Really Bad Boost SPIKE!!!

[AgntorangeDSM]

ok so lately i noticed that if i push my car half throttle it will hold around 15 psi and as the rpm's rise around 4500 to 5000 my boost just climbs fast to 25 30 psi and i did a leak test and just got my mbc hooked up and it still does it! WTF im confused and help thougths and ideas very helpfull thanks!!

 

[StaticXMtrsprts]

Is your MBC hooked up backwards? The side with the bleeder hole needs to be going to the wastegate. That happened to us when we noticed the MBC we ordered did not have a spring in it.

 

[kelvinb]

your mods do not list what mbc you have, so its possible that the mbc you have is hooked up correctly according to one mbc manf, but wrong with the other. also, what 02 housing do you have on your 18g?

 

[ddavisaf]

Make sure the vaccum line to your wastegate is not torn, damaged, or removed. This sounds less like boost spike and more like a faulty wastegate.

 

[AgntorangeDSM]

i believe its the 2gen o2 and the mbc is one that i got from my school i had a tech physics class and my instructor told me it would work cause we use the same thing to controll press. through neumatic lines with wall press around 100 psi so its pretty strong stuff. to strong?? i guess i'm just lost why i spike so bad around 5k i mean it fills my apex gauge to the max

 

[AgntorangeDSM]

its good that you mention that about my wastegate because dsmrevolution came over the other weekend and we looked at it and it seemed to have a hard time opening all the way. so we took it off and tested it off and it would work alright but when its on it didn't work smoothly so we think its gotta be that and may be a boost leak some were b/c it wouldn't hold press when we press tested it. it would drop off right away.

 

[AgntorangeDSM]

how do i see if it is my waste gate too? b/c hooked it up and applied press and it opened but not all the way really so what should i do since i have no job at the moment so no money either!! it sucks so were is a good place to get one and cheap too??

 

[ddavisaf]

Here what you should do.
1) Bypass the mbc by putting the vaccum lines back to stock.
See what happens now...
2) Disconnect the wastegate arm from the flapper.
See what happens now...
If step 1) fixes your problem, you have an issue with the mbc.
If step 2) fixes your problem, you have an issue with your wastegate.

 

[AgntorangeDSM]

ok will do that tomorrow first thing! thanks Damien i'll be sure to post my results asap!

 

[AgntorangeDSM]

one question that might sound stupid but, no question is a stupid one. when i unhook the flapper do i keep the vaccum line on the wastegate?

 

[ddavisaf]

It doesn't matter really. You might as well though.

Oh, and one more thing.
Don't let the boost get out of control. If you see it about to go crazy, let off.

 

[AgntorangeDSM]

alright sounds like a project tomorrow thanks again and i will let you know my results. i have a funny feeling its my waste gate actuator judging how rough it opens but thats just a guess and ill find out in the morning. any good ideas on were to get one just in case?

 

[ddavisaf]

I know a couple places
14b actuators aren't to hard to find.

 

[AgntorangeDSM]

were might those places be i have a wanted ad on here already? i tried ebay no luck there unless my search words are not very good searched for "talon eclipse waste gate" came up with one internal and a few nock offs the hks-s style not what i want

 

[AgntorangeDSM]

well i did the test and it seemed to work like this; i bypassed the mbc and it still spiked badly as always, then i disconnected the waste gate actuator arm and it barely reached 5 to 6 psi but around 5k+ it would still creep 10+ psi so i have a brand new waste gate from archer racing and a new boost controller as well as a future product to help fully open my flapper brought to in part by dpconcepts.com an awsome site to visit!! so i will do this all next week some time when the parts come in and report back to let you know if it worked or not!! thanks for all the input and help!

 

[kelvinb]

well the reason it creeps after 5k rpm is because of your exhaust. it pushes the flapper shut since there is no vacuum for it hold open. good luck with the rest i dont know.

 

[AgntorangeDSM]

ok sounds good i'll just have to wait till next week when i get all the parts and put it all on then i'll post me results! thanks

 

[SlowChild3]

well the reason it creeps after 5k rpm is because of your exhaust. it pushes the flapper shut since there is no vacuum for it hold open. good luck with the rest i dont know.

Isn't the wastegate open due to boost? The more pressure the less boost. Right?

 

[AgntorangeDSM]

thats kinda what i was wondering b/c it should open around 11psi and stay open to allow safe boost levels from my understanding and it creeps like that b/c it doesen't open at all really so it just stay's closed allowing for boost creep that what i'm getting from all of this

 

[underradar92]

well the reason it creeps after 5k rpm is because of your exhaust. it pushes the flapper shut since there is no vacuum for it hold open. good luck with the rest i dont know.

I believe this answer relates to when the actuator is disconnected. Then the backpressure acts on the flapper from the other direction, trying to close it up again, leading to a low level creep. If that's not what Kevin meant, ignore me.

 

[AgntorangeDSM]

well i could see where you would be coming from then yes!

 

[HearMeSpoolin]

u probly had the mbc hooked up wrong... all the stuff people say on here is the wrong way to hook it up.. what one do u have? i hooked mine up like they said and it would go to 20 no matter what and i finally read the right way and it works awsome and no spike or creep..

 

[AgntorangeDSM]

i don't have one yet! its in the mail as we speak