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12-27-2017, 04:43 PM
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#1
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Name: Justinsixseven
Title: Green Behind the Ears
Status: Not Here
Join Date: Feb 2016
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Posts: 54
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Measuring drive pressure
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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12-27-2017, 05:37 PM
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#2
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Name: jasonc
Title: Too Much Time
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Join Date: Nov 2009
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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.
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12-27-2017, 05:50 PM
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#3
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Name: Justinsixseven
Title: Green Behind the Ears
Status: Not Here
Join Date: Feb 2016
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Posts: 54
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Quote:
Originally Posted by jasonc
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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12-27-2017, 06:05 PM
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#4
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Name: jasonc
Title: Too Much Time
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No worries at 32psi boost, plenty safe.
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12-27-2017, 06:17 PM
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#5
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Name: Justinsixseven
Title: Green Behind the Ears
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Quote:
Originally Posted by jasonc
No worries at 32psi boost, plenty safe.
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But what about under acceleration? It builds boost really fast
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12-27-2017, 06:34 PM
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#6
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Name: jasonc
Title: Too Much Time
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When you said 32 psi I assumed peak? What is the max pressure in over drive?
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12-27-2017, 06:42 PM
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#7
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Name: Justinsixseven
Title: Green Behind the Ears
Status: Not Here
Join Date: Feb 2016
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Posts: 54
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Measuring drive pressure
Quote:
Originally Posted by jasonc
When you said 32 psi I assumed peak? What is the max pressure in over drive?
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Where would I find max pressure in overdrive?
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Last edited by Justinsixseven; 12-27-2017 at 06:53 PM.
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12-27-2017, 06:55 PM
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#8
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Name: Justinsixseven
Title: Green Behind the Ears
Status: Not Here
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Also I can hit 28 psi with a 75% stab of the throttle from a 15 mph rolling start
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12-27-2017, 07:04 PM
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#9
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Name: Justinsixseven
Title: Green Behind the Ears
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Posts: 54
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Quote:
Originally Posted by blackmega3500
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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12-27-2017, 11:07 PM
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#10
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Name: JWhite
Title: Trained monkey
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Location: F Burg Ohio
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Posts: 1,817
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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.
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12-28-2017, 12:27 AM
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#11
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Name: Justinsixseven
Title: Green Behind the Ears
Status: Not Here
Join Date: Feb 2016
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Posts: 54
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Quote:
Originally Posted by JWhite
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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12-28-2017, 01:46 PM
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#12
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Name: JWhite
Title: Trained monkey
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Location: F Burg Ohio
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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.
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GMC with a LiLLY
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12-28-2017, 01:59 PM
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#13
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Name: Justinsixseven
Title: Green Behind the Ears
Status: Not Here
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Posts: 54
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Quote:
Originally Posted by JWhite
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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12-28-2017, 02:04 PM
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#14
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Name: JWhite
Title: Trained monkey
Status: Not Here
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Location: F Burg Ohio
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Quote:
Originally Posted by Justinsixseven
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.
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GMC with a LiLLY
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12-28-2017, 02:18 PM
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#15
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Name: Justinsixseven
Title: Green Behind the Ears
Status: Not Here
Join Date: Feb 2016
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Posts: 54
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Quote:
Originally Posted by JWhite
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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12-28-2017, 02:29 PM
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#16
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Name: YoungDiesel27
Title: Never Enough Time
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Join Date: Jul 2010
Location: West Virginia
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Quote:
Originally Posted by Justinsixseven
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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You can’t open them far enough to do that.
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EFI Live, HP Tuners, Smarty custom tuning
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12-28-2017, 02:37 PM
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#17
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Name: Justinsixseven
Title: Green Behind the Ears
Status: Not Here
Join Date: Feb 2016
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Posts: 54
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Quote:
Originally Posted by YoungDiesel27
You can’t open them far enough to do that.
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Actually now that I think about it you're right about that
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12-28-2017, 02:48 PM
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#18
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Name: Justinsixseven
Title: Green Behind the Ears
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I really wish I had the money to just ditch the vgt
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12-28-2017, 03:47 PM
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#19
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Name: JWhite
Title: Trained monkey
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Location: F Burg Ohio
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Posts: 1,817
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Quote:
Originally Posted by Justinsixseven
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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Even if you can keep it around 2:1 you won't hurt anything
__________________
GMC with a LiLLY
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12-28-2017, 03:49 PM
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#20
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Name: Justinsixseven
Title: Green Behind the Ears
Status: Not Here
Join Date: Feb 2016
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Posts: 54
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Quote:
Originally Posted by blackmega3500
Your over thinking it wayyyyyyy to much!
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Ah I know. Just trying to avoid learning the hard way with a blown HG
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