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any way to reduce boost on 16g turbo?

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97grnrs

15+ Year Contributor
124
2
Nov 3, 2004
reading, Pennsylvania
i just bought a 95 tsi awd, i dont like buying cars that someone has already tampered with but from what the guy says hes done it has ARP head studs which i verified, act clutch, eprom ecu,big 16G turbo,and few other minor things. now the problem is at full boost i spike to 20psi then settle around 18-19 , i do not know if the block has been redone or anything like that ,this is my daily driver and i dont want to risk blowing it apart. will the 4g63 be ok at 20 psi on that turbo? the wide band under full boost is bet 10-11 afr which is ok. it feels ok also no detonation or anything but id be more confortable if i could get it around 15psi max. the wastegate arm on that turbo is not adjustable like ive seen on some others. is there any other bolt on wastegates i can buy for that turbo to lower boost a bit or will this be ok??
 
It sounds as if you dont have a boost controller. Thatll be all you need if you dont already have one. And as mentioned, what is being used to tune in which you can verify no detonation?
 
It sounds like you have an ebay 16g with an adjustable wastegate. You need to lower the tension on the wastegate.
 
its not an ebay turbo. he said its from an evo or something. def not ebay junk. its oem off something. and no its not an adjustable WG its just a solid rod. and a boost controller will only raise boost not lower it. im not sure what the oem WG pressure is supposed to be on a 16g i thought like 12 or 14
 
its not an ebay turbo. he said its from an evo or something. def not ebay junk. its oem off something. and no its not an adjustable WG its just a solid rod. and a boost controller will only raise boost not lower it. im not sure what the oem WG pressure is supposed to be on a 16g i thought like 12 or 14

A boost controller will lower boost if your boost is controllable, if that makes sense. Your turbo has nothing holding it back right now so it's over spooling due to the lack of back pressure forcing the exhaust gas through the waste gate. Either put a cat on if you don't have one or bust out the Dremel and go to town on your hot side. And oem pressure on your waste gate actuator is around 10ish I believe.
 
ya unfortunately it has 3" turbo back ex and only a muffler. so prob hardly any backpressure. and how would a boost controller help? ive never seen one that would lower boost only raise. ive got the WG line directly to the outlet pipe off the turbo . looks like porting might be my only solution.. i wish i knew if the car was setup to run 20 psi or not . i really have no way to tell
 
A boost controller won't be able to lower boost below what wastegate pressure is. The point of a basic boost controller is to hold the wastegate closed longer so that you can make more boost. It doesn't really work the other way around. If you have a 16G and you are running that much boost hooked up as you described, there's something not right with your WG actuator.

You have whats called boost creep, it's very common. Porting the o2 housing or getting an o2 dump will help. May I ask what you are tuning with? Just having an eprom ECU isn't a tuning solution. It needs to be chipped for ECM link or DSMlink or whatnot. At 18-21psi I would definitely be looking into a logger at the very least if you don't have one.
 
ya thats what i figured , i never saw one that lowers boost only raised
 
He has to have extra fuel. If his profile is correct and he is a NT w/ Turbo then the stock injectors could never even get close to supplying the fuel for 18psi. He'd have a blown motor. The highest I've seen reading threads on this forum is 9psi on stock injectors.
Hopefully it has link or something.
 
You misread his first post. He just bought a tsi. It could very well be that it has an 18 psi actuator on it. Either way, i would definitely look into a logger to check for knock. And check for fuel upgrades. It has to have a chip, otherwise you would hit fuel cut everytime you hit full boost
 
He has to have extra fuel. If his profile is correct and he is a NT w/ Turbo then the stock injectors could never even get close to supplying the fuel for 18psi. He'd have a blown motor. The highest I've seen reading threads on this forum is 9psi on stock injectors.
Hopefully it has link or something.

Did you even read his first post where he said he bought a 95 TSi? :thumb:
 
well the guy told me its an eprom ecu but he said it didnt have a chip in it so i dunno? i gotta find out somehow. and it doesnt hit any fuel cut at any boost level even up to 20 it feels smooth. thats why i wish i knew ### was all done to the car . the af readings are good at full boost. i dont have an egt gauge though. i was thinking about cutting the wastegate arm and adding about 1/8th inch to it and welding it back together to get it to open sooner and then use boost controller to dial it in higher if needed.
 
Take some pictures of your engine bay. A couple so we an see all around.
Also of the interior of your car.

If he did not give you a cable to connect to your car via laptop you probably dont have link installed.
If you have a boost controller just unscrew it all the way until it stops this will allow wastegate pressure on your evo 3 16g, and that will be safe for you to run until you can get a way to tune it.
(you have a wideband it sounds like so mabe he has had it chipped at one point? Ask)
If the car was chipped with your current settings I wouldnt change anything. But you need to know.
Having a wideband and not tuning makes no sense and I dont know why there would be one installed if he hadnt used it to tune.

Find out if you have stock injectors, or bigger.
I would call and ask him all hes had done to it so you know.
Ask about:
fuel pump -stock or other, rewired?
Adjustable Fuel pressure Regulator?
Manual Boost controller

PS:
Dont cut your actuator.
If you are stock everything you can run your 16g on stock wastegate pressure. If you are running at 18 or 19 I am assuming you have a MBC.
Post up some pics.
 
Ok tomoro iwill and the 20psi is on wastegate pressure.i took the mbc off already.

It has bigger fuel pump also
 
well the guy told me its an eprom ecu but he said it didnt have a chip in it so i dunno? i gotta find out somehow. and it doesnt hit any fuel cut at any boost level even up to 20 it feels smooth. thats why i wish i knew ### was all done to the car . the af readings are good at full boost. i dont have an egt gauge though. i was thinking about cutting the wastegate arm and adding about 1/8th inch to it and welding it back together to get it to open sooner and then use boost controller to dial it in higher if needed.

Take the ECU out of the car open it up and look at the chip for ID numbers. Most of the chips I have come in contact with will have a label on them showing what they are. IE 550cc injectors 2 stage rpm etc etc... You could even post a pic of it here.. FYI if you have a wide band and its staying steady I am very inclined to believe the car is tuned and running aftermarket injectors. If it was 450's you should be very lean around 20 psi! However, better safe than sorry in this case.
 
ya im going to disect the car today and try to find out whats all done to it.. ive built about 8 turbo hondas and even a turbo bike but im not too familiar with the dsm but once i find out whats all done to it ill feel better knowing if it can handle that 18-20 psi safely

ok i opened the ecu. it does have an eprom but the chip still says mitsubishi on it so im assuming the car is still running on factory boost settings??
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A boost controller won't be able to lower boost below what wastegate pressure is. The point of a basic boost controller is to hold the wastegate closed longer so that you can make more boost. It doesn't really work the other way around. If you have a 16G and you are running that much boost hooked up as you described, there's something not right with your WG actuator.

You have whats called boost creep, it's very common. Porting the o2 housing or getting an o2 dump will help. May I ask what you are tuning with? Just having an eprom ECU isn't a tuning solution. It needs to be chipped for ECM link or DSMlink or whatnot. At 18-21psi I would definitely be looking into a logger at the very least if you don't have one.

Sorry I wasn't clear. I knew that, but if the waste gate was working properly the boost controller should be able to bring it back down to stock levels if adjusted all the way down. But you are right, won't go below stock settings.
 
If you have taken out the MBC and it is still making boost higher than you want then you will have to and a restriction in the exhaust. Cheapest and easy way to do it is in the exhaust piping. If you do not know what mods you have in the car you need to keep the boost down until you have all the supporting mods to properly support the 16G. It may however, already have all the supporting mods. Good luck.
 
im curious on something, since you just got a dsm how is it that you are registered in 2004? you opened an account back then just for kicks until you actually owned a DSM or what? just curious.

edit: I saw you owned a 1.8 back then...
 
Easiest way to lower boost, get a 14b wastegate actuator. It will lower boost to around 9-10...

That's only IF you do not have a MBC in which you can adjust to boost by turning the knob counter-clockwise, and IF you do do not have an adjustable wastegate.

The only other way would be to run an external wastegate and then your talking about getting into a few hundred there IF you go new. If you would please post some pictures of your engine bay we can help diagnose any issues, and let you know what you have installed that we can see
 
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