Fuel Cut: What is it? How do I fix it? [merged]

[Slanted J]

All fuel cut threads are combined here.

I've tried doing a search but to no avail.

I was just wondering what Fuel Cut is. I've heard it tossed around alot, but do not actually know the details behind it. And, naturally, I can gather that its when the fuel is cut off, but when and why.


Thanx,
Jon

 

[RyanTSi]

Lower boost.

 

[shiftdrift06]

A better understanding of fuel cut.

http://www.dsmtuners.com/forums/showthread.php?t=186971

 

[Xplicit93AWD]

You can also get a fuel cut defensor. They go for pretty cheap on ebay.

 

[andymoraitis]

An EPROM ECU with a Keydiver Chip will also eliminate fuel cut as an option and is less expensive than buying DSMLink.

Andy

 

[xucpxeclipsex]

so if i get a 190/255lph fuel pump.. will that automatically eliminate the fuel cut??.. or do i still have to mess with the computer.. i have a s-afc.. can i do anything with that to eliminate it after i get the fuel pump??/

 

[xucpxeclipsex]

An EPROM ECU with a Keydiver Chip will also eliminate fuel cut as an option and is less expensive than buying DSMLink.

Andy

how can i get a kediver chip??

 

[GVR4592]

http://www.dsmchips.com/

 

[slugsgomoo]

you need an eprom ecu, and then just head over to www.dsmchips.com

 

[RS-RGS-T]

hks fuel cut defencer only cost about 100 bucks works great
TRUST ME READ THIS ACTUALLY EVERY ONE READ THIS! http://importtuner.com/powerpages/0311it_ppeclipse/
simple mods under 650$ msrp 500$ my cost and this
The Parts
1 APEXi N1 Downpipe $239.00
2 HKS FCD $150.00
3 Holley 255lph fuel pump $251.00
MSRP total $640.00


Conclusion: A two-hour-and-15-minute install netted a total of 106.7 horsepower and 79.8 lb-ft of torque. We only did six small modifications and are still on the stock turbo and that has me curious as to how far we can take the car in street trim.

Performance Chart
HP Level HP+ TQ Level TQ+
B Baseline 183.6 * 198.6 *
1 APEXi Downpipe 219.9 36.3 228.7 30.1
2 HKS FCD 267.1 47.2 252.8 24.1
3 Holly Fuel Pump 290.3 23.2 278.4 25.6
F Final 290.3 106.7 278.4 79.8

 

[CanadianTSi]

Fix your boost leak...

 

[Mr4G]

you do not wanna eliminate fuel cut. fuel cut is a safety mode for your car to save your engine. you have an apperent problem if your hitting fuel cut. Fix the problem and you should be golden.

 

[andymoraitis]

you do not wanna eliminate fuel cut. fuel cut is a safety mode for your car to save your engine. you have an apperent problem if your hitting fuel cut. Fix the problem and you should be golden.

This is actually incorrect. Fuel cut has nothing to do with the motor running out of fuel. When the ECU senses too much air (from higher boost levels or from the increased flow of a larger turbo) it will cut fuel supply to the motor because it thinks that safe limits of airflow have been reached. The ECU has no idea that a larger fuel pump and injectors may be present and this is the downfall of a VAF (volume air flow) system.

The fact of the matter is that fuel cut is perfectly safe, if the correct supporting mods are in place. There is nothing to fix to eliminate fuel cut,

Andy

 

[andymoraitis]

so if i get a 190/255lph fuel pump.. will that automatically eliminate the fuel cut??.. or do i still have to mess with the computer.. i have a s-afc.. can i do anything with that to eliminate it after i get the fuel pump??/

If you reference the post right above this one, you'll see what I mean when I say that fuel cut has nothing to do with an absence of fuel. It's more about the ECU seeing too much airflow and cutting the fuel off as a safety. In order to properly bypass fuel cut and therefore run more boost, you can use the AFC to compensate. This may not eliminate fuel cut, but it will delay it since the AFC works by subtracting airflow and fools the ECU into thinking that less air is passing through the MAF on the intake.

So, no, adding a fuel pump alone won't help (but it's a good idea to have a 190 for future upgrades anyway). If you don't know how to tune with the AFC, I would recommend that you have someone who does set it up for you or take it to a professional. Otherwise, you could subtract too much airflow and end up skewing the timing curves. The end result can be as minor as generating some knock, or as major as running the motor so lean as to create internal damage.

Additionally, you could purchase an EPROM ECU with a Keydiver Stage III chip that will eliminate fuel cut. The beauty of the EPROM ECU setup is that unless you make changes to the air/fuel and timing tables within the chip, the factory air/fuel and timing settings will be retained while fuel cut can be eliminated. I prefer this option since we can still scrape more power out of the motor by adding a few custom changes without being unsafe, provided you don't add a bigger turbo and yank on the boost.

Let me know if that makes sense,

Andy

 

[92awddsm]

This is actually incorrect. Fuel cut has nothing to do with the motor running out of fuel. When the ECU senses too much air (from higher boost levels or from the increased flow of a larger turbo) it will cut fuel supply to the motor because it thinks that safe limits of airflow have been reached. The ECU has no idea that a larger fuel pump and injectors may be present and this is the downfall of a VAF (volume air flow) system.

The fact of the matter is that fuel cut is perfectly safe, if the correct supporting mods are in place. There is nothing to fix to eliminate fuel cut,

Andy

I agree and the #1 cause of fuel cut is boost leaks. Do a boost leak test, fix leaks, and now see that fuel cut has been eliminated.

As far as removing fuel cut, I dont think you are ready for that. I myself have fuel cut elimination on my e-prom but I also know averything I can about my car and I stay on top of it as far as maintenence is concerned. IMHO, you will be ready to eliminate fuel cut when you dont have to ask how it is done.

hi.. i was wondering if there was any way that i could eliminate the fuel cut besides buying an hks fcd.. let me know if theres an easier way please.. thanx

You can also get a fuel cut defensor. They go for pretty cheap on ebay.

 

[xucpxeclipsex]

If you reference the post right above this one, you'll see what I mean when I say that fuel cut has nothing to do with an absence of fuel. It's more about the ECU seeing too much airflow and cutting the fuel off as a safety. In order to properly bypass fuel cut and therefore run more boost, you can use the AFC to compensate. This may not eliminate fuel cut, but it will delay it since the AFC works by subtracting airflow and fools the ECU into thinking that less air is passing through the MAF on the intake.

So, no, adding a fuel pump alone won't help (but it's a good idea to have a 190 for future upgrades anyway). If you don't know how to tune with the AFC, I would recommend that you have someone who does set it up for you or take it to a professional. Otherwise, you could subtract too much airflow and end up skewing the timing curves. The end result can be as minor as generating some knock, or as major as running the motor so lean as to create internal damage.

Additionally, you could purchase an EPROM ECU with a Keydiver Stage III chip that will eliminate fuel cut. The beauty of the EPROM ECU setup is that unless you make changes to the air/fuel and timing tables within the chip, the factory air/fuel and timing settings will be retained while fuel cut can be eliminated. I prefer this option since we can still scrape more power out of the motor by adding a few custom changes without being unsafe, provided you don't add a bigger turbo and yank on the boost.

Let me know if that makes sense,

Andy

k.. that makes alot of sense.. i guess i do have a boost leak.. but where is the most likely place that it would be.. ### when i turn up the boost.. it'll boost to 15 then drop back down to 8/9.. idk.. what do i need to do to figure out where my boost leak is??..

 

[andymoraitis]

You'll need to make a boost leak tester. Information can be found at http://www.vfaq.com under the Intake section. You'll want the system to hold 20psi for 30 seconds or more. Visual inspection can help, but don't count. Boost leaks bring on fuel cut sooner since turbo is spinning harder to reach the boost level you've set and is leaking air. The excess air being metered by the MAF is what's triggering fuel cut in this instance.

After a correct boost leak test, if your intact tract is tight, then I would look into the other options I mentioned above. Of the two, the EPROM ECU is preferred since you'll also be able to read knock and turn the boost down or add octane to reduce it.

As far as your boost not holding, the T25 is famous for this. A boost leak will cause it as will using the stock Boost Control Solenoid (BCS). Fixing boost leaks and switching to an aftermarket boost controller will help you keep steady boost levels.

Andy

 

[buugiewuugie]

Hi,

Every time I accelerate hard or let the engine rev up a little high the car jerks and I guess it back fires. But its fast. And it will do it a few times. Its like POP POP POP. It did this before but it only did a few times when I started it up. However I just install an Intake. Its a custom intake that I had to modify.

 

[red eclipse gsx]

Are you venting the BOV or recirculating? That would be it if your venting. If not then check your connection of the maf sensor on the intake and make sure it's connected.

 

[blcknspo0ln]

what are you mods, I didn't see any in your profile.

Fuel cut feels just like you're hitting a brick wall. it feels like the car violently shuts off for a second and then keeps going. a more pop pop pop stuttering feeling is more of a misfire. go back and make sure your clamps are tight on the intake and check your MAF (like the previous poster wrote).

then start your normal diagnostic process.. plugs/wires, BOOST LEAK, compression test, spark test, fuel, ignition timing, etc.

 

[buugiewuugie]

Its recirculating. However the hole is significantly smaller than stock. And its jolts me pretty hard. To the point that my seatbelt is REALLY tight...

 

[red eclipse gsx]

If the hole size in your intake for recirculation isn't extremely smaller then stock, then I wouldn't worry about it too much. To me, it sounds like your hitting fuel cut (hitting a brick wall). Running too rich or lean from recirculating or bigger injectors wouldn't really cause that. Instead they would just make you stutter and backfire. Still make sure your connections with the MAS are good and check your vaccuum lines to see if all of them are connected.

 

[oldman]

Ok I have not done this in a while, BOOST LEAK TEST.

 

[blcknspo0ln]

Ok I have not done this in a while, BOOST LEAK TEST.

what's that do?

 

[oldman]

what's that do?

For one thing, it will tell you if your pcv is defective.....oh wait nevermind, it would only help if you know where pcv is first.

 

[SLOWKID]

My buddy was behind me when i hit fuel cut and he saw white smoke come out of my exhaust.Whats this mean(good/bad).

thanks