WHat exactly causes fuel cut?

[jamesdem1123]

so i think i hit fuel cut tonight. i cranked up the boost to around 12 psi and when i would get there it would kinda buck and the check engine light would come on. is this fuel cut or some other situation saying my car is screwed up? lol

anyone that knows EXACTLY why fuel cut occurs plz tell me
thanks

 

[Yellow 13]

Sounds like fuel cut. From what I understand its your engines inability to supply enough fuel to the engine, hence the term fuel cut.

When you up the boost in your car you force more air into the cylinders. disrupting the fuel to air ratio. Now your car wants to keep the fuel to air ratio at some proportion, but with the large amount of air being fed into the engine it can no longer supply enough fuel to do this. Thats why people get the 550 cc injectors.

The AFM upgrade fools the engine into thinking its getting its normal amount of air when its actually being fed more, and the 550 injectors help componsate the ratio.


If im wrong someone correct me.

 

[xarewhyayen]

Fuel cut is a defense system for your motor. As you already should know, running lean is deadly. If your motor loses the ability to supply enough fuel for the amount of air your turbo is packing in, you will detonate. Detonation will not only mess up pistons, throw rods, etc, but also likely blow ur headgasket. So yeah, fuel cut is ur friend.

As far as the 550 injectors and the afm upgrade, yes yellow youre right, you get a bigger air meter and use the adjustment screw to let through some unmetered air and compensate for the air with bigger injectors. This is best combined with some good air fuel tuning using a Wideband.

 

[jamesdem1123]

so ecu is spitting out oo much fuel and cannot send more, injector duty cycle reaching the limit.

on the dyno with a wideband my car was running very rich, less than 10 (sensor only reads to ten). if i lean it out by letting unmetered air in thru stock bottom screw will it raise fuel cut? only plan on getting to 11.5 a/f, no higher.

thx

 

[staticpat]

If I understand correctly: The AFM sends a certain voltage for all the air it sees. If this voltage gets too high, it knows from maps that it does not have enough fuel to compensate. So it initiates "fuel cut". Letting in unmetered air would obviously make the AFM output less voltage from the same air flow. Also upping fuel flow physically and leaning your AFM signal (ie piggybacks or voltage clamps) would accomplish this. Fuel cut is there for a reason, to stop you from running lean. You shouldn't attempt to bypass it unless you are letting in more fuel, and have a way to monitor and tune it.

 

[jetjock]

In the case of a turbo car the AFM sends out a frequency (not a voltage) proportional to metered airflow. The ecu is programmed to cut injection when this frequency exceeds a certain amount. It's a function of the TCCS's fail safe mode. That's what happens. Why it needs to happen has already been explained but the designed purpose is to protect against various forms of wastegate failure.

 

[xarewhyayen]

I havent done any air fuel tuning yet, but i would think that a SAFC type controller would be very handy in doing this. Theres so many how to's on this site as far as the steps to achieve your goals goes. I'd suggest looking through some of those. Its not so easy to just up the boost to fuel cut and try to tune with the stock set screw. I'd suggest doing some research now rather than coming back crying later. Good luck though i hope this helps

 

[fatality]

does anyone know if fuel cut is related at all to the O2 sensor? I shimmed my wastegate and was hitting fuel cut every day. so I took one washer out on each side and it would still cut in third and fourth. One day I decided to add an octane booster into my gas, one of those premium ones and all of a sudden not fuel cut whatsoever. I've been adding that in ever since and never any signs of fuel cut. to test it one tank I let go with just premium gas and fuel cut reappeared. now my question is if the AFM alone is responsible or does the air/fuel mixture have something to do with it as well.

 

[jetjock]

Вы можете читать? Что я говорил? возможно если я напишу на русском языке то Вы поймете?

 

[Jeff Lange]

Thread Moved.

 

[Joel W.]

Lol, то будет некоторым юмористическим правом гречихи там.

 

[Yellow 13]

Вы можете читать? Что я говорил? возможно если я напишу на русском языке то Вы поймете?

I knew the Russians had something to do with it!

 

[GrimJack]

fatality, your octane booster is unrelated to fuel cut. Coincidence strikes again.

 

[whopwood]

I always thought fuel cut was the result of running off the map. Basically, the computer says "I don't know what to do based on these input values".

 

[Kyle87T]

If I were to just buy a walbro fuel pump, would I have a higher fuel cut?

 

[GrimJack]

FC is based off several factors. The primary one is the frequency returned by the AFM, telling the ECU how fast the air is moving in the intake tract, but there are several other inputs that affect the exact point as well.

JJ might know more on this, to date nobody who knows all the inputs has been willing to talk about it.

 

[GrimJack]

If I were to just buy a walbro fuel pump, would I have a higher fuel cut?

No. FC has nothing to do with how rich / lean your engine is actually running, it's all about how lean your ECU *thinks* you are going to run based on what air is going into it.

 

[Nick M]

Вы можете читать? Что я говорил? возможно если я напишу на русском языке то Вы поймете?

That is a damn good answer.

 

[jetjock]

Well he didn't seem to understand me the first time so I felt it appropriate, although badly written. My Russian isn't all that great. I can read and speak fairly well but writing is harder. The grammar alone makes me crazy. The wife is always after me to learn more because of all the time we spend in Ukraine but I'm too lazy.

 

[Jetfixr757]

Lol, то будет некоторым юмористическим правом гречихи там.

My question is what's up with the russian keyboard, ?? if you type in english and it comes out as russian where can i get one...
Jet