Best M20 powered E30 lap time at Buttonwillow CW13

[Smoove1]

How much front camber?

How was the turn in with that suspension? Seems frontal bias making it push on turn in. Learned that twice the hard way. First time was too much F:R bias on spring rates. The second time was using a 19mm rear sway, vert front bar and strut mount links. Both times the car felt like a dump truck. First time went from 450f/550r stock sways both ends, to 450f/900r stock front sway no rear sway. With a vert front bar and strut mount links, the front gets quite heavy. The 19mm rear bar had to be max adjusted (to the point of binding) to "almost" balance the car.

Front Camber was set at -3.8 degrees, rear was -2.7 degrees. 0 toe in front, 2mm toe in in the rear. I thought the car was great on turn in when entering the lower speed corners. During high speed sweepers there was a bit of understeer. Especially when on throttle. It was very easy to rotate the car and make line corrections simply by lifting which was nice. There was a good bit of the car squirming under hard braking due to the right front occasionally locking up due to the ABS issue which made things unnerving.

Was a little curious about the spring choice myself. I labored over the rates I chose quite a bit and went with 450/650 in the end, seemed like any more in the front would be counterproductive since I had to mind the adjustability of my shocks. Still haven't been able to track it :( Seemed well balanced at the autocross and pitching it into corners at scary speeds but what do I know?

We went with higher rates to minimize the body roll. I typically don't like to run more than a 150lb spring difference front to rear. I wish I got a chance to autocross my car first before taking it straight to the track. It would have gave me a better idea of what the car was going to do. IMO, a balanced autocross car makes for an easy to drive track car.

Where was the EF faster? Doesn't the E30 have a significant power to weight advantage?

It was all corner speed on entry. We chased each other around for 2 sessions just for fun. He was able to enter the tighter corners faster than I was. I put my car off the track twice trying to match his entry speed. Corner exit we end up the same and he didn't pull away but I was unable to make up the ground already lost. My car was faster the few times we drag raced down the front straight.

EF Hatchbacks are sub 2200lb cars AFAIK, and depending on which D16 it has 110-130hp by my quick googling. So that ranges from significantly worse than an E30 to about the same. Has to have been the cornering speed, the Civic is so much lighter and probably had better sorted suspension. Looks like Buttonwillow's #13 configuration has two decent straights (~1,700ft and ~1,100ft) so the E30 must have been just slaughtered in the corners.

His car has a D16ZC with bolt on mods and a ecu tune which was putting down 107hp at the wheels. I lost in the slow corners. When I drove his car I was blown away by how easy it was lift and rotate the EF into the corners with minimal braking. It was just unreal. It was like driving in a video game.

[glnr13]

Nice job, wish you had won but it was a valiant effort. I think that double wishbone suspension got you in the corners.

[varg]

I typically don't like to run more than a 150lb spring difference front to rear.

Spring rate doesn't matter, wheel rate does. The motion ratio of the trailing arm is such that you need a much higher spring rate than the front for an equal wheel rate. I saved some info on e30 wheel rates from a now defunct site and the front ratio was 0.88 and rear 0.45. Based on that info your wheel rates are 484lb/in front 293lb/in rear, a significant front bias.

http://web.archive.org/web/200708082.../eff_rate2.htm

Of course there are other factors in choosing spring rate but that's just something to point out with respect to the rate difference you were trying to avoid.

I put my car off the track twice trying to match his entry speed.

Spun off? Understeered off? Just couldn't slow down fast enough?

[ForcedFirebird]

We went with higher rates to minimize the body roll. I typically don't like to run more than a 150lb spring difference front to rear. I wish I got a chance to autocross my car first before taking it straight to the track. It would have gave me a better idea of what the car was going to do. IMO, a balanced autocross car makes for an easy to drive track car.



It was all corner speed on entry. We chased each other around for 2 sessions just for fun. He was able to enter the tighter corners faster than I was. I put my car off the track twice trying to match his entry speed. Corner exit we end up the same and he didn't pull away but I was unable to make up the ground already lost. My car was faster the few times we drag raced down the front straight.

Spring rate doesn't matter, wheel rate does. ..



Spun off? Understeered off? Just couldn't slow down fast enough?

I agree with Varg on the spring rates vs ratio. The e30 should turn in nicely for high speed turns.

Also a FWD car is very easy to enter hot, just point the wheels and keep on the throttle. They also rotate quickly on decel (which the e30 really does too).

[RoccoB517]

For what it's worth, I believe that your car, with a dead on setup, and being driven to the hilt, should be good for a high 2:04/low 2:05 on CW13. I really thought you were going to run a high 2:05 and the Civic a low to mid 2:06.

Is your rear sway bar hooked up? Front bar settings? Tire pressures?

Good try, man. Thanks for giving it an effort!