how much boost till hit fuel cut

[skatershawn]

At what boost level will i hit my fuel cut off??
I just installed a walbro 255 and im about to get a FPR to help manage the fuel?
Ive got everything pretty much stock but the fuel pump, turbo back, pistons and rods!!

will it be safe to hit 15psi without fuel cut?
and do you think i will have boost creep with my 3'' turbo back w/ text pipe?? :/

thanks

 

[Hubbell91Tsi]

fuel cut depends on the size of the injectors. Stock 450's ill say like 17 psi depending on where you fpr is set.

 

[Calan]

At what boost level will i hit my fuel cut off??
I just installed a walbro 255 and im about to get a FPR to help manage the fuel?
Ive got everything pretty much stock but the fuel pump, turbo back, pistons and rods!!

will it be safe to hit 15psi without fuel cut?
and do you think i will have boost creep with my 3'' turbo back w/ text pipe?? :/

thanks

This question has no answer. Your ECU only understands airflow...not boost. So you may flow too much air and hit fuel cut at 10psi, or hit 30psi without seeing it. (This is an exaggeration...but you get the point).

fuel cut depends on the size of the injectors.

Actually, it depends on several things. The only way to know is with monitoring and tuning.

Same thing with your creep question. No way to answer that as every car is different.

 

[matthewdesigns]

fuel cut depends on the size of the injectors. Stock 450's ill say like 17 psi depending on where you fpr is set.

This is absolutely 100% incorrect.

OP, Calan's response is spot on. You need to start thinking of airflow in lb/min not intake pressure in psi in order to tune your car, and you'll need some way to extend or eliminate your airflow cap to get around fuel cut.

 

[Red97Eclipseboy]

If we hit fuel cut do to a set PSI or small injector, we'd never lean out & pop motors. Fuel-cut=airflow issue. Over-run MAF, massive boost-leak, too much airflow, etc.

I wish all noobs would read this: http://www.dsmtuners.com/forums/frequently-answered-dsm-questions/186971-what-fuel-cut.html

 

[Calan]

If we hit fuel cut do to a set PSI or small injector, we'd never lean out & pop motors. Fuel-cut=airflow issue. Over-run MAF, massive boost-leak, too much airflow, RPM, engine load, failed injectors, planets in alignment, etc.

I wish all noobs would read this: http://www.dsmtuners.com/forums/frequently-answered-dsm-questions/186971-what-fuel-cut.html

Fixed

 

[Muzda]

Hack the maf, if you haven't done it. This will give you a little extra flow threw and help deter fuel cut a little.

 

[Project2G]

What made you go with a 255lph fp if your all stock? You should of waited on the instal until you get the afpr. 255lph is too much fuel w/o the afpr. Be prepared to get poor gas mileage. A 255 with stock regulator will make the car run rich. All the extra fuel will wash down the cylinder walls and eventually contamiate the rings.

 

[skatershawn]

well i actually haven't even broke the motor in yet... i swapped a rebuilt 6bolt into a DL and the fuel pump from the DL wasnt powerful enough i was told and i was told to get a 255... not knowing i needed an upgraded AFPR till i read it on here a few weeks back.. thats why im in the stage of getting one and putting it on!!

and i was just wondering about the fuel cut off before i turn the boost up after i break it in!!
I have a MAFT and 3" GM MAF i haven't put on but i wasn't going to till i got a fuel management system and a wideband, to tune correctly... but that would help a ton with the fuel cut correct??

and boost creep is easy to fix... just port out the wastegate hole right? :/ sorry i sound like a 16 year old kid with his first car right now huh??
:s

 

[Calan]

...and boost creep is easy to fix... just port out the wastegate hole right?

Check back in with us six months from now, after you've tried everything except lighting the car on fire.

Seriously though...it can be damn near impossible to resolve, or you may get lucky. Again, it depends totally on your specific setup.

 

[DeadsEvolution1]

before I installed my injectors and fuel pump i was running 15 psi without any problems but like they said it depends on your car

 

[skatershawn]

already... the boost creep info i got was just from reading forums on here about it and thats a way alot said they fixed that problem... and the cut off... well ill get it at stock boost for awhile tell i lear and experiance more with the car!

But thanks to all for the help, this is the exact reason im on the forum site!! For insight and the help to point me in the right direction!!

 

[Bluefire16]

All i can say is s16g ported, catless, and evo8 pump...18psi all day

 

[jdodds]

Ive seen 22psi on my 14b without fuel cut. Ive got a rewired gss317, fpr set at 43psi, and stock injectors. Nothing to tune with on the car either besides a datalogger. Timing is set to 7* btdc. Before any of you start flaming me, I see zero knock and have no issues running at 20psi daily. The motor has about 120k on it and still runs strong.


edit: Ive got a few other mods too. evo8 fmic, evo3 o2, catless dp, and 3" catback. Dunno if that would change anything or not.

 

[Calan]

...Before any of you start flaming me, I see zero knock and have no issues running at 20psi daily. The motor has about 120k on it and still runs strong.

Well nobody will flame you, cause it sounds like you have a pretty nice setup there. But as to the OP's question, it is irrelevant.

As mentioned, boost (pressure) really has nothing to do with fuel cut, which is determined by actual airflow through the engine and other factors. 22psi on one turbo and setup may flow the same amount of air as 13psi on another.

Nice numbers on your setup though. Any dyno logs?

 

[jdodds]

No numbers. I cant keep a 2nd gear in it long enough to make it to the track. Im saving up for a shep trans right now. The thing that kinda helped me clear up the knock was to run a little over 1/4 tank of e85 with every fill up.

 

[dsmfa9nutter]

Fuel cut USUALLY happens at 16/17psi with 450's and a 14b on a stock motor (assuming there are no air leaks).

 

[skatershawn]

thanks everyone for the knowledge and help!!