Need help from EXPERTS
Thread Starter
Racer
Joined: Jul 2008
Posts: 273
Likes: 2
Need help from EXPERTS
Hi,
I have a problem in my C5 TT. I need someone who can diagnose this issue in the engine. I can't reach the required boost?! I did engine compression test and boost bleed
everything was fine!! I increased the boost to 30 psi, but I couldn't see from that only 11 psi of boost
??!!
What is the problem? No sounds in the engine nothing is wrong with it!!!
Engine spec:
427 CID
LQ9 Iron block
LS3 ported heads 245cc
LS3 intake
Garrett Turbos 76mm T3T4
compressor wheel 70
inducer 76
.63 A/R
cam spec:
Intake Duration: 235@.050
Exhaust Duration: 242@.050
Intake lift:.603"
Exhaust lift:.608"
LSA:114
I have a problem in my C5 TT. I need someone who can diagnose this issue in the engine. I can't reach the required boost?! I did engine compression test and boost bleed
everything was fine!! I increased the boost to 30 psi, but I couldn't see from that only 11 psi of boost??!!What is the problem? No sounds in the engine nothing is wrong with it!!!
Engine spec:
427 CID
LQ9 Iron block
LS3 ported heads 245cc
LS3 intake
Garrett Turbos 76mm T3T4
compressor wheel 70
inducer 76
.63 A/R
cam spec:
Intake Duration: 235@.050
Exhaust Duration: 242@.050
Intake lift:.603"
Exhaust lift:.608"
LSA:114
Safety Car
Joined: Dec 2009
Posts: 4,754
Likes: 303
I mean a leak down cylinder test. A friends supra had this issue where the boost wouldn't go over a certain level and he had a bad cylinder.
Or maybe it was boost increased but power stayed the exact same...
That'd be a pretty obscure reason, just popped into my head looking at your displacement out of a lq9 and the wear or blowby potential of that setup
Or maybe it was boost increased but power stayed the exact same...
That'd be a pretty obscure reason, just popped into my head looking at your displacement out of a lq9 and the wear or blowby potential of that setup
Last edited by turbotuner20v; Jan 4, 2013 at 02:11 PM.
Drifting
Joined: Feb 2006
Posts: 1,585
Likes: 15
From: New Hartford IA
I'd be carefull with a 6.0 iron 427 since the pistons are so thin. If you have external wastgates check what springs are in them as said above. If you are using a low pressure spring (say 6 psi) and try to hit 20 psi the back pressure in the turbine housing can push the wastgate open. Backpressure can be higher then boost pressure+spring pressure (forces holding the gate closed), etc.
Last edited by slow ride; Jan 4, 2013 at 03:26 PM.
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Thread Starter
Racer
Joined: Jul 2008
Posts: 273
Likes: 2
I mean a leak down cylinder test. A friends supra had this issue where the boost wouldn't go over a certain level and he had a bad cylinder.
Or maybe it was boost increased but power stayed the exact same...
That'd be a pretty obscure reason, just popped into my head looking at your displacement out of a lq9 and the wear or blowby potential of that setup
Or maybe it was boost increased but power stayed the exact same...
That'd be a pretty obscure reason, just popped into my head looking at your displacement out of a lq9 and the wear or blowby potential of that setup
Thread Starter
Racer
Joined: Jul 2008
Posts: 273
Likes: 2
No, I haven't, but I did that from the boost control to increase the boost level to the max. I didn't do anything to the car after this test. sometime I hear misfire when I push much on the peddle!!
Last edited by lingenfelter200; Jan 4, 2013 at 10:54 PM.
Advanced
Joined: Jun 2011
Posts: 92
Likes: 0
What wastegate springs are in there? As a rule of the thumb you can only get about double to boost of the rated boost of this spring maximum, even with boost controller on full boost.
So if you have a 6psi spring you will only be able to achieve ~12psi..
So for 30psi you need AT LEAST a 15psi spring and that´s at 100% duty cycle of the boost solenoid or even directly connected hose from compressor housing.
What is your base boost w/o any boost controller hooked up to the WG at all?
Let us know then we can maybe rule that out or find it the root cause.
Gerd
So if you have a 6psi spring you will only be able to achieve ~12psi..
So for 30psi you need AT LEAST a 15psi spring and that´s at 100% duty cycle of the boost solenoid or even directly connected hose from compressor housing.
What is your base boost w/o any boost controller hooked up to the WG at all?
Let us know then we can maybe rule that out or find it the root cause.
Gerd