Fuel Cutoff on decel?

[Angry Joe]

We have a Haltech E6S, which has a feature that cuts off fuel on engine deceleration. There is a cutoff limit rpm that can be specified, but I can't figure out weather it is a lower or upper limit. Haltech's craptastic documentation offers no clues.

Also, is there any danger to the engine by enabling this feature? To be honest, I'd rather retire at the endurance because our engine blew up spectactularly than by running out of gas

Lehigh Formula SAE

www.lehigh.edu/~insae/formula (http://www.lehigh.edu/~insae/formula)

[Angry Joe]

We have a Haltech E6S, which has a feature that cuts off fuel on engine deceleration. There is a cutoff limit rpm that can be specified, but I can't figure out weather it is a lower or upper limit. Haltech's craptastic documentation offers no clues.

Also, is there any danger to the engine by enabling this feature? To be honest, I'd rather retire at the endurance because our engine blew up spectactularly than by running out of gas

Lehigh Formula SAE

www.lehigh.edu/~insae/formula (http://www.lehigh.edu/~insae/formula)

[B Lewis @ PE Engine Management]

Angry Joe,

I don't know for sure but it would make sense for this to be a upper RPM limit. Usually there is a load setting as well. For example, if the RPM is above XXXXX and the throttle is below XXXXX, cut the fuel.

An easy way to set this initially is to just rev the engine unloaded and adjust until the engine neither stumbles nor dumps a cloud of raw fuel out the exhaust as RPMs ramp down.

Brian Lewis
Performance Electronics, Ltd.
www.pe-ltd.com (http://www.pe-ltd.com)
"Complete Engine Management Systems"

[Jon Prevost]

GM calls it DFCO (Decell Fuel Cut-Off). It doesn't hurt the motor except for drying out the cylinder chambers quench areas. Although wasted spark ignition...nah. Anyways, real world: My 91 camaro TBI has it and the only reason I've been disabling it is for sound http://fsae.com/groupee_common/emoticons/icon_smile.gif . Nothing like having the exhaust backfire through an exhaust cut-out on decell to tell the guy behind you that you're having more fun than him.
No fuel = nothing to burn = safe.
We've used the Haltech ecu's for years past. Went with Brian's PE ecu and never looked back http://fsae.com/groupee_common/emoticons/icon_smile.gif

, Jon
"Success - it 's what
you do with what you've got." - Woody Hayes
Engine Team

[Sam]

Is the Haltech the only ECU that can do this?? We run a Motec M4

Sam Graham
Engine Group Leader 2003
UQ Racing

[Matt Ahl]

Almost all cars these days cut fuel above idle speeds at O% throttle. It improves economy and reduces emissions significantly. I see no need to run the injectors off throttle unless you are running anti-lag.

[Scott Harsila]

Sure you can do it with a MoTeC, just set your fuel table values to 0 at some load and RPM sites. Say above 7000rpm and, 10% throttle and under. Haven't tried it but I am sure it would do the same thing as the Haltech, anyone tried a full cut with a MoTeC?

University of Washington
Formula SAE 2001-2003

[Dan Deussen @ Weber Motor]

Cutting fuel above idle speed works with any ECU and is only a good idea if you have your injectors positioned close to the head. Otherwise you loose a bit of throttle response.

If you do have them shooting right at the valves, then there is no reason not to cut fuel. Unless by Matt already mentioned, you are running bang-bang anti-lag strategy on a turbo engine.

Dan

Daniel Deussen

Walbro Italy
Via Caduti di Melissa, 12
40033 Casalecchio di Reno (BO)
Italy
phone +39.051.6132113
fax +39.051.6132233
mobile +39.348.8623331