C4 Autocross Setup (Rear Sway)
04-12-2017, 07:12 PM
#41
Drifting
Two day event over the weekend, I lowered the pressures to 35F and 33R and the car handled real well. Checked them with a temp gun and temp stayed consistent across the tread.
Sat was a short course, I was 7 tenths off 1st In BS, and I am chasing a guy who trophy'd at Nationals last year. 1.4 seconds off him on Sunday 60 second course, So I think the car is good enough, just need to clean up my driving.
https://www.youtube.com/watch?v=FqyQtw3IoFY
Sat was a short course, I was 7 tenths off 1st In BS, and I am chasing a guy who trophy'd at Nationals last year. 1.4 seconds off him on Sunday 60 second course, So I think the car is good enough, just need to clean up my driving.
https://www.youtube.com/watch?v=FqyQtw3IoFY
04-13-2017, 08:03 AM
#42
Safety Car
You might want to consider using a data logger. Then at some point in the middle of week you can spend a few hours analyzing how things went.
You'll usually find inconsistencies in the different runs. Look at the various turns and you'll see that you were faster in one segment.
We're starting to get serious at this point. You may want to consider how serious you want to get.
Once I won a national championship I never ran a serious autocross again. I was just burned out. Think about that.
Richard Newton
C4 Autocross Legend
You'll usually find inconsistencies in the different runs. Look at the various turns and you'll see that you were faster in one segment.
We're starting to get serious at this point. You may want to consider how serious you want to get.
Once I won a national championship I never ran a serious autocross again. I was just burned out. Think about that.
Richard Newton
C4 Autocross Legend
04-13-2017, 08:09 AM
#43
Pro
Thread Starter
Heartland Park Topeka Divisional in about a week.
04-13-2017, 08:18 AM
#44
Pro
Thread Starter
You might want to consider using a data logger. Then at some point in the middle of week you can spend a few hours analyzing how things went.
You'll usually find inconsistencies in the different runs. Look at the various turns and you'll see that you were faster in one segment.
We're starting to get serious at this point. You may want to consider how serious you want to get.
Once I won a national championship I never ran a serious autocross again. I was just burned out. Think about that.
Richard Newton
C4 Autocross Legend
You'll usually find inconsistencies in the different runs. Look at the various turns and you'll see that you were faster in one segment.
We're starting to get serious at this point. You may want to consider how serious you want to get.
Once I won a national championship I never ran a serious autocross again. I was just burned out. Think about that.
Richard Newton
C4 Autocross Legend
I think the car to have in B Street is the BMW 1M or C5, I am going to try and put the good old C4 back in the showing. Have no idea if I can do it, but it will be fun to try.
I just figured there might be some people who used to autocross them back in their hay day and knew the car setup.
With the new breed of 200TW tires I think it evens the playing field for everyone.
Thanks for all the reply's.
04-14-2017, 11:06 AM
#45
Max G’s
My Goal for this year is to try and finish mid pack at nationals in a C4 and I think that is a hefty goal.
I think the car to have in B Street is the BMW 1M or C5, I am going to try and put the good old C4 back in the showing. Have no idea if I can do it, but it will be fun to try.
I just figured there might be some people who used to autocross them back in their hay day and knew the car setup.
With the new breed of 200TW tires I think it evens the playing field for everyone.
Thanks for all the reply's.
I think the car to have in B Street is the BMW 1M or C5, I am going to try and put the good old C4 back in the showing. Have no idea if I can do it, but it will be fun to try.
I just figured there might be some people who used to autocross them back in their hay day and knew the car setup.
With the new breed of 200TW tires I think it evens the playing field for everyone.
Thanks for all the reply's.
04-22-2017, 07:57 PM
#46
Safety Car
Solofast help me setup my car and his answer is spot on.
Also your split of 35/33 sounds reasonable. You could go lower yet if the tire wear isn't too bad. The lack of a larger front bar with the stiffer rear spring of a Z51 are really hurting you.
Too stiff on the back of a C4 compared to the front and funny things happen like snap oversteer.
You might try adjusting your camber to more square. My rear is very close to what my front is. Around a degree negative. Mid corner I can actually change the cars cornering attitude with the throttle or brake. C4's LOVE to be trail braked and it works really well to pivot the car. If you do it right you can get the car pointed and on exit, nail the throttle down and go. On the RE71R's C4's will PLANT all of their power for the most part.
Also your split of 35/33 sounds reasonable. You could go lower yet if the tire wear isn't too bad. The lack of a larger front bar with the stiffer rear spring of a Z51 are really hurting you.
Too stiff on the back of a C4 compared to the front and funny things happen like snap oversteer.
You might try adjusting your camber to more square. My rear is very close to what my front is. Around a degree negative. Mid corner I can actually change the cars cornering attitude with the throttle or brake. C4's LOVE to be trail braked and it works really well to pivot the car. If you do it right you can get the car pointed and on exit, nail the throttle down and go. On the RE71R's C4's will PLANT all of their power for the most part.
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Jstockton (04-26-2017)
05-20-2017, 01:27 AM
#47
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Member Since: Jan 2005
Location: Citrus Heights CA
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C4 autox set up
I ran a C4 for 10 years. I'd have a good alignment shop relook at your front Camber. Our buddy who also runs a C4 did mine and he said that most C4's will get around 1.7-1.8 without doing the frame modiication. I agree with the toe out in the front and would definitely put the rear camber to more like 1.2 with a little bit of toe-in.
In the past with stock setups, I have found that a 1/4" of toe out in the front definitely will help. First, I would look into the front shocks, insofar as the valving. I would have a shock expert knows what an autocross shock should be doing, put your shocks on a dyno and see what they are doing.
I don't know for sure if the single adjustable QA1 shocks will accommodate the Penske valving but, I do know that the non-adjustable QA1 shocks will. I did that with my road race car because of the spec shock rule. It was a way to skirt the spec shock rule.
Also, another trick is take your car to a body shop that is an expert on frame straightening. Ask him to bend the frame tabs that hold the front upper control arms, to edge of the factory spec, in the direction to get more negative camber. If my memoory serves me right, that would be in the direction of car's centerline.
This is legal as long as the tabs are within the factory specs. You'll be surprised on how much negative camber you legally gain by having that procedure done to those tabs. Back in the day we use to see at the minimum about 2-2.5 degrees of neg camber.
With the extra camber and the right valving shocks you'll be surprised on the handling in the turns, especially corner exit.
Another stock trick, since the rule says you can only touch one bar and if you decide to play/changeout with the rear bar, shim the front swaybar bushing mounts that attached to the frame. Put something to shim up in between the mounts and the frame and this will help soften up the front bar action some.
The front spring on a base suspension for an 89 C4 is a 797 pound spring rate. That is not too shabby for a front stock spring. That is 214 pounds at the wheel and with the stock .9" swaybar, I think I would concentrate on the front shocks at this point, then work on the rest.
Also, driving style change may help. I'm not saying that you're a poor driver, a stock C4 has to be driven differently than other cars. It just takes some work at it.
I hope this helps.
Oh, by the way, the frame thing and shimming the front swaybar mounts was an old C4 secret for stock and street Prepared cars, so don't tell anyone.
I don't know for sure if the single adjustable QA1 shocks will accommodate the Penske valving but, I do know that the non-adjustable QA1 shocks will. I did that with my road race car because of the spec shock rule. It was a way to skirt the spec shock rule.
Also, another trick is take your car to a body shop that is an expert on frame straightening. Ask him to bend the frame tabs that hold the front upper control arms, to edge of the factory spec, in the direction to get more negative camber. If my memoory serves me right, that would be in the direction of car's centerline.
This is legal as long as the tabs are within the factory specs. You'll be surprised on how much negative camber you legally gain by having that procedure done to those tabs. Back in the day we use to see at the minimum about 2-2.5 degrees of neg camber.
With the extra camber and the right valving shocks you'll be surprised on the handling in the turns, especially corner exit.
Another stock trick, since the rule says you can only touch one bar and if you decide to play/changeout with the rear bar, shim the front swaybar bushing mounts that attached to the frame. Put something to shim up in between the mounts and the frame and this will help soften up the front bar action some.
The front spring on a base suspension for an 89 C4 is a 797 pound spring rate. That is not too shabby for a front stock spring. That is 214 pounds at the wheel and with the stock .9" swaybar, I think I would concentrate on the front shocks at this point, then work on the rest.
Also, driving style change may help. I'm not saying that you're a poor driver, a stock C4 has to be driven differently than other cars. It just takes some work at it.
I hope this helps.
Oh, by the way, the frame thing and shimming the front swaybar mounts was an old C4 secret for stock and street Prepared cars, so don't tell anyone.
05-20-2017, 10:26 AM
#48
Max G’s
I ran a C4 for 10 years. I'd have a good alignment shop relook at your front Camber. Our buddy who also runs a C4 did mine and he said that most C4's will get around 1.7-1.8 without doing the frame modiication. I agree with the toe out in the front and would definitely put the rear camber to more like 1.2 with a little bit of toe-in.