Damian, it's been very good reading your posts, very informative. I especially like your quotes about the MGF as I have a work colleague with one!

Question: Is the rear wing on Impreza's actually a spoiler or a true inverted aerofoil? If it is the latter how much actual down force does it create or do you have to be driving very fast for it to have any real effect? I am thinking of the MY99 / MY00 wings and the Prodrive one.

Many thanks

Chris

 

Damian,

Well my relitive is my sister.... who was there with the local police as they use the same location for skid pan etc don'they ?

I'm fasicanted by the ATD principles and really look forward to when it becomes a reality on production cars or better still a retrofit !

One last question for me - does the unsprung weight make a vast differnce to the suspension systems on modern cars ? I find it odd that modern cars get heavier but companies such as BMW and Subaru and others fit Aluminium suspension componenents to reduce this i guess. Surely brake disks and hubs are heavier still - can these not be made durable enough for road use ???

Kev

 

ids - this was one of the first questions answered - check page 1

 

damn - its been soooo long ago since p1. Appols... :<

 

Thanks for your answer Mr. Harty, appreciate it.

As an aside it's a bit ironic to see you still have the "Scooby newbie" next to your name

Have you ever considered writing a book about this subject ? I appreciate there would be many non-disclosure areas, but your explanations are very clear and understandable to the average enthousiast, something you don't often find in books about this very subject.

 

Carl, in response to your question, I dont have ABS, so I am not sure what your noise is!

 

Trouble is Chris, which wing and on which Impreza?

The options are:

STi 1/2 small spoiler (presumably resists lift (perhaps ))
STi 3/4 spoiler (presumably resists lift)
STi 5/6 Large spoiler/wing? (perhaps creates a little downforce?)
MY98/99/00 Prodrive WRSport spoiler (I *think* creates a little downforce)
WRX 01/02/03 spoiler (presumably resists lift)
UK300 Front and rear spoilers (which Mike Wood did actually say created some downforce)
STi 02 (PPP)/03 spoiler (perhaps creates a little downforce)

Damian?

Matt

 

can you list the models of Impreza you have driven, what state of tune/modification they were in, how long you drove them, where you drove them and for what purpose.

 

IIRC these spoilers don't generate downforce but do reduce the amount of lift experienced by the car, though only at very high speeds.

 

Damian

I know you did mention about suspension settings but as it's cheap and easy modification I’d like you to examine closely on this, especially toe-camber settings.
Basically I thought that some front toe in and more negative camber with some rear toe out gives the best of both worlds, stability and agility , and “Prodrive settings” for pre MY01 as we all know them are more or less this way.
Although you say that you prefer little toe out front / toe in rear for stability and this is your personal style which finally confused me!
In my humble opinion a car with good steering response that is neutral or understeers a little in first phase of cornering, neutral in the middle and mild oversteering on exits is perfect, predictable, friendly and helps you to put down all the available power.
What are your suggestions about and without intention to bore you could you tell me if there are any differences on the new MY03 Impreza, I have heard that has exactly the same rear differential (available with Suretrak overseas) but multi valve dampers so hope a set of lowering springs (do you have any project running for this MY?) with little bigger rear anti roll bar will be a very good setup that doesn’t cost a fortune and doesn’t affect ride quality that new age Imprezas have.

Thanks in advance

JIM


[Edited by JIM THEO - 2/21/2003 9:54:43 PM]

 

Excellent Q's and A's!

My question, when are you going to sell ATD for my P1?

 

Dear Mr Harty

The words "Thank you" seem so inadequate for your contribution.

A son who is heading for University means that a 5 door Impreza Turbo may be needed soon to replace a 4 door. That is to accommodate video screens, bicycles, doting mothers, sleeping as a circuit marshal, etc.

You state that the rear bulkhead and bonded rear glass significantly benefit body stiffness to meet the needs stated in your early answers.

Have you any comments on the differences between the handling of 5 door and 4 door machines. Is this noticeable to someone of your driving ability?

Would a 5 door benefit from any bracing or would you suggest some other improvement route? I understand that Subaru claim that the latest shape cars (both 4+5 door) are stiffer, so answers may depend on age of the 5 door.

Mr Harty, you lucky man, it must be fascinating testing subtle differences to the suspension of cars; or even dialling in variations to the ATD. Ah yes, I forgot about the statisticians who demand boring repeatability testing.

Do you foresee eccentric suspension bushes under computer control as a future development path to adjust camber and caster in motion?

My thanks again.

Have we discovered how to contact the said Mr Wood?

 

Here's another one for you - game development is a very nebulous art. There are certain 'rules' of how to make a great game, but to make a great game is not just following these rules...it needs a little....erm, magic I suppose. You also find that even with the most detailed design doc at the start, you always get feature creep and / or cutting cool stuff due to time constraints. One of the biggest problems (ok, ok I'm getting there...) is when you are testing the game just before you are ready to release it to the public, but having been involved with it so much you tend to get 'snowblind' to some really obvious, small faults / changes etc. You also tend to 'tune' the game for yourselves, whereas as developers we are hardly the same as the 'massmarket' audience we are targeting.

Is it the same as this with vehicle / tuning development?

How do you stop yourselves getting 'snowblind'?

How do you ensure you don't release something to the massmarket that is suitable for you but maybe not suitable to them?

 

Matt, fair comment. I was thinking about the high level wing on the MY99 / MY00 cars and if they actually do anything or if they are just there for show.

Chris

 

It seems that Damian is very busy this time or he doesn't want to answer those type of questions!

 

Jim - I'd guess more likely that he is busy and also waiting for a few more questions to build up so that he can answer a load in one go.

Damian, here's another one - when's the test drive likely to take place?

 

I'm not dead and I certainly haven't lost interest, I'm hoping to post a bunch of answers this evening!

Ed and Carl - can you contact me via Simon so we can sort out a time? It will have to be a weekday and I don't know how you are for getting time off at short notice.

 

Hi Damian,
I would be very interested in the ATD system (ver 4 sti type r), will there be a retrofit kit? if so how much will it cost?

ed

 

Ed, lots of info here http://www.scoobynet.co.uk/bbs/threa...hreadid=167283

 

cheers Eb,
I would still like to know if the sys might be sold as a retro fit kit, looking at the motec sys as well.

 

It says in that thread that it is likely be sold as an aftermarket kit

 

No can do, I'm afraid
I'm an IT contractor and as such it would be an expensive 'free' ride for me if it's a weekday
How about I auction my go -- proceeds going to charity?

 

OK, finally some time to write some more answers:

Steering Over Crest Q: Difficult to be certain but it sounds awfully like something gets air in it because the reservoir fluid gets "unweighted" over the crest. Stopping and restarting may cause the system to self-purge? A complete guess but the best I can hazard....

Aerofoil Performance Q: I'm afraid I'm unable to answer this as I lack the specific data that would be needed to answer the question. In general, things need to be fairly well clear of the body (like the WRC rear wing) to generate effective downforce, otherwise they are more like "lift dumpers" that reduce lift but don't actually generate downforce. It's surprising how little force is needed to notice the effects in a back-to-back test; I would suggest you need speeds in excess of about 70 mph for the effects to be noticeable, so *obviously* you can only do this testing on a track and not on the public road...

Relative/Skid Pan Q: I see! I remember taking some of the police people out for a quick razz and showing them how great our car was compared to the Evil Evo. Yes, the police do use our facilities for training.

Book Q: Er, yes I have... the manuscript is due for completion around Easter and there is apublishing contract... thanks for the vote of confidence! I always think the ability to take a complex subject and make it seem simple is a mark of true understanding, so I'm flattered by your comments. I also think the ability to make a simple subject seem complex shows the reverse - I'm sure we've all met people like that...

Spoiler Aerofoil Q: I think Matt's descriptions are probably about right.

Which Impreza Q: Crikey, no idea - I don't keep records. I can remember my first drive in a turbo around roundabouts in Banbury was collosally disappointing because of the power-on understeer like a front-drive car. Most models I've just dabbled in, I've spent a reasonable amount of time in P1s (which I like quite a lot) and a great deal of track time in our ATD Impreza, plus a fair amount of time doing "set piece" demonstrations in the ProdriveLive Imprezas, which are part way between Japan-spec STi's and full-on Group N cars. I spend bits of time in PPP equipped cars under development, as much for interest as for any genuine input I have into their behaviour. I tend not to drive "aftermarket modified" Imprezas but that's mostly because the occasion doesn't arise, I have nothing against them.

Aero Q 3: I think the wings probably generate downforce in themselves but whether or not it's enough to cancel all the lift from the base shape of the car is a question I can't answer. It's reasonably unlikely since the base car plan area is significantly bigger than the "aero devices" plan area and so we would need to run a great deal of pressure change to cancel out the lift forces. "More Pressure Change" implies a form that is more radical than the shape of the car itself - check out the form of an F1 rear wing and you'll see what I mean. More important than the actual lift is the front/rear balance of lift, and splitters and wings can trim that balance to excellent effect with only a small drag penalty.

Ideal Suspension Settings Q: My answers were probably a little abbreviated there, so I'll try and clarify what I was meaning. On the track, Mike (Wood) and I have similar tastes and so I like what he likes. On the road though, one of the things I dislike intensely is a strong yaw reaction to power-off in a turn. The reason I power-off is that usually something isn't going according to plan; I could do with focussing all my energy on whatever is amiss and not wasting some of it collecting the car. Typically settings that give good fun and adjustability on the track become a little wayward on the road, which is a big reason why I'm a fan of adaptive damping technology and such like because you can change settings for road and track - or at least you could if us engineers had the wit to calibrate them thus! The other thing to bear in mind is that my "personal settings" tend to be quite generic whereas the Impreza settings are quite specific - try to think of Mike's settings as absolute numbers and mine as "a direction to go from the base setup" - so I might actually only like "a little less toe-in" (i.e. towards toe-out) than Mike on a specific car for road use. I haven't done any work towards specific numbers for particular cars, mainly because there are so many variations - the exception to that is the P1, but I can't remember the specific numbers that car ended up with. Bear in mind also that we had a lot of freedom with springs, dampers, bump rubbers and anti-roll bars there - my ideal goal would be to make the car with more-or-less no toe settings at all to give maximum scope for individual drivers to tune it either way according to their mood. One of the problems with talking of understeer and oversteer is that although they seem like perfectly clear terms, in fact different people mean different things when they use the terms. A lot of people refer to the rate of change of body slip angle - i.e. if the car increases body slip angle quickly it is described as "oversteer" and if the car refuses to adjust its body slip angle its described as "understeer" - but this is by no means universal; as I mentioned before the mathematical descriptions tend to be a bit more black-and-white but less useful. Sadly I've got no knowledge of the 03 MY except that it's "quite similar" to the 02 MY - Mike Wood is your man on that and I'm pretty certain we already have a suspension package for it.

ATD for P1 Q: We'll sell it to you tomorrow but I have a feeling the costs for a one-off might put you off...

Body-Style vs Handling Q: When the suspension is under development, the differences between body styles can be picked up under some conditions - often its cornering over poor surfaces that reveals the differences. One of the goals of the suspension development though is to make all the body styles feel quite similar, so if the manufacturers have done their job well then by the time they finish I shouldn't be able to tell the difference. That's a slightly glib answer but not a bad approximation. If you're buying a 5 door for practicality, you'll curse a brace every time you put something in the back, whereas you might well be hard pressed to remember the handling benefit on the public road so if it were me I'd leave out the bracing. As I mentioned before it's all about matching body and suspension stiffness, so if you modify the suspension a lot then the brace might become more necessary but if you stay fairly standard I think you're life will be better without it. And yes, it fascinates me endlessly playing with differences in cars, it never ceases to delight me that I can actually notice some difference in well controlled testing.

Snowblindness Q: A good Q and a genuine problem. Firstly, we try and have a "peer review" system that means someone who isn't snowblind takes a look at intervals through the work. Secondly, we always try and keep some kind of unchanging benchmark or baseline - an unmodified car, for example - that we return to regularly, to assess whether or not we are really moving. Finally, we make a lot of use of what I call "A-B-A" testing - we make a change and then undo it to see if we just thought it was better or the difference was noticeable when it was removed. These are all in conjunction with our usual numerical measures of behaviour and performance which by their nature are much less prone to "snowblindness" but are also sometimes less sensitive instruments than Mr Wood's vestibular system. As for releasing something that is suitable for us but not the market, it's an important part of our job not to do that and so we need to stay in touch with our market - one of the reasons why Prodrive support Scoobynet...

ATD Retrofit Kit: We're still going through this to see how the economics stack up for supporting different model types, so I can't answer it. When we have some idea I'll come back and ask "would you be prepared to pay £XXXX for the system?" Is the Motec kit a diff mod or an engine upgrade? Sadly I'm deeply out of touch with all this stuff but feel I can reveal my ignorance since I'm among friends...

Auction of Carl's Ride: Sounds like a great plan. My mum died of cancer last September so I can't help thinking I'd like cancer research to benefit. Any takers?

 

Damian -- probably better to keep the auction stuff off this thread. I'll e-mail Simon and see if he can set something up (for a start we need to nominate a charity and set an end date).

 

Thanks Damian for your answer keep us informed when the "03 kit is available - by the way is a full kit or only springs as "02?
JIM

 

Damian - very interesting, thats pretty much exactly how we avoid snowblindness here.

Carl - I can't believe you are going to auction your place, I wouldn't sell mine for any money, are you sure you can't make it? Failing that I'd also agree with cancer as I lost someone to brain cancer last year.

Damian / Jim - any news on the sti7 prodrive / eibach springs yet date-wise?

 

As an aside, some numbers about lift/downforce taken from the German magazine Sport Auto. They test the cars in a windtunnel at 200 km/h / 125 mph

The top 10 of production cars/street legal cars:

(Car / kg lift at the rear axle, minus means downforce)

Lotus Exige -58 kg
Lotus Esprit Sport 350 -39 kg
Porsche 911 GT3 Cup -19 kg
Mitsubishi Carisma GT Evo VI -14 kg
AC-Schnitzer CLS II -11 kg
TechArt GT street -10 kg
Mitsubishi Carisma GT Evo VII -8 kg
Porsche GT2 (996) -8 kg
Porsche 911 Turbo (996) -6 kg
Lamborghini Murciélago -1 kg
...
MY00 UK Impreza 11 kg
Audi TT 58 kg

Impreza is with the half high spoiler as standard on the MY99/00
So it is fair to assume (I know )that the STi spoiler might bring the car close to 0 kg lift/downforce.

 

Damian,You couldn't give Mike a prod could you and get him to hurry up the release for the MY02 STi suspension package could you? (I don't suppose you could tell us (or get "Woody" () the lift/downforce figures for the MY02 STi Prodrive Style as well? )

Theo, keep your eyes open for figures on the MY02 STi Prodrive Style or MY03 STi....?

Matt

 

Matt, from a thread Simon Lines posted on the I-Club/Nasioc BBS: (hope it is permitted to quote ?)

 

1) If I don't go to work, I don't get paid
2) I'm a **** driver anyway

Make sure you take a digital camera and post up on here. If you're a SIDC member you could submit an article to True Grip

[Edited by carl - 2/27/2003 9:28:06 AM]