Scangauge II fuel cut off seems to work very well

Shrek · #31 03-12-2008, 09:53 AM

Quote:

Originally Posted by ksstathead

My 2000 Honda CRV Auto Trans seems to have fuel cut on decel with a bit of delay per scanguage.

I think there is a technical challenge for the automakers to avoid the fuel-cut kicking in too suddenly while driving on slippery ice/snow. the sudden fuelcut could give enough increase in engine brake power to make the wheels start slipping. Imagine the lawsuits!

Because of this I believe that the fuelcut is gradual, and possibly even (easy enough to program) coupled with the ABS sensors.

There is already enough of a problem with 4x4's sliding out of the road because drivers let go of the gas pedal while cornering on icy roads here in Norway.

ksstathead · #32 03-12-2008, 06:11 PM

Quote:

Originally Posted by 2way

Make sure your SGII cutoff is set correctly.

Pretty sure your Tacoma has it. Its just that auto trans don't do DFCO as often as sticks do. I've noticed the same thing w/my Avy. It doesn't stay in DFCO for that long..... and it stops DFCO when you reach a certain RPM threshold. It was kind of wild the 1st time I watched it.... when DFCO kicked off at the RPM threshold..... the RPMs bumped back up.

I've never seen the 2003 AT Tacoma go open loop after brief warmup (closed loop at around 62F). I never go WOT, so I assume it would go open loop there. Anyway, I've tried cutoff at default 24 and at 15 (idle tps is 14ish). I should have raised the default, I guess, but if it never goes open loop it won't show DFCO.

What makes you think the Tacoma has DFCO?

2way · #33 03-13-2008, 08:28 PM

Quote:

Originally Posted by ksstathead

I've never seen the 2003 AT Tacoma go open loop after brief warmup (closed loop at around 62F). I never go WOT, so I assume it would go open loop there. Anyway, I've tried cutoff at default 24 and at 15 (idle tps is 14ish). I should have raised the default, I guess, but if it never goes open loop it won't show DFCO.

What makes you think the Tacoma has DFCO?

15 should be fine.

It being a late model EFI Toyota makes me think it has DFCO. Its probably the automatic tranny. Like I said... about the only time I see the Avy go DFCO is when I come off the accelerator @ highway speed and let it coast to an offramp or I come off on a good size down hill. I checked the Celica Service Manual... and it too comes out of DFCO @ 1.5KRPMS.

I'm checking your Service Manual now.... http://www.ncttora.com/fsm/2003/2003_FSM.zip if you don't have a copy

Your fuel return is @ 1.2K RPMs for a 2003 A/T Tacoma. And yes, you do have DFCO

ksstathead · #34 03-13-2008, 09:24 PM

Thanks, 2Way!

I had the FSM, but lack familiarity with it. Haven't had it on highway since SGII was upgraded.

2way · #35 03-14-2008, 10:05 AM

No problem

BTW:

Quote:

Originally Posted by ksstathead

My 2000 Honda CRV Auto Trans seems to have fuel cut on decel with a bit of delay per scanguage.

there is a comm delay from the SG <-> ECM... so, some of the delay is actually from that.

ksstathead · #36 03-24-2008, 07:06 PM

I can confirm now that the 2003 Tacoma AT has DFCO. It is triggered at highway speeds on the off ramps, and I can induce it by downshifting approaching stops/turns at lower speed (but I'm usually in N).

Overall, it is less inclined to go into DFCO than our 2000 CRV and FAR less inclined than our new 2008 Honda Fit with the 5AT.

Thanks again to 2way for leading me on the Taco.

mtbiker278 · #37 03-25-2008, 07:52 AM

Just to update some of my experiences...

The scanguage has been recognizing fuel cut-off most of the time. I say this because about a week ago it started to not recognize the cut, and my MPG numbers were noticeably lower compared to the previous week (no driving style changes).

I set the scangauge to defaults and entered in my old calibration values afterwards and everything worked ok. Not quite sure what was going on with it, but I'll see if it happens again.

Arizona Notch · #38 04-09-2008, 12:08 AM

2way is correct. Most automatic trans won't do Dfco that much do to the fact that an auto, when coasting in gear, is actually not directly linked to the engine and using the engine to slow the vehicle. The torque converter will unlock and most, not all, of the engine braking never actually gets utilized. For that reason, the ECU must continue to burn fuel in the ICE to keep it running since most of the vehicles kinetic energy is not being scrubed off by the vehicle's drivetrain (a good thing for glide situations). A manual trans doesn't have that problem since there is a direct link to the wheels through the clutch. So, the weight of the vehicle, and its kinetic energy, during the coast in gear time can be used to keep the engine turning over even though there is no fuel being shot by the injectors.

I know Ford had Dfco in the late 80s because I have a 5.0 Mustang that I can adjust all of the ECU functions, one of which is the fuel cutoff point - basically, the RPM at which the fuel cutoff stops working. I had it adjusted way down to something like 1,000 RPM, but the motor didn't like it too much. I think the default was somewhere around 1,500 RPM and it worked in any forward gear. The car is a 5-speed manual.

mtbiker278 · #39 04-11-2008, 07:33 AM

I've just had a new issue occur with my scangauge II today. While driving to work the gauge suddenly read 9999MPG and 0.00GPH while I was accelerating (although slowly and on flat ground). I'm not sure what would cause it to do this, but I'm pretty sure if the computer was saying no fuel was being injected the car would have stalled out.

I re-set to the defaults again and everything seems to work ok. The only trending I can think of is this usually occurs right after I'm at a light in which I had the ICE off. Maybe the scangauge has issues after repeated on/off cycles?

Thoughts?

P.S.- I e-mail linear-logic with my questions as well.

Shrek · #40 04-11-2008, 07:39 AM

Quote:

Originally Posted by mtbiker278

I've just had a new issue occur with my scangauge II today. While driving to work the gauge suddenly read 9999MPG and 0.00GPH while I was accelerating (although slowly and on flat ground). I'm not sure what would cause it to do this, but I'm pretty sure if the computer was saying no fuel was being injected the car would have stalled out.

I re-set to the defaults again and everything seems to work ok. The only trending I can think of is this usually occurs right after I'm at a light in which I had the ICE off. Maybe the scangauge has issues after repeated on/off cycles?

Thoughts?

P.S.- I e-mail linear-logic with my questions as well.

Your car goes open-loop at full throttle. The scangauge need to know what is your idle throttle position (there is a menu called fuel-cut for that) so that it knows that it should not indicate fuel-cut in this situation.

The default value is quite high, and on some cars this can happen. Find the TPS at idle, then add 1 and set that as the value in the fuel-cut menu.