[RESOLVED] fuel cut?

[Needsoles]

so i just finished breaking in my car and i'm running a stock fuel pump with a small 16g. i can give it gas and it boosts fine, but if i pin it the car falls flat on its face around 4500 rpm. so could this be fuel cut?

 

[BigSorn]

that kinda sounds like what happend to me, I'd check the mass airflow sensor.

or a REALLY bad boostleak.

 

[Needsoles]

i'm running stock boost. i ordered a walbro 190 for my car. i was just wondering if my car was hitting fuel cut because i'm running a stock fuel pump

 

[BigSorn]

fuel cut is like hitting a brick wall.

is that what your feeling or is it just decreasing power?

 

[Needsoles]

like i hit a brick wall

 

[bastarddsm]

i think he misstated it...like your engine locked up and it got ripped from the car...its a pretty severe feeling. scares the hell out of you the first couple times

 

[Needsoles]

thats what i felt. i can go to 5k if i'm not punching it but if i punch it the car falls flat on its face

so could it be fuel cut?

yeah it scared the shit out of me. i thought i broke my engine

 

[matt98eclipse]

It sounds like ful cut but i dont think its cus the stock fuel pump cus i have ran 15psi on a 16g with stock fuel pump before.

 

[EvansF]

You can run 16 psi fine on a 14b with a stock fuel pump , on a small 16g, maybe its possible. But your problem is kinda wear, maybe its not a fuel cut.

 

[Needsoles]

i am running wiseco 9:1

 

[spyderturbo007]

Fuel delivery has nothing to do with hitting fuel cut. You could be running 1600cc injectors and a 1000lph fuel pump and you would still be hitting fuel cut. Most likely it's a boost leak causing inflated airflow numbers and the ECU is imposing fuel cut to protect the motor.

Check for boost leaks and if you don't find any, then you'll have to drop the boost until you get something to tune with and larger injectors.

 

[ApexVIII]

boost leak test FTW!!!

really you need to check it ### im sure thats it,

is your TBE catless?

 

[kenamond]

If I search for fuel cut specifics I get 123095871203587 pages to read through, so I'll ask for a link if someone knows...

What is the fuel cut threshold? Is it a load value (like max g/rev) or is it otherwise rpm-dependent? Or is it a MAS Hz limit? Or something else? I'd like to know specifically what it'd be for future reference. Both 1g and 2g info appreciated. And a link or five would be fine.

 

[TunaTalon]

Fuel cut is strictly a function of mass air flow. The Essential Primer on the Diamond-Star Engine Control Units - Chapter 7

The factory threshold is intended to cut fuel when the injectors have reached their limit.
I couldn't find the limit in pounds/hour of air or pulse count from the MAF.

When I had Jeff at DSMchips burn my chip I asked that the fuel cut be increased by the ratio of new/OE injectors. (720/450). Since Jeff was unfazed by that specification I'm sure he knows the factory setting for fuel cut.

 

[Needsoles]

i don't know how to do a boost leak test. i know i don't have any leaks at my piping.

 

[spyderturbo007]

For some stupid reason 2.6g/rev jumps into my head. But let me do a little research and I'll let you know what I find.

i don't know how to do a boost leak test. i know i don't have any leaks at my piping.

Here you go. Since you have never seen that before, I suggest you nose around over at www.vfaq.com where you can find tons of answers to the most common DSM questions.

 

[Zenja]

Load of 2.55 grams per rev = fuel cut

 

[spyderturbo007]

Crap, off by 0.05g/rev.

 

[Needsoles]

hey thanks alot guys you've been great help

 

[spyderturbo007]

That's what we are here for.

Let us know how big of a boost leak you find. I'm betting on the throttle body and / or the BOV gasket.

 

[kenamond]

Thanks for the ~2.6g/rev number, too

Now I need to search on how to convert Hz to lb/min and back for both 1g and 2g MAS/MAF. I wonder if it's dependent on baro pressure and IAT.

 

[spyderturbo007]

Thanks for the ~2.6g/rev number, too

Now I need to search on how to convert Hz to lb/min and back for both 1g and 2g MAS/MAF. I wonder if it's dependent on baro pressure and IAT.

If you figure it out, let me know. It would be so nice for the 1g guys to be able to read actual airflow as opposed to some frequency that means nothing to me.

Since the title was changed to "Resolved", I'm guessing it was a boost leak?

 

[JayRolla]

Yea I'm wondering too, did you find a leak? A lot of times the injector seals on these older dsm's start to leak.-

 

[Ice Racer]

Boost Leak Tester

 

[Needsoles]

i haven't had time yet to run aa boost leak test. i put new seals on my injectors so that cant be the problem. i installed my fuel pump today. i floored it and the same thing happened fell flat on its face. oh and i hooked up my boost gauge and when i was got on my car. about 3/4 throttle my car boosted 14psi. i don't even have i boost controller abd it hitting boost that high. how and why is that possible