Back pressure test results, when is it too much?
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Back pressure test results, when is it too much? Ok so I made a real nice piece to install in an exhaust bung I welded in right before the flange to the turbo. I hooked it up to a boost gauge and did some street testing.
Comp 80/79 t4 on a 1.32ar
9.5 compression 370
Stock ported 241 heads
Stock ls6 intake and tb
232 236 115lsa 609ish lift cam
4 inch k&n right on turbo
Large ebay ic with 3 inch piping
9lbs intake, 20lbs exhaust
14lbs intake, 30lbs exhaust
Tried 18lbs intake but boost gauge only goes to 30. Id say it was at least 35 probably 40lbs back pressure.
Now I'm running a good size ar with a 3.5 dp. I think this is high but then again I bet everyone with a t4 has to be right around the same.
Is this something to worry about?
Alex
Comp 80/79 t4 on a 1.32ar
9.5 compression 370
Stock ported 241 heads
Stock ls6 intake and tb
232 236 115lsa 609ish lift cam
4 inch k&n right on turbo
Large ebay ic with 3 inch piping
9lbs intake, 20lbs exhaust
14lbs intake, 30lbs exhaust
Tried 18lbs intake but boost gauge only goes to 30. Id say it was at least 35 probably 40lbs back pressure.
Now I'm running a good size ar with a 3.5 dp. I think this is high but then again I bet everyone with a t4 has to be right around the same.
Is this something to worry about?
Alex
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From: Norn Iron
2:1 certainly isnt good. But on a low boost setup provided that pressure ratio offers fast spool, then wouldnt worry too much
However if it is laggy and with 2:1, something is wrong. It certainly isnt the d/p size.
I'd be much happier around 1.5:1 EGBP pre turbine vs Intake pressure
However if it is laggy and with 2:1, something is wrong. It certainly isnt the d/p size.
I'd be much happier around 1.5:1 EGBP pre turbine vs Intake pressure
FormerVendor
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From: WWW.SPEEDINC.COM
It's nothing to 'worry' about, and those numbers are pretty normal for a single T4 on a 370.
Also consider that for every PSI lost to the cold side is another pound of backpressure. (You can reduce exhaust backpressure by increasing cold side efficiency as the engine doesn't need to drive the turbine as hard).
It goes without saying that you could pick up a ton of power/rpm with twins or a good T6 based single.
Also consider that for every PSI lost to the cold side is another pound of backpressure. (You can reduce exhaust backpressure by increasing cold side efficiency as the engine doesn't need to drive the turbine as hard).
It goes without saying that you could pick up a ton of power/rpm with twins or a good T6 based single.
It's nothing to 'worry' about, and those numbers are pretty normal for a single T4 on a 370.
Also consider that for every PSI lost to the cold side is another pound of backpressure. (You can reduce exhaust backpressure by increasing cold side efficiency as the engine doesn't need to drive the turbine as hard).
It goes without saying that you could pick up a ton of power/rpm with twins or a good T6 based single.
Also consider that for every PSI lost to the cold side is another pound of backpressure. (You can reduce exhaust backpressure by increasing cold side efficiency as the engine doesn't need to drive the turbine as hard).
It goes without saying that you could pick up a ton of power/rpm with twins or a good T6 based single.
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Thread Starter
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From: Northwest side of Chicago
Jim, I'm going to look into getting a better quality IC and correct the way the cold side is routed to it. I have a harsh 90 on both sides going to the IC.
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From: Norn Iron
I would try and aim for 1.5 or less. But again it is very dependant on spool and power delivery.
I'd sacrifice some for a fast spooling setup at the expense of a little power. Or if you wanted ultimate power at higher rpm's you'd sacrifice some spool to achieve the lower pressure with a better flowing turbine.
I'd sacrifice some for a fast spooling setup at the expense of a little power. Or if you wanted ultimate power at higher rpm's you'd sacrifice some spool to achieve the lower pressure with a better flowing turbine.
Staging Lane
Joined: Jul 2006
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From: F22 Secret Lair (aka) The "Austin Millbarge"
In my opinion you should've measured back pressure downstream (at the downpipe), to get a better overall view of how effecient the turbo/exhaust system is as a whole. High pressures upstream is not as detrimental to performance as it is downstream. In fact higher pressures in the header helps turbo performance more than it hurts. Look at what a quick spool valve does and how much higher it raises perssure, yet improves spool-up.
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From: Norn Iron
