Took my 1990 vette to the track after adding true dual exhaust with magnaflow mufflers,no Cats, underdrive pullies, and removed frisbee,,, I only picked up .01 of a second going from 14.08 to 14.07 . I was at least expecting high 13's ,,, .2 seconds.

Like I said it is a 1990 L98 auto with 2.59 gears [I know] other mods are k+n , cooler thermostat.

Do I need a new Chip or reprogram the Computer ?

Help / suggestion ?

Paul

 

lower gears.

 

I know gears will help,, but I thought the exhaust and pullies would have helped,,why didn't they?

 

Because the exhaust can easily move the power band from low rpm-mid range to mid range-higher rpm, or trim off some power at one end or the other without actually making any new power. Making more power is very expensive.
Rearranging what you have already got is usually what happens with bolt-on mods. The HP supposedly made available with the under-drive pulleys was always there. Not as much was lost to parasitic drag as before, but its not actually new found power, its new applied power. That gain is tiny...alot like the 6-hp it takes to turn the oil pump...accurate number? maybe. Any help to the over-all performance with a near stock car? Probably not. Those are the things that someone looking for .001 of a second at a 7 second run would be looking at.

Opening an exhaust system is not as simple as some folks think it is...thats part of the "tune" and intake, fuel, airflow all have to be "matched" or tuned to get the maximum benefits. You could have taken a laxative and picked up
.01 sec...
When people go spend $1200 on a new exhaust system thinking it'll run better...they are sometimes dissappointed. It will run different, not necessarily better...

Best way to get some immediate results is to gear it, then get a tune for the gear but remember that the tune has to be updated with each mod if you want to see progress at the track. Find someone with the software and the knowlege to do tunes in the driveway...that way you can experiment and try this, that.

 

you dont need to be faster, you need to be quicker, thats what gears do

 

Because either:
1. Your stock exhaust, pulies and frisbie weren't exhibiting a meaningful burden or...
2. Conditions at the track were inconsistent
3. Your driving was inconsistent from the 14.08 run to the 14.07 run.

What do your break outs look like? 60'? What RPM's were you shifting at?


We don't know WHAT he "needs", b/c we don't know all the data from his passes. If he's trapping 90 mph, he needs to be faster, too.

 

If you are in the midwest like me, the 95° air is costing you at least .10, maybe .20.

 

None of that is right.
1. The exhaust system has absolutely to ability to move the RPM at which tq occurs at. Cat back exhaust is NOT a tunning device. Certainly, the cat back isn't going to take away low end power, although it could allow for more upper RPM power, if the stock system was a restriction.
2. The (ECM) tune does not NEED to be tuned with every mod...ESPECIALLY mods that simply reduce load on the engine (such as UD pullies and "Frisbee" removals). Tunning the ECM can and often does optimize the combination, but it is FAR from "has to be", "to see progress at the track". I took a car from 170hp to about 300hp on the stock ECM/chip/tune, and you can bet that I absolutely saw "progress at the track". Over 2 seconds worth.
3. How do you "do tunes in the driveway"?? This is something that I'd like to see...

 

Post a time slip so we can take a look. I'm sure those 2.59 gears are not doing you any favors. The stock exhaust manifolds pretty much suck so it is hard to get results when you still have "pinch" points like that in a system...get some long tubes headers if you've got more $...you'll see 13's for sure.

 

You need to compare weather conditions, depending on when you ran the 14.08 and the 14.07 the weather conditions may have eliminated all of your gains. Two to three tenths of a second worth of varation can be caused by weather conditions. List the weather conditions when you ran the 14.08 and the 14.07 were they the same or even close?

The other reason could be that the changes you made were very limited, maybe the stock exhaust is not very restrictive at your power level so the change to dual exhaust added very little power.

 

60 foot and mph too.....

 

Ditch the 2.59 gears....

 

weather was similar.

60 foot 2.11
330 foot 5.9438
1/8 et 9.1010 @77.08
1000 foot 11.7577
1/4 14.0749 @100.28

 

fyi. i gained approx. 25 rwhp when i did full exhaust including headers. i also noticed a solid gain in mph and e.t.

more air in, and more air out makes power.

 

Where is the "before" time slip?? We need both! In this one, your ET to trap ratio isn't great but that is likely due to your gears. When I trap 100mph on 2.1x 60' time, I'm ET'ing in the 13.8 range and that is with 3.45 gear (LT1). No doubt that your gears are a barrier, but still, we can't very well compare w/o that "before" time slip.

 

Your times sound pretty good coming from a crossfire owner. You could try a few other bolt ons and you should be in the 13's with no problem. For best results a cam change is the best bang for the buck with a TPI engine. The mild zz9 cam works well. You should be low 13's with it.

 

We need to see the difference in Density Altitude (DA) between the 2 track outings as well.

Go here and select your track and the dates of the 2 track outings.

http://www.dragtimes.com/da-density-...calculator.php

Will

 

last night it was 79 degrees 62% humidity 29.83 BP

still lookin for the last time slip [got it somewhere] I'll look tonight,, but I know I ran 14.082 @98.04 temp 76 humidity 67% BP 30.18

I'll find the slip for the other times

Thanks to all for the advise !

 

There is some of it; 98.0 mph compared to 100.2 mph.

You ARE making more hp.

Just maybe not delivering it to the ground efficiently to get the ET you want.

 

How many miles are on the car? How has it been maintained?

2.59s suck. Too me it feels no different other than driving a 70's car with a 350 in it.
I'm pretty sure I seen a guy post his 92 with 2.59s is in the low 13s and basically stock.

Intake, Heads, Cam, Headers, Gears, tune, seems to be the cure.