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#1
07-04-2008, 04:41 PM
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Exhaust back pressure
I finally decided to measure the exhaust back pressure of the stock exhaust system. I believe it is the same for all 617 123s, but just for reference, this is a 300TD. I didn't have a good gauge around for this measurement but I tried my 60 psi gauge just to see what would happen. I have a pyro in the down pipe just after the turbo. I removed that and inserted a pressure tap. I measured zero pressure up to about 3000 rpm full throttle. Then at as the rpm increased, the pressure climbed and maxed out at about 4-5 psi. I don't know what RPM because I was too busy watching the gauge. Anyway, there does seem to be a significant back pressure at higher rpm. Anyone else ever make a measurement? I would like to compare my observations to others.
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For Sale: 1982 MB 300TD 1995 Chevrolet Suburban 6.5TD Sold: 1980 IH Scout Traveler- Nissan SD33T Diesel 
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#2
07-04-2008, 04:45 PM
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I am going to guess that I have 0.0psi of back pressure at any rpms....as I have a 2.5" straight pipe from the turbo to the back bumper.
  My dad's SD has the stock (ANSA) exhaust on it, and it is noticeably more lethargic feeling than mine.......my turbo spools up way faster and I have better high end power output.
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-diesel is not just a fuel, its a way of life-  '15 GLK250 Bluetec 118k - mine - (OC-123,800) '17 Metris(VITO!) - 37k - wifes (OC-41k) '09 Sprinter 3500 Winnebago View - 62k (OC - 67k) '13 ML350 Bluetec - 95k - dad's (OC-98k) '01 SL500 - 103k(km) - dad's (OC-110,000km) '16 E400 4matic Sedan - 148k - Brothers (OC-155k)
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#3
07-04-2008, 05:35 PM
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The stock turbo is much more restrictive and inefficient than the exhaust.
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#4
07-04-2008, 10:20 PM
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I am planning on ditching the stock turbo, but I am still chasing down this smoke demon, and would like to get it back to stock performance levels before improving. I don't really think that the exhaust is the culprit, but I thought I'd check it out. I don't think that 4 psi is insignificant either.
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For Sale: 1982 MB 300TD 1995 Chevrolet Suburban 6.5TD Sold: 1980 IH Scout Traveler- Nissan SD33T Diesel
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#5
07-05-2008, 06:51 AM
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I don't know what is normal but I would have guessed less than that.
Tom W
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual. [SIGPIC]..I also have a 427 Cobra replica with an aluminum chassis.
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