How much boost is too much with an otherwise stock 1993 6.5?
Diesel Fan
Joined: Oct 2012
Posts: 30
Likes: 0
From: The Catskills, NY
I wouldn't recommend running 20psi on a older, higher mileage gm 6.5 motor. With a amg motor or the new p400, 20psi should be just fine.
your better of uprgrading then trying to force more out of what your working with. better to be safe then sorry. 
Diesel Fan
Joined: Dec 2012
Posts: 47
Likes: 1
From: san clemente ca
How can you not have to much boost
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Oh ok great thanks guys
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Do you think 15psi is to much for the engine?
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I have 163000 on my truck
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Oh ok great thanks guys
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Do you think 15psi is to much for the engine?
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I have 163000 on my truck
Last edited by dom1505; Dec 21, 2012 at 12:14 PM. Reason: Automerged Doublepost
Diesel Fan
Joined: Oct 2012
Posts: 30
Likes: 0
From: The Catskills, NY
Running 15psi through a larger freer flowing turbo will be just fine.
Diesel Enthusiast
Joined: Jan 2009
Posts: 240
Likes: 24
Often more boost is just hot air
You obviously don't know much about the 6.5, for starters the stock CR is 21:1 +/- a few tenths depending on yr , plus the configuration of the head clamping does not lend itself to more boost than what OEM set the turbo to be able to produce. 6.5s can take on more boost but not necessary for most and not until the engine has been set up for it, and bolting on a bigger turbo or hogging down the waste-gate for more boost on the factory turbo is not wise until you KNOW the health of the engine.
To the OP, more boost is tolerable for the 6.5, 12 psi is upper limit IMO especially with GM turbo without some sort of aftercooling; but boost without extra fuel is pretty much a waste in effort especially with the GM turbo as above say 10 psi the drive pressure required redards engines abilites, and overworks/overheats the engine ie 20 psi boost = 40psi in backpressure to get that much boost with the GM turbo.
A bettter turbo & IMO the best is the ATT for simplicity of install and better boost within GM design constraint, to whit I'm capable of 100mph with just 10psi boost and fuel programming modifications, not required in your mechanical IP but the mech IP can not match performance of an electronic ip (trade off electronic ip has more parts to go wrong)
You obviously don't know much about the 6.5, for starters the stock CR is 21:1 +/- a few tenths depending on yr , plus the configuration of the head clamping does not lend itself to more boost than what OEM set the turbo to be able to produce. 6.5s can take on more boost but not necessary for most and not until the engine has been set up for it, and bolting on a bigger turbo or hogging down the waste-gate for more boost on the factory turbo is not wise until you KNOW the health of the engine.
To the OP, more boost is tolerable for the 6.5, 12 psi is upper limit IMO especially with GM turbo without some sort of aftercooling; but boost without extra fuel is pretty much a waste in effort especially with the GM turbo as above say 10 psi the drive pressure required redards engines abilites, and overworks/overheats the engine ie 20 psi boost = 40psi in backpressure to get that much boost with the GM turbo.
A bettter turbo & IMO the best is the ATT for simplicity of install and better boost within GM design constraint, to whit I'm capable of 100mph with just 10psi boost and fuel programming modifications, not required in your mechanical IP but the mech IP can not match performance of an electronic ip (trade off electronic ip has more parts to go wrong)
Often more boost is just hot air
You obviously don't know much about the 6.5, for starters the stock CR is 21:1 +/- a few tenths depending on yr , plus the configuration of the head clamping does not lend itself to more boost than what OEM set the turbo to be able to produce. 6.5s can take on more boost but not necessary for most and not until the engine has been set up for it, and bolting on a bigger turbo or hogging down the waste-gate for more boost on the factory turbo is not wise until you KNOW the health of the engine.
To the OP, more boost is tolerable for the 6.5, 12 psi is upper limit IMO especially with GM turbo without some sort of aftercooling; but boost without extra fuel is pretty much a waste in effort especially with the GM turbo as above say 10 psi the drive pressure required redards engines abilites, and overworks/overheats the engine ie 20 psi boost = 40psi in backpressure to get that much boost with the GM turbo.
A bettter turbo & IMO the best is the ATT for simplicity of install and better boost within GM design constraint, to whit I'm capable of 100mph with just 10psi boost and fuel programming modifications, not required in your mechanical IP but the mech IP can not match performance of an electronic ip (trade off electronic ip has more parts to go wrong)
You obviously don't know much about the 6.5, for starters the stock CR is 21:1 +/- a few tenths depending on yr , plus the configuration of the head clamping does not lend itself to more boost than what OEM set the turbo to be able to produce. 6.5s can take on more boost but not necessary for most and not until the engine has been set up for it, and bolting on a bigger turbo or hogging down the waste-gate for more boost on the factory turbo is not wise until you KNOW the health of the engine.
To the OP, more boost is tolerable for the 6.5, 12 psi is upper limit IMO especially with GM turbo without some sort of aftercooling; but boost without extra fuel is pretty much a waste in effort especially with the GM turbo as above say 10 psi the drive pressure required redards engines abilites, and overworks/overheats the engine ie 20 psi boost = 40psi in backpressure to get that much boost with the GM turbo.
A bettter turbo & IMO the best is the ATT for simplicity of install and better boost within GM design constraint, to whit I'm capable of 100mph with just 10psi boost and fuel programming modifications, not required in your mechanical IP but the mech IP can not match performance of an electronic ip (trade off electronic ip has more parts to go wrong)
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