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undrprzur · Joined: 27 Apr 2003 Posts: 18 Location: Eastern Washington

I'm trying to improve the handling of my car. I have been autocrossing the car for the last year and won the E stock class for the 2002 season. This season my 81 turbo has been lowered in the rear , with kumo Victoracers on the rims and a 1 bar spring in the wastegate. So far it has been competitive and has won its class every event this year. Because of the mods to the wastegate the car has been moved to A Street Prepared class, as per SCCA rules. In this class I have to race against New Cobra SVTs, Any improved 911s and Corvettets. The times have been very close and I have been lucky, I need to increase my margins on these cars.

I posted the same on the "parts wanted" section.

Any other help would be appreciated.
Thanks
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81 931 Always on Boost.

Lizard · Posted: Mon Jul 21, 2003 3:22 am Post subject:

as I stated there as well thought about an IC, also the other thing you can think about doing is upgrading the torsion bars in the trailing arm w/ ones out of a 944 as they are a larger diameter, and they should be very easy to find and fairly cheap at a wrecking yard, and highly unlikely that they were damaged in the accident
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3 928s,

undrprzur · Joined: 27 Apr 2003 Posts: 18 Location: Eastern Washington

I thought about an IC but really it has more than enough power unless there is a quick bolt on out there other than the 937 type which is very rare and expensive. I posted in the "part wanted" hoping to get bigger sway bars, my car has 23mm in the front and 14mm in the rear. I feel I have to much lean on hard corners.
thanks for the reply.
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81 931 Always on Boost.

Lizard · Posted: Mon Jul 21, 2003 4:01 am Post subject:

the other thing you should consider if you dont already havethem is #250 autocross springs performance products carry them, the 1980 931 that I am selling to munkpuppy I am positive has them and the car rides like it is on rails it is really nice
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3 928s,

924RACR · Posted: Mon Jul 21, 2003 10:06 pm Post subject:

Consider the rear Cup Car bar as sold by Paragon or 944Racing.com:
http://www.944racing.com/Search/ViewDetails.asp?hidSearchType=Acc&PartNumber=944.333.701.01

Bolt-on 19mm new factory bar, and is adjustable to boot.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

undrprzur · Joined: 27 Apr 2003 Posts: 18 Location: Eastern Washington

Thanks for the link. Anybody out there try these bars on a 931? What do the guys on the road course use?
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81 931 Always on Boost.

924RACR · Posted: Tue Jul 22, 2003 1:31 am Post subject:

That's what I use with my stock 23mm front bar, on the racecar (same chassis).
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

undrprzur · Joined: 27 Apr 2003 Posts: 18 Location: Eastern Washington

do you find more oversteer or more nutral steering? I have 23's in front and 14's in the rear, with the Victoracers 225/50/15 set at 38psi front and 30 in the rear, my car seems to have understeer going in to a hard turn. To get it to oversteer or drift I have to keep the gas on and use the brakes at the same time. I'm hoping with bigger bars to get more nuetral or a bit of oversteer with out much effort. That way I can stay on the power curve( boost) thru the corners.

I have tried harder springs but were only really good on smooth surfaces. Most of the autocross surfaces around here are bumpy and need softer springs, so I went back to the stock ones. check the picture under my name, that was a hard left then right turn, notice the cars attitude. Lots of lean into the corners.

Thanks very much for the replies.
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81 931 Always on Boost.

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

I can't contribute to technical aspect of this discussion, but in your avatar it looks as if there is a person in the right hand seat. Are you running races here in the USA with a RHD car? Not being a racer, I have no earthy idea, but I wouldn't have thought that sanctioning bodies would allow a mix of LHD & RHD cars on the track at the same time.
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'79 Eurospec 931

Lizard · Posted: Tue Jul 22, 2003 7:13 am Post subject:

try raising the rear tire pressure to create less traction in the rear as to make it aesier to break loose, or lower the front to give it more grip.
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3 928s,

924RACR · Posted: Tue Jul 22, 2003 8:35 am Post subject:

That would likely be because he has a passenger.

Yes, raising the rear would loosen up the car. However the goal here is not to make the car more neutral - it's to make it FASTER!!! If you loosen up the rear, you reduce traction in the rear to match the minimal traction in the front. You need more traction in the front. The 19mm rear bar might make you slower.

You ned to pull out the old Shelby book, Engineer in your Pocket, or the like.

You need to increase front grip. Softer front spring or bar. For a cheap dramatic change - disconnect the front bar! That'll wake it up!

Seriously, a smaller front bar might be all you need.

However, why are you running your tire pressures so far off? I run mine as close to even as I can get. That will give you massive understeer. Try dropping the fronts down to 30 also. That may be a little too low, but try and compare, then go from there.

Also, what alignment settings are you using? Do you have stock rubber bushings or not? What are you running for toe?

Have you cornerweighted/balanced the car? You do mention you lowered it. Front as well as rear? What are you running for shocks? The shocks could impair your ability to handle rough pavement.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

undrprzur · Joined: 27 Apr 2003 Posts: 18 Location: Eastern Washington

Yes that is a passenger, we have fun runs aftr each event. It brings more people out to the autocross and we charge $1 for each run.

Back to the handling, the tire pressures were recomended to me. After looking at the scrub marks on the sidewall thefronts are at it's limit, any lower pressure rolls the side over. as for the rear well, I was just trying to get the tailend to come out for a "off throttle oversteer". I have no idea if the dynamics of roadracing and the slower speed and more severe corners in autocross are the same.

I had the rear of the car lowered to the max adjustments. Front of the car is back to stock after trying out autocross 250 springs. Shocks are Koni yellows. Rebuilt the complete supension using factory bushings, reason for this is that I like driving this car on long cruises and fun rallies. My experience with poly bushings were on a 912 I had, it made it uncomfortable and jarring for me on the road.

Just had the alignment done:
FRONT LEFT RIGHT
camber -0.3 -0.3 deg.
caster 2.0 2.1 deg.
toe 0.11 0.11 deg.
total toe 0.23 deg.
set back 0.23 deg.

REAR LEFT RIGHT
camber -1.0 -1.0 deg.
toe -0.1 0.03 deg.
total toe 0.01 deg.
thrust angle -0.02 deg.

it sure is nice to be able to discuss the car with other owners, I have owned this car for most of it's life and where i live most guys are either into monster 4X4's or rice cookers with soupcan mufflers. All they really know is how to buy from a catalog and have some theory that thier cars are better because it looks cool.
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81 931 Always on Boost.

924RACR · Posted: Wed Jul 23, 2003 2:40 am Post subject:

Yes, without question the dynamics are comparable and similar, though your design considerations (in picking your setup) will be different.

However the answers to your questions are in your setup, very clearly. Just about every aspect of your alignment and the rest of the setup will help increase understeer. Less camber up front, higher tire pressures... is your toe setting toe in or toe out?

I'd recommend equal camber and tire pressures front/rear (maybe around 32 cold). Level the car out front/rear to exactly level; that will get your corner weights reasonably close. Leave your rear Koni's at full soft; stiffening them up will increase the lifting of the wheels on breaking, sure, but will lead to traction problems getting on the power. Leave the fronts soft too, to help get more power-on oversteer. The amount of camber you want to run; well, depends how much you wish to run and still take it on the street. Those tires likely want 2.5-3 deg, but you may not wish to run more that 1-1.5 on the street.

Again, start with this setup; if it's not agressive enough, try a smaller front swaybar.

I understand what you're saying about bushings; I chose the same for my 82 so that I could comfortably drive it on the street. The racecar has full spherical bearing suspension.

HTH...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

undrprzur · Joined: 27 Apr 2003 Posts: 18 Location: Eastern Washington

Thanks for the info. I'll try the setup. Next race Aug 17.
some pics of the car.

http://www.autosportsnorthwest.org/albums/20030406/MVC_004F.jpg

http://www.autosportsnorthwest.org/albums/20030406/MVC_010F.jpg
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81 931 Always on Boost.

Lizard · Posted: Wed Jul 23, 2003 4:38 am Post subject:

tsk tsk tsk knocked over cones

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3 928s,