cyrus Posted July 13, 2005 Share Posted July 13, 2005 Hypothetical Question on Turbo Back Pressure Engine A, at sea level, makes 100 horsepower with 14.7 PSIG intake manifold boost (above atomspheric). At this conditon it has 20 PSIG exhaust before the turbo, and 5 PSI exhaust pressure after the turbo, then: 1. If the after turbo exhaust pressure was lowered 1 PSIG, how much will the exhaust pressure before the turbo decrease? 2. How much will the engines power increase? Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted July 13, 2005 Share Posted July 13, 2005 Are you making the assumption that the pre-turbo exhaust pressure is the same as the intake boost pressure? What is controlling the intake boost pressure? Quote Link to comment Share on other sites More sharing options...
cyrus Posted July 14, 2005 Author Share Posted July 14, 2005 I edited the question for clarity. Quote Link to comment Share on other sites More sharing options...
johnc Posted July 14, 2005 Share Posted July 14, 2005 42 Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted July 14, 2005 Share Posted July 14, 2005 I would say the answer to number 1 would depend on whether the intake boost was regulated to a constant value at the manifold. If it is, I would say you will retain a constant pressure across the turbine, so exhaust pressure would drop by 1 psi. There is not enough information to answer number 2. Since that is a WAG, I retain the right to be wrong. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted July 14, 2005 Share Posted July 14, 2005 42 If you don't understand the question, then how can you possibly expect to understand the answer? Quote Link to comment Share on other sites More sharing options...
Sean73 Posted July 18, 2005 Share Posted July 18, 2005 I'll take a stab at this. The exhaust manifold pressure represents the total back pressure of the exhaust system, including the turbine, dowpipe, cat, muffler, etc.. If you reduce the pressure after the turbine by 1 psi, then the exhaust manifold pressure also drops by 1 psi. Some power would be gained through better flow efficiency, less reversion, and cooler combustion chambers. The power gains would be difficult to predict because of all of the variables involved. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted July 18, 2005 Share Posted July 18, 2005 42LOL! Hitchhiker fan? Quote Link to comment Share on other sites More sharing options...
icewtr Posted July 19, 2005 Share Posted July 19, 2005 Well for the answer on dropping 1 lb of pressure in the downpipe side after the turbo there is no set answer as all turbo and engines are different and it will not make an even drop in pressure on the front side of the turbo i took off 9 lbs on the exhaust side of my 80 mm turbo setup on my 408 and the result was a drop of 19lbs of pressure before the housing and a climb from 8lbs of boost to 21 and needed another waste gate to contol the boost back to 8 Quote Link to comment Share on other sites More sharing options...
spork Posted July 20, 2005 Share Posted July 20, 2005 I'm definetly with John on this one 42... Quote Link to comment Share on other sites More sharing options...
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