David_Wallis

Its not quite 200mph.. Just would like to do the top speed run and not have to take off.. (190mph ish)

David

Phil Harrison

Damian....Thanks for a really informative answer re the suspension rattle: tends to confirm what I'd deduced by applying "Scientific Method" to the series of events. Motor Engineer I'm not - Just a Chemist!!

Interestingly, and per contra your last sentence, I know of at least a dozen rattling STi7s every single one of which is NSR-only, and I do not know of a single OSR problem!!! In my case I have to transit a potholed single-track drive which means that my suspension gets equally worked NS & OS, and my OSR is silent at ALL times! And no, not only have I not ever abused the car along said track (I haven't paid £29K for the car I've always wanted just to abuse it!!!), but also the problem was evident within the first 45 miles of ownership. This 'sidedness' led me to the conclusion that there's a problem with a "handed" component, or in the suspension/bodyshell interaction or subsystem, whether as a result of manufacturing tolerance or design weakness.

Thanks again,

Phil

911

Wow! just read all 8 pages this morning....What a fantastic thread and working wonders in my mind for my hill climb STi V3.
Fully agree that this 'favorite' thread should be fixed at the start, and he must write a book. Tuning 4x4 chassis is a subject beyond most books, fantastic stuff!

Best thing I've read on the Scoobynet forever I think. Congrats to all the superb questions from you all too.

Graham.

nigel rsx

I've just spent my entire morning reading this fascinating thread when I should have been working!

Damian, thanks for your obvious enthusiasm and eloquent answers.

I have two questions which I hope you are still available to answer:

1. Could you explain how tyre pressures affect the grip/handling combination? I sometimes read that you get less grip but sharper handling with increased psi, but I have also read that psi has no effect on grip. Are manufacturer recommended settings designed to give the safest handling ie understeer?

2. Why do you think the Evo is evil? Is it the AYC that you hate? I have an EVO VI RSX which doesn't have AYC and it feels better to drive than my previous car which was a MY98 Impreza (standard UK). In fact the only car I've owned that made me feel more "connected" to the road was my Integrale. The Evo does understeer a bit on slow roundabouts, so maybe it needs a version of your ATD system!

Cheers

Nigel

carmad

Are there any further developments or prices on the ATD system as a retro fit kit???

Damian Harty

Aftermarket ATD is still in the pipeline, we have a "product matrix" for all the different Subaru models and are in the process of deciding whether to use an existing ECU or design a new one. Keep watching this space....

Fat Boy

Still watching

Jza

Now that would be one Prodrive Package i would not say no to

Jza

Claudius

Thanks for that

The suspension shop I use now did the following:
- slightly lower the gas pressure (by 1 or 2 bars from 13 bars)
- use lower viscosity oil in the dampers

The car is less jumpy from the rear now when going straight.

However, it isnt perfect yet. They offered to make some rigid top mounts from metal, which seems to be along the same lines as what you said about moulding prototypes. Is there a specific material they should use for that? Are the materials they could use (ie. materials which supension shops usually have handy) that would not be right? What do I need to pay attention to?

Damian Harty

Lowering the pressure will definitely have helped because the seal friction (a significant part of the overall friction) is greatly influenced by the pressure in the dampers. The fact that lowering the pressure has made a noticeable difference means that the strut friction definitely is the thing you are feeling, which is helpful in terms of sorting out the problem.

Going to a metal top mount will be a helpful diagnostic step, if a little extreme. You could think about using the hard nylon or urethane (or whatever it is) that people use for suspension bushes instead of the metal since it will undoubtedly increase the "road roar" noise as you go away from the standard mounts. The difference in behaviour between urethane and any type of metal won't be very much compared to the difference between rubber and something "rigid", whatever it is. In terms of recommending a metal, more or less any metal will be plenty stiff enough so the choice comes down to cost and ease of machining. There are some easily machined aluminium alloys around that will be fine, with the added bonus they are quite easy to anodise into a sexy colour if you like the performance and decide to keep them.

As a bonus, you should notice that the stiff top mounts improve precision at turn-in and mid-corner disturbance rejection by improving the location of the damper top, which controls camber on the wheel.

Make sure the people making the metal mounts understand the the strut needs to change its inclination as the suspension moves, so that they aren't just planning to bolt the strut rigidly to the inner wing via an adaptor plate; if they do that the suspension will just be locked out - I'm probably teaching them to suck eggs of course, but it's always nice just to check; I'd rather look like someone who worries too much than pillock who didn't notice something fundamental!

If you find the stiff mounts sort the "jiggle" problem but find the noise too much then there is some interesting tomfoolery possible with the OE mounts once you know a direction. Presuming the test with the solid ones confirms the direction from standard (i.e. stiffer is better) then you can drill the rubber and push in aluminium or steel rod to the holes to progressively stiffen the top mount. Leaving the holes unfilled makes them softer, but they tend not to last too long if you leave the holes open. With a bit of planning of the pattern of holes you would make, you can start with a single hole and rod and then keep going until it gets just stiff enough to do what you want - which hopefully will be an improvement in noise compared to the "full solid" top mounts. It all depends how much fiddling you want to do...

Edcase

Damian,

lost the bit of paper with your email address on. Some interesting developments with the game stuff we talked about at the ATD day. Drop me a mail offline. If you lost my card too, use ejbartlett@lineone.net

cheers

Ed

Fat Boy

Hi Damian,

any chance of an update on where ATD is in the process?

Cheers

John

Phil

Probably on this P*SS in Wales

I'm sure he played a small part in todays victory

[Edited by phil_stephens - 11/9/2003 4:15:08 PM]

JIM THEO

I bring back this old thread as it's very interesting and I want to ask something to Damian (I know he is busy and may be couldn't find the time to answer but I give it a try).
Are the 8” the right width for an 18” wheel with 225/40/18 tire on WRX?
I know that Prodrive’s wheels are all 18x7,5 inches (except Speedline PFF7 in 18x8") but OZ as many other manufacturers produces all their Subaru dedicated wheels in 18x8” and local OZ dealer claims that it’s better to stay with 18x7” wheel rather go for an 18x8” due to better behavior of the tire with the narrower wheel!
I am thinking of a wider from the factory wheel to full the arches of my WRX (18x8 with say 51 offset means 1,45cm wider outside wheel compared with the factory one) but don’t want to spoil the comfort and performance of my car cause of the same phenomenon.
Also wheel weight is critical in this case as the Impreza 17x7” weights only 17+lb and only SuperL” is about the same weight (18lb) and if you add tire and that wider wheel with less offset (from 53 > 51) means more "external" loaded weight I wonder how this affects steering, suspension and whole cars behavior!
May be I am a little exceeding but such a small things play a huge rule on how our cars drive and Damian mentioned it in a previous post!
JIM

MikeWood

Jim

Easy answer, if it wasn't right, we wouldn't sell that spec! The only time an 8x18 won't work is if you have either an early car (Classic shape) or a 5dr where you may get the tyres catching on the rear arch in extreme conditions

Suggest that the OZ dealer is just trying to sell you what he's got in stock..........

Mike

STi Paul

Hi,
I am having problems on the track.
I have an STi8, which I have run with Pirelli RS5 (rally tarmac tyre). What seems to happening is that the car is rolling too much, causing the tyre to overheat, and the tread is rolling over on itself, if this makes any sense. I am having the spring kit fitted soon, hopfully to reduce COG, therefore roll??
Will this work, or do I need to do other things??, or are the tyres totally wrong for the application??
I am enjoying the car on the road, but also like to track it occasionally, but at the cost of a set of tyres per trackday, (approx 100 miles) does seem excessive.
I am sure a uprated ARB be benificial on the track, but how would it perform on the road. If it affects the car in a bad way, what would be the effects.

Any help would be very much appreciated.

Paul

Phil Harrison

While you're there, Mike.....

Was a version of the new system fitted to Sollberg's car for Italy?

What, if anything, can you tell us if so??

Phil Harrison

MikeWood

Paul

Not that you should be using your car on a Race Track, you are probably finding the limit of the tyres. As they are rally tyres you will find that they are a little soft for track use, bearing in mind that your car is heavier than a WRC car and it's much easier to lean on the tyres too hard on a track.

The new roll control system we used in Sanremo helps keep the car level during cornering which stops bodyroll reducing wheel camber in roll. What you are experiencing is the car rolling so much that the tyre sees too little camber on the road surface which then overheats the outside edge of the tyre. More camber would help, as would suspension that is stiff enough to keep the tyre at the right angle to the road surface. The only problem is that when it's that stiff, it ceases to be practical for the road. Adding camber is a much better solution as would be increasing tyre pressures to reduce temperature build up.

Our spring kit will help slightly but does not provide the ultimate track performance, it's been developed primarily for road use.

Mike

STi Paul

Cheers Mike.
Thanks for the quick reply.
I will try finding a different tyre type, and keep an eye on the pressures.

Thanks again,
Paul

Edcase

Quote: "Paul

Not that you should be using your car on a Race Track"

Ummm, not being funny Mike, but WTF????

JIM THEO

Thanks Mike.

MikeWood

Edcase

As in 'you shouldn't be using your car on a Race Circuit and expecting Subaru UK to be picking up the bill when bits break, wear out or fall off' not that this applies in this case.

Mike

dowser

LOL

I run -4.5 degrees front and -3.5 rear camber - reduces tyre wear on track....increases it on road. It also affects straight line braking stability.

As mentioned above, I could probably get away with less if I fitted harder suspension, but I still need to drive to and from events, and road tyres are cheaper than track tyres

As a side note - uprated rear ARB was a great mod for road use, but led to front tyres overheating on track. I ended up fitting an uprated front and strengthening the rear to balance it out a bit. Everything is a compromise - we should all buy formula fords for weekend work.

Richard

Edcase

Mike - I know exactly what you meant! I was just surprised to hear you saying it.

This topic has been discussed at great length both on this and other forms and in performance driving magazines such as Evo.

The reason for the discussion, as I am sure you are aware, is the confusion caused by manufacturers such as BMW and indeed Subaru, selling performance models on the back of racing heritage, many of whom use trackdays as a marketing tool.

You can no longer use the true performance of your car on the roads, so the track is the only option. But then they say you cannot use your car on the track either!!! There was a massive outcry about this in Evo magazine recently, and all 'performance' manufacturers, including Subaru, backed down and gave a nebulous 'track use is OK as long as it is properly moderated' answer, whatever that means.

Given the proper key components (few trackday regulars take standard cars on track), lubricants, warming up and cooling down procedures, you can keep your car incredibly reliable on track. I would warrant my cars componentry gets a much harder time on our regular b-road jaunts (complete with 3-figure bumps and jumps).

Also you can never regulate exactly how the car is used on track. I know many people (SIDC events such as Japfest and Trax are a good example) for whom this is just a great opportunity to use their car without speed limits, so the car only really sees 6/10ths anyway. Whereas others who do regular arranged track days, like to push to 10/10ths (and beyond.)

The ones who are using 6/10ths are not causing any greater wear or tear, and 99.9% of the ones who are pushing 10/10ths, will have 330mm brakes, coilovers etc etc. which wouldn't be replaced by Subaru anyway!!!

Okay you might see wheel bearings needing replacing slightly earlier, but then think of the countless peer-to-peer marketing that has been done by the owner of the car, when other track day uses driving other marques have seen so many Subarus at track days performing well.


[Edited by Edcase - 10/10/2003 6:43:31 PM]

DrEvil

Edcase - calm down mate.

Edcase

Alex - I thought that was a perfectly calm and fair post/point?

There was certainly no intonation or aggression, you should know me better...

DrEvil

Edcase - OK matey, I may have read to much in - apologises.

Hope things went OK today BTW.

Edcase

NP mate, are you at the festivities tomorrow???

Phil Harrison

FWIW, Edcase, I took the same view as Dr Evil on first reading your post. I've looked to see why it comes across stronger than intended.

IMHO, you write with great eloquence and obvious feeling on the topic of Manufacturer views of Trackdays. So, having taken your reader to a justifable level of indignation there follows...
and this, with its very direct "Mike" comes across as a finger-wag in the context of what went before. And Mike (W) did put in the appropriate smiley!!

The spirit of the above is intended as neutral analysis, and I hope will be taken that way. I hope it might encourage Mike to say something about Sollberg's car in return..........

Cheers, all

Phil

Edcase

Phil, fair point, well made. I have talked about this with Mike offline today, and whilst he didn't seem to see it as a personal attack (at least he didn't say he did ) either I appreciate that email and text can be easily misinterpreted. If two people I consider (fairly ) intelligent have misconstrued me then I'm sure others will, so I will remove the comment.

The whole area is extremely complex and will never be made satisfactory for each and every case or person. I just hope these manufacturers realise that, when the roads finally grind to a halt through traffic and speed cameras, and owners are unable to drive on racetracks, there will no longer be a market for their performance cars.