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Still runs sucky.. no top end pull! any suggestions?

926 views 15 replies 11 participants last post by  Thunder5.0 
#1 ·
Ok, took the car to LaSota racing last fall to have them dyno tune it. Car put 484/559 to the tires. Very pleased!! So it got parked for the fall, and took it to the strip in the last few weeks. Ran a whopping 11.8 :eeek:

Slips all very similiar, from 11.8's to 12.0's

60 ft 1.7's
1/8 et 7.6's to 7.7's
1/8 mph 93 to 94-5
1/4 et 11.8's to 12.0's
1/4 mph 114-115 mph

I did not change anything from the dyno tune, lol. I took it apart and found a few little boost leaks, fixed those, and ran the exact same way tonight. Even added two degrees of timing, same exact thing. Will not run faster than 115 mph. Not picking up enough on the back end!!!

Thought's? Suggestions?? questions??? Pulling my hair out here :pain:

Will
 
#5 ·
Should be closer to 123 in the top end from everything I'm seeing.

It straight out FALLS on its face into 4th. Even some other guys with boosted cars there noticed it at the big end. Boost is there and a/f looks good but it is an older wideband. Gonna try the basics since it's due (plugs, wires) first and see what happens. Then back to the track to see if it helped, lol
 
#6 ·
IDK, it seems to me that maybe you are asking too much from a mild combo. 484hp is a lot, but it isn't going to change the world. How much do you weigh? SN95's are a bit heavier than a fox. You may be just experiencing the size of the car. Maybe you should try some 3.55's. A bit more gear for the heavier car

Chris
 
#7 · (Edited)
i have the exact same turbo and kit you have. Do you have the .81 AR? I have it on my 347 and it really chokes my motor up above 4500 RPMS. Maybe you need to goto a .96 or upgrade the turbo alltogether. On my heavy 95 with my old procharger I could trap 120 mph with like 480hp/500tq to the wheel. With this turbo I doubt I would get that much mph.
 
#9 ·
That mph is low for sure with those numbers.

Again, what are your plugs gapped at? Check the continuity of all of your plug wires.

Are you running an auto or manual tranny?
 
#11 ·
With 480 at the tires and even more torque....you should be doing A LOT more than 115 mph.

maybe go make another pull on the dyno and make sure the numbers are still the same?

I'm around 450/450 and go 126 in the 1/4....
 
#12 ·
I might just try going back to the dyno again, and see if something has happened.

Plugs are Autolite 3923's gapped at .028"

I just replaced them, and cap and rotor since it was due. I'll see if that helps at the track next weekend. Plugs LOOKED ok, but I had just driven to work, not ran the crap out of it at the track so thats deceiving. Wires test ok cold.

I haven't done anything with the fuel. It's just regular 93 octane on low timing (16, i put it to 18, no change)

Trans is t-56 w/ 3.27's. Spec Stage 2 clutch


I'll try it at the track again, and if it's still the same. I'll do a leakdown test first. I'll try all the free stuff before spending money, lol
 
#13 ·
Are you sure the clutch isn't slipping?

FYI, I run 24* total @ 8psi. With those heads your timing is waaaay too conservative. Hell, most people running stock iron heads and 8-10psi are running 18* total.
 
#14 ·
what tires are you running. as stated, with your fat assed sn95 put a 3.55 gear in it. you have the uber fancy t56 so dont be afraid. you have that nice 6th gear we are all jealous of. i had 3.55 changed to 3.27 for on day at the track and went back to 3.55. i do not have enough power for the 3.27 to make them work where i need them to. im only pushing 600+ based on weight and trap of 135mph

whats your a/f though the run ? any logs ?
 
#15 ·
Millhouse- I'm not smelling any clutch, and the rpm's don't seem to be climing quicker than normal, but that doesn't mean it's not.

I know the timing is conservative, but w/ that power from the dyno, even on low timing, I'd think it should still run out better than it does?

Baer- Tires are M/T ET streets. I launched fairly soft (3700) on the 2 step, so I might try coming out of the hole at like 5k as some suggested.

I know my car is a little overweight, so that might be the final thing to try after everything else is done. Although shifting into 4th puts me in a pretty good spot RPM wise at the top end.

A/F WOT are 11.5- 11.8 according to the wideband. I'm not hearing any detonation, and the plugs did not show evidence of detonation either.

Will
 
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