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Old 07-27-2006, 07:23 PM
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How to measure backpressure on turbo motor?

Quote:
7 psi: 590 hp at 5500 rpm, 650 ftlb at 4200
10 psi: 690 hp at 5400 rpm, 770 ftlb at 4200
12 psi: 770 hp at 5500 rpm, 785 ftlb at 4200
14 psi: 800 hp at 5500 rpm, 906 ftlb at 4500
15 psi: 860 hp at 5300 rpm, 930 ftlb at 4700
18 psi: 929 hp at 5400 rpm, 1049 ftlb at 4500
?? psi: 929 hp at 4600 rpm, 1070 ftlb at 4500 (backfired and run aborted)

At 14 psi boost, backpressure was 22 psi. At 18 psi boost, backpressure was 26 psi.
That is a quote from another thread... those are numbers from a 377 with a turbo and blow-thru carb setup.

Anyways, how do you measure backpressure on a motor? I've never heard of that before.

Thanks,
Sean

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Old 07-28-2006, 07:15 AM
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If you are referring to the driving pressure of the turbo as backpressure, you would measure it the same as you would the boost pressure.
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Old 07-28-2006, 07:32 AM
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Oh cool so just tap into the exhaust manifold before the turbo? Won't the hot air ruin any gauge hooked up to it though? Or are there special gauges for this?

Thanks,
Sean
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Old 07-28-2006, 05:53 PM
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I know they sell a nifty lil setup that screws into the o2 sensor bung. So maybe you could modify that a lil and use it.
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Old 07-30-2006, 06:40 PM
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that chart is intake boost pressure, with some exhaust back pressure readings noted.

Backpressure should be inconsequential if your turbo is sized correctly.

It is only AFTER the turbo in the exhaust pipe that you should look into backpressure.
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Old 07-31-2006, 10:48 PM
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Use a length of metal tubing between the exhaust pipe and the gauge. The hot gas doesn't really flow through the tube very far, so the metal will dissipate the heat.
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