faster at 75% throttle

tbird420

Registered User
Hi,
I have 1990 5 speed SC with a bunch of bolt on mods done 3.5 intake, 76mass air, 85 TB, MP inlet plentium, 95 super charger, 10% over drive, under drive pullys, AC delete, power steering delete, custom front mount inter cooler, MP sc top, 36 pound fuel injectors with the matching sampling tube, upgraded fuel pump 255LPH, midlength headers, custom exaust, 93 gas tank, 327 rear gears, light weight fly wheel and up graded clutch. There is probably more but thats all that comes to me right now. So my problem is that after 75% throttle, it feels like it loses power I even think it might be worse in the lower RPM's - it can barely even squeek the tires in second which it never had a problem with before. I have replaced all my vacuum lines, made my spark plug gaps a bit smaller, new belts and upgraded tensioner springs. So, am I just desperately in need of a tune or chip or is there something wrong with my car? The last thing I want to do is bring my car to get dyno tuned to find out it is not even running right. My older buddy from work was thinking it needs a tune and he mentioned open loop and closed loop affecting it but not sure. There are no check engine lights. Any help would be very apprecited. Sorry for the long post.
Thx
 
Different injectors, different maf, smaller pulley. You'll need a tune. At least strap it to a dyno and get your AFR. You could be running lean and losing power or running rich and losing power. You'll never know without a wideband.
 
classic lean issue...you need a wideband Air/Fuel gauge to see what you are running at WOT and then most likely you will need a tune and I would invest in 42lb injectors minimum
 
I had the same problem when the list of bolt on's for my car became quite long. Scratched my head & thought "It was supposed to go faster, not slower" I thought I had wasted all my $$. Turns out, I just needed a tune. The difference was night & day. It was like I had just picked up a new car! Sideways in second & hanging with the Cobra's on the freeway.

I don't by any parts now w/o a plan. And they won't be installed unless I'm ready for the whole system to work together with a new tune every time. If it wasn't for the Super Coupe professors around St. Louis, I'd still be wasting my money. (thx guys)

Get a tune. I think that's your problem.
 
Yeah, get bigger injectors and MAF. You setup is not very well thought out. The 76mm MAF is choking the supercharger and the injectors are TOOOOOO small.

My suggestion, no less than 42lbs injectors though I think something over 50lbs would be better. Get a 85mm MAF and follow it up with tuning. Till then keep out of the throttle.
 
I disagree with the bigger maf...I have a fully built engine with MPx and I run the 76mm MAF no problem...
Dave says 76 is fine, but bigger would be better. not needed though.
 
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