L-92's w/ forced induction what's wrong?
The turbo could be the problem. If you're getting excessive back pressure it will cause you to lose tons of power. NA$TY-TA had a GT47-76 on his 370 and had major back pressure issues. He switched to a S88 and see below:
Originally Posted by NA$TY-TA
15 psi of boost.
10.80@126 mph.
Even adjusted more the car would not make more then 15 psi of Boost.
After some testing it was determined there was a huge amount of back pressure using this 76mm turbo with my 370ci motor.
10.80@126 mph.
Even adjusted more the car would not make more then 15 psi of Boost.
After some testing it was determined there was a huge amount of back pressure using this 76mm turbo with my 370ci motor.
Originally Posted by NA$TY-TA
23 JUL 2006
Some people dont think the above with a 76mm Turbo is true.....
but this below proves it.......
My shake down Passes
http://www.stenodperformance.com/kyle.wmv
S88 88mm Turbo was put in place of the GT42-76.
14 psi of Boost
1.474 60'
6.47 @ 107.89 1/8
10.07 @ 135.55 1/4
1 psi less boost then the GT42-76 passes and ran .7 tenths quicker @ 9 mph faster.....
2nd pass.... in the vid... it was the last pass..
tried 22 psi and spun the tires....
3rd pass... really 2nd pass of the day.
1.45 60'
6.055 @ 120.97 1/8
9.263 @ 150.50 1/4
Out of gear the last 150 ft.
Some people dont think the above with a 76mm Turbo is true.....
but this below proves it.......
My shake down Passes
http://www.stenodperformance.com/kyle.wmv
S88 88mm Turbo was put in place of the GT42-76.
14 psi of Boost
1.474 60'
6.47 @ 107.89 1/8
10.07 @ 135.55 1/4
1 psi less boost then the GT42-76 passes and ran .7 tenths quicker @ 9 mph faster.....
2nd pass.... in the vid... it was the last pass..
tried 22 psi and spun the tires....
3rd pass... really 2nd pass of the day.
1.45 60'
6.055 @ 120.97 1/8
9.263 @ 150.50 1/4
Out of gear the last 150 ft.
Originally Posted by M3 Muscle
Is that yank 3000 setup for a turbo? A turbo converter needs to be setup a good bit different than a N/A converter. Might be part of the problem.
TECH Enthusiast
Joined: May 2007
Posts: 538
Likes: 0
sounds like its time for 72pph low z injectors and a Bigstuff or similar system. Also that turbo is just way to small.
Yes a turbo thats to small will kill power.
Yes a turbo thats to small will kill power.
Originally Posted by phildo
I got pissed and pulled the waste gate hose off and let her eat while monitoring the afr. It made 15psi and started to lean out at 4200rpm. This was through full exhaust. My injectors are at 83% duty cycle at 4400rpm(mototron 60) with my meth kit(big nozzle 100% meth) Car felt o.k. I only reved it to 4500rpms. I have had alot of fast cars this felt like 450 to 500 rwhp. There was no tire spin! I am running a 4l80e,yank 3000 stall,and a 2:73 gear. This car is way down on power. I did notice the header wrap on the down pipe starting to burn or discolor. There is a big problem with it. My question is can the turbo be causing such a dramatic power loss alone or do I have a couple of issues?
Originally Posted by NA$TY-TA
As stated above.... measure the back pressure.....
how does the car load??? should come up on boost nice with those gears and converter....
Kyle
how does the car load??? should come up on boost nice with those gears and converter....
Kyle
Loads o.k. I give it 50% tps and it spools pretty fast.
Originally Posted by phildo
How are you gues measuring back pressure?
Loads o.k. I give it 50% tps and it spools pretty fast.
Loads o.k. I give it 50% tps and it spools pretty fast.
Wire a gauge into the exhaust.... i have spare O2 Bungs...
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Originally Posted by phildo
I have a 402 with Livernois stage 2 L-92's, 28cc dish pistons, Stock Gm multi-layer steal gaskets,l-76 intake, 76mm turbo .96ar exhaust housing, .600/.600 232/230 115+2. Is it the heads that are not performing? Did I figure out the compression wrong? Mis-matched cam? I am only running 6psi on it but it seems weak. It will not break the tires loose at 30mph. Just trying to use others experiences and knowledge to save some head aches. Thanks for any input.
Now I'd leave the cam alone it's plenty big and a swap to something a lot bigger won't be necessary for your goals.
Is that a T4 or T6 flange? If you can only fit a T6 flanged turbo, you might want to caucus the FI guys and see if they think a T4 80mm or 88mm is the ticket.
I'm running a completely different combo from yours, I'm running:
GT47.88 T6
348ci, 7.9:1
234/234/113
AllPro heads
A2A
LS2
90MM
4" DP
26 psi, C16, 20 degrees of timing, 867rwhp
T400, unlocked
I built my car to be friendly for the GLD True Street class, and I already had this shorty, though I might go up to a 370ci if I can run it in that class.
But focus on whether you ran out of turbo, and go from there.
Originally Posted by Pro Stock John
If I were you I'd cross-post this in the FI forum, but just from reading over the years I think you are out of turbo. When you run out of turbo, a few things happen. You end up trying to push more air through the turbo than it can handle, which leads to (a) backpressure and (b) heat. Ultimately if you keep pushing it too hard you can create engine issues. I've been told that you should look for compressor maps, but you should also measure the backpressure if you don't believe it. Anything over 2:1 is problematic.
Now I'd leave the cam alone it's plenty big and a swap to something a lot bigger won't be necessary for your goals.
Is that a T4 or T6 flange? If you can only fit a T6 flanged turbo, you might want to caucus the FI guys and see if they think a T4 80mm or 88mm is the ticket.
I'm running a completely different combo from yours, I'm running:
GT47.88 T6
348ci, 7.9:1
234/234/113
AllPro heads
A2A
LS2
90MM
4" DP
26 psi, C16, 20 degrees of timing, 867rwhp
T400, unlocked
I built my car to be friendly for the GLD True Street class, and I already had this shorty, though I might go up to a 370ci if I can run it in that class.
But focus on whether you ran out of turbo, and go from there.
Now I'd leave the cam alone it's plenty big and a swap to something a lot bigger won't be necessary for your goals.
Is that a T4 or T6 flange? If you can only fit a T6 flanged turbo, you might want to caucus the FI guys and see if they think a T4 80mm or 88mm is the ticket.
I'm running a completely different combo from yours, I'm running:
GT47.88 T6
348ci, 7.9:1
234/234/113
AllPro heads
A2A
LS2
90MM
4" DP
26 psi, C16, 20 degrees of timing, 867rwhp
T400, unlocked
I built my car to be friendly for the GLD True Street class, and I already had this shorty, though I might go up to a 370ci if I can run it in that class.
But focus on whether you ran out of turbo, and go from there.
I think I just need to suck it up and buy a turbo.
FormerVendor
Joined: Jan 2002
Posts: 173
Likes: 0
From: Mpls., MN
Phildo,
How has this car been tuned? Are you running the stock PCM? If you had it tuned using a wide band in the tail pipe, you will NOT be seeing the correct A/F ratio! Turbo cars consume a greater quantity of fuel to drive the compressor (turbo) and a large quantity of that fuel is burned in the exhaust system. Measuring A/F in the tail pipe allows time for ALL the fuel to burn and show an artificially rich reading. You should locate the wideband about 6" after the turbo outlet. Testing has consistantly shown proper readings of about 11.5:1 at the turbo will read as richer than 10:1 at the tailpipe. If you can't get a bung in the exhaust at the turbo, you need to throw fuel at it until it goes off the chart rich. Keep adding fuel until it quits making more power and even then add another 5%. Hope this helps.
How has this car been tuned? Are you running the stock PCM? If you had it tuned using a wide band in the tail pipe, you will NOT be seeing the correct A/F ratio! Turbo cars consume a greater quantity of fuel to drive the compressor (turbo) and a large quantity of that fuel is burned in the exhaust system. Measuring A/F in the tail pipe allows time for ALL the fuel to burn and show an artificially rich reading. You should locate the wideband about 6" after the turbo outlet. Testing has consistantly shown proper readings of about 11.5:1 at the turbo will read as richer than 10:1 at the tailpipe. If you can't get a bung in the exhaust at the turbo, you need to throw fuel at it until it goes off the chart rich. Keep adding fuel until it quits making more power and even then add another 5%. Hope this helps.
FormerVendor
Joined: Dec 2001
Posts: 2,444
Likes: 2
From: WWW.SPEEDINC.COM
Fwiw all of the turbo cars that I have tuned read within a half point from the downpipe to the tailpipe. (comparing BS3 wideband to dynojet)
On cars with open downpipes where the dynojet probe is near the BS3 wideband, they read less than half a point from each other.
On cars with open downpipes where the dynojet probe is near the BS3 wideband, they read less than half a point from each other.
Originally Posted by HTMtrSprt
Phildo,
How has this car been tuned? Are you running the stock PCM? If you had it tuned using a wide band in the tail pipe, you will NOT be seeing the correct A/F ratio! Turbo cars consume a greater quantity of fuel to drive the compressor (turbo) and a large quantity of that fuel is burned in the exhaust system. Measuring A/F in the tail pipe allows time for ALL the fuel to burn and show an artificially rich reading. You should locate the wideband about 6" after the turbo outlet. Testing has consistantly shown proper readings of about 11.5:1 at the turbo will read as richer than 10:1 at the tailpipe. If you can't get a bung in the exhaust at the turbo, you need to throw fuel at it until it goes off the chart rich. Keep adding fuel until it quits making more power and even then add another 5%. Hope this helps.
How has this car been tuned? Are you running the stock PCM? If you had it tuned using a wide band in the tail pipe, you will NOT be seeing the correct A/F ratio! Turbo cars consume a greater quantity of fuel to drive the compressor (turbo) and a large quantity of that fuel is burned in the exhaust system. Measuring A/F in the tail pipe allows time for ALL the fuel to burn and show an artificially rich reading. You should locate the wideband about 6" after the turbo outlet. Testing has consistantly shown proper readings of about 11.5:1 at the turbo will read as richer than 10:1 at the tailpipe. If you can't get a bung in the exhaust at the turbo, you need to throw fuel at it until it goes off the chart rich. Keep adding fuel until it quits making more power and even then add another 5%. Hope this helps.
Thanks
