Measuring drive pressure

J

Justinsixseven

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I'm wanting to know if I'm putting too much turbo into my tunes. Is there a way to measure drive pressure without paying $120+ for a gauge? I'm running a max of 32 psi but I'm more worried about drive pressure at acceleration and cruise range. Just wondering if there is a tell-tale sign that there's too much boost at the wrong time. On a 60 Hp tune I haven't seen EGT's get past 850* under WOT but I haven't towed with it yet so not sure what it will be. Also I'm on a stock VGT with stock head bolts.


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Just run a copper gauge line and tap it in to your ex manifold. Leave the copper line as long as possible and make a coil out of it to cool it down as much as possible. Then just a cheap mechanical pressure gauge.

It will become clogged over time if ran non stop, but works fine if you are tuning. Then just pull the line and plug the manifold till you need it again.
 
jasonc said:
Just run a copper gauge line and tap it in to your ex manifold. Leave the copper line as long as possible and make a coil out of it to cool it down as much as possible. Then just a cheap mechanical pressure gauge.



It will become clogged over time if ran non stop, but works fine if you are tuning. Then just pull the line and plug the manifold till you need it again.
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That makes sense. What is an acceptable drive to boost ratio


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When you said 32 psi I assumed peak? What is the max pressure in over drive?
 
Also I can hit 28 psi with a 75% stab of the throttle from a 15 mph rolling start


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Don't waste your money,and just save for head studs and ditch the vgt. The stock 6.7 under full load on the exhaust brake is capable of upwards of 80-90psi drive pressure.
 
blackmega3500 said:
Don't waste your money,and just save for head studs and ditch the vgt. The stock 6.7 under full load on the exhaust brake is capable of upwards of 80-90psi drive pressure.
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I'm thinking of doing a 2nd gen swap but for now am I anywhere close to that amount of drive pressure


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Should be able to watch the EBP sensor on a data log. IIRC Cummins has the limit on a stock tune setup for ~550kpa or 80psi during turbine braking.

Try opening the vgt position up and see if the boost stays where it is. If so, then you had it clamped down too tight. You don't need a lot of drive pressure to make boost, but it's hard not to with the stock vgt.
 
JWhite said:
Should be able to watch the EBP sensor on a data log. IIRC Cummins has the limit on a stock tune setup for ~550kpa or 80psi during turbine braking.

Try opening the vgt position up and see if the boost stays where it is. If so, then you had it clamped down too tight. You don't need a lot of drive pressure to make boost, but it's hard not to with the stock vgt.
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So the point where the vgt is as open as possible but still making the same amount of boost is where it should be?


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IMO yes. A lot of vgt's will make the most power when the nozzle / vanes are close to all the way open (on the top end), it'll depend on how much fuel is being injected too. You'll still need some drive pressure down low to get things going, that's what makes it fun to drive.
 
JWhite said:
IMO yes. A lot of vgt's will make the most power when the nozzle / vanes are close to all the way open (on the top end), it'll depend on how much fuel is being injected too. You'll still need some drive pressure down low to get things going, that's what makes it fun to drive.
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True! I'm just worried about too much drive pressure at the wrong time. Wouldn't it make the truck lug a bit if there's too much back pressure?


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Justinsixseven said:
True! I'm just worried about too much drive pressure at the wrong time. Wouldn't it make the truck lug a bit if there's too much back pressure?


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Yes you can choke it off per say. There's always a fine line between good spool up, but low enough drive pressure to keep decent mpg.
 
JWhite said:
Yes you can choke it off per say. There's always a fine line between good spool up, but low enough drive pressure to keep decent mpg.
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Makes sense. I'm gonna put together a DP gauge. Will tuning the vgt to keep the drive pressure close to 1:1 get me in the sweet spot so to say


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