Wastegating compounded vgt turbo

T

TwinTurboTim

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Nov 25, 2019
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I have been running an S480 that I added to my stock HE351vgt turbo. I like the exhaust brake and the looks of the big turbo on top. I know people can make 1000hp on a S480 but I know I can't put that drive pressure through the stock turbo so I am going to add a wastegate or 2. Has anyone ever done this before? I can't find anything or anyone who has done it. I am going to run a 44mm gate on the rear egr port and plumb it back into up pipe with 1.5 inch tube to my big turbo.
 
I'm thinking that to do this right you would need to bypass the he351vgt compressor as well.Basically turning the setup into a compound/sequential.Bypassing the he351vgt on the exhaust side only would actually decrease the maximum air flow available.

Have a look in the link below under "2-stage Variable twin-turbo" for a good OEM example.

AutoZine Technical School

So It has been done before and on a diesel but requires some engineering.
 
I think I am going to do some testing to make that decision. Right now it's doubling the boost of the big charger. Luckily I have 2 boost gauges and a back pressure gauge. If it's still raising boost a significant amount I am not going to consider it a restriction.
 
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Please let us know what comes of this. I plan to run a 351vgt with a 71mm Garrett on a 5.9 CR. I too want exhaust brake function and share the same concerns you have.
 
Any reason you can't plumb both EGR ports together and run a larger single wastegate into the hot pipe? I don't see it being an issue with a single scroll manifold and charger.
 
Put a manifold mounted external(40mm or 50mm)plumb the wastegates output and turn it through the big turbo still.
 
I just plumbed the back one since it was closest to the turbo flange. I didn't want gas flowing backwards out to the front flange. Yeah a 44mm wastegate is pretty close to the size of the stock turbo turbine flange. I think it's 57mm.
 

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Looks good. What is the difference in the pressure reading on your gauges?
Hopefully your AC system doesn’t need servicing in the near future. Looks like tight under there.
 
I am in process of swapping in a built Allison hence why I was wanting to make more power. I should be finished next week them I will update.
 
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