1G Fuel cut question

[96talonchick]

I have a stock fuel pump and stock injectors in my 2g 6 bolt swap. I am running 8:3:1 pistons as well. And lastly my timing is completely set right (had an issue with crank timing last wk)

Now to my question. Before we adjust my crank timing we.were running 16psi for boost on 91 pump gas and had no fuel cut except a weird stutter in first gear. Now that my crank timing is fixed we can only run 9psi on 91 pump. Anything after that and I fuel cut bad, as in I almost face planted the steering wheel when it did it.

Today we decided to try out 2.5 gallons of T111 mixed with 6 gallons of 91. We turned the boost up to 12 and had no fuel cut...

So why do I fuel cut with lower boost and 91 pump gas? Yet it loves the race gas mixed and can turn up the boost. I was under the assumption that I needed bigger injectors and a 255 fuel pump, yet higher octane and I can turn the boost w/o fuel cut. Guess my female brain just isnt understanding why this is.

Thanks in advance!

 

[lasershark]

Fuel cut is maf related, the ecu see's too much airflow and as a fail safe it cuts the fuel. Fuel cut has nothing to do with the type of fuel that is used.

If you believe you are experiencing fuel cut, you are either running too much boost (on stock ecu tuning) or you could have a boost leak.

If you have a boost leak(s) the maf will register more air than the engine is getting, the turbo doesn't care you have boost leaks it will pressurize the system to whatever you have boost set at. The turbo will pull more air through the maf by means of compensating for the boost leak.

So I suggest a BLT! Hope the explanation makes sense whether it's related to your issue or not is another story.

Also suggest at least a wally 190, evo 9 or 10 pump (or 8 I guess) rewired, is your stock pump rewired at least?

 

[EvilGST]

Go speed density and don't look back!

 

[pauleyman]

If switching fuels solved the problem it wasn't fuel cut.

 

[TravisB]

Go speed density and don't look back!

Speed density isnt the answer to any problem except the MAF being an restriction. I dont know why people are so quick to jump to SD when its completely not needed nor should it be used as a band aid for another issue.

 

[EvilGST]

Speed density isnt the answer to any problem except the MAF being an restriction. I dont know why people are so quick to jump to SD when its completely not needed nor should it be used as a band aid for another issue.

A bandaid? It's an upgrade. How the hell is speed density a bandaid? A bandaid is shimming a pivot ball.

 

[Mello]

I've never seen a sensor make power. I have seen incorrect (or improperly matched) sensors cause restrictions. The 2G MAF can support quite a lot of power. So how is switching to speed density an up grade? Anyway back the the question, it's hard for me to think your issue is fuel cut. Boost leak is very likely & you should test to rule this out.

 

[mantega4g63]

SD isnt necessarily an upgrade, just a must have for people who outflow the stock maf. Him switching to sd has nothing to do with his problem, don't know why you would recommend it. If he can't figure this problem out, why would he move to a more complicated system than the stock maf?

 

[TravisB]

SD isnt necessarily an upgrade, just a must have for people who outflow the stock maf. Him switching to sd has nothing to do with his problem, don't know why you would recommend it. If he can't figure this problem out, why would he move to a more complicated system than the stock maf?

Exactly this!

 

[96talonchick]

Fuel cut is maf related, the ecu see's too much airflow and as a fail safe it cuts the fuel. Fuel cut has nothing to do with the type of fuel that is used.

If you believe you are experiencing fuel cut, you are either running too much boost (on stock ecu tuning) or you could have a boost leak.

If you have a boost leak(s) the maf will register more air than the engine is getting, the turbo doesn't care you have boost leaks it will pressurize the system to whatever you have boost set at. The turbo will pull more air through the maf by means of compensating for the boost leak.

So I suggest a BLT! Hope the explanation makes sense whether it's related to your issue or not is another story.

Also suggest at least a wally 190, evo 9 or 10 pump (or 8 I guess) rewired, is your stock pump rewired at least?

Well my assumed fuel cut was a nasty lil ordeal. At 9psi on 91 pump gas I would hit boost just fine except when I neared 5k rpm. Anywhere past 5k it could do it, it wasn't always there and it ranged at rpm. The assumed fuel cut was harsh to say the least. While climbing rpm's there would be a "bang" with total loss of sound. Almost like the engine killed, no exhaust sound... nothing. Then when ya let off the gas going "what did I just break" everything was back to normal. I really wish we had taken a video of it doing this because in my honest opinion, if that is how fuel cut feels then its nasty and I never want to feel it again. Seriously made me freak out the first time it happened and I even pulled over and shut the car off. I have yet to see a video anywhere close to what I was encountering with my car.

As for a BLT, we do them weekly just to make sure crap isn't leaking. Last test we did had a minor seep from a blocked off line, put a clamp on the screw blocking it and it stopped. I do know as of a few days ago I got an exhaust leak from a connector piece not being tight, but my issue has been present since day one of running and we now have about 1300 miles on it. I am currently in the market for a new pump, just haven't gotten one yet. And lastly, no my current pump isn't rewired.

 

[96talonchick]

If switching fuels solved the problem it wasn't fuel cut.

Then what should I be looking at as a problem? My local people are telling me it is fuel cut. I have very limited knowledge of cars but like I said in my original post... I just cant understand how a higher octane fuel would allow me to run more boost w/o it doing its nasty cut issue. I can understand how T111 mixed with 91 would allow me to increase boost but at some point I should still encounter the exact same issue as just 91 octane, and I haven't yet. I do know that my MAF is gross and really could be cleaned (which how do I clean it? CRC says to not use it on dsm cars)

 

[pauleyman]

Fuel cut is based on airflow as stated above. You probably had a severe misfire. What are you using for tuning? How much boost? What plug and gap? How does a mas get dirty? Just wipe it out.

 

[Mello]

Our MAF's are Karman/vortex and not Hotwire. Although a lot of folk say they clean there's it just a waste of time. Do you have any way of log/monitoring your knock count? In some ways this sounds like your getting a lot causing the Ecu to pull a bunch of timing. Enough pulled will make things feel like things are being held back hard and can cause misses & backfires. May also be phantom knock.

 

[96talonchick]

Our MAF's are Karman/vortex and not Hotwire. Although a lot of folk say they clean there's it just a waste of time. Do you have any way of log/monitoring your knock count? In some ways this sounds like your getting a lot causing the Ecu to pull a bunch of timing. Enough pulled will make things feel like things are being held back hard and can cause misses & backfires. May also be phantom knock.

Other than a scan tool I have no way to monitor anything. Been waiting on my rims to sell so I can buy dsmlink and fix my issues. Also as a reminder I have a 6 bolt swap in a 2g. I do know this will cause issues with a few sensors and codes, which I keep my misfire code cleared due to it running like crap when the code strikes.

 

[Mello]

Are you using the 2g knock sensors or the 1g that came in your 6 bolt? Is it new or in good shape with no visible oozing? If it's the 1g put a 2g in.

 

[96talonchick]

Are you using the 2g knock sensors or the 1g that came in your 6 bolt? Is it new or in good shape with no visible oozing? If it's the 1g put a 2g in.

It is a 2g sensor, 1300 miles on it. Purchased new when I was ready to fire my car.