Stardust

Hey guys

96 Z28, Mods in sig

The last 2 times at the dragstrip, the car was unusually slow. The first time around, the air was bad, and humid, and I just chalked it up to that. Yestersay the air was average, and the car is even slower. It goes to 60' OK, but just feels down on power after that, and the numbers show it. It's off .3 seconds to the 330 and .4 to the 1/8 mile, and down a couple MPH. I also had where it did a hick up coming off the line a couple times.

Plugs and wires only have 8,000 miles or so, but the car has been drag raced a lot. They are MSD street fire wires (or something similar to that) and NGK plugs. I have been thinking about changing it all back to AC Delco stuff, and also replacing the ignition coil with a new AC Delco unit just to eliminate that. Cap and Rotor are stock as far as I know, but a PITA to change.

cardo0

Does the car get slower each pass? My old A4 would get slower as it got hotter/heated up. Trans was slipping. New/rebuilt trans was the cure. Now my car is consistently slow.

BALLSS

hotter summer days, track prep, DA all have effect on ET/MPH

you should confirm you don't have any mechanical issues causing your slower times. A look at all 8 plugs to compare color, compression or leak down test. If those tests show a problem on 1 or more cyl...you would need to attend to that issue

NewOrleansLT1

My car ran a 12.23 @ 110 1.62 60ft with a cracked spark plug and an opti with a bad bearing and a wobbly rotor. I didn't think my car was running bad until I went to the track and got the time slips. I went to change the plugs and found the bad plug. I drove the car and couldn't even make it back up the driveway! I went to change the opti after that and after inspection found the issues I've stated above. Went back to the track and ran 11.37 @ 119 1.52 60ft. while hitting the limiter during the 2-3 shift!

Dannyac500

Hows the transmission and shifts feel? Hows the fuell pressure? Done any data logging? The warmer/damper air will effect your ET quite a bit. Ive found the hotter the car, the worse the pass. Once the car has 20-30 mins to cool it will make a better run. I upped the shift pressures a little to compensate for slow shifts ive been having and it showed a quicker ET. Im thinking of a new trans this winter anyways.

Stardust

I have been racing the car for 2 years, in all weather conditions, and I keep track of density altitude. I can usually tell within .1 seconds what I am going to run based on my notes from the past. Something is defiantly
up with the car. Seems to be shifting ok, just down on power. I don't feel any misfires really, if anything just slightly sluggish.

Dannyac500

Have you done a fuel pump in the car? If the pumps getting weak it could be starving you on the top end and giving you that sluggish feel. Had that same issue this spring. Hooked up a fuell press gage, at idle pressure was good but presssure dropped once the car was under load.

Stardust

Original fuel pump

BALLSS

if you don't have a FP gauge, get one you can see while under "sustained" WOT.....if pressure drops....you have a fuel pump problem

also valve springs get weak and even though you don't experience valve float they can slow a car down if they become weaker than their original spec

Always2Slow

iTrader: (8)

Please check your valve springs before you need a new motor.

Kevin Blown 95 TA

When I was going through various phases with the blower and increasing power, there was a point where I outpaced the fuel system, and the symptoms were that the car would fall flat on its face during the burnout or when hard off the line and top end was lethargic and logged lean (it ran good in between those events). I suggest as Danny says to at least get a gauge on your fuel system and see if the pressure drops when you mat the gas pedal. It could end up being something else, but I would consider the 18 y/o pump to be a prime suspect.

And, yeah, if ya still got the stock valve springs, those have to be shot by now...

Stardust

I'll look into valve springs.

By accident, I found what I think is a broken baffle in the muffler (Hooker).
My leg brushed the one side exhaust tip and I heard a rattle noise. I assumed it was a loose clamp or something, but sure enough, I crawled under and banged on the exhaust and muffler, and the metal rattle noise is coming from inside the muffler. Could a broken baffle be restricting flow when I am on the gas and causing the slight performance loss??

BALLSS

if the baffle "broke" off and lodged itself in a way it was not "blocking" exhaust flow or rattles to the point it restricts exhaust than yes