fuel cut I have no idea whats wrong. help

[Merkles]

I have no idea what is wrong with my car. My mods are listed in my profile. Here is my problem. My car rips until 15psi where I have my boost set and holds until anywhere between 4500 and 5500 rpms then hits fuel cut. I have no clue why. I ran a boost leak test and had 1 tiny leak at the throttle body but I fixed that and I changed my spark plugs and put new ones in. Any ideas?

 

[CanadianTSi]

Either you have another undiscovered boost leak or that 18g is just flowing too much air, then you will need to get some sort of tuning device to either hide the airflow or disable FC.

 

[v8s_are_slow]

I certainly doubt it's fuelcut you're getting. What's your gap? Are you still using the BRP7's? What's your afr's?

 

[Merkles]

My gap is .028 and I am running BRP6ES plugs now, I should of changed that. I am on the factory ecu with no tuning which is why I am only running 15psi. I will be getting DSMlink or a keydriver from dsmchips soon. It feels like fuel cut, its most definitely the brick wall feeling. Could bad plug wires cause this? I have no CEL but could it be that my MAS is bad?

 

[viperlp01]

Well as you should know a way bigger turbo like that flows way more air more efficiently. So say that 15 psi isn't that hot coming out of that 18g but it is pretty hot coming out of the t-25. SO by being hotter makes that air less dense making those fuel molecules able to have the amount of air needed to run at a safe a/f on the stock t-25. the 18gs can flow way more air at a cooler temp. What im trying to say is that you could possibly hit fuel cut on 15 psi on a fmic 18g running "stock" boost on stock injectors. That air is way more dense and there is not enough fuel coming out of stock injectors to satisfy its needs. Thats that way i understand the whole concept. That is why we put fmic's on, to make the air more dense for a better burn and less psi for the same amount of power.

 

[JayRolla]

My gap is .028 and I am running BRP6ES plugs now, I should of changed that. I am on the factory ecu with no tuning which is why I am only running 15psi. I will be getting DSMlink or a keydriver from dsmchips soon. It feels like fuel cut, its most definitely the brick wall feeling. Could bad plug wires cause this? I have no CEL but could it be that my MAS is bad?

That turbo should not be pushing enough air to cause fuel cut at only 15psi. There is pretty much only one explanation for the fuel cut and thats a boost leak. What level of boost did you pressure test the system? How long did it hold?

 

[Merkles]

I pressure tested the system at 20psi, I'm not sure how long it held it because my boost gauge is in the car, I was too busy spraying soapy water over everything intake related in site. I found a few minor leaks that I fixed but still fuel cut. I guess tomorrow when I am out of work, I will do a couple more tests and see how long it holds the 20psi for and spray some more soapy water. Its just a PITA to do right now because Im in VA for the summer and my air compressor and most of my tools are home in NY. The gas station is my boost leak testing station right now. ha. I will post back my results tomorrow night.

 

[dsm-onster]

That turbo should not be pushing enough air to cause fuel cut at only 15psi. There is pretty much only one explanation for the fuel cut and thats a boost leak. What level of boost did you pressure test the system? How long did it hold?

Oh but it will. The 18g is a very efficient compressor. From my experience fuel cut is on a 79 degree day at 15-16 psi with stock cams/intake/manifolds with the needs of this compressor. The compressor uses less energy to maintain 15psi. It wastegates the rest leaving you with much better overall VE in the midrange. High VE is what leads to fuel cut as it is determined by a gram/rev number.

Well as you should know a way bigger turbo like that flows way more air more efficiently. So say that 15 psi isn't that hot coming out of that 18g but it is pretty hot coming out of the t-25. SO by being hotter makes that air less dense making those fuel molecules able to have the amount of air needed to run at a safe a/f on the stock t-25. the 18gs can flow way more air at a cooler temp. What im trying to say is that you could possibly hit fuel cut on 15 psi on a fmic 18g running "stock" boost on stock injectors. That air is way more dense and there is not enough fuel coming out of stock injectors to satisfy its needs. Thats that way i understand the whole concept. That is why we put fmic's on, to make the air more dense for a better burn and less psi for the same amount of power.

It is not about how much cooler the airflow is. The intercooler, even stock, cancels too much of the temp increase from the adabiatic process of fluid compression for it to be a concern. The compressor IS however much more efficient. That efficiency does lead to fuel cut, but not because of the lack of heat. However because of the reason I stated above. Because of the less energy needed by the exhaust to maintain the boost since the compressor turns more work into boost instead of heat vs. other compressors. The 18g compressor is VERY efficient.

 

[DSM4me44]

Back when, I hit fuel cut with my T25. I ended up using an SAFC to fix it.

I haven't had a problem since. I have a 14b w/ 16g hotside and DSMlink.

For whatever reason, my car loved to hit fuel cut before any tuning device was used.

 

[v8s_are_slow]

I misread your mod list. I was thinking you had 780cc injectors, etc. So you're on stock injectors, stock ecu, nothing for tuning, no wideband, and just running 15 psi on that turbo correct? Are you using ANYTHING for tuning?

 

[ApexVIII]

stock injectors? boost creep maybe?

 

[v8s_are_slow]

When I 1st got my car, it'd kick really hard as soon as I threw it into 3rd gear. I had a wideband laying around so threw it in and my afr's were at 10 and didn't move any higher (very rich). Was just running so rich that the spark plugs couldn't ignite the fuel and therefore the kick. I made a couple of clicks on the maft and car ran GREAT!!! A few clicks of a maft can make your car very rich or very lean very easily and without a wideband, it's very risky. I don't run without one. Just a suggestion to your next mod.

 

[JayRolla]

Oh but it will. The 18g is a very efficient compressor. From my experience fuel cut is on a 79 degree day at 15-16 psi with stock cams/intake/manifolds with the needs of this compressor. The compressor uses less energy to maintain 15psi. It wastegates the rest leaving you with much better overall VE in the midrange. High VE is what leads to fuel cut as it is determined by a gram/rev number.



It is not about how much cooler the airflow is. The intercooler, even stock, cancels too much of the temp increase from the adabiatic process of fluid compression for it to be a concern. The compressor IS however much more efficient. That efficiency does lead to fuel cut, but not because of the lack of heat. However because of the reason I stated above. Because of the less energy needed by the exhaust to maintain the boost since the compressor turns more work into boost instead of heat vs. other compressors. The 18g compressor is VERY efficient.

Maybe you had some type of issue. My brother is running 28psi on an evo16g and a stock 2g maf with no fuel cut. I have a buddy running 22psi on a 20g with a 2g maf and no fuel cut. The 2g maf should beable to lay down 400-450whp before cutting out and thats hard to break with an 18g. Im not saying your lieing just in my experience the 2g maf can go a long way!!

 

[v8s_are_slow]

Yeah, I'm not thinking it's fuel cut either. You have an aftermarket fuel pump right? Do you have the stock regulator? The fuel pressure might be bumped up some, adding more fuel. You could pull the plugs just to see if they're looking black at all. I'm thinking that it's either too much fuel (and you can't really tell because you don't have a wideband), or a boost leak as mentioned above.

If your maf was bad, you'd probably be running really rich as well. Doubt that's your problem but anything's possible. I've ran my T-67 when I had my 2.3 liter stroker with stock injectors just to drive the car while waiting on some injectors. It ran okay on that huge ass turbo with no problems but I'm sure the injector duty cycle was probably screaming.

If nothing else, recheck your gap just to make sure the gap is set correctly.

 

[CanadianTSi]

Fuel Cut is based solely on the Amount of Airflow the ECU see's, nothing else.

 

[dsm-onster]

Maybe you had some type of issue. My brother is running 28psi on an evo16g and a stock 2g maf with no fuel cut. I have a buddy running 22psi on a 20g with a 2g maf and no fuel cut. The 2g maf should beable to lay down 400-450whp before cutting out and thats hard to break with an 18g. Im not saying your lieing just in my experience the 2g maf can go a long way!!

Not on stock fuel injectors with proper tuning: which pushes back fuel cut. The 2g ecu reaches fuel cut at the same time as a 1g: at 2.55g/rev. I've hacked the binary for 1g and 2g eproms and seen the number. Gram/rev is purely based on overall VE.

You're confusing fuel cut with maf overrun... we're talking about the point where the ecu cuts off fuel not where the maf begins skipping hz counts and flattens or dips in output.

 

[Merkles]

Spark plugs are black, car is running very rich. Is it possible some of my emissions things are messed up? Could my EGR valve be internally leaking? I really have no clue what to do at this point because regardless tuning or not I should not be hitting this brick wall (fuel cut) at 15psi.

 

[v8s_are_slow]

Did you keep the stock fuel pressure regulator with the new pump? Ya may just wanna throw the stock pump back in until you can get something for tuning. Wideband and something to lean out the fuel with. Your fuel pressure regulator can go bad if you have too much fuel pressure on it....making you run rich as well.

Also, if your maf does go bad, you'll be running rich as well. Just something to try and swap out if ya have a buddy to exchange parts with to diagnois the problem.

 

[Merkles]

Well I have an Evo 8 fuel pump which flows a little more then a Walbro 190 so there is a possibility that I am overrunning my FPR, I may get an adjustable FPR and test my MAS. I'm going to keep trying different things, something is obviously wrong I will keep everyone posted. If you have an idea feel free to chime in. Thanks

 

[risknjtsi]

i had the same problem when i was running my e316g stock fuel system but i was running 11psi my problem was i was using cheap spark plug wires wasnt giving enough spark to burn the fuel what wires are you using ?

 

[Merkles]

Bosch wires..... maybe the wires are toast.... Ill check it out.

 

[risknjtsi]

ditch the bosch those were the ones i was using i switched to ngk wires or look at magnacore 8.5

 

[Merkles]

Put new wires in and removed the emisssions stuff for the time being just to rule all of that stuff out. Its still doing it. Could my stock FPR be overrun by the Evo fuel pump?

 

[v8s_are_slow]

Yes it could. But might not be the problem. Have someone near who can let ya swap parts to narrow down your problem?

 

[Merkles]

Thats one issue, I'm working in Sterling, VA for the summer for an internship and I'm from NY so I don't really know anyone with a DSM around here. Its has to be either my FPR or my MAS. At this point I have no idea what to do other then order a new FPR and MAS and pray that it fixes my problem.