraid I have no idea. I think I'd be surprised if the driveline hardware was unique to the body style though, I would have expected them to all be the same but with different suspension settings.
19 February 2003, 07:42 AM
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Brilliant reading, hats off.
Question if you don't mind: is there any importance to the "overhang" of (rally) cars when it comes to handling ? The Peugeot virtually has none and I constantly read it would be ultimately more "nimble" on the limit, Skoda will change to a smaller model later in the year, Mitsu wasn't really doing well last year. Would the Subaru benefit from a smaller shape with less overhang or do they make up with the engine/gearbox layout (or doesn't it really play a role) ? If you were free to redesign the Impreza shape from a handling POV, what (if anything) would you change ?
Question if you don't mind: is there any importance to the "overhang" of (rally) cars when it comes to handling ? The Peugeot virtually has none and I constantly read it would be ultimately more "nimble" on the limit, Skoda will change to a smaller model later in the year, Mitsu wasn't really doing well last year. Would the Subaru benefit from a smaller shape with less overhang or do they make up with the engine/gearbox layout (or doesn't it really play a role) ? If you were free to redesign the Impreza shape from a handling POV, what (if anything) would you change ?
19 February 2003, 08:20 AM
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Damian,
Excellent reading.
Just to add to the above post. Subaru started with a 4 door shell and then went to a 2 door and is now back with a 4 door. Other teams such as Peugeot and Citroen have gone with 2/3 door shells which have translated into instant success. Ford on the otherhand have the 3 door Focus but have not translated this into much success.
Your earlier post about the shell seemed to suggest that the 2 door shell is superior. Are you able to give a view on comparisons as Subaru has had a number of different shells over the years and I would have thought by now they would have the overall best shell for a starting point or is it just a case that Prodrive have to use, or any rallyteam has to use the shell provided by the manufacturer. The latest Scoob is supposedly had input direct from the rallyteam resulting in the new facelift.
Damian.
Excellent reading.
Just to add to the above post. Subaru started with a 4 door shell and then went to a 2 door and is now back with a 4 door. Other teams such as Peugeot and Citroen have gone with 2/3 door shells which have translated into instant success. Ford on the otherhand have the 3 door Focus but have not translated this into much success.
Your earlier post about the shell seemed to suggest that the 2 door shell is superior. Are you able to give a view on comparisons as Subaru has had a number of different shells over the years and I would have thought by now they would have the overall best shell for a starting point or is it just a case that Prodrive have to use, or any rallyteam has to use the shell provided by the manufacturer. The latest Scoob is supposedly had input direct from the rallyteam resulting in the new facelift.
Damian.
19 February 2003, 08:55 AM
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AFAIK one of the reasons they changed back to a 4 door shell was access to the rear components such as suspension tops.... how many of you have seen on the old 2 door shell them popping out the back windows and stuggling to get at the tops.
I'm also guessing that the 4 door shell has to be stiffer due to it having two extra big holes for the rear doors. Then again with all the seam welding and additional strenghtening its probably not so much of an issue.
Damian - I have a question .... I believe that you guys havnt limited the ATD work to just Subaru's as one of my rel's has been in a 4wd Turbo Focus (!!!) at your Midlands site. Can you talk about this and what difference using a Ford Focus shell (which I belive are verfy strong and stiff) compared to the Impreza shell. Im guessing it must be very modified to handle 4wd transmission unless it was an ex-M Sport shell....
Ids
I'm also guessing that the 4 door shell has to be stiffer due to it having two extra big holes for the rear doors. Then again with all the seam welding and additional strenghtening its probably not so much of an issue.
Damian - I have a question .... I believe that you guys havnt limited the ATD work to just Subaru's as one of my rel's has been in a 4wd Turbo Focus (!!!) at your Midlands site. Can you talk about this and what difference using a Ford Focus shell (which I belive are verfy strong and stiff) compared to the Impreza shell. Im guessing it must be very modified to handle 4wd transmission unless it was an ex-M Sport shell....
Ids
19 February 2003, 10:33 AM
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RE bodyshell, a 2 door coupe type shell is also limiting FHI's market for the Impreza. Probably why they are now looking at producing a specific coupe?
20 February 2003, 01:50 PM
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Overhang Q: The overhang dimension itself isn't critical but usually there is a certain amount of weight in it; what matters is the weight and the square of the distance from the CG. If you think of it a bit like a dumbell and that you are trying to "twirl" the dumbell, then the longer the dumbell the harder it is to both start and stop it rotating. If you move your hands out from the centre then you have more control over the dumbell. The length of the dumbell and the position of your hands are quite a good analogy for the length/overhang thing and there is an "optimum" match between where the wheels are and the "effective length" of the dumbell. The quantity we use for evaluating that is called "moment of inertia" (some people stick the word "polar" on the front but if it's a moment then it's about an axis by definition, so the word "polar" is mainly bollocks) and we try to match together the moment of inertia with the wheelbase and weight distribution. It's generally true that less overhang means less inertia and so a better match. However, with good design we can play with the weight distribution to improve the quality of our match too. So the Subaru might benefit from less inertia but if we can achieve it by changing weight distribution - e.g. driveline layout, among other things - then we can stay "up there". In general for road cars there is such a thing as "too little" moment of inertia, it makes cars tricky to handle when things go wrong because the car turns faster than the driver can work out what's going on. Small mid-engined cars are usually the worst for this and the MG-F is the worst of the worst. A dead cert clue to this type of behaviour is bigger rear tyres than front on a car with "not that much" power.
2 door vs 4 door: We're basically in the hands of the manufacturers and yes, we did get some input into revisions for the latest facelift, though I can't be specific there. One of the nice things about the Scoobies in comparison with the other hatches is the use of two bonded screens (front and rear) instead of only one. That helps shell stiffness a great deal, even on the road cars. Your're right that once we've started to modify things the number of closures is less of an issue.
ATD on Other Cars Q: You're right that we haven't limited ATD work to the Subaru. However, I can neither confirm or deny rumours of "another" car at our facility but you'll get us both in trouble if you mention the "F" word again... Who was the relative? He's just guaranteed he'll never get another ride in anything again!?! In general there is a reasonable amount of modification necessary to a 2WD shell to make it take 4WD, yes.
2 door vs 4 door: We're basically in the hands of the manufacturers and yes, we did get some input into revisions for the latest facelift, though I can't be specific there. One of the nice things about the Scoobies in comparison with the other hatches is the use of two bonded screens (front and rear) instead of only one. That helps shell stiffness a great deal, even on the road cars. Your're right that once we've started to modify things the number of closures is less of an issue.
ATD on Other Cars Q: You're right that we haven't limited ATD work to the Subaru. However, I can neither confirm or deny rumours of "another" car at our facility but you'll get us both in trouble if you mention the "F" word again...
Who was the relative? He's just guaranteed he'll never get another ride in anything again!?! In general there is a reasonable amount of modification necessary to a 2WD shell to make it take 4WD, yes.
20 February 2003, 01:55 PM
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Dear Mr Harty,
Just wanted to thank you for spending the time to post.. you must have spent ages typing!!! Its been great to read and very informative (even if some of it is well over my head!!)
I'd like to see your answers stored somewhere on our BBS so we can find them and re-read what you say. Any ideas Simon?
Thanks!
Jza
Just wanted to thank you for spending the time to post.. you must have spent ages typing!!! Its been great to read and very informative (even if some of it is well over my head
!!)I'd like to see your answers stored somewhere on our BBS so we can find them and re-read what you say. Any ideas Simon?
Thanks!
Jza
20 February 2003, 02:09 PM
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A a bit of a weird question here, I have a 99 type R, sometimes if I am moving along quite quickly, and then go over a hill in the road quick enough to lift off the ground, when I land the steering stiffens up (ever so slightly) and when you turn the wheel there is a medium tone whining, like the power steering pump is pumping fluid, but louder than it usually is. If I then stop, and turn off the engine, and then restart it, the whining stops, I have asked several people and they haven`t got a clue, as you are in the business of flying cars! what is it?
20 February 2003, 02:23 PM
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I'd like to see your answers stored somewhere on our BBS so we can find them and re-read what you say.
Scoobdoo -- is that the same sort of noise you get after the ABS has activated (i.e. the ABS has been on, but now you've let off the brakes)? If so, I've noticed it too and wondered if it was ABS related -- I assume it could get a bit confused when some of the wheels are off the ground.
[Edited by carl - 2/20/2003 2:25:45 PM]
20 February 2003, 02:40 PM
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JZA - I suggested locking the thread to the top of the suspension forum, as done in the 'general' and 'for sale' forums?
Might even be worth someone compiling it into an FAQ-type doc.
Might even be worth someone compiling it into an FAQ-type doc.