Setup Notes road racing - in progress

[HarrisRacing]

I finally finished the car enough to bring it ot the track. It was a private open lapping day on the state police training facility track (1.9 miles) and I made about 50 or so laps in the newly-finished Mr2.

My setup:
1991 MR2 turbo
stock engine, stock turbo (very tired), exhaust, intercooler, intake, 10-12 psi boost (need new controller this one only puts 8 psi from 3-4.5).

Stock springs, cut the front 3/4 of a coil, but 1 coil off back.
ST swaybars Front and Rear.
Rear bar on softest setting
All new bushings in arms, new ball joints, end links, tie-rod ends.
Adj Front end links
Stock shocks

Car is 70% gutted. 6 point roll bar.

Tires:
front: 205/50?/14 Avon Tech RA pressure cold = 28
Rear: 245/45/16 Hoosier R3S05's pressure cold = 32

I worked with the pressures, but forgot the actual hot values

Alignment:
Front Toe = 1/4" total out (going back to zero...didn't help only killed tires)
Front Camber = 3 degrees (with smallest crash bolts - going lower - couldn't get tire wear right at all).
Front caster - max = 5-5.5 deg or so
Rear Toe - in 1/8 on each side might drop this just a little
Rear camber - whatever it was at 1.xx deg


Alright, I had to play with the pressures for a little while, but the front made the biggest difference. I think this was due to the extreme amount of camber I have for the car in the front and the STIFF ST swaybars that are there. I decided that I am going to drop the front camber in half for the next event because I felt I was having a good bit of grip lost off of the front of the car. It was understeering through a constant turn and I even tried to upset it a few times by blipping the brakes to get it to rotate. It NEVER felt like it was coming around except on extreme upset situations at lower speeds and very hard braking. Even then I felt comfortable with it. Granted this is probbably due to my extreme tire size differences, but I know I'm not using all of the front tires yet anyway (not even close).

Anyway, I was amazed at the stock springs cut plus the ST swaybars did for the stiffness. While I will add Koni's and some adjustable camber plates up front I feel that the stock cut springs will be more than sufficient. I like the ability to rotate the car by braking and transferring weight to the front, which seems to work better with STIFF bars and softer springs. My opinion here.

Anyway, I ran down one of our fastest cars in this layout...the car is definitely fast, but it does need more power. The stock turbo is blowing oil and it is bound to die soon.

Anyway It was a blast and I'll have video up soon.

[Jaicvc]

nice nice ......

[Sylvan]

Good stuff. What are you goals for the car?

[Ben]

Your 2 is missing its eyes!

[Gairloch]

My findings for the alignment are very similar to yours. I'm running 1.8* camber front and rear, about the same amount of castor you have then zero toe in front and just a touch in back. It depends on what you like the car to do of course but even a touch of toe in back really settles the car down.

I use the same tire pressures you have listed also but that changes with the track. Different track surfaces and textures call for slightly different pressures. Since you don't have adjustable dampers yet they can be a powerful tool in adjusting the car's dynamics. I've found that even a half pound change in pressure (cold) can make a significant difference.

Which club do you intend to run with?

[kbrew8991]

not enough front grip and you want to reduce camber? I hope your pyrometer was telling you your tire temps are way out of wack to come to that conclusion

try dropping a bit less rear toe-in, or add some more rear swaybar to get that rotation you need

[HarrisRacing]

My goals are to have a reliable FAST car that I can race on the weekends. It has also become important for me to stay on a budget as far as expensive hard parts goes, and to "tweak" the car by use of setting it up and really learning how to drive it. To say it one way, I will probably generate faster lap times by spending money on tires and entry fees than to put 2k shocks on the car.

Initially I wanted to throw all the parts in the world at it, but I really want to go as fast as I can for the money now. Actually after thinking more about the camber plates I started thinking that I could just put a stock crash bolt in the bottom of the shock and see what that does for the camber in the front. I have the smallest bolts in both of the locations and am right around 3 deg. Maybe 1 will give me 1.5?

Anyway, that's what I plan to do with the car for now. I don't even think I am going to address the one-wheel-peel until the tranny starts giving me problems - and it's got 233k on it.

Thanks,
Patrick

[HarrisRacing]

Yes I want to reduce front static camber for what could be a couple of reasons:

1) The front tires are being killed on the inside. The tire was barely scrubbed in on the outside if any at all. Therefore it's not on the ground when I'm turning and I'm losing grip. There is such a thing as too much camber...especially with the lack of weight to cause body roll on those tires. Trust me, it will result in more grip.

2) I have a lot of caster, therefore as I turn, the tire lays over and ADDS camber - this just makes the problem worse.

3) Tightening a rear bar too much will result in LESS grip in the back...I want to add to the front, not remove from the back and the evidence is clear from the damage to the tires. I will take pictures for you tonight. I didn't have the tools to remove my crash bolts (180 ft-lbs) at the track.

Thanks for the input.
patrick

[HarrisRacing]

I probably said this wrong, but here's a clarification: I don't want the car to "rotate"...I want to front to stick as much as the back does.

I also will start work on a front splitter and air dam since 75-80 mph is about the average speed around turns on the 2 main tracks that I race at.

Then If I get the front to stick, I'll pull the stock wing and add a huge one on the back.

Right now my logger shows about 1.00 G average in turns and 1.06 spikes.

Patrick

[kbrew8991]

yes I know there is such a thing as too much camber. But its usually hard to achieve, especially with macpherson strut suspension designs.... sounds like you may have. Just beware that your increased wear might be coming from the toe-out, and not the camber. It may take you a few alignments to nail it (I'm on my 5th version and I'm almost 100% stock suspension...)

you shouldn't be adding so much steering angle that caster has THAT much of an effect, but IIRC the track you are on is on the tighter side. You'd see more of an issue at autocrosses than higher speed tracks

yes - the most ideal solution is to always add grip, but balance and ease of driving can lead to lower lap times as well... worth experimenting with at least

[kbrew8991]

Originally Posted by HarrisRacing

Right now my logger shows about 1.00 G average in turns and 1.06 spikes.

Patrick

thats getting there, especially if you're on pretty old pavement. my bests on RA1s were 1.28 spikes with 1.10 range sustained, and V710s (195/205 14) were 1.45 and 1.20 range sustained though you do have a bit more suspension parts that I do, only Koni yellows & crash bolts on otherwise 100% stock springs, swaybars, etc here

the Avons are supposed to be more on par with Hoosier Rs / Kumho V710s than the RA1/NT01/R888 aren't they?

[PVpower]

Hey man this is kind of off topic but, was it hard to change your headlights?

[Gairloch]

Originally Posted by HarrisRacing

Yes I want to reduce front static camber for what could be a couple of reasons:

1) The front tires are being killed on the inside. The tire was barely scrubbed in on the outside if any at all. Therefore it's not on the ground when I'm turning and I'm losing grip. There is such a thing as too much camber...especially with the lack of weight to cause body roll on those tires. Trust me, it will result in more grip.

2) I have a lot of caster, therefore as I turn, the tire lays over and ADDS camber - this just makes the problem worse.

3) Tightening a rear bar too much will result in LESS grip in the back...I want to add to the front, not remove from the back and the evidence is clear from the damage to the tires. I will take pictures for you tonight. I didn't have the tools to remove my crash bolts (180 ft-lbs) at the track.

Thanks for the input.
patrick

You might want to consider leaving the camber in front alone and just zero out the toe, that's why you're going through too much tire. You have to hae a monstrous amount of camber (more than 3*) before it will cause fast wear on the inside.

Like Ken was saying if you reduce the camber in front you will only aggravate the car's understeer issue. You are correct in your assessment of the tire sizes being the problem. I am running 205/40-17 in front and 225/40-17 in back and find that my car is almost perfectly neutral. What you've got is more appropriate for a dragster than a road course car.

One thing you might do until you're ready to replace the tires is play with the tire pressures. You probably can't increase the traction threshold in front much with what you've got but you can decrease the traction threshold in back easily.

What I would do is increase the pressure of the tires in back by 5 lbs and try it out. If that isn't enough keep adding a pound of pressure at a time until you get closer to what you want. You will want to watch the tire wear closely to make sure you're not causing the tires to crown.

Dialing in traction and suspension is a major project and kind of a black art. Ultimately it's all about reaching the result that you want the most efficient way possible. One of the best rules to follow when you're trying to figure out that fine tuning is to try and only change one thing at a time. The dynamics of the situation are so complex and interactive that if you change a bunch of things at once you can easily create whole new problems.

Originally Posted by PVpower

Hey man this is kind of off topic but, was it hard to change your headlights?

If you look closely you'll see that all he did was pull out the pop up headlights and cover the holes with plexiglass.

[kbrew8991]

if it were me, I'd nix the front toe and try a bit of rear swaybar

YMMV

[HarrisRacing]

Ok I have totally agreed, the toe out in the front is definitely causing the increased wear to the inside of the front tires - not doubting that. I'm saying that I have 3 degrees of camber and the OUTSIDE of the front tires is barely even scrubbed in and that tells me that there's just too much camber there. The point of adding negative camber is to account for the body roll that will cause the tire to stand up straight during HARD cornering, resulting in more rubber on the road. If I'm not doing that then I'm wasting my time running all of this camber and using a narrower track of rubber up front. Lowering the front pressures made this immensly better, but then I dropped too much and resulted in poor response.

The other factor here is the 245 vs. 205 difference. No doubt is that contributing.

Anyway, I am going to zero the front toe for sure and pull a deg of front camber, then I'm going to drive it and log it, then swap the rear bar to the stiff hole. And I'll let you guys know what I find out.

Thanks for the advice.

Patrick

[kbrew8991]

do you have a pyrometer to take tire temps by chance? that would sharpen up your learning curve regarding pressures and camber choice immensely

[HarrisRacing]

My friend was supposed to bring his, but forgot...but I did not have a way of changing camber there anyway. We played with pressures for quite awhile. The outside of the tire was no where NEAR the inside even by touch. It was a very noticeable difference in temps.

I think the new plan will bring a lot of things to light. And yes I will get a pyrometer.

225's ey? Dang...that's skinny! I have 9 more 245's in the shop so I'm gonna be killing those for a while. When I kill the Tech RA's then I'm going to a 225 on a 15 or 16 x 8 up front.

Another factor that might help would be putting wider wheels up front. that would reduce the "bulge" in the center of the tires now.



Patrick

[Gairloch]

Originally Posted by HarrisRacing

225's ey? Dang...that's skinny!

Plenty for an NA Might be 235, I don't remember for sure.