Dispelling myths of the P1

[johnfelstead]

it's not parallel with the ground that counts, its keeping the steering arms following the same arc as the suspension under bump rebound.

Some designs need the rack moving up/down to achieve this, others need the rack going forward/back.

I am pretty sure the impreza needs the rack lowering. Like i say though, this needs a dedicated test and adjust session.

[This message has been edited by johnfelstead (edited September 28, 2000).]

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It is PART of a ensemble of tweaks.I've read on the Sidc or the Scoob board about the settings. It was written that it wasn't as harsh as autocross settings and worked WITH the bumpsteer adjustment.... and consequently did not eat tires fast like the autocross settings.I think I could be happy with the bumpsteer shim and some matching camber caster settings.Along with good tires which is more important anyway.
This has been a very entertaining thread.

[wrxwannabe]

John,
Thanks for the info. Bummer Powerstations is so tight lipped, its just a little difficult for someone in the states to bring them our cars...

Now all I have to do if find a confident race shop that understands how to do this. I feel like I'm sitting in a field with 20 haystacks and the damn needle is in one of them and I gotta check all 20...

Oh well.

Thanks again
Eric.

[johnfelstead]

please read http://www.i-club.com/ubb-files/Foru...ML/004885.html

[adam99rs]

Everyone has raved about this mod, so I am eager to try it. Even with the Prodrive suspension, 20mm bar, antilift, Gr. N bushings throughout...yada yada yada, it still understeers. That being said, my car will be at Rallispec as of this week having a wee it of work done (they are doing the engine swap for me, since I had no esire to tackle the wiring). If it can be done, I will do it, and hopefully, it will be something they can offer to the public. Promise to keep you posted.

[Simon Lines]

Chaps!

Please remember that the P1 has significantly more power and torque than even an RS and it is very easy to get power understeer if you are too eager with the gas. Do this a few times and the edges are gone on the front tyres. Hello understeer!!

I run a 2.0 Sport with std suspension and P1 tyres. It has no understeer as it hasn't got the power to destroy the tyres.

The P1 suspension has unique springs designed specifically for this car, the idea being to tune the suspension for the Uk and retain good road manners and ride comfort with 17" wheels and tyres. Engineering understeer into the chassis was not an objective and we did not achieve it either.

The best handling Subaru I have ever driven was a Legacy 2.0 fitted with our springs and P1 size wheels and tyres for exactly the same reasons. We used this car for a Drive day in Greece and all the drivers, including Simon Jean-Joseph our latest WRC driver, preferred it to either an Impreza WR or P1 as it was more fun. Simon was actually approaching the corners backwards in complete control! (some of the time)

I hope this helps!!!!

Mike Wood

[skidplatez]

WOW I am so flattered one of my posts has attracted the attention of Prodrive! Cool! Anyway I still standby what I said about the P1. If I was wrong why did they just introduce the P1 WR? And by the way why in the face of overwhelming evidence do people insist that the P1 comes with Bilsteins?

[Jaxx]

bummer he didn't comment on the part numbers that we are tring to verify

P1 Front spring 20330FA160
P1 Rear spring 20380FA450

[Simon Lines]

The P1WR uses a 225/35x 18 PZero without changing any other suspension components. As the tyre is larger and therefore less likely to have the edges destroyed it gives less understeer.

Virtually all magazines take pictures of the cars first when they do a test. This normally involves attempting to get spectacular cornering shots which as previously explained will scrub off the edges of the front tyres. This can be so bad that all the letters are scrubbed of the sidewall!!! Then they do a driving assessment and hey, the front tyres have less grip than the rears!

Anyone who has driven either the P1 or one with the 18" wheels (or any other Impreza) will realise that the car does have a slight amount of understeer like all four wheel drive cars, but when encountered a slight lift on the gas will remove it. A big lift will result in oversteer that can then be controlled on the throttle.

Jaxx

Not sure what the spring part numbers relate to but they are definately NOT P1 springs. These will probably be STi5/6 and are black?
The P1 springs are different in both rate and ride height to any STi spring, thats why we specified them as STi did not have anything suitable

Mike Wood

[Jaxx]

YAY!
finnaly a definate anwser
thank you VERY much for posting Mike.

[Scottie]

Mike,
It's great to see you and Simon posting here.

Since we're on the subject of the P1, I have a couple questions.

In the past, some have said that the P1 was designed to be used with 17" wheels. (I see from your post that you also mate the P1 with 18" wheels. I'm more or less referring to 17" vs 16") Is there any truth to that, and if so, why?

Also, could you quickly comment on how the P1 compares to the other Prodrive options available to us yanks. The Prodrive GT and the WR Sport.

[johnfelstead]

Hi Mike, good to see you posting on this side of the world as well as scoobynet.

I am a fellow Impreza Sport driver and run my car on standard suspension, 16" turbo alloys and SO2 PP 205/50/16 tyres(tires )

The sport has enormous grip in the wet in particular with its soft suspension and no anti-roll bars giving great mechanical grip.

I do find the car beautifully balanced.

I also have the pleasure of driving a 22B both on track and road and found at the limit the 22B did suffer from understear, very safe but frustrating, especially considering i drive a very powerfull RWD car in the main on track and enjoy overstear handling.

The 22B was modified at powerstation to eliminate the bump steer and i have to say this transformed the car at the limit, making it perfectly balanced and eliminating the understeer.

I am a little intrigued by your statement about the P1 handling.

Engineering understeer into the chassis was not an objective and we did not achieve it either.

This does tend to contradict what has been posted on scoobynet by simon in reply to a question posed by a P1 driver, Aaron Bird (who is a ex BTRDA Gold Star Rally Champion)

Mike thanks for your reply.
I am not too bothered about power figures I was at Powerstation getting the car to handle the way I think it should and I decided to put it on the rollers out of interest really.
I`m not to sure about the figures, something doesn`nt ring true.
I can honestly say that I love the car now but why did`nt the car get a quicker steering rack?
Also why did I have to pay another £100 to get it to handle?
Did you launch the car so that anybody could drive it?
Was sfety a concern because I think that its safer now than it was before.
The car still lacks outright grip because of the thickness of the tyres but I begrudge spending more money on it.
To me it should have come with all the trimmings for the £34k price that I paid.
Interestingly I also think that the car you so kindly let me test somehow felt a little different to the car I had deliverd.
Felt more like the car I have now.

simons reply was

Mike is away for a few days so I’ll add my two-penneth today.
As most of you probably know I look after export sales and so do not sell P1’s, however I have a fair amount of “time” on several different vehicles.
The “P1” that is delivered to dealers HAS to be safe for ALL to drive, it is set-up with the lowest common denominator in mind. This has nothing to do with economising or defrauding the buyers. This is true of ALL production vehicles (to a greater or lesser extent)
You did not pay £100 to “get your car to handle” you paid it to change the handling of you vehicle to match your driving style, surly it would be unreasonable to expect all 1000 vehicles to be set-up to match your driving style?
Having said that, I am sure that in reality most of the P1 owners would prefer it like this – BUT, as I said, it has to be set to be “safe” for the least capable driver, you may feel it’s safer now but a poor driver may not.
The rack question has been approached before, to reiterate, it was originally envisaged that the car would come with a quicker rack than is normally fitted to the STi cars. Extensive testing has shown that steering feel, turn in performance and NVH was significantly better with the “normal” WRX STi rack. The decision had NOTHING to do with money or marketing or availability or anything else.
At the end of the day you have bought a production car, it may be low volume but it is still a production car with production car compromises. Those compromises may be more shaded or hidden on a P1 but they still exist, it is a very good car but it is not possible for it to be perfect for all of the people all of the time…

The way i read that reply it states that the P1 does have some understeer engineered into the chassis as it is delivered to the dealers. This does tie in with my own and Aaron's experiences of Impreza's when driven enthusiastically.

It does seem to be a major bugbear of Impreza drivers accross the world that the car understeers, to date the best solution to this i have found has been to remove the inherant bump steer, that admitedly is there to protect us from ourselves.

Do you agree that this modification reduces the understeer inherant in the Impreza or am i making a bad judgement on what i am feeling when driving the cars in there diferent specs.

best regards
john

[Mike Wood]

John

Perhaps I should have added the word 'more'!

As you say, all Imprezas understeer. What we achieved with the P1 was a safe handling car with minimal understeer and neutral characteristics in most circumstances, particularly emergency situations like braking on corners.

You know yourself that ALL Imprezas with a viscous centre diff and as much power as the P1 generally suffer from power understeer and it's quite easy to wreck the front tyres by trying too hard which then leads to understeer.

This is improved with the wider 18" tyres, that's why the reports have been more favourable.

I have never driven a car that has 'had the bumpsteer removed' so I can't comment on it's effectiveness. All I can say is that all cars are built to a tolerance so very few will be absolutely perfect but should all be within tolerance.

To answer some of the previous questions, the P1 suspension was designed to suit both 17 & 18" PZeros but that does not mean that the suspension would not suit 16" wheels.

The P1 was developed as a discrete model wheras the WR Sport parts are upgrades for the standard Turbo models available in the UK. Most of these parts are also suitable for the normally aspiratred cars and we now have a rear silencer available specifically for the non-turbo models.

Mike

[johnfelstead]

Thanks for the clarification Mike, much appreciated.

Please don’t take this the wrong way as I respect what Prodrive does enormously.

Can I make a suggestion to you, get yourself down to PowerStation and have the bump steer modification carried out on some of your test cars.

You never know, you may think it is so good you decide to market a Prodrive kit of parts to give what most enthusiastic Impreza drivers want. Less understeer.

PS. I want 10% royalties

[rsquire]

hey, John

You could always pop down to Banbury and take Mike for a ride in mine

Richard

[johnfelstead]

thats a good idea richard!!

Mike, you fancy a spin in a modded 22B??

Not literally i hope

[Mike Wood]

John

If you're passing sometime, then why not!
You could have a shot in our P1 with the 18" wheels etc

Mike

[iwatkins]

Mike, John and All,

John, I think you should do this. Take Richard's car down (with his kind permission) and have Mike drive it. If he doesn't love it, then you will have to shoot him

Seriously Mike, I'm good mates with the guys at Powerstation who spent the time to work out what needed doing to sort this bump steer out.

I have yet to hear a negative response to this modification, in fact most seem overly postive

But Mike also has a point, I bet if say the P1 was released with this modification, then quite a few of them would have been off into the weeds by now.

Maybe if Mike likes it, it could be added to the modification list for the P1 or P1 WR.

Of course, I also would want 10% royalties

And to fight the Powerstation corner, it would only be fair to discuss this modification with Powerstation and maybe some kind of back-scratch could happen as they spent a lot of time (hence money) working on this mod.

Cheers

Ian

[rsquire]

John, Mike..

Go for it mate..

I'd be very interested to find out Mike's reaction to the setup on the car..

Richard

[johnfelstead]

OK Mike, i will get in touch soon. Been away since thurs night testing and on a rally.

Working away monday so probably contact you on tuesday.

Regards
john

[Scottie]

Mike Wood,

I guess I need to rephrase my question about the P1 and wheel/tire sizes.

First let me quote the October 2000 issue of CAR. In an article on the P1 WR on page 44,it read "The OZ Racing rims are the same as those of the standard P1, but an inch larger in diameter at 18 inches, and they're fitted with 225/35ZR18 Pirelli P Zero tyres. Not only do these changes sharpen up the steering's responses but they also make the helm feel calmer and less prone to tramlining."

Now I think they misspelled that last word. I think they meant "trampolining", but I could be wrong. If it was trampolining and going to 18 inch wheels reduces the tendency of this happening vs 17 inch wheels, then I would think 16 inch wheels with 205/50ZR16 P zeros would be more prone to trampolining. To me trampolining basically means you're getting some bounce from the tires, which would get annoying on long trips. It is also the basis for my original question about the P1 being design around 17" wheels instead of 16".

Now an additional question. You have clearly stated that the part numbers 20330FA160 and 20380FA450 are not P1 springs. What about the strut part numbers? People who have supposedly gotten P1 kits in the US have listed the strut part numbers as 20311FA960 left front, 20311FA950 right front, 20360FA960 left rear, and 20360FA950 right rear. Are these correct?

[8Complex]

Scottie - I think tramlining means following the cracks and such in the road... I think the wider tires would help with that so they probably got it right.

[rsquire]

8

Spot on Dude

I hate to see my Scoobie trampolining

Richard

[Scottie]

Richard & 8,

I guess I thought CAR meant "trampolining" versus "tramlining", because either "Road & Track" or "Car & Driver" used the word "trampolining" in a short review of the 22B versus M3 a year or so ago. I'll have to dig that article up.

[This message has been edited by Scottie (edited October 09, 2000).]

[rsquire]

Scottie,

Don't worry about it.. It was probably just a misprint in the magazine

Mind the thought of Scoobie doing layouts, and front somersaults, just doesn't bear thinking about..

Richard