disapointing sts dyno #'s
Thread Starter
Joined: Sep 2004
Posts: 4,904
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From: Stockbridge GA
disapointing sts dyno #'s 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.
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
John
Last edited by 99SS-T; Jun 6, 2005 at 11:15 PM. Reason: opps
Thread Starter
Joined: Sep 2004
Posts: 4,904
Likes: 906
From: Stockbridge GA
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.
Originally Posted by ZL1Killa
11.5 is kind of rich i would think....i haven't messed with forced induction yet tho
11.5 is a good a/f for a turbo car. I run my car at 11.0-11.2 for extra safety.
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Originally Posted by Zombie
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.
11.5 is a good a/f for a turbo car. I run my car at 11.0-11.2 for extra safety.
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On The Tree
Joined: May 2003
Posts: 151
Likes: 0
From: Gastonia,NC
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.
12 Second Truck Club
Joined: Feb 2002
Posts: 5,574
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From: Sacramento, CA
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
#s look decent though. Just wait till you get it fixed. You'll be happy
nice numbers and you have an easy fix dont stress.good luck 
Thread Starter
Joined: Sep 2004
Posts: 4,904
Likes: 906
From: Stockbridge GA
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.
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
-Geoff
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
Clint
Thread Starter
Joined: Sep 2004
Posts: 4,904
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From: Stockbridge GA
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.