DIYEFI.org Forum

Here are a couple of pics of the inside of the actuator for the VGT mechanism as supplied by a kind HMT member :




I thought some of you might find that interesting. According to a quick google, the nozzle area is between 9 and 25 cm^2. Using this turbo in place of the one I have would free up top end significantly, but shouldn't affect spool at all (positively or negatively).

Fred.

Place holder for more pictures if I should manage to get hold of some.

was this turbo designed for diesel? if so, it probably won't last on gasoline

Not like you to be cynical Alex :-)

Have you heard of Inconel? It's used on both. EGT's aren't all that much different. (yes, I know you mean the VGT aspect)

More pics :












And a vacuum activated variety (HE431VTI) :






Enjoy :-)

Fred.

Fred wrote:Not like you to be cynical Alex

Have you heard of Inconel? It's used on both. EGT's aren't all that much different. (yes, I know you mean the VGT aspect)

not cynical at all, just prudent
from what i read, production gasoline powered cars don't get VGT turbos precisely for the reason of high EGTs. Porsche recently released theirs that is full of exotic materials (=very expensive) to make it somewhat reliable i imagine.

As we both know, diesels operate at much higher compression (= lower EGTs) as well as significantly above the stoich (= again lower EGTs + no trail-burning as all the fuel gets to burn inside the chamber and not in the manifold), so it makes sense that VGTs don't stand the gas engines for very long.

... but, it may work with some amount of water injection

but, of course, i have no practical experience, just the theory and the stuff i read , so i may very well be wrong (and i would be glad if i am)

EDIT: I'd take vacuum-activated any day over the elec-motor'ed one. I wonder what kind of vacuum does this thing needs? Does it need a standalone vacuum compressor? (or do you call it uncompressor? ) Or does it use the boost that the coldside generates?
If i were to design that thing, i'd make it differential this way: no pressure on actuator = vanes become tight, then there would be a solenoid valve(s) which would control the amount of boost entering the actuator (to control the whole VGT operation). As boost is fed into the actuator, it will expand the vanes.

sounds good?

Water injection (believe it or not) doesn't affect EGT all that much except to bring it back to normal by allowing a reasonable amount of advance.

Those diesels that burn lean, when were they produced? I've witnessed liquid diesel coming out the back of various diesel powered craft. Also, that black smoke you see...

Maybe on a modern POS electronically controlled beast that doesn't belong anywhere near serious/critical/commercial application, but not with an unmetered injector pump slapped on the side. Couldn't be much further from the truth really.

The vacuum unit was apparently operated by an engine brake system. I imagine, at least for a short time, EGT would be quite high when you block off the exhaust completely.

Finally, diesel gear is usually continuously rated, whereas you might feel a little bad about holding your beemer at 7500rpm and WOT for more than a few seconds ;-)

In summary : non-issue

It's going on a 4g63 if/when he gets some suitable electronic control happening with MS for it.

Fred.

I feel the VGT is less likely to have issues with heat that the Garrett designs do. Many of the concerns I've heard voiced is due to thermal expansion causing possible siezing in the complex VNT mechanism that the Garrett uses. The VGT only has one moving part subject to the exhaust gasses and the vanes are cast/machined as one piece with the backing plate so it has a better means of heat conduction away from the vanes themselves.

I think the HE351VE will close up a lot more than 9cm due to the reported effectiveness of using it as an exhaust brake in the stock application. Guys say it provides more engine braking than many aftermarket exhaust brakes. If it only closed to 9cm it wouldn't be any different than a HE351CW found in the slightly older cummins trucks. How far closed is practical who knows due to possible surge issues.

The HE431V pictured has the same compressor wheel but a larger turbine wheel as compared to the HE351VE. The actuator actually uses brake system pressure rather than vacuum. More pressure closes the VGT down, as a failsafe to prevent overspeeding during an air supply failure.

Yeah, that doesn't surprise me about Garrett gear at all. Not a fan :-)

Thanks for chipping in. And thanks for allowing me to swipe your pictures too!

Fred.

Thanks for the info Aero, but the last sentence didn't make sense