Why no VNT turbo discussion?

[deerefanatic]

Hi all. I'm somewhat new amongst the 6.5 diesel enthusiasts circle, but I am not new to diesels in general. Most of my knowledge is centered on the OM617 3.0L I-5 Turbo diesel made by Mercedes through the 70's and 80's.....

It is common practice as a performance mod to outfit the VNT turbos off of the new Sprinters to these benz motors.... As the VNT allows boost to build practically at an idle, while have less restriction at high revs than even the stock turbo....

How come nobody's tried putting the GT37 VNT off of the ford 6.0L powerstroke on a GM 6.5? That would be a good sized turbo, that could build our measily 10psi of boost almost instantly, while having almost no appreciable back pressure at higher rpms...... Shouldn't be hard to control one as most VNT's are vacuum actuated, just like the GM4 is....

Just a thought I had....

[njdevi11]

First I'll start off by explaining with A VNT Turbo does. Basically the geometry of the turbo changes such that it will produce higher boost at lower speed and then when the engine is up to speed it changes back to allow normal operation.

I have no experience with these turbo's, (hell i have limited experience with normal turbo's) I don't know how difficult it would be to regulate the turbo and what kind of electronics/actuators are required. One limiting factor for these 6.2/6.5 engines is the minimal amount of boost they can use, 12 psi is about the limit. What do the benz's run at? What are they're compression ratios?

All I have to say is show me where I can get a VNT turbo for a reasonable price and I'll throw it on my rig. If were talking $1000-$1500 for a conversion then you might as well just go out and get a d-max or a cummins.

[deerefanatic]

The Benzes run about 11psi of boost stock.... Compression ratio is 21:1 if I remember correctly..

The advantage of a VNT is yes, quick boost build..... I understand the theory very well.....

Actually, Garret GT37 VNT's off the Ford 6.0L can be had for less than $500 from junkyards quite often.... And they have a much larger A/R turbine size than the GM4, so when the vanes are opened up, the restriction will be WAYYY less on the motor......

[njdevi11]

Found a turbo off a sprinter on ebay at $40 and a turbo for a 6.0 at $300. It looks like there will be a significant amount of custom fab to get one of those on a 6.5 because the compressor intake/output and the turbine input/exhaust. Dont even come close to matching up with the 6.5's manifolds.

I dont even have my rig operational yet and im having a hard time saying no to more upgrades.

What controls the vanes on the turbo? Is it electronic? Is it boost regulated, engine tach regulated, turbo tach regulated?

[deerefanatic]

Sprinter turbo is WAYY too small...... They, actually, are even a bit small for the benz 3L....

Yah, the 6.0L VNT uses V-bands for both inlet and oulet..... GT37's (not from Fords) are available with standard rectangular flanges..

VNT vanes can be controlled a variety of ways..... For instance, vacuum, electronic, or oil-pressure control......

IF the VNT was designed for vacuum, then you can use it as-is, or remove the vacuum actuator and put a pressure actuator in its place... Same for electronic, though you'd have to make a custom actuator bracket. Some are oil operated with a special electronically operated oil valve... Those take a little more effort.. :)