Drive pressures with a VGT swap?

2002nightmare

2002nightmare

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Jul 1, 2011
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I just completed swapping an HE351 onto my '01 using a 6.7 manifold and an '06 downpipe. Only driven the truck a couple times since and I've been afraid to push it too hard because of the drive pressure horror stories. Has anyone running a VP truck with the VGT swap measured drive pressure? And is it as horrible as you hear? I am in the process of hooking up a gauge, but I'm kind of anticipating higher than I'd like pressures. Looking towards an WG once I've confirmed such pressures. I'm using the Fleece controller so I may have some tuning ability to eleviate some of the issue.
 
I have the fleece controler on my vgt on my 01 and u can drop the drive pressure down if u want, i first thought i had a drive pressure gauge hooked up and was seeing 65+ psi and after about 5k miles the filter broke off the maniflod and found out it was boost!

But if u run it around 40psi i wouldnt think u would have a problem with drive pressure. I got a gauge setting here to go on for drive but havent got it put on yet.

Mine runs good at 50+ psi though, and i love how this thing lites down low, i love the set up so far hope i havent done any damage to the charger but it doesnt seem to have!
 
What injectors are you running? That's my next step is to step up to 150s but not before I know what drive pressure is now. I love how the truck runs with this turbo and it's still using the stock tuning from Fleece. I just want to keep this turbo and my headgasket while running it as efficiently as possible.
 
I ran the stock injector that had 150k on them while braking the engine in and the turbo was still impressive if u keep it on the tight side, but after adding the 150's and another box it is a different truck.

I can hit 60 psi down low in the rmp's and it has great torg, im hopping this new 6 speed i got off another member on hear likes it while rolling into it in 6's going up a hill.

But if u dont have studs i wouldnt tighten it up alot with bigger injectors, if i had to guess i have had this thing passed 100psi drive pressure and it lived.

Puis ask me if i was going to take it to the twilght zone and i told him yes!
 
From what I saw with drive vs. boost that turbo likes about 15-20 PSI more drive than boost pressure. If I ran it under that towing heavy (20K+) the EGT's got toasty quick. With no load on the truck it could be run much looser and do very well.
 
Got my drive gauge hooked up this pasted weekend and got a few readings, in high gear going up a steep hill i crossed my figures as i rolled into it and cranked the housing tight after the charger started to light and the gauge spiked way past my 100psi that i have to go by!lol My prediction was right, the best i could figure it was close to 118ish.

Then last night i took the truck out again and it will hit 100psi if i have the tst cranked up on a higher setting down low with the dial probley at 8 percent of the 20percent that u can change on the fly (before 1500rmp) love how this thing lights! And there was once i caught both boost and drive (55-80). Runs good around there!

This is all factory software on the contoler, and i found out the controler with it set where the housing is fully open the boost and drive is close to one an another up to around 25psi after that the drive has the bigger number. At 30psi i think the drive was around 42ish but i maybe wrong.

There has been a few that said this 351's have a low flowing exhaust housing for a high performance ap, and i think they maybe right but i still think u could make more than 650hp with this charger as a compound with out gating around it, but maybe wrong (it would be a fun 650) on the street i think!

And i really like this new ultra light auto meter gauge (the lates one) that is LED, looks great in the dark!
 
ouch, you pegged a 100psi gauge on drive pressure?? At 30 psi boost you are already at 42 psi drive? That is a 1:1.4 ratio, already getting high.
 
Yea it will not see 100psi much if i can help it but i was testing what it would do, like i said i think it was 42psi of drive and 30psi of boost with the housing fully open but the housing may not have been fully open!

Will have to try it in a little while and report back to make sure, i had some more readings but i may have them misted up if i tell them, like one it was 52-69.

I need to have someone with me to help watch the gauges and write this stuff down, had a friend with me when i had my fingers crossed but i told him to watch the inches of water colum gauge and he said it when to 15 so i may need a little bigger air filter also!
 
on a 6.7 the boost and drive are the same 1 to 1 at 24lb. at 32lb of boost the drive pressure is about 60 lb. i dont know how much different this would be on a vp truck.
 
diesel pap said:
on a 6.7 the boost and drive are the same 1 to 1 at 24lb. at 32lb of boost the drive pressure is about 60 lb. i dont know how much different this would be on a vp truck.
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Not that much, the turbo just needs lots more drive pressure than boost, it's how it seems to work.
 
I would assume that tuning it to replicate the 6.7 pressures would be ideal, maybe slightly decreased drive pressure to reduce parasitic loss. The VP trucks should have a better head gasket than the 6.7, being that it's thicker, so it should handle the drive pressure. I have my gauge hooked up, and as soon as my valve cover is back from powdercoating, I'll be able to see what it's like and mess with the controller a little bit.
 
I had modified the tuning on the controller following another users maps before I had a drive pressure gauge which was ran a little more open than the stock tuning, and keeping in mind I still have stock injectors (Smarty level 8, Comp level 5:5), the drive pressure seems to not be astronomical. It stays about 1:1 up to 17-19psi and then gradually climbs to a 25 psi boost 32 psi drive and from there ramps a little more to 40 psi boost 60 psi drive. It seems I need to start with the VGT closed more, more drive on low end and open it up more at higher RPM.
 
Yeah sounds like it. Might take a while to tune it in. Not sure about that head gasket part though. 6.7s use a MLS gasket.
 
I have it set pretty well now. Smoke is controllable, EGT's are kept in check, and drive pressure is never above 1.3:1 at worst. It's still a little laggy with low to mid throttle when it shifts into O/D but I've never liked how soon it shifts into O/D anyways so I usually use the button to hold it off a little longer. Other than that, it's sure fun to drive! I'm just a short road trip away from Fleece, so I think when it gets a little nicer out, I'm gonna head down there.
 
diesel pap said:
on a 6.7 the boost and drive are the same 1 to 1 at 24lb. at 32lb of boost the drive pressure is about 60 lb. i dont know how much different this would be on a vp truck.
Click to expand...

Above ~36 psi my old 351ve felt like it was hitting a wall of drive pressure, never measured it though...
 
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