Another fuel cut, confused.

[marcelo_caz]

So, i've been looking on the forum for a while and still couldn't find an answer for my situation, so here it goes.

Yesturday I took my car to english racing for them to install my GM MAF-T, mine 3.5" intake pipe and tune the car.

Everything went well... intallation was really good and I got the car tuned at 15psi (peaks at 17psi).

I do have the 450cc, 14b turbo, and non-eprom ECU.

After talking to Lucas he told me to get the 580cc injectors so in the future to pump my boost up to 20psi (but I think he doesn't know I still have the non-eprom ecu.)

When I left his shop, the car was a beast, pulling really hard and holding 15psi at boost with no problem, but when I go from a dead stop and launch the car, I get fuel cut, my boost goes to 15psi, but the car doesn't pull.

Basecaly from a rolling start, I get that 15psi with no problem... pulls really hard, but from a dead stop I get fuel cut.

What should I do?
Will just the 580cc injectors take care of this? or would I need an EPROM ECU so I can get an eprom with no fuel cut?

Yes all the manitance on the car is done, there are no boost leaks or anything.. car is runing awsome, and I know that the stock 1G if you go over 15psi the ECU will cut my fuel.

But what can do???


Thanks for any help guys.

 

[delta448]

I don't think that's fuel cut. Fuel cut is based on airflow, what rpm are you launching at?

 

[marcelo_caz]

around 4000rpm.

It is really strange, because it only happens once in a while.

 

[turboglenn]

I would say it's detonation or engine noise setting the knock sensor off and pulling a ton of timing if it just feels like the car wont' accelerate even though you've built boost. Fuel cut is when the car just straight cuts of for a second or so at a time until the boost falls and the airflow is back under "fuel cut levels" It's like turning off a switch to the power on your motor all at once. If the car revs high but doesn't move it could be the clutch, but usually fuel cut and clutch issues show up in the higher gears first. Most times I've dealt with knock holding a car back when you step on the pedal it's most of the time happening in first gear.

 

[marcelo_caz]

I don't know if it is knock, I just got a brand new knock sensor in the car in February (if this has nothing to do, just correct me).

An example from hat happened yesturday was here on my street, I stoped the cars and launched (around 4000rpm) in first gear, the boost went up to 15psi and it pulled hard (it felt awsome), then when I shifted to second, the boost built up, and i didn't feel that pull (did not feel awsome)... so I let my foot off, and steped on the gass again, then I felt the turbo pulling again.

another example was when I was showing to my friend I was giving him a ride, i took off from his drive way normal and when I shifted to second and hit the gas all the way, it didn't pull, but my boost was at 15psi and car felt it had no turbo on it, so I let my foot out and hit the gas again, than it felt I had a turbo.

 

[r1991_4g63t]

I would say it's detonation or engine noise setting the knock sensor off and pulling a ton of timing if it just feels like teh car wont' accelrate even thouhg you've built boost. Fuel cut is when the car just straight cuts of for a second or so at a time until the boost falls and the airflow is back under "fuel cut levels" It's like turning off a switch to the power on your motor all at once. If the car revs high but doesn't move it could be the clutch, but usually fuel cut and clutch issues show up in the higher gears first. Most times i've dealt with knock holding a car back when you step on the pedal it's most of the time happening in first gear.

look for anything that could be loose, im having a problem i believe is due to my a/c pulley not being hooked up and rattling.

 

[marcelo_caz]

look for anything that could be loose, im having a problem i believe is due to my a/c pulley not being hooked up and rattling.

I checked all mine vacum lines and they are all good, pulleys and belts looks good too.

 

[No_Skillz]

I'm gonna go with turboglenn on this one. Hook up a logger, I'll bet you're pulling timing due to knock.

 

[marcelo_caz]

I'm gonna go with turboglenn on this one. Hook up a logger, I'll bet you're pulling timing due to knock.

this is what is bothering me.. I had the car tuned yesturday (MAF-T, CAS, and he was using a logger).

 

[turboglenn]

True knock that you're getting while wide open is usually not as intense as the knock we get from other things making noise (with a proper tune anyway).. It's probably not real knock, it's something making noise/rattling that's transferring it's noise through the engine and the KS is picking it up. That would be my bet anyway....

I can and do have 10* of timing pulled at 2500 RPM and 20% throttle from the AC compressor making noise.. and it looks and feels fine, but it is making noise.. I've proved it by eliminating the issue by removing the AC belt.(this is on MY car though..not saying i know your AC is the issue, but it is mine). When wide open I'll maybe pull one degree at 5500 if any at all (this is from "real" detonation or knock)...

The difference... The 10 degrees is from Phantom knock/ false knock etc but either way a noise from something else around the motor that's making more noise than a knocking motor.... not real knock. The REAL knock that is picked up under WOT is only a degree or 2 because the noise isn't that loud it's just true mild detonation. Your knock sensor is a small microphone, it takes noise, amplifies it and relays it to the ECU, I've even seen bad ball joints cause PK under hard shifts, so anytime there's a lot of timing pulled/knock readings especially at anything less than 50% throttle i always start looking for things outside the motor that are making the noise..when it's picked up only at WOT then i look for trouble in the tune or components inside the engine

 

[marcelo_caz]

So i've been asking my problem around, and my friend came with the most resonable answer so far (its what I think)

Here is hat he said:

"your not melting the clutch your glazing the flywheel. its where the cluch just slips and leaves a resadue on the flywheel. that what happens when i try and launch my car. it jumps and pulls for a second but when you shift its like you have no power to the wheels. then if you let off and let the cluch grab again it will take off. sounds like its time for a new cluch dude. or just dont launch at 4000 rpm."

does it make sense?

 

[r1991_4g63t]

do you have a logger? if not i would get one, theyre not expensive. i had a loose A/C pulley and it was affecting the knock sensor and made my car run exactly like yours is. the reason it runs better after stepping on the clutch is because it resets the knock count and timing.

 

[marcelo_caz]

ill check that, I think I know a guy ho has one that can help me out.

 

[LucasEnglish]

If you wanted to come back out I would be more then happy to go out with you and see what it is doing.

 

[marcelo_caz]

heyyy Lucas... I thought you were on vacation.
hahahahaha
yeah... that whould be awsome, mike might wanna go too, he said his car is overheating I think.

Ill call you tomorrow to schedule a day and time.