Fuel cut Options

[97TalonTSI]

The talon is running good. Tuning is where it`s at now. My boost creep is under control for the most part the AVCR finally went into self learning mode and seems to be working better but at WOT in 3rd gear I get fuel cut. That is at about 18 psi and around 4800 to 5200 rpms. I know I will have to start upgrading my injectors and ecus stuff at some point but do you guys think the injectors (stock) or my plugs might be causing any of my problems? Also I am running a ported 14b turbo.

[natedogg]

Fuel cut is caused solely by the ECU reading too much air coming into the engine. The way to combat this is to get larger injectors and tune for them so the ECU reads less airflow but still supplies the fuel needed for the increased airflow. The cold air makes DSM's more apt to fuel cut as well.

[turbohcar]

Injectors do not cause fuel cut. You are overrunning the MAF currently at 18psi. You will need an Eprom ECU with the proper programming to fully eliminate fuel cut from the equation (the chip burned will halve the MAF value reading and remultiply it in the ECU, somehow it bypasses the fuel safety cutoff). Injectors would be a nice addition along with it as well since I'm sure you're already overrunning the stockers.

If you plan on keeping the 14B:
550cc injectorts (at least)
Eprom w/ chip burned for injectors and fuel cut elim.

If you want to go to an EVO III 16G since it seems to be popular:
650cc injectors (at least)
Eprom w/ chip burned for injectors and fuel cut elim.

Correct fuel injector selection is critical. Always go bigger than what you need. You can always take more fuel out but at a certain point you hit the limit of the injectors and you can't add any more fuel.

80%Duty Cycle is the suggested maximum for any fuel injector. You're probably running about 100-110% currently on the stockers.

[ncgalant]

Injectors do not cause fuel cut. You are overrunning the MAF currently at 18psi. You will need an Eprom ECU with the proper programming to fully eliminate fuel cut from the equation (the chip burned will halve the MAF value reading and remultiply it in the ECU, somehow it bypasses the fuel safety cutoff). Injectors would be a nice addition along with it as well since I'm sure you're already overrunning the stockers.

If you plan on keeping the 14B:
550cc injectorts (at least)
Eprom w/ chip burned for injectors and fuel cut elim.

If you want to go to an EVO III 16G since it seems to be popular:
650cc injectors (at least)
Eprom w/ chip burned for injectors and fuel cut elim.

Correct fuel injector selection is critical. Always go bigger than what you need. You can always take more fuel out but at a certain point you hit the limit of the injectors and you can't add any more fuel.

80%Duty Cycle is the suggested maximum for any fuel injector. You're probably running about 100-110% currently on the stockers.

Injectors up to 720cc can be controled fairly easily with a SAFC/Maft

An EPROM ECU is a better solution, but can be very costly.

[turbohcar]

From the TOONING MASTAH himself^^^^

[awd4kicks]

To clarify: Larger injectors will help fuel cut...

If you have an AFC or a MAF Translater that you can tune them with (That's the key). Tuning the AFC or MAF-T is modifying the MAF (Air measurement) reading to the computer. When you program it for larger injectors, it will tell the computer there is less air coming into the engine than there really is... hence the elimination of fuel cut when you get below that preset air measurement for it.

Be carefull though. The tuning is where the best are made, but also where many burned up pistons and valves are produced. Stay conservative and keep it safe.

[natedogg]

80%Duty Cycle is the suggested maximum for any fuel injector.  You're probably running about 100-110% currently on the stockers.

This depends on the brand of injector and how large it is. Generally, the larger the injector the more dead time you have, thus you are allowed a smaller maximum duty cycle. For example, a Denso 660 runs 180 microseconds of dead time so I would be comfortable tuning those up to 90% duty cycle. On the other hand Denso 720's run 450 microseconds of duty cycle. I wouldn't want to tune those much beyond 75%. Kinda funny when you think about it. Considering the dead time values, Denso 660's have almost as much high RPM fuel metering capability as Denso 720's.

I you tune an injector with any amount of dead time beyond its duty cycle capabilities you get uncontrolled amounts of fuel from the injector and tuning goes out the window.

[97TalonTSI]

Thanks guys. That is what I thought. I think I am going to port out the turbo (wasegate) then try to hold at about 17lbs then I will do a AFC and larger injectors come spring time. Shocks and new bump stops are a must right now.

[ncgalant]

80%Duty Cycle is the suggested maximum for any fuel injector.  You're probably running about 100-110% currently on the stockers.

This depends on the brand of injector and how large it is. Generally, the larger the injector the more dead time you have, thus you are allowed a smaller maximum duty cycle. For example, a Denso 660 runs 180 microseconds of dead time so I would be comfortable tuning those up to 90% duty cycle. On the other hand Denso 720's run 450 microseconds of duty cycle. I wouldn't want to tune those much beyond 75%. Kinda funny when you think about it. Considering the dead time values, Denso 660's have almost as much high RPM fuel metering capability as Denso 720's.

I you tune an injector with any amount of dead time beyond its duty cycle capabilities you get uncontrolled amounts of fuel from the injector and tuning goes out the window.

A good point to consider. My denso 720s were real fun to tune out with a SAFC, but it can be done very effectively. If you chose to go that route there are plenty of us around that can give advice on tuning. If you are looking to run injectors bigger than 550s and not get an eprom, I'd also recommend an AFPR. That allows you to scale down bigger injectors until you buy a bigger turbo and really need the fuel.

[97TalonTSI]

WEll I am not sure that I will go larger than a EVo 16. But I have thrown around the idea of selling the car but that would be until the summer. There are a couple of things that I need to get done first. Thanks for all the advice. I will let you guys know before I upgrade anymore.