Boost cut/Fuel cut?

[JAP63]

Hey evryone.
Got a quick question,Im running the wastegate actator line straight into the aircan,bypassing the standard boost controller,using only wastegate spring tension,the car runs about 12 pound,sometimes goes to a bar the bleeds back to maybe 12 pound...its ran fine like this but lately iv been hitting some sort of cut,usually around 5 grand,the boost is still only about 12 psi at this point so i cant understand why its cutting.

When it cuts im getting a reading of around 1800 karmaans,and sometimes it goes higher than this and doesnt cut,so i cant see how it is an airflow problem.

Any one had this prob?

AND

Will Colder air cause a cut at the same pressure because it is denser and more filling?

Thanks

 

[Entaran]

Is your cut a momentary hesitation? or a fuel cut in a vr4 which very nearly throws you through the windscreen?

The latter is an issue. The former is solved by increasing the diameter of your exhaust as the gasses can't escape and are strangling your engine.

 

[JAP63]

No..its definantley a cut
its preety rough...
Wat u think?
Cold air?

 

[amulday]

I get the same problem,

I was talking to barry about it, he also had the same problem, it seems to happen alot more when the air is cold and dense, I think he said his problem was fixed when he had the wolf put in, and I was talking to dre, one of his mates had a boost cut as well and it turned out to be the ecu. I'll be booking my car in for a wolf in a week or two, I'll let you know if the ecu is causing my boost cut.

sam

 

[matress]

its an air-flow cut isnt it?
after it detects a certain volume of air it cuts out a bit, or something like that.
it used to happen on my car at around 15 psi.
now i have a Wolf3D and it's all good

 

[JAP63]

The thing is i get the cut at an airflow readings of around 1800-1850 Karmaans,then other times i dont.Ive seen it go up to 2200 karmaans,When i had my boost controller in......and it only did it now and then,infact it would cut and id take some fuel out on the SAFC 2 and it stopped,it ran fine.

Does anyone know if Karmaans is what the computer "sees" and reads as its airflow signal,or does it have something else that looks at the "volume" of air going in?

How bad is the cut on the car,damage stuff?gearbox etc?

 

[ENGINR]

I'm suffering the same problem, I'm running stock VR4 afm, 450cc injectors and ecu, 16G turbo and 3" exhaust and am getting the "throw you through the windscreen" cut when the boost spikes over about 12psi.

From the sounds of what's written here it's fuel cut, how do I tackle this issue whilst retaining the stock ecu? Will an e-manage help?

 

[VR-4-PLAY]

you could swap in an EVO AFM, and 550cc injectors, which will allow u to run more boost before fuel cut. But the only way to truly avoid fuel cut is to chip ur ecu. (the VR4 EVO ecu MD165808 has a higher fuel cut if ur engine is jspec)

 

[aurace]

I always assumed the boost cut was determined by volume of air AND air temp. (to account for denser air) - hence why it seems to happen more at night.

 

[VR-4-PLAY]

I always assumed the boost cut was determined by volume of air AND air temp. (to account for denser air) - hence why it seems to happen more at night.

yup ur correct, its a 'Mass air flow' cut.

 

[JAP63]

And of course.Colder air is denser,Which equals more volume..even at the same pressure.

So does any one know the answer to my question?
Is Karmaans a volume measurement?
And if so,why does it not always cut at the same amount on everyones car?
Is it because a better turbo can supply more volume at lower pressure?
Thats why it will cut at 12psi on some cars?

 

[ENGINR]

I've got an EVO AFM, am chasing 560cc injectors. Next question is how do I wire in an EVO AFM without spending $$$ on one of those cables from e-bay?

I could make one up but what is it exactly that the cable does? (Feel free to move this to another tech thread if it hijacks the original too much!)

 

[BobWrinkle]

can i run 560s with an evo afm without it running super rich?

 

[VR-4-PLAY]

can i run 560s with an evo afm without it running super rich?

it will run, and wont be far off at WOT, but part throttle etc will be crap.
Either get a chip to suit, or get a SAFC.

 

[VR-4-PLAY]

I've got an EVO AFM, am chasing 560cc injectors. Next question is how do I wire in an EVO AFM without spending $$$ on one of those cables from e-bay?

I could make one up but what is it exactly that the cable does? (Feel free to move this to another tech thread if it hijacks the original too much!)

VFAQ is your friend :wink:

http://www.vfaq.com/mods/2GMAF-1G.html

note: if ur car is Jspec, then the wire colors are different, just go by the pin positions.

 

[ENGINR]

Thanks for that link!

Very helpful

Cheers

 

[Evil_Mx6]

hey guys, as u know i got an auto vr4 jspec....
wat is my boost cut ?
been a jap ecu wat do u think the boost cut is ??
im gonna be boosting it up really soon to about 14psi....
just wondering if i will hit cut or not....

cheers
Barbs

 

[jett]

hitting boost cut = time for a new ecu...

Don't F*ck around - get a decent aftermarket one - there are quite inexpensive options available if you look..

Check out http://www.adaptronic.com.au

PM me for a decent price...

 

[basshead69]

i had the same problem when i hit exactly 15.6Psi on a cold night, when it did that the air fuel mixture was starting to get to the lean side. now just by putting a fuel regulator in , i am actually running close to 17psi on stock ECU, 450cc injectors, no aftermarket exhaust. Just for your info if you wish to try it, i am running 42psi fuel pressure on that regulator.