The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support Rix Racing
Please Support Rix Racing

Turbo Boost Creep Creeping T25 14B 16G [Merged]

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Thanks for muddying up the already muddy water forcefed, what you're trying to say is so much clearer now.

We'll end this convo of confusing, bass-ackwards, and un-enlightening boost creep theory for those that want to read it with your last post and hopefully they can decipher which posts makes sense.

Good talk.

:dsm:
 
Also 20psi with an internal gate is.20psi with an external. Off course course you lose power with a, wastegate versus one without but without one you lose all reliability and run out of effiency.
turbos have wastegates for the same reason an engine has a rev limit. To keep it from over revving/spinning. No matter what size size engine you can't match a turbo perfectly, its not a perfect world. Either the engine or turbo would need a limit. Or the turbo would eventually destroy itself.
Exhaust gas must be limited for the sake of the turbos life. To run a turbo without a wg and keep its reliabilty you'd have to limit the engines rpm to limit the exhaust expelled. Without exhaust limitation a turbo would never last.

It was just a statement made to argue a point. But you are wrong as well. It has been done... many times. It's just not practical for a street car as I said you have to find a happy median.

I know of several land speed as well as diesel and compound setups that operate with a huge turbo(s) and no gate. The turbo will not overspeed if it is sized properly.

Thanks for muddying up the already muddy water forcefed, what you're trying to say is so much clearer now.

We'll end this convo of confusing, bass-ackwards, and un-enlightening boost creep theory for those that want to read it with your last post and hopefully they can decipher which posts makes sense.

Good talk.

:dsm:

No problemo chief.... :thumb:
 
It was just a statement made to argue a point. But you are wrong as well. It has been done... many times. It's just not practical for a street car as I said you have to find a happy median.

I know of several land speed as well as diesel and compound setups that operate with a huge turbo(s) and no gate. The turbo will not overspeed if it is sized properly.



No problemo chief.... :thumb:

I guess that is somewhat what I was meaning. but idk if thats properly sized, I guess sized for its purpose. As its just the engine can't make enough exhaust flow to overflow the turbo which is, exhaust restriction. Top speed is the only way that could be done though. Which like you said its no good for the street. Anyways before anymore confusion comes, I'll just stop here.
 
Have you tried using a different o2 housing yet? I have an evo III 16g, PR Recirculated o2 housing, 2.5-3" Downpipe, No cat, 3" muffler and my 16g starts at 10psi and FALLS to around 8psi at redline.

The only two things that have been done are 1. Porting of the turbo's wastegate area after the flapper and before the flapper in the exhaust entry area. 2. Using an o2 housing that has a less restrictive wastegate side than the stock housing.

I have also heard from others that an aftermarket o2 housing has helped their creep issues so it isn't just me that this worked for. Worth a try if you have one laying around.
 
Well gofer, going back to the old exhaust didn't help either.. :banghead:
Anymore ideas? I'm stumped.
So you were NOT seeing boost creep with exhaust setup A but when you switched to exhaust setup B you started getting boost creep. You went back to exhaust setup A and it still crept?

Since you're running straight off the stock wastegate actuator (12psi) what is it creeping to and at what RPM does it start?

What gear are you seeing it creep, all or just one or two?

How is your wga line hooked up exactly and there's absolutely no boost controller in between?

:dsm:
 
what i did with my j-pipe rather than had it welded was i got a steel bolt in valve stem from the auto parts store "not a typical rubber one". the steel valve stems are used on omnie busses so they hold high pressure. they come with a valve stem, a nut, a washer and an o-ring. then just drill a hole in your j-pipe, take the valve core out and bolt it in. and since they are made of steel they look professional and work as good as a welded tap minus the cost.
 
I been stuck about this for a while!
I been reading about this before i even put the 16g on.
Any ways i have a true mhi 16g on my 98! Running on a 2g o2 housing

I get into the gas and i have steady boost for a few secs,
Then boost spike / creep then fuel cut:(

What am i doing wrong? I just want to run low boost till i get more mods

Is it the 2g o2 housing wont let the any flow through the wast gate passage?
I need help!
 
1. Is it spike or creep?
2. Based on your mod list, I'm going to assume creep

Bigger flapper.
 
^^^ What Lando said. Or you can get rid of the internal wastegate altogether and get an external wastegate so if you do decide to go higher in boost, you wont have to worry about boost creep. I had the same problem with my 14b. I plugged the linkage hole, reamed out the flapper hole and put on a tial 38mm and problem solved. Running 20 psi steadily in every gear and I'm going to upgrade to a 16G one day so I can just keep the same system and change out the spring if I need to on the Wastegate. Goodluck!:thumb:
 
^^^ What Lando said. Or you can get rid of the internal wastegate altogether and get an external wastegate so if you do decide to go higher in boost, you wont have to worry about boost creep. I had the same problem with my 14b. I plugged the linkage hole, reamed out the flapper hole and put on a tial 38mm and problem solved. Running 20 psi steadily in every gear and I'm going to upgrade to a 16G one day so I can just keep the same system and change out the spring if I need to on the Wastegate. Goodluck!:thumb:

The higher the boost the less wastegate you need. Large wastegates bypass more gasses around the turbine. The more boost you run the smaller your wg needs to be because you want less exhaust bypassing the turbine.
 
Kind of a long explanation, question is at end:
My modification and repairing of my car was in rapid flux when I got it...seeing very little drive time between each repair/mod session... That being said, I am almost certain that when I initially put my 20g(internally gated)on and ran off of the 13 psi wastegate, that I was not fuel cutting, but it also had an aftermarket o2 housing with an open dump wastegate. Because of a major boost leak, followed by a slipping clutch, and plethora of other issues I only drove it on that setup once or twice. And in the next session of repair/modding I installed a FMIC, and during the install discovered the wastegate dump was aimed right at the intercooler output pipe, and perilously close to a boost reference line, that being said I downgraded to the factory o2 housing, not even thinking about the possibility of boost creep. Driving the car since then it seemed to almost certainly be hitting fuel cut at ~4k rpm, I thought the MBC might not be working correctly, or that maybe someone messed with it. But I double checked it and was hooked up fine. But just now while browsing exhaust systems, I came across someone stating that a 16g had a 2.5" outlet, and that the factory o2 housing was only 2" diameter(is that correct?). Causing me to wonder if perhaps ever since I switched o2 housings the car is boost creeping to the point of fuel cut because of insufficient wastegate dump? Not having a boost gauge really isn't helping me right now...its high on the list though.
 
Last edited:
I recently fixed all exhaust leaks and intake leaks.
I had lowered boost to start tuning all over again. And to my surprise, I either am getting piss poor spoolup, or pretty bad boost control.

I am eventually targeting ~25 psi so the creep is not bad, as long as I can hold boost at higher levels.

Now It appears that I have a creeping issue. It did not exist before. A quick google search revealed what a boost spike looks like, but I would just like a confirmation.

Logs and .JPGs attached (for easy viewing).
In order:

Creeping log (suspect)
Old 2nd gear pull (compare apples to apples)
Old 3rd gear pull (just ### yo)

And I also added an old low boost pull. (not in the picture, but attached as a log) I honestly don't remember if this was on a 14b or 20g. (I'm pretty sure 20g). I went to my current Wastegate when I swapped the 20g in.

It is an ebay [Wyntonm] "knockoff style" wastegate. Absolutely nothing changed since it was installed. It did work perfect at some point.

All I did was:
Remove all exhaust stuff (mani, turbo, o2 housing, Ext. WG)
Cleaned and trued all flanges.
All new OEM gaskets
Some Copper rtv in trouble spots (WG flanges were warped. Got them very close to true, (~.005" at the peak in center of gap. A .001" feeler indicates the gap is along .5" of circumference)

Reassemble, let RTV cure. Proceed to beat on it some more (Retune)

I can only think of a few things causing this:

1- Fixing all the leaks, made the turbo that much more efficient to overcome the gate (Doubt it, but I hope it is the case LOL)
2- I didn't get the WG stem seated properly against its own fire ring.
3- I put too much RTV and its blocking something in the wastegate area.
4- I am a tuning retard and I have no idea what effect my terrible VE/AFR tables have on spoolup.

I disassembled the WG and cleaned it out. I saw no visible tears in the diaphragm (I stretched it also to check). Then I reassembled it, and blew comp. air into it. No leaks, and the valve sounds to be opening and closing correctly.
 

Attachments

  • CREEPER.elg
    14.5 KB · Views: 64
  • Old SECOND gear pull.elg
    11.1 KB · Views: 67
  • Old THIRD gear pull.elg
    14.6 KB · Views: 60
  • old LOW boost.elg
    15.6 KB · Views: 61
  • LOG comparison.jpg
    LOG comparison.jpg
    24.6 KB · Views: 102
38mm 2 bolt Waste-gate is off of the o2 housing.

No porting, no flapper either.

The other logs illustrate it running just fine before. Clean up all the old leaks, spend over $100 on gaskets (oem) and this is what I get. I'm fed up with this POS WG, but I need it to last just a few more months :pray: Then ordering a tial mvs. Till then...

Any ideas what can cause this? I have no exh/intake leaks. Checked as soon as I had it all back together again.
 
I just fixed my boost creep on my evo 3 16g. I've been fighting it for a year.. But sometimes simple things seem bigger... All I had to do was put a bigger vacuum line the wastegate and pressure source = problem solved. Give it a shot!
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top