Lost some power
Thread Starter
12 Second Club
Joined: Jun 2008
Posts: 185
Likes: 0
From: Twin Cities, MN
Lost some power 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.
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.
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
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
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
11 Second Club
Joined: Jan 2010
Posts: 1,707
Likes: 13
From: New Orleans, LA
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!
Teching In
Joined: Nov 2013
Posts: 34
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From: N. Berwick, Maine
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.
Thread Starter
12 Second Club
Joined: Jun 2008
Posts: 185
Likes: 0
From: Twin Cities, MN
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.
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.
Teching In
Joined: Nov 2013
Posts: 34
Likes: 0
From: N. Berwick, Maine
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.
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.
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Verdad Gallardo TECH Veteran
Joined: Apr 2008
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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
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
On The Tree
Joined: Mar 2006
Posts: 123
Likes: 10
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...
And, yeah, if ya still got the stock valve springs, those have to be shot by now...
Thread Starter
12 Second Club
Joined: Jun 2008
Posts: 185
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From: Twin Cities, MN
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??
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??
TECH Veteran
Joined: Apr 2008
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