Stock ECU.... How much boost?

[MaxPSITalon]

I have read a lot about fuel cut... and my understanding is once the MAF pulls "too much" air it will fuel cut. I plan on putting a 255lph fuel pump and 550 injectors before going over 15psi. my question is: once i have the fuel system to support 15+ psi can I run that much boost?? or will the computer still fuel cut over 15 psi? if so how can i get around that. i plan on someday being able to run 20+ psi on a t3/t4 turbo. has anyone ran over 15psi without modifing the ecu? thanks

 

[just2asian]

Last summer we did a turbo swap on a 2nd gen awd from the t25 to a evo 16g with a 255 walbro and had the ecu tune itself. We were able to get the boost to about 17 or so before it hit fuel cut. The only thing I would say is, if you plan on running more power someday you can get DSMlink to tune around fuel cut, some people go with SAFC2, but personally from every DSM my friends have owned, they have had SAFC2 and they like DSMlink so much more, you can fine tune so much more with DSMlink, it's worth saving the money and getting if you plan on putting down some serious numbers in the future. Plus it reads knock too

 

[slipstream808]

No, the ECU will do fuel cut when it figures it would cause the injectors to go over a certain duty cycle. Unless you can either eliminate fuel cut or fool the ECU into seeing a different airflow value that is lower than the stock one (ie and AFC or something) then there is nothing that you can do.

BUT 15 psi is entirely dependent upon the compressor efficiency. Anything more than a T25 and it's just not a good idea.

And yes, 550's with a 255 will be good but it wont do you crap unless you have someway of controlling it. Again you'll need an AFC or EPROM chip or DSMLink.

As for right now, though 15psi is fine on the stock system with a T-25.

 

[brute]

You get around fuel cut by having enough fuel to support the air entering the engine. If you're pushing xxx amount of boost, you need enough fuel mods to support all that air. So if you're hitting fuel cut, you need to get a pump and injectors to supply more fuel.

If you get a 255, rewire it. You'll also need a fuel pressure regulator. And if you get injectors, I'd highly suggest getting a logger and possibly a way to control the fuel (SAFC, DSM Link, EMS, DSM Chip, etc.). Not to scare you, but you need to do stuff orderly. You can't just drop in a huge turbo and push 30psi. You need to mod your car systematically, and it looks like you're being good about that.

The only thing you should EVER need to do for your ECU is socket the EPROM chip or replace capacitors. Other than that, you mod other stuff, not your ECU.

 

[MaxPSITalon]

yea, like i said i plan on upgrading the fuel system before running high boost. My understanding of fuel cut is that it is based on the amount of air going through the MAF... not the amount a fuel available. I am just worried that if i put a 255 pump and big injectors... will i still get fuel cut?

Looks like before i can run over 15 psi i have to get DSM Link. Thanks for your help


I do plan on getting DSM Link.... but i was hoping to wait until i am ready for a T3 conversion which will probably be next summer.

 

[TrystanGST]

Well what turbo are you using right now? The T-25 doesn't do much after 15 pounds anyways. So regardless of fuel mods/DSMLink/whatever turning the boost over 15 on a T-25 will just blow more hot air.

 

[Spooling99]

The 2g Maf is good for around 400hp anyway. You shouldn't have a problem if you have the fuel. Make sure you get a AFPR as Brute said.

 

[oldman]

If you guys are hitting fuel cut at 15psi, you all need to do a boost leak test. I have hit 25psi with my old small 16g (ripped actuator vacuum hose) without hitting fuel cut.

You get around fuel cut by having enough fuel to support the air entering the engine. If you're pushing xxx amount of boost, you need enough fuel mods to support all that air. So if you're hitting fuel cut, you need to get a pump and injectors to supply more fuel.

Not exactly Derek, fuel cut is not there to guard against fuel starvation, the ecu does not know nor does it care which fuel pump and injectors you have, it cares only for air flow. The fuel cut trigger value is pre-program into the ECU and will not change because you swapped in 660s and 255, the only reason you can get around fuel cut with larger injectors is because you're altering air flow signals to the ECU.

 

[No_Skillz]

If you are running 660s and a 255, you will have to "modify" the ECU with either a piggy back or stand alone engine management system anyway.

Like oldman said... it doesn't matter what fuel mods you are running because fuel is not a factor in the ECU's decision to fuel cut. The ECU decides to fuel cut when it sees too much air from the MAF. However, since your MAF is pre-turbo/intercooler/piping/tb/intake manifold, there are lots of places for leaks and your engine may not be getting as much air as the MAF sees. This is why you are only boosting around 15-20 and getting fuel cut. A car with no boost leaks (nearly impossible to achieve) will cut at well above 20psi with all stock fuel and ECU parts. A boost leak test is the the first procedure and a MUST when considering fuel cut issues.

 

[zippyshoe]

If you do choose to go with DSMLink for your tuning needs, fuel cut will be eliminated entirely - it simply does not exist in an ECU programmed with DSMLink. Of course, the tuner is still responsible in ensuring their car does not run too lean.

 

[MaxPSITalon]

Right now i am just running a t-25 and i dont intend on making over 15 psi.... since it will be pointless with that turbo. I have some boost creep problems i need to resolve before moving forward with a better fuel system. i cannot hold a constant boost... every gear makes more or less boost. i think it is because of my cheap boost controller. i have it set to about 14 psi... but it will only go to 14psi in 4th gear and 5th. the other grears the boost stays around 7-10 psi. sometimes it will fuel cut in 4th and 5th and sometimes it wont. any ideas?

 

[oldman]

Right now i am just running a t-25 and i dont intend on making over 15 psi.... since it will be pointless with that turbo. I have some boost creep problems i need to resolve before moving forward with a better fuel system. i cannot hold a constant boost... every gear makes more or less boost. i think it is because of my cheap boost controller. i have it set to about 14 psi... but it will only go to 14psi in 4th gear and 5th. the other grears the boost stays around 7-10 psi. sometimes it will fuel cut in 4th and 5th and sometimes it wont. any ideas?

Already answered.

If you guys are hitting fuel cut at 15psi, you all need to do a boost leak test. I have hit 25psi with my old small 16g (ripped actuator vacuum hose) without hitting fuel cut.

Also, what you're describing is no boost creep.

 

[mwracing]

yes boost creep is when you hit your target psi lets say 14.

then as your rpm goes up your boost will CREEP up aswell.... maybe to 17-20 by red line.