There's something wrong with my car, but what is it?
 

Last year I ran 13.48 @ 106.41 mph with a 2.21 60'. Yesterday I ran 13.7 @ 104.2 mph with a 2.28 60'. Between the two runs I tuned the car with a MAFT to 13.2 a/f (that equated to 0.93 on the 02 sensor, previously it read 0.98). In addition, I descreened my MAF, removed both baffles in my hood, installed NGK TR55s, Pro 5.0 shifter, and ployurethane trans and motor mounts. Now my e.t. is 2/10 slower and I trapped 2.2 mph less.

My SES light is not on, but the car is running rough. Prior to going to the track I though that I was just feeling additional vibration due to the polyurethane. Now I think I must have hurt the engine some how between the two track outings and the polyurethane made the problem more obvious. Unfortunately, I did have a 3rd gear to 2nd gear shift at about 100 mph (before the Pro 5.0 and between the two track outings). I thought I caught it in time and pushed the clutch back in. Could I have possibly broken a spring or bent a push rod and not realized it until I put the motor mounts in? Is there any was to check with Atap? Or does anyone have an idea of what might be wrong?

Thanks,

Jim

Re: There's something wrong with my car, but what is it?
 

I think you'll find some of your lost time in your 60' time.

How is the weather today vice last year? If it is hotter today than last year that could be part of the problem.

What kind of tires are you running? You are close to 12's. Better tires = higher launch = lower 60's = better 1/4 times. Even some Nittos or my favorite BG DR.

One bad thing: once you start mod'ing these cars it is hard to stop.

David

Re: There's something wrong with my car, but what is it?
 

David,

Thanks for the reply! As for the weather it was pretty comparable to last years track outing. As for the 60', I agree that I could be losing some e.t., but I don't think it should affect my mph that much. I was expecting to go low 13s at around 108 mph with a 2.20 60'. I was no where close. The car felt pretty flat and really didn't seem to rev like it should. On a side note, if I hold the engine at 1300 rpm's it vibrates the steering wheel pretty good. Once I bring it up to about 1500 rpm's it smooths out considerably. However, once I get into the higher rpm's (say above 3000) it starts to vibrate again. This is kind of confusing me. I definitely feel that there is something wrong with the car, I just don't know what or where to start looking.

Thanks,

Jim

Re: There's something wrong with my car, but what is it?
 

I hate to be the one to say this, but if you went from 3rd to 2nd you probaby did do some valvetrain damage; if everything is stock the pushrods will bend first. There's a way to use LS1edit to reprogam the Skip Shift to work as a missed shift guard.

Re: There's something wrong with my car, but what is it?
 

Cal,

Do you know if there's any way to use Autotap to determine if there is a bent pushrod? I'd rather exhaust all my options before I resort to pulling the valve covers and physically inspecting the push rods.

Thanks,

Jim

Re: There's something wrong with my car, but what is it?
 

your clutch has a whole year of wear, you could have did something in your shifting different. It can be anything. Try some more runs. Try also to run it without the MAFT

Re: There's something wrong with my car, but what is it?
 

Sorry, the only way I know of is to pull them all out and roll them around on a flat table. You might post this question over in the Internal Engine section. Also, check all the obvious tune-up related stuff like plugs, wires, fuel quality, and fuel filter. It wouldn't hurt to log a bunch of stuff with Autotap and see if anything is out of line.

Re: There's something wrong with my car, but what is it?
 

Well I just disconnected the MAFT and logged a couple WOT runs. The only thing that I found unusual is: O2 Sensor (B1S1) = 0.956 and O2 Sensor (B2S1) = 0.919

It seems the drivers side bank is running a lot richer than the passenger side. Any other time I logged WOT runs (either with or without the MAFT) the drivers side and passengers side O2s were always close to each other. I don't know if this means anything, but I found it unusual.

I'll try posting this question in the internal section. However, please keep your comments coming.

Thanks!!!

Jim

Re: There's something wrong with my car, but what is it?
 

It is normal to get a slightly different reading on one side than the other, but that sounds like too much difference to me. I'm going to borrow this quote from Wrencher: "I would have to say you need to do compression testing. Then if any cylinders are found to be low,like #4 & #5, do a leak down test. This can confirm a suspected bent valve. "

Re: There's something wrong with my car, but what is it?
 

Cal,

Thanks for the input! I took your advise and did a compression test today.

Cyl. #1 = 167 psi
Cyl. #2 = 158 psi
Cyl. #3 = 170 psi
Cyl. #4 = 165 psi
Cyl. #5 = 165 psi
Cyl. #6 = 165 psi
Cyl. #7 = 165 psi
Cyl. #8 = 165 psi

Do my O2 readings and compression test shed any light on the source of my problem? I really do not know how to interpret this data, but if I had to guess I'd look at cylinder #2, because it's a little lower than the rest.

Thanks,

Jim