STS pressure drop
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STS pressure drop Anyone else ever measure it? I've got a car on the dyno making 10psi at the manifold, 552rwhp and on the same run we measured 19psi at the turbo compressor housing. This is a standard system with no intercooler, no maf, tuned speed density.
Hmm.. thats' almost twice the psi at the turbo. So how are the guys running the base kit with the 5 psi waste gate spring referencing pressure right off the turbo getting also 5 psi at the manifold?
Originally Posted by 02Vortech
i run mine from the brake booster line on my truck. you got a bad leak some where. mine is only running 12.5 psi @ the compressor housing but 10 @ the intake manifold.
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Thanks but there is definitely not a boost leak. I pressurized the entire system from the turbo to the engine with a regulator and shop air. Not only that, but if boost was low at the engine due to a boost leak it would also measure low at the turbo compressor. The only way it is lower at the engine than the compressor outlet is pressure drop across the plumbing.
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Originally Posted by INTMD8
Thanks but there is definitely not a boost leak. I pressurized the entire system from the turbo to the engine with a regulator and shop air. Not only that, but if boost was low at the engine due to a boost leak it would also measure low at the turbo compressor. The only way it is lower at the engine than the compressor outlet is pressure drop across the plumbing.
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Pick a point about halfway between the turbo and the manifold, and insert a probe. That way you can start narrowing it down as to where the loss is occuring. Doesn't sound right. You would have to have a bunch of u-turns and tight 90-degree angles to get a 9psi loss.
Jim
Jim
That's strange. My LT1 doesn't have that problem. I set the regulator on the boost controller to 2 psi, so with the 5 psi wastegate spring I should get 7 psi at the compressor. I measure just under 7 psi at the manifold at WOT with my boost gauge.
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Originally Posted by engineermike
Subscribing. . . I always thought that long 2.5" pipe was going to cause a problem based on some testing I did with short 2.5" pieces.
The tubing on this car is 2.25in.
I read a magazine article and STS claims about a 3 Psi drop. I am about 2.5-3 with my front mount intercooler. Something not right! Where on the manifiold are you reference. I'm getting mine off the brake booster line. 8psi at the intake about 11.5 at the compressor cover
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Originally Posted by 2002ws-6
I read a magazine article and STS claims about a 3 Psi drop. I am about 2.5-3 with my front mount intercooler. Something not right! Where on the manifiold are you reference. I'm getting mine off the brake booster line. 8psi at the intake about 11.5 at the compressor cover
I'm curious what you would see for a pressure drop with another 112rwhp.
I'm running 2.5" tubing, and I have custom made every piece of my system. Its got no actual STS parts in it. Most of my pipes are straight, I'm running under the axle up to the FMIC where the inlet is on the driver side. The outlet comes up where the battery used to be, and from there its just one more turn into the throtle body. I 'm just guessing but I think I'll be a lot closer to 500 rwhp after my next dyno tune. I was bleeding off pressure cause of where my wastegate ref was coming from. While I was trying to figure out what was wrong I was checking my pressure. With the 7psi spring I was only getting about 5psi at the motor, Then I moved the wastegate ref to the intake and with all else = my boost jumped to 7.5. Thats was my math on how much pressure I was losing. 7.5-5=2.5 This may not be correct its my theory
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Originally Posted by Tiger2o69
Im going to say there is no way its because of the length of pipe.. I dont know what caused it but that's definitely not it..
Are you using the same gauge?
Are you using the same gauge?
Manifold pressure was measured by in-car boost gauge and 3-bar map sensor via HP tuners.
Compressor outlet pressure was measured with the shops Autometer gauge.
2002-ws-6 - Now compare your system to one that has a 2.25 charge pipe that goes over the axle (4 90's right there) on a car that makes 110+ more RWHP. Seems to me like a signifigantly higher pressure drop is not only reasonable, but expected.
Originally Posted by INTMD8
Isn't kind of hard to definitely rule something out when you don't have the answer?
Manifold pressure was measured by in-car boost gauge and 3-bar map sensor via HP tuners.
Compressor outlet pressure was measured with the shops Autometer gauge.
2002-ws-6 - Now compare your system to one that has a 2.25 charge pipe that goes over the axle (4 90's right there) on a car that makes 110+ more RWHP. Seems to me like a signifigantly higher pressure drop is not only reasonable, but expected.
Manifold pressure was measured by in-car boost gauge and 3-bar map sensor via HP tuners.
Compressor outlet pressure was measured with the shops Autometer gauge.
2002-ws-6 - Now compare your system to one that has a 2.25 charge pipe that goes over the axle (4 90's right there) on a car that makes 110+ more RWHP. Seems to me like a signifigantly higher pressure drop is not only reasonable, but expected.
If you used 2 different gauges that may be a problem.. I assume the front gauges is right but what about the rear gauge?
2002-ws-6 should have more of a pressure drop than you.. He has larger piping and a FMIC which causes a good bit of drop.. Also he has larger pipe.. Also the FMIC has several 90 bends.. Probably as many as your under the axles pipe.. I not sure where you see a significantly higher pressure drop? Only thing I see about your setup that may make you lose more pressure is the extra hp.. However I dont think thats it..
Also I have sts kit w/o fmic and im not losing that many psi.. I am only running 8 psi but at the turbo its 9......
Last edited by Tiger2o69; Mar 3, 2007 at 12:27 PM.
I'll take some measurments with a vacuum boost guage tool, and see what I actually run. Not what I figure with math. I also want to do a exhaust back pressure test to see what kind of pressure ratio I'm running. My guess is that if your compressor is at 19psi and you have a 2:1 ratio thats nearly 40psi and I'm betting the pressure ratio will be more like 2.5:1 thats nearly 50 psi. Thats a lot of pumping loss to make 50psi!!! just for 10psi intake?? To eliminate any other parts, is this a Stock STS? and what turbo? and sizes?
