why such a big diff in boost?
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why such a big diff in boost?
Alright guys don't eat me alive here but I do not understand this. My buddy that I shoot with has a 24 valve cummins with 90 over injectors and up grade Turbo (don't know which one) and is Smarty tuned. He tells me he sees 72 psi of boost HOW IN THE WORLD IS THERE SUCH A BIG DIFFERENCE? I know my truck is not set up for anything like that kind of boost such as injectors, Turbo, head studs, and other supporting mods but the beat boost I have seen was like 28 psi and i was really giving it HELL....but my point is even if i did have the upgraded parts I still do not think I would ever see that kind of boost. I know some one will say that boost doesn't mean more horse power and stuff like that, but what does it mean I have not been able to full comprehend why more boost is better? But can someone please explain why the cummins motors seem to produce more boost than ours do? Thanks everyone.
Hotshot
Joined: Jan 2011
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From: Puget Sound
More boost in means you can add more fuel and it will burn instead of smoke. It brings up the compression stroke pressure, which means more heat to ignite the fuel better.
28 PSI max? That's about where I'm at, the boost jumps to 27-28 and hangs there until I crawl back out of the throttle. I'm satisfied with that because it's cheaper than the alternative.
72 PSI? Tell him the boost sensor is not supposed to be on the exhaust side, it's probably melted and reading wrong. Other than that, I'd be looking for solid proof before I bought into any boost gauge that said that. The intercooler would have real issues trying to cool down 72 PSI enough to not melt plastic unter the hood. Remember, the exhaust out has to pump that up - and that means the exhaust side could be sneaking up on 80-85 PSI, depending on the turbo design. EGTs would warm right up with a buried foot. If somebody were able to coax that much boost out of a turbo, they would know precisely how they did it - because it wasn't an accident and it costs a bundle. I'd ask him how he did it, and his reaction will yield some impressive hardware, or be unrecognizable techno-babble, or he'll just say "I dunno, my mechanic did it".
I envision a scenario where somebody put a different face in the boost gauge, or he has an air compressor on the surpentine belt and it's connected to the biggest boost gauge he could find.
28 PSI max? That's about where I'm at, the boost jumps to 27-28 and hangs there until I crawl back out of the throttle. I'm satisfied with that because it's cheaper than the alternative.
72 PSI? Tell him the boost sensor is not supposed to be on the exhaust side, it's probably melted and reading wrong. Other than that, I'd be looking for solid proof before I bought into any boost gauge that said that. The intercooler would have real issues trying to cool down 72 PSI enough to not melt plastic unter the hood. Remember, the exhaust out has to pump that up - and that means the exhaust side could be sneaking up on 80-85 PSI, depending on the turbo design. EGTs would warm right up with a buried foot. If somebody were able to coax that much boost out of a turbo, they would know precisely how they did it - because it wasn't an accident and it costs a bundle. I'd ask him how he did it, and his reaction will yield some impressive hardware, or be unrecognizable techno-babble, or he'll just say "I dunno, my mechanic did it".
I envision a scenario where somebody put a different face in the boost gauge, or he has an air compressor on the surpentine belt and it's connected to the biggest boost gauge he could find.
Postmaster
Joined: Jul 2006
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From: Bend, OR
You cant make more boost then add more fuel, its the other way around.
Hotshot
Joined: Jan 2011
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From: Puget Sound
If your vehicle has a capacity for more boost, you can have bigger sticks and add more fuel to the tune without getting unburned fuel and smoke.
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This is coming from a good buddy of mine that I shoot archery professional with....he is a very knowledgeable guy and I respect his word. But when I first heard it I was in disbelief. So what your saying is that if he had the boost gauge hooked up on the exhaust side that then he could be seeing these boost numbers? And if it is hooked up on the exhaust side does that mean it is wrong?.......Thanks guys I just want to get to the bottom of all this cummins is better than powerstroke thing......ALL MY BUDDYS LIVE AND DIE CUMMINS........my uncle and I are the only smart ones haha..
Fleet Mechanic
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From: Marseilles IL
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Postmaster
Joined: Jul 2006
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From: Bend, OR
This is coming from a good buddy of mine that I shoot archery professional with....he is a very knowledgeable guy and I respect his word. But when I first heard it I was in disbelief. So what your saying is that if he had the boost gauge hooked up on the exhaust side that then he could be seeing these boost numbers? And if it is hooked up on the exhaust side does that mean it is wrong?.......Thanks guys I just want to get to the bottom of all this cummins is better than powerstroke thing......ALL MY BUDDYS LIVE AND DIE CUMMINS........my uncle and I are the only smart ones haha..
Dont care how much you trust your buddy, if he says he is making 72# boost with only 90hp injectors then he is FOS. Not enough fuel there to make those boost numbers, short of maybe a set of compounds.
Cargo Master
Joined: Jul 2011
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From: Walpole, MA
Exhaust side of the turbo is called Exhaust Back Pressure or Drive pressure. It is NOT boost, but the worker that creates boost.
Dont care how much you trust your buddy, if he says he is making 72# boost with only 90hp injectors then he is FOS. Not enough fuel there to make those boost numbers, short of maybe a set of compounds.
Dont care how much you trust your buddy, if he says he is making 72# boost with only 90hp injectors then he is FOS. Not enough fuel there to make those boost numbers, short of maybe a set of compounds.
Even with a set of compounds on that truck there is no way he could make that much boost off 90 horse injectors...please tell me he is not running the stock POS dodge lift pump either...cause if so he is most certainly pulling fuel pressure below 10 psi and his VP44 is on borrowed time.
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Exhaust side of the turbo is called Exhaust Back Pressure or Drive pressure. It is NOT boost, but the worker that creates boost.
Dont care how much you trust your buddy, if he says he is making 72# boost with only 90hp injectors then he is FOS. Not enough fuel there to make those boost numbers, short of maybe a set of compounds.
Yes... I run 60psi boost gauges in my truck, I have 100 psi one's as well. I have 180psi air pressure gauges that with a slight tweak in the programing would react as a boost gauge as well.
Dont care how much you trust your buddy, if he says he is making 72# boost with only 90hp injectors then he is FOS. Not enough fuel there to make those boost numbers, short of maybe a set of compounds.
Yes... I run 60psi boost gauges in my truck, I have 100 psi one's as well. I have 180psi air pressure gauges that with a slight tweak in the programing would react as a boost gauge as well.
Cargo Master
Joined: Jul 2011
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From: Walpole, MA
Man Good lookin gauge set up..........Eventually I would like to move mine up on the pillar, currently they are mounted on the dash behind steering wheel can be hard to see sometimes......but back on subject.......So basically from what I understand is with his truck only having 90 over injectors there is no possible way he could get 72 psi of boost? But it is accomplish-able with bigger up graded parts?
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