gametech

iTrader: (1)

Finally got to the dyno today, and at about 4300rpm my torque curve takes a nosedive. Peak results were 449HP/530TQ. The curve gets really choppy as it drops, so I think I may be blowing out the spark and/or getting valve float. I did not hear any valve float, though. I have NGK TR6 plugs gapped at .35, but I think I might need to close that down to .28 or.30. The dyno was a dynojet and the air temp in the shop was 98 degrees with high humidity from a full day of rain. The GTO pulls great with all that torque, but I have to figure out why it drops so fast. The HP starts dropping at 5k rpm.

99SS-T

iTrader: (5)

I had sameexact issue. I have the phamspeed kit. My main problem was plugs and wires. That made it alot better but it stil had alot of hesitation over 5k. Changed the pushrods and valvesprings and all better. I doubt that you are blowing out the spark as that seems to be the gap that most FI peeps run. GL mate



John

gametech

iTrader: (1)

What kind of power did your kit make? BTW, I'm running 10#'s of boost with fairly conservative timimg and 11.5/1 AF ratio. And I was already planning to throw on some comp 918's and hardened pushrods. The only reason I dynoed the car today was that my friend took his '70 vette with a shafiroff 434 in to see what it made since we put a holley stealthram FI unit in place of the carb and super victor intake. He forgot some paperwork, and when I drove the GTO there to bring him the paprework, the shop owner wanted to see what power the sts kit makes since he had never dynoed one.

Ferocity02

iTrader: (60)

Most likely valve float if the power drops and it gets wavy.

KissMySSo1

iTrader: (2)

valve springs 100%

ZL1Killa

iTrader: (17)

11.5 is kind of rich i would think....i haven't messed with forced induction yet tho

Zombie

iTrader: (2)

stop thinking
11.5 is a good a/f for a turbo car. I run my car at 11.0-11.2 for extra safety.

LSs1Power

iTrader: (5)

I agree... Im running 11's AF all the way to 6000 RPM then down to high 10s for extra safety. Of course running 12's AF will lead to more power, but im not willing to risk the engine blowing up after heating too much from road racing.

snkchrmr

My buddies TA was doing the same thing yours is, we thought it was the valve springs so we changed them. Took it back and it was still doing it. Well we finally found that it was some exhaust leaks. fixed those and whalaa problem solved. Before with springs and PR on 10# it made 437/456, after the exhaust was fixed it made 470/515.

PurEvl

iTrader: (2)

valve float is most likely it, also the gap may be a little too much

F8L Z71

You probably sould have titled this something different. People assume there was a problem with the STS kit when in reality there is a problem with your car

#s look decent though. Just wait till you get it fixed. You'll be happy

ddnspider

iTrader: (26)

there IS a problem with the STS kit...the Turbo is at the wrong end of the car! nice numbers and you have an easy fix dont stress.good luck

CHRISPY

Close the gap, check for leaks and put in a set of springs. Should make a BIG difference

Which turbo did you go with?

gametech

iTrader: (1)

I went with the gt67 turbo. I'm not really stressing over it, because I was actually planning to do springs, pushrods, and maybe rocker arms before dynoing it. I originally gapped the plugs at .35 because I didn't expect to go over 5 or 6#'s of boost, but 10#'s seemed like a nice round number. I'm sure that taking care of the valvetrain and closing the plug gaps will probably clear up the problem. BTW, I didn't mean for the title of the post to be misleading.

White_Hawk

iTrader: (3)

Go find a load bearing dyno (like a Mustang). On a dynojet it is very hard to get a consistent load on a turbo car. Once the thing loads up at peak torque, it starts dropping right off.

-Geoff

gametech

iTrader: (1)

It wasn't just the dyno, the power falls off on the street, too.

HUGGER ORANGE SS

iTrader: (2)

It's not the Gap in the Plugs.. .035" is fine.. There's another problem there.. Most likely Mechanical, like valve float, or possible bad lifter. Something in the valvetrain.. Also check your Volumemetric Eff Tables.. A Screw up in there for the tune will result in strange A/F ratios at higher rpms and cause a power loss...

Clint

CHRISPY

Are you running a stock shortblock?

gametech

iTrader: (1)

Yep, stock shortblock. I can't justify the expense of building a forged stroker while this motor is still good. If it blows, there's my excuse for the new engine.