Fuel Cut at 9 PSI?????????

[hvfracingwilly]

The specs,

FMIC 2.25" piping
3" Exhaust from the turbo back
Waste gate dumps to atmosphere
Aftermarket BOV
Engine internals are all new with about 1000 miles on them, I have had the car for a week. Hitting fuel cut I assume......


I guess the main question is should I be hitting fuel cut at these low boost levels? If not I have read that could be a waste gate issue, boost leak, or????????


Car runs great untill i try to mash the throttle, I hit 9 PSI and it just cuts out. Also seems to take awhile to build boost, doesnt hit till 4,000-4500 RPM.

Please HELP......

 

[radiod]

I'd check for boost leaks before even getting started.

http://www.supramania.com/forums/showthread.php?t=19718&highlight=boost+leak+tester
http://www.vfaq.com/mods/ICtester.html

Take your pick

 

[GrimJack]

What turbo?

Premature boost cut is almost always due to a boost leak.

Whether yours is premature or not depends on how much air you're pushing, not what the pressure is, and this is dependant on the turbo, IC, IC pipes, throttle body, ambient temp and pressure, and a bunch of other minor factors.

 

[hvfracingwilly]

It is a stock turbo, I was hoping to be able to jump to 10-11 PSI but untill I figure out this fuel cut issue I'm scared....

Thanks will be running around the car looking and listening for leaks.

I am still confused on what the ECU is looking at to determine if it should cut fuel or not. If I could understand that I might not have to ask another question.

 

[radiod]

What the ECU is doing is essentially looking at the volume of air coming through your intake at your MAF sensor and adjusting the fuel to compensate for rich/lean. If your injector duty cycle gets dangerously high, your the ECU will "fuel cut" in order to stop catastrophic lean out detonation. Basically, it's trying to do you a favour and keep you from blowing up your engine.

If you have air leaking out of your intake system PAST the sensor, your sensor is reading more air than your engine is actually getting, therefore will cut sooner.

As air gets cooler, it is denser and thus measured as a higher volume of air coming in at lower pressures. That is how temperature will affect your fuel cut level.

On my current setup I have a 57-trim CT26 and 2.5" SS IC pipes to a stock IC and I hit fuel cut at about 12psi on a hot day, 10 psi on a cold day.

 

[hvfracingwilly]

By far the simplest explanation that has made the most seance. Thanks.

 

[paradox616]

i wouldn't say the duty cycle is gets dangerously high. but yeah ive noticed its based on many other factors as well such as knock counts, air temp etc.

mine hits boost cuts on a hard shift... and round 9-9.5psi pending on weather really.

 

[hvfracingwilly]

Found some of the issue tonight, it seems the BOV was set really soft and possibly leaking out boost. I adjusted it and now the car spools up faster and accelerates harder.

I also noticed the boost is now jumped up to 15 PSI, they have about a 1/2 inch of spacer on the waste gate so the next step is to reduce the amount of shims and bring boost back to a safe level.

Thanks for all your help!

 

[Ozz89supra]

make sure you check and double check ALL your IC piping. I had the same problem and I swear I went through the whole system many times (or so I thought) and finally I found a huge tear in the hose coming off the turbo to the intercooler. So make sure you completely check all your ic piping, than go from there. Hope it helps and good luck

 

[radiod]

I don't know how you'd even get to 15psi with out stuff done to your MAF/ECU with out hitting fuel cut, but that aside, yes, get your boost down. 15psi on a stock turbo is just...well...not good.