Hitting fuel cut at 9 psi

[Devin LeBlanc]

My car likes to hit fuel cut at the top of 2nd gear (automatic).. I am NA-T on a 7M with stock internals and cams.

Here is how the car is setup:

Stock CT26 turbo
GTE intake manifold
GTE electronics(ECU and wiring Harness)
Cone style intake
Drift-motion big front mont 2.5 inch aluminum pipes
2.5 inch exhaust with one high flow cat, Other than that cat is cut out of stock down-pipe and is straight the rest off the way after the high flow cat

TPS Set in spec per TSRM
Timing at 10 degree's BTDC
AFM Tested
AFR's at 10.5-10.8 under full boost
No boost leaks (Unless IACV is leaking)

Now when I first got the car running I was running no exhaust and boosting 11-12 lbs but never hit fuel cut.. Now with the exhaust on I am at like 9.5-10 and hit fuel cut only in 2nd gear

Anyways wondering what would cause this

Thanks

 

[radiod]

Cold day vs warm day? That can make a difference of a psi in fuel cut. Especially with the larger IC piping. I typically hit it around 10psi on my car on a cooler day (50F).

 

[mkiii222]

How are you measuring max psi before fuel cut? Peak and hold gauge, eyeballing your gauge...?

Boost leaks can cause fuel cut to kick in sooner. Using myself as an example I raised my fuel cut from 11.5 psi to just over 13 psi by replacing the fuel injector o-rings (FI to head side).

 

[Devin LeBlanc]

did you not read my post? I stated that I have no boost leaks, That was checked with pressurizing the intercooler and piping with compressed air up to 12 PSI..

 

[mecevans]

Bov?

 

[mdr40z]

sounds rich to me, how are you controlling a/f?

 

[Devin LeBlanc]

I am in the mid-low 10's AFR's waiting to get my new updated neo back from Apexi.. I had the old version that doesn't work with Karman

 

[mkiii222]

did you not read my post? I stated that I have no boost leaks, That was checked with pressurizing the intercooler and piping with compressed air up to 12 PSI..

Do you know how many times people come in here and say 'I have no boost leaks' and it turns out to be a boost leak? And pressurizing the pipes will only cover 90% of what can leak anyways (why I mentioned my fuel injector gasket problem, 1.5 psi drop in fuel cut). You can still lose pressure in the manifold (2 manifold gaskets, 6 injector gaskets, ISCV, throttle body gasket, and several 'vacuum sources').

Now if all you did was swap out the exhaust and are experiencing a 2-3 psi drop in fuel cut then something doesn't add up. You are running way rich which would indicate a boost leak.
mecevans could be right with the bov question as well. If the bov is stuck open it will cause similar issues. The air comes in but bypasses the turbo.

 

[gottadiesel]

Do you know how many times people come in here and say 'I have no boost leaks' and it turns out to be a boost leak? And pressurizing the pipes will only cover 90% of what can leak anyways (why I mentioned my fuel injector gasket problem, 1.5 psi drop in fuel cut). You can still lose pressure in the manifold (2 manifold gaskets, 6 injector gaskets, ISCV, throttle body gasket, and several 'vacuum sources')..

Yep for sure for sure... When I did a leak test (when still running an AFM - I am now SD) but I capped in front of the AFM housing (removed and sealed up electronics holes), capped the exhaust tail pipe, removed vents from valve covers and capped, isolated EGR from plenum... Did full test @15psi, used soapy water and went looking everywhere for any leaks... This is one of the ways to get a full leak test (even better if I has a smoke machine and did the same thing)

 

[Devin LeBlanc]

Every Hose and vacuum line was replaced and is zip tied on, Injector O rings have been replaced upper lower and insulator, every gasket on the top end of the motor has been replaced. Every hose either has a zip tie or a screw type hose clamp on it.. My Blow off valve is not open. I am sure it is just because I am pig rich, that is what they run from the factory.. Also the temp dropped 15-20 degree's. I am on 9.1:1 compression pistons as well so I spool a bit faster than stock GTE's that could also play a part in fuel cut.. My brother was at 18 PSI on a T4 making over 400 HP and did not have a FCD.. He was on stock injectors and was tuned in the mid 11 AFR's, That turbo spooled late though

 

[hvyman]

Do you get fuel cut at 8psi?

 

[Devin LeBlanc]

no I only get it at like 5000 rpm only in 2nd gear At 9.5 PSI

 

[hvyman]

Not in 3rd or 4th?

 

[Devin LeBlanc]

No, not at all Im Automatic as well

 

[Supra0089]

Okay. I have an automatic. Do you hit fuel cut between shifts? Or during gear?

If you get it between shifts, this is because with all automatics, you will spike boost between gears while keeping throttle from half to WOT.

If during a gear and under throttle...it's probably a boost leek...or you are boosting higher than you think you are or than your gauge can read...and you're hitting fuel cut.


------

Edit: You have a big intercooler on...was this on when you bought the car, or did you put it on? I ask because...bigger cooler=denser air=fuel cut at a lower PSI (like 9.5)

---------- Post added at 08:43 PM ---------- Previous post was at 08:30 PM ----------

did you not read my post? I stated that I have no boost leaks, That was checked with pressurizing the intercooler and piping with compressed air up to 12 PSI..

I'm also interested in how you are measuring boost? Do you have a gauge...in the car...that remembers highest boost? Sometimes you can't see the boost visually when it cuts (cause it might spike faster than you can read).

---------- Post added at 08:44 PM ---------- Previous post was at 08:43 PM ----------

I am in the mid-low 10's AFR's waiting to get my new updated neo back from Apexi.. I had the old version that doesn't work with Karman

Low 10's under WOT on an untuned 7m with upgrades...isn't uncommon for what I know...yes it's rich...but it shouldnt be creating fuel cut? SHould it?


"I have questions...questions that need answering"

 

[Devin LeBlanc]

I am watching it with an aftermarket boost gauge and it spikes to 10-11 lbs during a shift.. My boost gauge reads up to 30 psi so thats not the problem

The car is a N/A so never had an intercooler on the car.. I am still running N/A Block and pistons ( I hit full boost sooner so can also cause fuel cut)

Once we lean it out the AFM wont see as much (intake air "boost") so will most likely not hit fuel cut anymore! I get my SAFC Neo back from Apexi (new software reflash) today so will retune this week and shoot for 300HP on what ever boost it takes probably around 11-12 lbs

 

[mecevans]

Did you port ur wastgate?

 

[Devin LeBlanc]

no that is all stock lol turbo has 220k on it lol