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944 Turbo S suspension
10-25-2010, 11:20 AM
Post: #1
 
So I have a 88 944 Turbo S that I have now taken to two DE events. First was at Watkins Glen, long fast sweeper turns, car felt nice and planted. This past weekend was at Thunderbolt at NJMP. Some much tighter turns really showed how soft even the Turbo S's suspension is. Through the tight stuff the rear end felt really loose, lots of body roll, and the rear tires just felt greasy. As I progressed a bit through the weekend, I used this to throttle steer around the tighter stuff, but coming out of the turn the car would be prone to wobble a bit back and forth.

The car only has 45k miles on it. Front suspension is stock, when I got the car some OEM black shocks were on the rear and the yellow Koni's were gone for some reason. Replaced them with some new yellow Koni adjustable shocks, left the adjustment as is out of the box, which from what I read should be set to the middle. Plan is to tighten these all the way up to see if it helps control the "wobble" and rear end looseness feeling.  Tires, are Toyo T1R's. Not R-compounds, but pretty sticky summer tires.  Tires were not even singing that much when the rear end was feeling loose. Tire pressures were set to 34 psi all around cold, and got up to about 41 when hot.
Looking to make it corner a bit flatter and get rid of that unnerving wobble when exiting a turn.  Instructor was suprised at how much body roll and how loose the rear felt even from the passenger seat, but the car still had grip.

I think that's enough information to get the ball rolling.......Suggestions?

Adam
______________________________________
1984 911
1988 944 Turbo S -Sold
1999 996 Cab - Father's ride
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10-26-2010, 08:05 AM
Post: #2
 
Sounds like you have a good platform to start with. I think your best bet is to just register for events, learn to drive your car for a couple of seasons, then start modifying your car slowly one thing at a time so you fully understand what each thing does and how it affects the dynamics of your car. Sorry if that's not what you were hoping to hear. I've been told that many times and I can't tell you how much it has paid off.

Best of luck to you!!

 

mike

89 Carrera

#402
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10-26-2010, 08:19 AM
Post: #3
 
I will agree with Mike Lang.  For my 968, which is essentially the same car underneath as a 944, I modified the suspension over three seasons.  Pete Fitzpatrick, RSBarn, specializes in these cars.  He laid out the multi year plan that built the car up as my skills increased, and my budget permitted. 

Now that it is complete, every instructor has been very complentary about the car's abilities.  Pete does offer parts without installation, don't know if you are a DIY or not.  I am a WTC, (Write The Check).  RS Barn, 215-968-2599.

 

Mike

 

Mike Kling
PCA National Instructor #201305138
2012 High Speed Driver Award
2008 Broken Crankshaft Award
1995 968
1988 944
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10-26-2010, 08:34 AM (This post was last modified: 10-26-2010 08:36 AM by DJbrand1.)
Post: #4
 
I agree that is a very capable platform already. Not looking for drastic changes, really just want to get the unnerving wobble.  I doubt I am over driving the current suspension, but the feeling in the rear is something I'd like to figure out.

First step I think is to tighten up the new Koni's I put in the rear and go from there.

I have been taking the car to the RS Barn. Pete went over the entire car when I first got it as well as doing the tech inspections for me. They did an alignment on the car when I got it, slightly more aggressive then factory specs I was told. 

Another thing that I'd like to talk to him about is the brake bias valve they put in. It put a bit more pressure to the rear. Didn't notice any ill effects up at the Glen because I was using some cheap brake pads that really were no good. For Thunderbolt I put some Pagid Black's on the car and really getting on the brakes at the end of the front straight started to give the car a slight hydroplaning feeling like the rear end was floating. I did not feel any ABS intervention though.

Adam
______________________________________
1984 911
1988 944 Turbo S -Sold
1999 996 Cab - Father's ride
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10-28-2010, 02:31 PM
Post: #5
 
Pete tells me this seems to be a characteristic of our cars.  The rear end gets nervous under hard straight braking.  I just tighten my grip on the steering wheel and say two Hail Marys.  Seems to take the wobble out pretty good.

Mike Kling
PCA National Instructor #201305138
2012 High Speed Driver Award
2008 Broken Crankshaft Award
1995 968
1988 944
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10-28-2010, 03:36 PM
Post: #6
 
Plus the t1r tires don't have that much grip.
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10-30-2010, 03:07 PM
Post: #7
 
Two things:
1. Many think that braking hard, as late as possible is faster than braking less a little sooner. Just think about it.......... when you brake hard, you shift the weight of the car forward, thus making the rear light (whoboly and loose). Try to brake a little bit less (pressure) and earlier into the turn. You will achieve 2 things, a little higher corner entry speed and probably NO looseness in the rear.
2. I believe that 41 lbs. in the rear is too high. For street tires, I recommend 2 lbs. less at the rear than the front where the engine is. If you really want to maximize the alignment and tire pressures, keep accurate records at every event using a tire pyrometer. If you learn to interpret the results of this tool, you will maximize the grip any tire you use.
Obviously, Porsche made these car quite well and adjusted the design of their suspension based on their factory test drivers, so maybe your driving style should be modified somewhat as I said in part 1.Smile

JUST CALL NICK
__________________
The deer in the headlite
PCA DE instructor #200904037
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10-31-2010, 05:55 AM
Post: #8
 
Nick has made  similar recommendation to me with my braking and it transformed my car. Was going into braking zones and trying to brake at the last moment. Car would lock rear brake and feel horrible. Now braking sooner the problem was not the car but me.
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10-31-2010, 07:21 AM
Post: #9
 
In which part of the turn does the car feel "loose"? 

I agree with Nick about not trying to do ultimate hero last millisecond braking.  I see a lot of people making that mistake and then they try to ask the car to turn when the weight is shifted forward and the front tires are on fire.

Is it possible that some of the looseness is throttle induced oversteer?  That car has an LSD diff right?
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11-01-2010, 06:32 AM
Post: #10
 
Now were talking about two different scenarios. Hard and late on the brakes will make the rear end float.  RS Barn put a different brake bias valve in with more rear brake bias than stock. Never drove the car at a track with race pads in until Thunderbolt and experienced this feeling.

The original scenario is through the turns, rear end just feels like it is very loosely sprung and damped. Coming out of a turn and through quick transitions like the last couple of turns coming onto the the front straight at Thunderbolt, the rear just seemed like it was way behind the front to get settled. Which is the wobbly feeling I was trying to describe.

The car does have a factory LSD.

Adam
______________________________________
1984 911
1988 944 Turbo S -Sold
1999 996 Cab - Father's ride
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