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And does a gutted EBPV raise that number at all? Sorry, my search didnt find anything.
What PSI of boost does the stock turbo lose 1:1 drive pressure?
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I don't know about 1:1 but the max boost you want to run is 25psi.
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Yeah I know. The reason I am asking is because if the stock turbo is as non-efficient as everyone says, then my concern is that at 25psi of boost are you creeping up towards the 1:2 drive pressure range? Then that would be 50psi of boost pressure on your head gaskets......unless I am understanging drive pressure wrong.
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drive pressure will not be 50 pounds of boost on the head but will be 50 pounds on the valve springs. Boost in your engine (under your heads) will be what your gauge reads and drive pressure will be what leaves the exhaust valves.
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Hmmm, I read on one of the vendors websites that boost was the measurement in PSI that is built up before the intake valve waiting to enter the cylinder, and not a measurement of cylinder pressures. Drive pressure was the restriction, also measured in psi, between the combustion chamber and the outlet of the exhaust housing on the turbo.
Im not arguing, you could very well be right. I am not too familiar with this area of turbo diesel mechanics. Let me go back and reread some more.
Im not arguing, you could very well be right. I am not too familiar with this area of turbo diesel mechanics. Let me go back and reread some more.
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641 Posts
What I should have said is boost is what goes into your engine threw the intake valves and drive pressure is what comes out of your engine threw the exhaust valves.
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460 Posts
[ QUOTE ]
Yeah I know. The reason I am asking is because if the stock turbo is as non-efficient as everyone says, then my concern is that at 25psi of boost are you creeping up towards the 1:2 drive pressure range? Then that would be 50psi of boost pressure on your head gaskets......unless I am understanging drive pressure wrong.
[/ QUOTE ]
The "drive pressure" is the pressure in the exhaust side of the engine, between the exhaust valves and the turbine inlet. If you're making 25 psi of boost (on the intake side), and the drive pressure ratio is ~2:1, then your drive pressure would be expected to be around 50 psi (on the exhaust side).
The head gaskets aren't seeing the "drive pressure", their seeing combustion pressure.
Make sense??
Yeah I know. The reason I am asking is because if the stock turbo is as non-efficient as everyone says, then my concern is that at 25psi of boost are you creeping up towards the 1:2 drive pressure range? Then that would be 50psi of boost pressure on your head gaskets......unless I am understanging drive pressure wrong.
[/ QUOTE ]
The "drive pressure" is the pressure in the exhaust side of the engine, between the exhaust valves and the turbine inlet. If you're making 25 psi of boost (on the intake side), and the drive pressure ratio is ~2:1, then your drive pressure would be expected to be around 50 psi (on the exhaust side).
The head gaskets aren't seeing the "drive pressure", their seeing combustion pressure.
Make sense??
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63 Posts
Yes that does.....thanks.
Just so I am clear, the drive pressures take their toll on the turbine shaft then?.....and raise EGT's probably too?
**On EDIT....I think ive seen the truck in your sig running/smoking around Santee a few times.
Just so I am clear, the drive pressures take their toll on the turbine shaft then?.....and raise EGT's probably too?
**On EDIT....I think ive seen the truck in your sig running/smoking around Santee a few times.
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38 Posts
[ QUOTE ]
Yes that does.....thanks.
Just so I am clear, the drive pressures take their toll on the turbine shaft then?.....and raise EGT's probably too?
**On EDIT....I think ive seen the truck in your sig running/smoking around Santee a few times.
[/ QUOTE ]
Yes more or less. I've heard people claim that high drive pressures will take out head gaskets but they didn't have a good reason why. The stock turbo is NOT 2:1 Drive:boost ratio. It might reach that if you have some huge injectors and are trying to make big power with the stock turbo but that ratio is not constant through the range. It will be very close to 1:1 and sometimes even less than 1:1 in normal everyday driving in low to moderate throttle positions and light load situations. It won't start getting up there until you are WOT on a hard pull where you are trying to cram to much exhaust through the turbine housing. And yes excessive drive pressure will increase EGTs.
Yes that does.....thanks.
Just so I am clear, the drive pressures take their toll on the turbine shaft then?.....and raise EGT's probably too?
**On EDIT....I think ive seen the truck in your sig running/smoking around Santee a few times.
[/ QUOTE ]
Yes more or less. I've heard people claim that high drive pressures will take out head gaskets but they didn't have a good reason why. The stock turbo is NOT 2:1 Drive:boost ratio. It might reach that if you have some huge injectors and are trying to make big power with the stock turbo but that ratio is not constant through the range. It will be very close to 1:1 and sometimes even less than 1:1 in normal everyday driving in low to moderate throttle positions and light load situations. It won't start getting up there until you are WOT on a hard pull where you are trying to cram to much exhaust through the turbine housing. And yes excessive drive pressure will increase EGTs.
Joined
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857 Posts
[ QUOTE ]
[ QUOTE ]
Yes that does.....thanks.
Just so I am clear, the drive pressures take their toll on the turbine shaft then?.....and raise EGT's probably too?
**On EDIT....I think ive seen the truck in your sig running/smoking around Santee a few times.
[/ QUOTE ]
Yes more or less. I've heard people claim that high drive pressures will take out head gaskets but they didn't have a good reason why. The stock turbo is NOT 2:1 Drive:boost ratio. It might reach that if you have some huge injectors and are trying to make big power with the stock turbo but that ratio is not constant through the range. It will be very close to 1:1 and sometimes even less than 1:1 in normal everyday driving in low to moderate throttle positions and light load situations. It won't start getting up there until you are WOT on a hard pull where you are trying to cram to much exhaust through the turbine housing. And yes excessive drive pressure will increase EGTs.
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You're not completely accurate, atleast per most testing/posting in the last several years. Even oem sticks have given 2:1 drive pressure indications in the mid/upper flow range. It does vary somewhat, but the oem turbo is quite under rated for it's application. The bb turbo was seen to be around 1.5:1 and the h2e around 1:1. I believe these pressure delta's were in the upper 20's/lower 30's of boost. If you compare the maps, you'll see the differences in efficiency.
Along with drive pressures, timing and exhaust restriction are almost as deadly to turbo life, as well as proper cool down.
[ QUOTE ]
Yes that does.....thanks.
Just so I am clear, the drive pressures take their toll on the turbine shaft then?.....and raise EGT's probably too?
**On EDIT....I think ive seen the truck in your sig running/smoking around Santee a few times.
[/ QUOTE ]
Yes more or less. I've heard people claim that high drive pressures will take out head gaskets but they didn't have a good reason why. The stock turbo is NOT 2:1 Drive:boost ratio. It might reach that if you have some huge injectors and are trying to make big power with the stock turbo but that ratio is not constant through the range. It will be very close to 1:1 and sometimes even less than 1:1 in normal everyday driving in low to moderate throttle positions and light load situations. It won't start getting up there until you are WOT on a hard pull where you are trying to cram to much exhaust through the turbine housing. And yes excessive drive pressure will increase EGTs.
[/ QUOTE ]
You're not completely accurate, atleast per most testing/posting in the last several years. Even oem sticks have given 2:1 drive pressure indications in the mid/upper flow range. It does vary somewhat, but the oem turbo is quite under rated for it's application. The bb turbo was seen to be around 1.5:1 and the h2e around 1:1. I believe these pressure delta's were in the upper 20's/lower 30's of boost. If you compare the maps, you'll see the differences in efficiency.
Along with drive pressures, timing and exhaust restriction are almost as deadly to turbo life, as well as proper cool down.
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6,286 Posts
[ QUOTE ]
drive pressure will not be 50 pounds of boost on the head but will be 50 pounds on the valve springs. Boost in your engine (under your heads) will be what your gauge reads and drive pressure will be what leaves the exhaust valves.
[/ QUOTE ]But the area of a valve is 2.1 square inches. So 50 psi drive pressure is 105 pounds pressure on the valve springs which is nearing the limit that they will hold. 135 pounds IIRC. The aftermarket "rev" kits hold nearly 400 pounds per inch!
drive pressure will not be 50 pounds of boost on the head but will be 50 pounds on the valve springs. Boost in your engine (under your heads) will be what your gauge reads and drive pressure will be what leaves the exhaust valves.
[/ QUOTE ]But the area of a valve is 2.1 square inches. So 50 psi drive pressure is 105 pounds pressure on the valve springs which is nearing the limit that they will hold. 135 pounds IIRC. The aftermarket "rev" kits hold nearly 400 pounds per inch!
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38 Posts
[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
Yes that does.....thanks.
Just so I am clear, the drive pressures take their toll on the turbine shaft then?.....and raise EGT's probably too?
**On EDIT....I think ive seen the truck in your sig running/smoking around Santee a few times.
[/ QUOTE ]
Yes more or less. I've heard people claim that high drive pressures will take out head gaskets but they didn't have a good reason why. The stock turbo is NOT 2:1 Drive:boost ratio. It might reach that if you have some huge injectors and are trying to make big power with the stock turbo but that ratio is not constant through the range. It will be very close to 1:1 and sometimes even less than 1:1 in normal everyday driving in low to moderate throttle positions and light load situations. It won't start getting up there until you are WOT on a hard pull where you are trying to cram to much exhaust through the turbine housing. And yes excessive drive pressure will increase EGTs.
[/ QUOTE ]
You're not completely accurate, atleast per most testing/posting in the last several years. Even oem sticks have given 2:1 drive pressure indications in the mid/upper flow range. It does vary somewhat, but the oem turbo is quite under rated for it's application. The bb turbo was seen to be around 1.5:1 and the h2e around 1:1. I believe these pressure delta's were in the upper 20's/lower 30's of boost. If you compare the maps, you'll see the differences in efficiency.
Along with drive pressures, timing and exhaust restriction are almost as deadly to turbo life, as well as proper cool down.
[/ QUOTE ]
I'd like to see those testing numbers because I highly doubt they are accurate. With 175cc injectors on a nonwastegated housing on an early model with the stock turbo I've never seen close to 2:1 actually measured. Even with a smaller housing. And the drive didn't start going up substantially until around 30lbs of boost. A SD should be even less with the waste gate. If people are useing a scan tool they have to deduct about 14.7 psi because it reads in absolute pressure not gauge pressure. There are just to many people on here who post that a stock turbo is 2:1 and then everyone else just takes it as gospel without actually testing or knowing what they are talking about.
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[ QUOTE ]
Yes that does.....thanks.
Just so I am clear, the drive pressures take their toll on the turbine shaft then?.....and raise EGT's probably too?
**On EDIT....I think ive seen the truck in your sig running/smoking around Santee a few times.
[/ QUOTE ]
Yes more or less. I've heard people claim that high drive pressures will take out head gaskets but they didn't have a good reason why. The stock turbo is NOT 2:1 Drive:boost ratio. It might reach that if you have some huge injectors and are trying to make big power with the stock turbo but that ratio is not constant through the range. It will be very close to 1:1 and sometimes even less than 1:1 in normal everyday driving in low to moderate throttle positions and light load situations. It won't start getting up there until you are WOT on a hard pull where you are trying to cram to much exhaust through the turbine housing. And yes excessive drive pressure will increase EGTs.
[/ QUOTE ]
You're not completely accurate, atleast per most testing/posting in the last several years. Even oem sticks have given 2:1 drive pressure indications in the mid/upper flow range. It does vary somewhat, but the oem turbo is quite under rated for it's application. The bb turbo was seen to be around 1.5:1 and the h2e around 1:1. I believe these pressure delta's were in the upper 20's/lower 30's of boost. If you compare the maps, you'll see the differences in efficiency.
Along with drive pressures, timing and exhaust restriction are almost as deadly to turbo life, as well as proper cool down.
[/ QUOTE ]
I'd like to see those testing numbers because I highly doubt they are accurate. With 175cc injectors on a nonwastegated housing on an early model with the stock turbo I've never seen close to 2:1 actually measured. Even with a smaller housing. And the drive didn't start going up substantially until around 30lbs of boost. A SD should be even less with the waste gate. If people are useing a scan tool they have to deduct about 14.7 psi because it reads in absolute pressure not gauge pressure. There are just to many people on here who post that a stock turbo is 2:1 and then everyone else just takes it as gospel without actually testing or knowing what they are talking about.
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857 Posts
I don't have anything saved to show you. My reference was refering to testing back about 3-4 yrs ago IIRC. I think dieselsite might have had some intel, but I think there was more discussed prior to Bob selling the H2e kits. I'll keep an eye out for some related data.
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38 Posts
Yeah saying the stock turbo is 2:1 would make for good advertizing if you were trying to push a 1:1 turbo neither of which is there such a thing.
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460 Posts
[ QUOTE ]
**On EDIT....I think ive seen the truck in your sig running/smoking around Santee a few times.
[/ QUOTE ]
Smoking? ME?? Why...I wouldn't hear of such a thing!
LOL /ubbthreads/images/graemlins/wink.gif
Well, okay...maybe on occasion...
**On EDIT....I think ive seen the truck in your sig running/smoking around Santee a few times.
[/ QUOTE ]
Smoking? ME?? Why...I wouldn't hear of such a thing!
LOL /ubbthreads/images/graemlins/wink.gif
Well, okay...maybe on occasion...
Joined
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534 Posts
Too high drive pressure does not pop head gaskets, it will float valves if you don't have higher rate valve springs. The valves float into the piston and you bend pushrods, valves, and rockers.
Cylinder pressures during the power stroke is what will pop a head gasket . . . the pressure at this point is much greater than 50psi, this is where timing comes into play, too soon an injection will drive the cylinder pressures up and pop head gaskets and frag rods.
Cylinder pressures during the power stroke is what will pop a head gasket . . . the pressure at this point is much greater than 50psi, this is where timing comes into play, too soon an injection will drive the cylinder pressures up and pop head gaskets and frag rods.
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1,881 Posts
[ QUOTE ]
Yeah saying the stock turbo is 2:1 would make for good advertizing if you were trying to push a 1:1 turbo neither of which is there such a thing.
[/ QUOTE ]
I have all the measurements, and do many others. The stock turbo at times can have more than double drive pressure to boost-its not something made up. The results have been posted here many times-do a search.
Yeah saying the stock turbo is 2:1 would make for good advertizing if you were trying to push a 1:1 turbo neither of which is there such a thing.
[/ QUOTE ]
I have all the measurements, and do many others. The stock turbo at times can have more than double drive pressure to boost-its not something made up. The results have been posted here many times-do a search.
[ QUOTE ]
[ QUOTE ]
Yes that does.....thanks.
Just so I am clear, the drive pressures take their toll on the turbine shaft then?.....and raise EGT's probably too?
**On EDIT....I think ive seen the truck in your sig running/smoking around Santee a few times.
[/ QUOTE ]
Yes more or less. <font color="red"> I've heard people claim that high drive pressures will take out head gaskets but they didn't have a good reason why.</font> The stock turbo is NOT 2:1 Drive:boost ratio. It might reach that if you have some huge injectors and are trying to make big power with the stock turbo but that ratio is not constant through the range. It will be very close to 1:1 and sometimes even less than 1:1 in normal everyday driving in low to moderate throttle positions and light load situations. It won't start getting up there until you are WOT on a hard pull where you are trying to cram to much exhaust through the turbine housing. And yes excessive drive pressure will increase EGTs.
[/ QUOTE ]
Excessive drive pressure will increase cylinder tempratures thus causeing early ignition. This advance in ignition will spike cylinder pressures and raise the heads.
[ QUOTE ]
Yes that does.....thanks.
Just so I am clear, the drive pressures take their toll on the turbine shaft then?.....and raise EGT's probably too?
**On EDIT....I think ive seen the truck in your sig running/smoking around Santee a few times.
[/ QUOTE ]
Yes more or less. <font color="red"> I've heard people claim that high drive pressures will take out head gaskets but they didn't have a good reason why.</font> The stock turbo is NOT 2:1 Drive:boost ratio. It might reach that if you have some huge injectors and are trying to make big power with the stock turbo but that ratio is not constant through the range. It will be very close to 1:1 and sometimes even less than 1:1 in normal everyday driving in low to moderate throttle positions and light load situations. It won't start getting up there until you are WOT on a hard pull where you are trying to cram to much exhaust through the turbine housing. And yes excessive drive pressure will increase EGTs.
[/ QUOTE ]
Excessive drive pressure will increase cylinder tempratures thus causeing early ignition. This advance in ignition will spike cylinder pressures and raise the heads.
Joined
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38 Posts
[ QUOTE ]
[ QUOTE ]
Yeah saying the stock turbo is 2:1 would make for good advertizing if you were trying to push a 1:1 turbo neither of which is there such a thing.
[/ QUOTE ]
I have all the measurements, and do many others. The stock turbo at times can have more than double drive pressure to boost-its not something made up. The results have been posted here many times-do a search.
[/ QUOTE ]
At what boost levels? I'm sure there is a point that it would get there but I highly doubt at anywhere between 25 and 30 psi. If you are running 35+psi then I wouldn't doubt it but at that point you obviously need a bigger turbo anyway. The point I was trying to make is there is no such thing as a 2:1 or 1:1 turbo. They will all be at either ratio depending on what you are doing with them and how you have them set up.
[ QUOTE ]
Yeah saying the stock turbo is 2:1 would make for good advertizing if you were trying to push a 1:1 turbo neither of which is there such a thing.
[/ QUOTE ]
I have all the measurements, and do many others. The stock turbo at times can have more than double drive pressure to boost-its not something made up. The results have been posted here many times-do a search.
[/ QUOTE ]
At what boost levels? I'm sure there is a point that it would get there but I highly doubt at anywhere between 25 and 30 psi. If you are running 35+psi then I wouldn't doubt it but at that point you obviously need a bigger turbo anyway. The point I was trying to make is there is no such thing as a 2:1 or 1:1 turbo. They will all be at either ratio depending on what you are doing with them and how you have them set up.
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38 Posts
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Too high drive pressure does not pop head gaskets, it will float valves if you don't have higher rate valve springs. The valves float into the piston and you bend pushrods, valves, and rockers.
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That's why I asked them to give me an explanation why it does pop head gaskets but they couldn't give me a good one. I personally don't really see how it would pop head gaskets either. Mech's explanation sounds reasonable but how much can the timeing really be advanced by the heat? The injection process doens't start any sooner and I would think there would have to be some HUGE increase in EGTs to make it advance that much.
Too high drive pressure does not pop head gaskets, it will float valves if you don't have higher rate valve springs. The valves float into the piston and you bend pushrods, valves, and rockers.
[/ QUOTE ]
That's why I asked them to give me an explanation why it does pop head gaskets but they couldn't give me a good one. I personally don't really see how it would pop head gaskets either. Mech's explanation sounds reasonable but how much can the timeing really be advanced by the heat? The injection process doens't start any sooner and I would think there would have to be some HUGE increase in EGTs to make it advance that much.
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