Drive pressure VS. Boost pressure - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 7 (permalink) Old 01-28-2012, 05:52 AM Thread Starter
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Drive pressure VS. Boost pressure

I put a DP (drive pressure (exhaust back pressure)) gauge on my a while back and noticed the DP was about 10-15% lower then the BP (Boost Pressure). then I have a 60 psi BP gauge and a 100 PSI DP gauge. I though maybe the 100 psi gauge was not accurate.

So today I put a 60 psi DP gauge on and drove my truck around, and at no time could I make the DP go higher then the Boost pressure. At 30 psi of boost pulling A hill the DP was at about 28-29 psi.

Could my turbo be this efficient? I have a s362/12cm with the 2 waste gate ports, 12" of 3.5" to 5' straight back, a 1350 Air filter, 13.2* timing.

I ported out the exhaust housing pretty good on the turbo, the head has a little porting done to it.

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post #2 of 7 (permalink) Old 02-09-2012, 02:18 AM
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You can get a positive drive pressure. On the cr dodges it can go really negative at high boost and rpm. My 97 dodge I had would do 33 psi and only hit 1200 on the pyro but that was up hills. Check out your fuel pressure I had to put on new lift pump and overflow valve. Get a Tork technology overflow valve. It is amazing how the truck will run with correct fuel pressure.

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post #3 of 7 (permalink) Old 02-10-2012, 04:25 PM
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I have the gauges in the dash for BP when I put the motor back in it will be hooked up and will post what it is.

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post #4 of 7 (permalink) Old 12-19-2013, 12:00 AM
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Old thread, but its definitely something that can be tied into head flow! Opened another view of how flow is in a turbocharged engine for me anyhow.

Anyone come up with answer to the problem?

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post #5 of 7 (permalink) Old 01-27-2014, 03:12 AM
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Originally Posted by Fahlin Racing View Post
Old thread, but its definitely something that can be tied into head flow! Opened another view of how flow is in a turbocharged engine for me anyhow.

Anyone come up with answer to the problem?
I will take a silly wild guess, as back pressure to boost ratio increases flow is reduced.
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post #6 of 7 (permalink) Old 02-02-2014, 03:01 PM
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Yes, increase in pressure usually means we are seeing some sort of flow slowing down. I can't put it into words right now but I have something else still brewing in what options that may be apparent.

Could we size a turbo to the capability of the CSA on the exhaust side and maybe see an efficiency difference? hoping in the positive direction any ways. Of course many many variables in the mix.

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post #7 of 7 (permalink) Old 02-02-2014, 05:54 PM
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Exhaust back preasure is measured in inches of Mercury on most every OEM spec sheet, anything above 3.2 inches of mercury is above spec.
The preasure is taken after the turbo.
Turbo drive preasure, is less than the boost, it can create because there is a difference in volume of air hot air expands.
Just a thought!

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