Overboosting

[SNE2040]

My GSX keeps overboosting at high rpm. I thought it was the old EBC that came with the car so i put in my turboxs dual port MBC and even on the low setting, it boosts to ~12 and then once it reaches over like 5k RPM, the boost shoots up to 21 PSI, hits fuel cut and backfires. There is also a big boost leak somewhere (gauge shows -15 PSI on idle); not sure if a boost leak would cause overboosting. It's not a spike cause it's actually holding the 21 PSI to redline...

 

[Boostjunki84]

When did this start? All of the sudden or after some new modification? It sounds like boost creep to me.
Also, I don't know what modifications you have; 21 psi will destroy a stock turbo, fast. When your boost shoots up to 21psi, your more than likely running out of fuel

 

[sadc]

+1 for the boost creep. Check out your WG see if there are any problems with it. Having a boost leak should give you less boost. not more

 

[DSMvroom]

Your car doesn't have -15psi at idle or any psi. Vacuum is measured in inHg (inches of mercury).

I agree with the others, your 16g is creeping (not "creap" as sadc called it). You need to get some injectors, pump, and fuel/engine management .

 

[SNE2040]

yeah i got the 255, 550rc and safc; still need to install and tune

 

[Mr Peepers]

Be sure to pick up a logger as well so you aren't tuning blind.

An adjustable fuel pressure regulator may be needed as well so you don't overrun your stock fpr with the 255.

Try to stay below 15psi in the meantime.

EDIT: Rewire the fuel pump while you're at it too- http://www.vfaq.com/FAQlocator-fuel.html

 

[SNE2040]

Be sure to pick up a logger as well so you aren't tuning blind.

An adjustable fuel pressure regulator may be needed as well so you don't overrun your stock fpr with the 255.

Try to stay below 15psi in the meantime.

EDIT: Rewire the fuel pump while you're at it too- http://www.vfaq.com/FAQlocator-fuel.html

i've been looking at different ones. will i need a 1g fuel rail or does my 2g work; also do i need to tap anything out?

I do boost ~14 then when it starts to pick up RPM, flies to over 20 by ~5-6k and cuts. I've been maybe considering getting a high flow cat and welding it to my downpipe

 

[Boostjunki84]

i've been looking at different ones. will i need a 1g fuel rail or does my 2g work; also do i need to tap anything out?

I do boost ~14 then when it starts to pick up RPM, flies to over 20 by ~5-6k and cuts. I've been maybe considering getting a high flow cat and welding it to my downpipe

You need to first port your o2 housing. This will help to eliminate your boost creep problem. Also you may want to consider a 34mm flapper upgrade for your wastegate.

Slowboy Racing, Inc. :: DSM :: Do It Yourself Parts :: Misc. :: 34mm Flapper (Just the Flapper)

Your stock fuel rail will work fine with your current set up.

 

[Mr Peepers]

I doubt it is the o2 housing. In most cases its the turbine housing and porting it for creep often helps; if not cures it. Follow this guide: http://www.dsmtuners.com/forums/art...oler/186525-how-cure-boost-creep-porting.html

It is important to note that the flapper only opens ~30* so porting behind it so it can open 90* is a little pointless.

Here is another thread with a good amount of pics:
http://www.dsmtuners.com/forums/turbo-system-tech/290438-another-rate-my-porting-thread.html

This will require you to take the turbo off. If you are planning on running 20ish psi soon I wouldn't worry about it and just get the supporting mods.

 

[DSMvroom]

I doubt it is the o2 housing. In most cases its the turbine housing and porting it for creep often helps; if not cures it. Follow this guide: http://www.dsmtuners.com/forums/art...oler/186525-how-cure-boost-creep-porting.html

It is important to note that the flapper only opens ~30* so porting behind it so it can open 90* is a little pointless.

Here is another thread with a good amount of pics:
http://www.dsmtuners.com/forums/turbo-system-tech/290438-another-rate-my-porting-thread.html

This will require you to take the turbo off. If you are planning on running 20ish psi soon I wouldn't worry about it and just get the supporting mods.

Agreed. That's the route I went. Op you said you've already got the fuel setup, so just install them and tune for 20+ psi

 

[SNE2040]

Agreed. That's the route I went. Op you said you've already got the fuel setup, so just install them and tune for 20+ psi

would boost creep be fixed by putting on a high-flow cat? i'm considering getting one due to NJ lately being out of control with random checkpoints

 

[DSMvroom]

Neg. A high flow cat would only help exhaust flow, thereby increasing not only the rate of creep, but also possibly the peak psi it would creep to.

edit : this would be similar to porting in "the wrong way" since you could say that there are two purposes of porting.
1) For increased exhaust flow for faster spooling and generally maximum performance
2) To promote exhaust flow through the wastegate passage for the purpose of controlling creep <-- "the wrong way"

I say in quotes because I think most people would agree with me, but I'm sure some would say otherwise.

edit v2 : Wait sorry I failed to realize you currently don't have a cat; The answer to your question is 'yes,' but IMO trying to fix boost creep is not a good reason to do so Keeping the man off your back . . . maybe.

 

[hpexperts]

just install your fuel mods and tune it for 20 PSI

 

[Flitzr951]

I'm having the same exact problem in my 1G. Boosts hard to about 14psi and then slowly makes its way up to about 20psi, this does not happen when my silencer is installed (I have a full 3" exhaust). What I don't understand is how my fuel system is supporting it. My WBO2 reflects a 14:1 at idle, and about 10:1 WOT all the way to redline. As far as I know my fuel system is completely stock. Although I've wondered about the fuel pump as it whines quite a bit and the plate that covers it looks like it was removed at some point in time. Either way, my custom emprom chip was burned for a stock 1G with a 2G MAS compensation, so I don't think there's any way the injectors could be anything but stock.