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Can't figure it out. Boost creep on a hx40

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blktalon3

Supporting VIP
545
77
Aug 30, 2006
Stanford, Kentucky
Ok here's my issue. Mods are in profile but basically I have hx40 w/.63 pte t3 hot side, punishment t3 mani and 2.5" o2 housing, tial MVS wastegate w/open dump and 3" exhaust with a straight threw muffler. I've got boost creep something fierce. I can't hold anything under about 27psi. Now before you start, it's hooked up right, 100% positive. It's got a line from the compressor housing to a hallman pro to the WG. I've talked to tial and they said they think it's the design of the manifold. Like it's to sharp of a turn from the collector to the WG. I also sent it back to
Tial and they said it was working correctly. I'm just having a hard time being convinced that the MVS is not enough gate to hold even 20psi? Does or has anybody had a similar setup and problems with boost creep? Frustrated
 
Have you tried running it straight from the compressor housing without the mbc? What is the spring in the gate?
Yes tried that. It currently has a 5psi spring in it out of desperation to try to get it hold something, but have tried many different spring combos. The boost controller is turned all the out by the way.[DOUBLEPOST=1414807816][/DOUBLEPOST]
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Here's some crappy pics also
 
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FWIW, my bep .70 hx40 with a MVS and punishment racing manifold creeps up to 27lbs as well. It doesn't really bother me because I was always planning on running that or more. You could contact Punishment and see if they can replace your 38mm flange with a 44mm flange.
 
I'm running the same setup just a standard 2 bolt tial instead. I had a 14 psi spring and then just went to a big and small blue for 24 psi minimum wastegate pressure. I have never had boost creep issues. Maybe the .63 housing with that 2 1/2'' o2 housing is causing to much back pressure resulting in your wastegate not being able to hold the exhaust pressure. Have you thought about porting the turbine housing to match the gasket?
 
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Wish, good to know. I did actually contact PR and they said couldn't modify the mani. I can't remember the reason. I also am planning on running at least 30 psi but for tuning purposes I wanted to be able to run lower pressures.
Fury, if I'm thinking right and it actually is creeping, then doing anything to make the exhaust flow better is going to worsen the creep. I actually had the thought of getting a 2.5in dp and see if that helped.
 
For some reason, the gate is not bypassing enought air. The 90* turn into the wastegate port is just like the 90 degree turn inside the turbine of an internally gated turbo. The air is going to find/follow the path of least resistance which should be the massive hole created by the wastegate.

I know that you sent the gate to tial but you could use regulated air from a compressor to check the actual opening pressure with your current spring setup. How well was the wastegate entrance polished?
Can you hear the gate opening under boost.

FWIW I was able to hold 16lbs on an HX35 using a 38mm gate, 2.5 in 02 housing to a 3in downpipe with no issues. This was also on a recirculating setup not atmospheric dump.

Robert
 
I've put compressed air to the gate even before I sent it in and opened really easy with very little pressure, this with a 8psi spring. I can hear the gate open so I jnow it is. Everything seems to point to the gate being too small or the mani just hard to believe its so bad I can't even hold 20psi. I have looked at the mani. It's not polished and really there's not much that can be done in the way of porting either where the WG outlet connects to the collector it makes a pretty sharp angle and I would end up porting away the joint.
 
Your vacuum line is too large that your using on the WG. That one is subject to leak. I would also do a boost leak test.

If that didnt show anything then i would say its the combination of your exhaust housing being too small and your wg being too small to handle the back pressure.

You could go with a larger turbine housing and fix the issue. or go with a larger WG size, but if you go with the larger WG size you could have a problem trying to run higher boost.
 
As stated above, a boost leak test will insure that you have no leaks slowing the opening of the wastegate.

With that being said, every setup is different and pj91gsx may be on to something.

Maybe its time to consider running a conservative tune (low timing and AFRs on the richer side) instead of chasing an issue that will not exist after a tune anyway? At some point (changing hotsides and re-welding flanges (voiding your warranty) to run larger wastegates that may cause you to have issues running your target boost numbers) we must look at the end goal here and the most logical solution.

Robert
 
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go to a bigger wastegate flange try a 44mm

Is there a reason you suggest this? OP states that he plans to run higher boost once properly tuned so making the drastic change of a 44mm gate may hender the future boost goals of the car.

Something to consider when handing out advice.

Robert
 
I had the same problem on a HY35. MVS isn't big enough to hold 20 PSI. I think Mine ran a MIN boost of around 26PSI. Its also why all of our manifolds run 2x MVS gates as well. You can do things like making the collector area smaller so the wastegate takes up a larger portion of the flow but you are restricting flow. Best solution if you want to run under 27 PSI is run a 44mm Gate or add another 38mm gate on the other side.
 
Did a boost leak test and it holding solid. Yeah it not a huge deal. Cause like Robert said I'm gonna be running at least 30 psi. I would like to hold lower psi if I could. But sometimes you can't have it both ways I guess.
 
Is there a reason you suggest this? OP states that he plans to run higher boost once properly tuned so making the drastic change of a 44mm gate may hender the future boost goals of the car.

Something to consider when handing out advice.

Robert

The reason for this advice was a solution for the current problem. whether he goes 10psi or 50psi is his choice this was just the answer to help get lower boost levels.
 
FWIW I was able to hold 16lbs on an HX35 using a 38mm gate, 2.5 in 02 housing to a 3in downpipe with no issues. This was also on a recirculating setup not atmospheric dump.
Smaller housing a/r, smaller turbine wheel...both add restriction which makes the wastegate system work better. Housing a/r can have a lot to do with it- that's the reason an Evo III 16G will creep all day while a 14B will not on the same car.

Big turbine wheel, big turbine housing, low boost = large wastegate.

Small turbine wheel, small turbine housing, high boost = small wastegate.
 
Smaller housing a/r, smaller turbine wheel...both add restriction which makes the wastegate system work better. Housing a/r can have a lot to do with it- that's the reason an Evo III 16G will creep all day while a 14B will not on the same car.

Big turbine wheel, big turbine housing, low boost = large wastegate.

Small turbine wheel, small turbine housing, high boost = small wastegate.

To finish, is this correct?

Big turbine wheel, big turbine housing, high boost= large wastegate

Small turbine wheel, small turbine housing, low boost = small wastegate
 
No, The larger turbine wheel and turbine housing flow more air. Trying to run low boost with this setup requires you to bypass more exhaust requiring a larger wastegate.

Higher boost will use more of the exhaust gas to spin the turbine and requires less to be expelled through the wastegate allowing you to use a smaller wastegate to maintain higher boost.

High boost - Smaller wastegate
Low boost - Larger wastegate

Robert

P.S. Thanks for the lesson Justin
 
No, The larger turbine wheel and turbine housing flow more air. Trying to run low boost with this setup requires you to bypass more exhaust requiring a larger wastegate.

Higher boost will use more of the exhaust gas to spin the turbine and requires less to be expelled through the wastegate allowing you to use a smaller wastegate to maintain higher boost.

High boost - Smaller wastegate
Low boost - Larger wastegate

Robert

P.S. Thanks for the lesson Justin

So if I were to run a turbo big enough to flow 80lb/min and run it at 25psi and let's say peak efficiency on a map is 40psi (just an example). Now, that's not considerate "Low boost" but I would ask is a 38mm wastegate enough to bypass the exhaust to keep at it 25psi when the turbo can flow easily 40psi? So more so I guess the saying:

High boost- Smaller wastegate
Low Boost - Larger wastegate

Should say:

High boost (relative to the size/efficiency of turbo) - Smaller wastegate
Low Boost (relative to the size/efficiency of turbo) - Larger wastegate

Or am I over analyzing too much and just bored :boring:
 
To run low boost on any turbo, you're diverting a large amount of airflow around the turbine to keep from generating additional boost pressure. The turbo size itself doesn't *technically* matter, but you don't need a 60mm wastegate to control boost on a 16G nor would a 38mm gate do much on a 115mm Borg.

Too small of a gate when you're trying to run low boost will cause creep. Too large of a gate, larger than what you may need, is difficult to keep closed at higher boost levels. I can't think of an example where anything larger than a 44mm gate is needed on a DSM...with many racing applications using 38-40mm gates to keep boost levels high by keeping more of the exhaust flow passing through the turbine housing.
 
To run low boost on any turbo, you're diverting a large amount of airflow around the turbine to keep from generating additional boost pressure. The turbo size itself doesn't *technically* matter, but you don't need a 60mm wastegate to control boost on a 16G nor would a 38mm gate do much on a 115mm Borg.

Too small of a gate when you're trying to run low boost will cause creep. Too large of a gate, larger than what you may need, is difficult to keep closed at higher boost levels. I can't think of an example where anything larger than a 44mm gate is needed on a DSM...with many racing applications using 38-40mm gates to keep boost levels high by keeping more of the exhaust flow passing through the turbine housing.

That's the part I was getting at. Thanks justin.
 
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