VGT + External Wastegate thoughts

bna5017

bna5017

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Jan 15, 2008
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I have had a HE351VE on my truck since last spring. So far I have liked it everywhere except in the upper rpm's. It seems that no matter how far I let the housing open it falls on its face shortly after it spools up. It spools quick, and pulls pretty good considering I have basically no fuel mods other than 4k governor springs and no plate.

Basically, I am wondering what kind of opinions/thoughts anyone would have on trying to run an external wastegate with it and not letting the housing open up very far.

Thanks,
Brett
 
I think that would work pretty well. I'd still let your vanes move like they do now, just set the wastegate so it will open up when you reach your max boost pressure.
 
How are you actuating the vanes? Is it opening too quick on boost and then falling on its face, or do you know for sure its choking out? If you're going with an external gate, I'd agree with Forrest and go to a tight fixed geometry housing.
 
I have a wastegate actuator on it right now. It seems to open at a decent rate compared to the air cylinder, and the spring that I had on it. I think I will try to spend some more time on designing a mechanical controller for it over the winter while it is parked. My thinking was that if I run an external gate with the VGT housing, I would be able to maintain the quick spool up..
 
bna5017 said:
I have had a HE351VE on my truck since last spring. So far I have liked it everywhere except in the upper rpm's. It seems that no matter how far I let the housing open it falls on its face shortly after it spools up. It spools quick, and pulls pretty good considering I have basically no fuel mods other than 4k governor springs and no plate.

Basically, I am wondering what kind of opinions/thoughts anyone would have on trying to run an external wastegate with it and not letting the housing open up very far.

Thanks,
Brett
Click to expand...


I'll bet that two things are affecting your truck.
1. The housing is opening too quickly.
2. Your lift pump setup is not keeping an adequate supply of fuel to the injection pump and your truck is falling on it's face in the upper RPM range 2600+ rpm.
 
I feel like the housing opens too fast as well. I suppose I could try a metering in flow control and use the SMC air cylinder that I bought for it.

I do have an external fuel pressure regulator on it with an empty overflow valve. I have my regulator set to ~40 psi at idle, in the middle of summer I disconnected the gauge because it is mechanical and makes too much noise (need to find a decent needle valve with a male 1/8" NPT on one end and a female 1/8" NPT female on the other). But my lift pump is only about a year old and only drops to about 30 psi on a wide open run.

This turbo does seem to clear up the fuel very quick, but I expected that to be the case since I am still on stock injectors and delivery valves.
 
how are you running the wastegate actuator controlling the vanes? what is the spring pressure in it? is it referenced off drive pressure or boost pressure? what about just running a manual boost controller to the wastegate actuator so you can dial-in exatly when you want it to open (I would reference it off the drive pressure so if the vanes open too quickly and the drive pressure drops, the actuator will close up the vanes). Also what about limiting the travel of the arm so that the vanes wont open up completely
 
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Maybe you aren't pushing it hard enough. Toss some injectors in and see how she runs then. I doubt your really getting to a point where your chocking out based on your modifications.
 
The wastegate actuator is run off of drive pressure. I plan on making a manual boost controller/needle valve, I will do that this weekend if I can find the time.

Last weekend I tried limiting the housing so that it will not open very far, it doesnt act much different, just a little weaker on the top end.

I'd just like to know why it falls on its face so fast.
 
The idea of not letting vanes fully open and opening external wg is BAD. When vanes aren't fully open, the turbo won't flow decently. When you open wg and thus reduce drive press and boost, you have to close vanes even more to remain the boost.

A wg actuator is not good for controlling vanes as it is too much on-off style. VGT is not a wastegate, it must be controlled all the time rather than just switch between closed and open.
 
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muuris said:
The idea of not letting vanes fully open and opening external wg is BAD. When vanes aren't fully open, the turbo won't flow decently. When you open wg and thus reduce drive press and boost, you have to close vanes even more to remain the boost.

A wg actuator is not good for controlling vanes as it is too much on-off style. VGT is not a wastegate, it must be controlled all the time rather than just switch between closed and open.
Click to expand...

So what exactly is the best way to control these turbos? I just got one off ebay and was just planning on using an external wg but sounds like it may not be the correct way to go.
 
muuris said:
The idea of not letting vanes fully open and opening external wg is BAD. When vanes aren't fully open, the turbo won't flow decently. When you open wg and thus reduce drive press and boost, you have to close vanes even more to remain the boost.

A wg actuator is not good for controlling vanes as it is too much on-off style. VGT is not a wastegate, it must be controlled all the time rather than just switch between closed and open.
Click to expand...

I had the same thoughts about using a wastegate, but thought maybe I was wrong.

I do know that an actuator is too much like a switch as well, which is why I have had 3 different mechanical controllers on it. I do like the air cylinder that I had on it, but I need to make/buy a flow control for the return side port.
 
It's very much stock-ish. Basically all I have done is put a 4kgsk in it, no plate, and tuned AFC. I have some plans for it for this winter while it is parked, mack rack plug, advanced timing, hopefully build a decent fuel delivery system, and a set of injectors.
 
I was playing around with controlling my vgt with a wastegate actuator using boost and I figured something out by accident ... I used a manual boost control valve and swapped the ball and spring positions in the valve. Now I can control how fast the actuator rod retracts. It's pretty cool. Tighten the adjuster screw and the actuator rod retracts slowly. Loosen the screw and it retracts faster. By swapping the ball and spring positions it traps the air between the boost contoller valve and the wastegate. Then the air leaks past the ball seat in the valve letting it close slowly with more spring tension. Less spring tension allows more air to seep past the ball seat which makes the actuator close faster. Eliminated the "on off" part of the wastegate actuator.
 
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