Won't build more than 18 psi on my Big 16G

[4gfun]

I am targeting 21 psi of boost on my 91 GVR4 before I start tuning. Today I installed FIC 650 injectors and tried to crack the boost up by turning the boost controller a few turns. The previous owner had the boost set at 16 psi and it sure pulled hard then.

To my dismay, I cannot get boost to reach higher than 20 psi at any point and it falls to 18.

This is even when I open the boost controller up all the way.

Any idea what could be going on?

Here are the performance mods if this helps:

Ported Big 16G Turbo, ETS FMIC & Piping, Counterfeit XBC MBC, Custom 2.5" tubular SS O2 housing with 40mm TiAL gate, Buschur 2.5" mandrel bent SS exhaust turbo back, CATCO cat, Socketed EPROM ECU with Ostrich and ROM emulator, Stutterbox and Check Engine shift light, Warlboro 190 lph pump, Fuel Pump Rewire, FIC 650 injectors, Innovate LC-1 Wideband O2 with guage

 

[kenuwine4g63]

I am targeting 21 psi of boost on my 91 GVR4 before I start tuning. Today I installed FIC 650 injectors and tried to crack the boost up by turning the boost controller a few turns. The previous owner had the boost set at 16 psi and it sure pulled hard then.

To my dismay, I cannot get boost to reach higher than 20 psi at any point and it falls to 18.

This is even when I open the boost controller up all the way.

Any idea what could be going on?

Here are the performance mods if this helps:

Ported Big 16G Turbo, ETS FMIC & Piping, Counterfeit XBC MBC, Custom 2.5" tubular SS O2 housing with 40mm TiAL gate, Buschur 2.5" mandrel bent SS exhaust turbo back, CATCO cat, Socketed EPROM ECU with Ostrich and ROM emulator, Stutterbox and Check Engine shift light, Warlboro 190 lph pump, Fuel Pump Rewire, FIC 650 injectors, Innovate LC-1 Wideband O2 with guage

Boost leak man. Or take apart you mbc, some counterfiets have have restrictors in em or the bleeder valves are too small

 

[4gfun]

Boost leak man. Or take apart you mbc, some counterfiets have have restrictors in em or the bleeder valves are too small

Thanks for the info. How does a boost leak just develop like that? Vacuum is good, it is exactly the same as it always was (not sure if this is any indicator of a vacuum leak though).

Also, do you have an idea if counterfeit is actually a name brand....or does it mean that it is fake .

I am just looking at the previous owner's mod list and that's what it said "counterfeit XBC MBC".

Thanks so far!

 

[donniekak]

Your wastegate is blowing open. What spring is in it?

 

[4gfun]

Your wastegate is blowing open. What spring is in it?

Don't know, it came with the car. I had to take the top of it when I replaced the alternator though. Didn't seem like there was much too it...although I hope I didn't wreck anything!

Any ideas what to look for? Do I get a choice as far as springs go?

Thanks!

 

[Talon2139]

How big is your intercooler piping? not sure it matters, but if you think about it such as with stock intercooler piping it is much smaller, so you have a smaller area to fill, thus a higher psi; with your bigger intercooler piping maybe thats as much as the turbo can produce with your piping.

 

[4gfun]

How big is your intercooler piping? not sure it matters, but if you think about it such as with stock intercooler piping it is much smaller, so you have a smaller area to fill, thus a higher psi; with your bigger intercooler piping maybe thats as much as the turbo can produce with your piping.

This is what is on the car (as far as I know).....2.5 inches?

ETS (90-92) Mitsubishi Galant VR4 10" Intercooler Kit VR4IK

 

[Talon2139]

Ok, maybe something is wrong with your wastegate like someone stated above. that and a slight boost leak. Try a leak down test.

 

[jrohner]

If your MBC is a bleeder style, get a real boost controller. If not, test it with an air compressor with a pressure regulator to see what kind of pressure holds.

 

[JusMX141]

Too soft of a wastegate spring.

 

[Bluefire16]

^^ Ah Jus, you beat me to it

And to answer your question, "why would i get a boost leak randomly or slowly?". Couplers are basically rubber, which expand and contract with the pressure. After so long, they start to get weak and crack or rip, thus a slow or little boost leak. That is how.

Ok, maybe something is wrong with your wastegate like someone stated above. that and a slight boost leak. Try a leak down test.

Why would he preform a leak down test? This wouoldnt help

 

[esoteric]

Wastegate was my first thought.

 

[pboglio]

Boost leak, improper external wastegate spring or preload, bad mbc, and the restrictive catalytic converter. Could be any of those to start.

 

[4gfun]

Thank you very much for taking the time to point me in the right direction and help me understand more.

I am not sure if I did this right as a test, but I capped both vacuum lines to the boost controller and went for a drive.

I couldn't make more than 12 lbs. of boost. Wouldn't that eliminate the wastegate?

What about the BOV does it need to be crushed?

Mine is stock.

 

[Bluefire16]

Ahhhh, this could deff be the reason for your problem.

You BOV is most likely opening then and releasing air, so yes, considering you have a 1g you will want to crush it or otherwise purchase a different bov that can withstand more psi.

And also, if you ment you took the MBC off, and just ran straight from the turbo to the wastegate, this should run around 12psi (on stock wastegate), this could be the same with your tial so you should only run 12psi then (im not familiar with tial though so dont quote me).

One last thing, please fill in fully your details on your profile, for future it will help.

 

[4gfun]

Ahhhh, this could deff be the reason for your problem.

You BOV is most likely opening then and releasing air, so yes, considering you have a 1g you will want to crush it or otherwise purchase a different bov that can withstand more psi.

And also, if you ment you took the MBC off, and just ran straight from the turbo to the wastegate, this should run around 12psi (on stock wastegate), this could be the same with your tial so you should only run 12psi then (im not familiar with tial though so dont quote me).

One last thing, please fill in fully your details on your profile, for future it will help.

Thanks so maybe it is the stock uncrushed BOV. I have read bad things about crushing it and I am concerned that I won't do it right. However, I believe that a replacement BOV is alot of money and I am broke. Such is life.

Actually what I did is try to run with the wastegate open as a test.

I eliminated the boost controller and capped both lines going to it. Now I am wondering if I did that wrong.

I know that there is something that you can do as a quick test to achieve full boost.

This is what I was trying to achieve. Does anyone have have an idea what that would be?

 

[Bluefire16]

What you want to do is unhook your boost controller.

Take the rubber line and hook it straight from the wastegate to the turbo itself. This way it will only run at "wastegate" psi. Which i am assuming is around 12. So if you did this your car is running fine and like stated, your problem now lies with a uncrushed BOV. If you are running 18psi you deff want to crush it. Dont be afraid, just read carefully the write ups that are on the forum and do as it says. If your still scared but a extra (cheap in the marketplace)

 

[4gfun]

Well everyone, thanks for working with me on this.

I opened up the External Wastegate and found a blue spring by itself which is set for the wastegate to open at 14.5 psi.

I will get another spring. If I am still having trouble (which I guess I will from some of the latter BOV posts) I will crush the BOV.

Thanks for your time.

 

[Bluefire16]

New wastegate spring for higher load and crushed BOV and youll be fine.

No problem man, good luck with the car. And take care of that thing, that VR4 is a rare thing of beauty.

If you have anymore questions feel free to ask. Good luck!

 

[4gfun]

New wastegate spring for higher load and crushed BOV and youll be fine.

No problem man, good luck with the car. And take care of that thing, that VR4 is a rare thing of beauty.

If you have anymore questions feel free to ask. Good luck!

Thanks! I try to keep the GVR4 off the road as much as I can.

Well I took the Tial Wastegate apart and it is a 14.53 psi spring.

For all of you who suspected a wastegate spring that was too soft, do you feel that a MBC should be able to get boost up to 21 psi if nothing else was wrong?

In other words, is this solely a BOV issue or should I get a higher rated spring? Should a MBC be enough to bring the pressure up to 21 psi with that spring if everything else is ok?

Thanks!

 

[gsx4g64]

Thanks! I try to keep the GVR4 off the road as much as I can.

Well I took the Tial Wastegate apart and it is a 14.53 psi spring.

For all of you who suspected a wastegate spring that was too soft, do you feel that a MBC should be able to get boost up to 21 psi if nothing else was wrong?

In other words, is this solely a BOV issue or should I get a higher rated spring? Should a MBC be enough to bring the pressure up to 21 psi with that spring if everything else is ok?

Thanks!

If I understand you correctly. You have an external wastegate. Hoping that your BOV is working properly, you should be able to keep the standard spring that came in the wastegate and be able to turn up the boost. If the boost controller is open, then your boost should stop at whatever rating of the wastegate spring. You should be able to go at least 1 1/2 times higher than the rating of the spring.

I would suggest looking at the MBC first. Then, take apart the wastegate. Make sure nothing is broken, ripped, or stuck. After that, check all lines going to and from the MBC and turbo. By doing a step process of ruling things out, you will find the problem. DON'T WASTE MONEY, WHEN MAY NOT NEED TOO.

 

[4gfun]

If I understand you correctly. You have an external wastegate. Hoping that your BOV is working properly, you should be able to keep the standard spring that came in the wastegate and be able to turn up the boost. If the boost controller is open, then your boost should stop at whatever rating of the wastegate spring. You should be able to go at least 1 1/2 times higher than the rating of the spring.

I would suggest looking at the MBC first. Then, take apart the wastegate. Make sure nothing is broken, ripped, or stuck. After that, check all lines going to and from the MBC and turbo. By doing a step process of ruling things out, you will find the problem. DON'T WASTE MONEY, WHEN MAY NOT NEED TOO.

Thanks for the specifics. This issue is resolved. My new issue is getting the turbo to hold 21 psi close to redline.