Setting up a C900 for the Track

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DeLorean
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Re: Setting up a C900 for the Track

Postby DeLorean » Thu Sep 18, 2014 8:36 am

Hey, sounds good to me. Next time I'm doing the crazy-rays circuit, we should meet up, get parts and hoon around Baltimore in the 900's. We are having an autocross planned by one of the hillclimbers early in Nov. up our way which I am planning on attending. This is being put on by the Ackermans (the ones with the VW Golf) - and likely will be a fast course that's not too technical (these are hillclimbers after-all), probably good for a classic 900. That would be a great time to really put your car through it's paces and get a feel for it, as well as compare your driving / your car to some others that show up.

There is of course also the rally-cross coming up in Kempton PA on the 19th of Oct, however I do not think it would be a great idea to use a car that is optimized for road/track use there. It's not that bad of a surface, but full use of the skid plate will happen. I will probably be running my 1993 1.0/MT Geo Metro there.
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Re: Setting up a C900 for the Track

Postby jdwertz » Thu Sep 18, 2014 10:50 am

DeLorean wrote:Hey, sounds good to me. Next time I'm doing the crazy-rays circuit, we should meet up, get parts and hoon around Baltimore in the 900's. We are having an autocross planned by one of the hillclimbers early in Nov. up our way which I am planning on attending. This is being put on by the Ackermans (the ones with the VW Golf) - and likely will be a fast course that's not too technical (these are hillclimbers after-all), probably good for a classic 900. That would be a great time to really put your car through it's paces and get a feel for it, as well as compare your driving / your car to some others that show up.

There is of course also the rally-cross coming up in Kempton PA on the 19th of Oct, however I do not think it would be a great idea to use a car that is optimized for road/track use there. It's not that bad of a surface, but full use of the skid plate will happen. I will probably be running my 1993 1.0/MT Geo Metro there.


Sounds like a plan. I could go for a CR run, maybe we could get a group of mid Atlantic guys together to go.

I would be interested in the autocross event, I will have to keep an eye out for the event info.

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Re: Setting up a C900 for the Track

Postby DeLorean » Thu Sep 18, 2014 11:01 am

Well, I'll have to make a post on the mid-atlantic Saab facebook page I guess!
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Jordan
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Re: Setting up a C900 for the Track

Postby Jordan » Thu Sep 18, 2014 8:49 pm

First step we are taking is taking out some of the bushing deflection with some sort of stiffer bushing, probably bronze. The bushing blocks will probably need to be modified since they have a taper to them.

We also get the rear tire lift, but if you are still getting bad understeer then I don't really see it as the biggest problem. Unless it is a symptom of transferring too much weight forward, but I'm not sure how much control you have over that.

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Re: Setting up a C900 for the Track

Postby tirediron » Fri Sep 19, 2014 5:12 pm

one thing to note: normally (assuming no other changes) a stiffer front spring will tend to make the car understeer more. however, if you are compressing the suspension enough to get on the bumpstop, spring rate ramps up to near infinite very quickly. in that case, installing stiffer front springs will keep the front end off the stops, and work to get rid of understeer.

carrying the inside rear tire into the corner along with chronic understeer is pretty typical when this is happening. i use zip ties on each shock rod to mark how far the suspension travels in corner.
-matt

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Re: Setting up a C900 for the Track

Postby Jordan » Sun Apr 17, 2016 7:50 pm

Just the bring this topic back from the dead. The race car has come a long way since this post originally. The springs we had settled on were 375lb in the front, which is on the soft side when running a 225/50/15 and 205/50/15 , F/R stagger. Handling was pretty good. With the added power and straight line speed we added a little toe-in to stabilize the car, it used to dance pretty heavily.

The current biggest change is moving up a wheel tire size, which has a couple of advantages and a couple of disadvantages. I'm hoping the advantages win out.

The new tire size of 235/40/17 and 215/40/17 on 17x8".

Advantages:
Wider tire = more mechanical grip
Taller Tire = taller gearing (we actually run out of gear at larger tracks)
More Tire = longer wear
Tire availability = better tire compounds available in larger wheel sizes. Last year they ran out of the endurance compounds and tires would last about 4-6 hours.

Disadvantages:
More weight = Tires and wheels a few lbs heavier
Raised Ride Height = 23in diameter vs 24.4in means raising the ride height 3/4"
Less clearance = these things really fill out the wheel wells, although they do provide for better brake caliper clearance.

So I'm back to setting up the car. We have some modified motor mounts now that should provide us for more room for camber adjustments and increasing caster as well. I'm thinking of stepping up a little bit in spring. This tuesday will be the Test & Tune at Limerock, so we'll get some time to make some changes and actually have some real world data as well.

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Re: Setting up a C900 for the Track

Postby gmreider » Mon Apr 18, 2016 9:09 am

Jordan , I like the front spring rate, but what are you using on the rear? I get so much front lift and rear squat on acceleration that I am considering maybe 600 lbs. on the rear.
"Red" just got torn apart for a little trans work and after doing an engine leak down, maybe a quick motor change. Leak down # 1 @20%, #2 @ 50%, #3 @ 45% and #4 @ 60%. all done on a warm motor. Had been getting lots of blow by into the turbo / intercooler stream.
Got plenty time though . First event is May 27-29.

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Jordan
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Re: Setting up a C900 for the Track

Postby Jordan » Mon Apr 18, 2016 10:46 am

One thing about blow by is that the PCV system never seems to be up to the task at long periods of high RPM + higher than stock levels of boost. Also, I noticed the stock (even pricey Pierburg) PCV check valves were constantly blowing out on us which was making matters worse. I switched to the 9000 TCS (red/white) check valve which I think have a silicone diaphram and that stopped happening. This season , I opened up valve cover to run a -10 breather tube out to a catch can. I was thinking of maybe adding a vacuum pump down the line or maybe a drain back, but I figured I'd try this out first before over complicating it.

Rears I couldn't remember the rate, but I have it written down somewhere. But they are rear turbo springs with a coil cut out of them

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Re: Setting up a C900 for the Track

Postby hutch » Mon Apr 18, 2016 7:53 pm

Gary I'm not sure what setup you are currently running in Red but I have a set of rear Intrax springs that are too stiff and miserable for my street cars if you're interested in experimenting a little bit...

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Re: Setting up a C900 for the Track

Postby Jordan » Tue Jun 14, 2016 7:35 pm

Quick update:

The switchover to the larger tires required some stiffer springs to prevent /fender rub. This sort of threw a monkey wrench into all of the alignment setup done previous. The next stiffer front spring we had on the shelf causes the front to sit higher and it was clear that the rear was now too soft. Since then a softer front spring was used and a rear stiffer spring was installed, this fixed the "stance" issue , but the were still complaints of too much "push" during our practice session. Tire readings indicated a little too much air, not enough camber and too much toe in.

With a little time I've been able to maintain the slightly uprated front springs (425), but modified them to drop front of the car an additional 3/4 of an inch. I think this will be a good compromise between responsiveness and overall grip. For the rear I've found that the same 5" circle track springs we use for the front appear to fit just fine. These are usually available in 25lb increments for fine tuning. So after doing some rough calculations a 500lb spring seemed to be a good starting point. After some ride height adjustments with some ikea cutting boards. I got things where I want and will be setting the car up with more negative camber and a little more caster. Usually we run a bit of toe in or the car feels really squirrelly under acceleration.

Results to follow this weekend at the next AER race in Palmer , Mass

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Re: Setting up a C900 for the Track

Postby tirediron » Thu Jun 16, 2016 12:12 pm

automatic transmission clutch plates work really well to shim those 5" springs. really fine adjustments and they stack nicely. I think most of mine came from ford explorers, but any trans shop probably has a bunch they are throwing out.

ive always run 0 to -1/8" toe in the front and 0 to + 1/8 toe in the rear. but you guys are going faster than I, I'm sure the toe in creates more stability.
-matt

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Re: Setting up a C900 for the Track

Postby Jordan » Thu Jun 16, 2016 9:08 pm

Yeah our rear axle ( although we just changed to a different one) landed at factory toed in. We are currently a hair less than an 1/8th in in the front. But I wanted to give that a shot , it's easy enough to change.

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Re: Setting up a C900 for the Track

Postby tirediron » Fri Jun 17, 2016 11:33 am

oops, I just notice I said toe in for the front. I mean toe OUT.
-matt

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Re: Setting up a C900 for the Track

Postby Jordan » Sun Jun 19, 2016 8:28 pm

So others can chime in but I thought our setup was really good this weekend. Car handled pretty amazingly. The car ran some 7 seconds faster lap times than last year with probably the same amount of power.


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