I lost 7 seconds!

J

jimbbski

New member
I just got back from a MCSCC race at Road America. I qualified at 2:56 which while not fast was faster then a CRX and a 1/2 doz. Miatas. I messed up the start when I missed a shift, that's on me but during the rest of the race I went backwards and all due to lack of speed on the straights!

The engine did seem to rev slower during the race but the water temp never went above 190 and the oil ran 220-230. My wideband O2 meter showed A/F reading in the mid to low 13:1 range at full throttle, which at RA I'm at 97% of the time! The A/F could be a bit lower but it actually read a bit higher during the morning qualification! The air temp was a bit higher for the race but no more then 10 deg.

While I haven't looked at the car yet I did find one thing different after the race. I built an air dam for this race and the material I used while cheap is brittle. I cracked it loading the car on the trailer but repaired it. When I returned to my paddock space after the race I found a piece of the air dam material laying there where it broke off as I must have pulled out to go to grid before the race. It was only 15 inches long and while about 2 inches at the widest it tapered to nothing at the ends. It would constitute about 10-15% of the total area of the air dam but along the lower edge. Cound this be the problem?

Ground clearence for the air dam was only 2 7/8 inch which is actually to low as the wheel rim is 3 inches from the ground. I was 1/8 inch illegal! I am going to raise the cars ride height a bit for the next race so this problem will go away.
 
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Did weather or track conditions change between Q and R?
Is the clutch wet?
Was there a brake dragging?
Some sort of intake restriction?
Throttle cable stretch/linkage failure?

No way no how that was a little piece of aero.
 
shwah said:
Did weather or track conditions change between Q and R?
Is the clutch wet?
Was there a brake dragging?
Some sort of intake restriction?
Throttle cable stretch/linkage failure?

No way no how that was a little piece of aero.
Click to expand...

Weather was unchanged other then being a bit warmer as I mentioned in my first post.
Clutch seemed fine. No hint of slipping.
Same on the brakes.
I do have to look at the intake.
Funny you mentioned this one.

At the end of the day on Saturday drivers who have passenger seats in their cars lined up and took the corner workers for rides. I did this and on the second lap with my "worker" coming out of Canada Corner I felt something strange in the throttle feel. I let up a bit on it and the car didn't slow at all! I had a stuck throttle. I didn't panic. I figured that I was OK for turn #13 as that is taken flat but at turn #14 I was going to have to do something. As I approched my normal braking point I switched off the ignition, coasted through the turn and then turned the ignition back on. Zoomed up the pit in road and then shut off at the beginning of pit lane, coasted a way and then one last burst of power to make it to the drop off zone for my passenger.

I found the reason for this problem and will attend to it this week as well.
 
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well, what was it?? In the future, keep a log with the cranking comprssion values, timing, Ox values.
Mon am, check the compression. Do it the same way every time. Pick a temp, and use it the same way.
That way you will know if the engine is going soft.
I write some of mine on the underhood panel. date it and have a good and NG value. IE the stocker needed to come apart evry 10 races to lap the valves.

The engine will make good power longer if the AF ratio is at 12.5 or even more. 12.3- 12.6 shows very little power loss. 13/1 will burn the exhaust valves sooner .
 
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