ECU Tuning and Overrun Fuel Cut - AU3 XR8

[madmelon]

Hi All,

Hoping for some insight on changing the overrun fuel cut (ORC) parameters on AU3 XR8. The factory settings appear to have activation above 2500rpm and deactivation below 2100rpm. (That's to say, you need to exceed 2500rpm to activate the mode and it will cease cutting fuel below 2100rpm. More modern cars, including later Falcons, have these parameters set considerably lower- The BF I used to own seemed to be more like 1300rpm activate, 1000rpm deactivate.

With the factory parameters set so high, it's rare that ORC is actually enabled so huge amounts of fuel are wasted at 0% throttle when coasting.

Has anyone successfully changed these parameters with an X3 or any other tuning device on an AU XR8? I did ask to have it changed when I got mine tuned years ago but it was overlooked and I didn't realise until after I'd left. Having personally tuned MoTeC M800s before for race engines with a specific emphasis on fuel economy, I know there are big gains to be had by setting these parameters where they can actually be used - 10% or more reductions.

All insight welcome!

Cheers
Dan

[te5000]

Originally Posted by madmelon

Hi All,

Hoping for some insight on changing the overrun fuel cut (ORC) parameters on AU3 XR8. The factory settings appear to have activation above 2500rpm and deactivation below 2100rpm. (That's to say, you need to exceed 2500rpm to activate the mode and it will cease cutting fuel below 2100rpm. More modern cars, including later Falcons, have these parameters set considerably lower- The BF I used to own seemed to be more like 1300rpm activate, 1000rpm deactivate.

With the factory parameters set so high, it's rare that ORC is actually enabled so huge amounts of fuel are wasted at 0% throttle when coasting.

Has anyone successfully changed these parameters with an X3 or any other tuning device on an AU XR8? I did ask to have it changed when I got mine tuned years ago but it was overlooked and I didn't realise until after I'd left. Having personally tuned MoTeC M800s before for race engines with a specific emphasis on fuel economy, I know there are big gains to be had by setting these parameters where they can actually be used - 10% or more reductions.

All insight welcome!

Cheers
Dan

Interesting to see what comes out of this thread. My recently tuned AU seems to over run quite a bit at zero throttle. Holds around 1200 rpm for a few seconds then drops to some where aroud 800 ( from memory ).
Would have thought it should go back to idle so what quicker?

Sent from my SM-G930F using Tapatalk

[madmelon]

Originally Posted by te5000

Interesting to see what comes out of this thread. My recently tuned AU seems to over run quite a bit at zero throttle. Holds around 1200 rpm for a few seconds then drops to some where aroud 800 ( from memory ).
Would have thought it should go back to idle so what quicker?

Sent from my SM-G930F using Tapatalk

I've had that occur a few times, a quick blast at WOT seemed to eliminate it. Probably something (IAC Valve?) sticky. On another note, if you clutch in at freeway speed, you may notice the idle is set quite a bit higher- over 1000. At least, that's what mine has always done.

Overrun fuel cut should only be active when above idle (typically a minimum of 300rpm above to prevent stall-out) when the engine is being driven by the car and only operate when throttle is at 0%.

[Bossxr8]

Originally Posted by te5000

Interesting to see what comes out of this thread. My recently tuned AU seems to over run quite a bit at zero throttle. Holds around 1200 rpm for a few seconds then drops to some where aroud 800 ( from memory ).
Would have thought it should go back to idle so what quicker?

Sent from my SM-G930F using Tapatalk

That's the dashpot doing it's thing, to prevent revs dropping too quick and stalling, or overshooting idle speed requiring correction.

[hales231271]

I believe there is a parameter that is related to vehicle speed.
In manual when car speed is above 10kmh isc is activated with increase percentage and revs up from idle.
When car slows below 10kmh isc proceeds to normal idle speed.

[undertow]

You can do it with a quarterhorse or J3 chip and a suitable definition. Pretty sure the SCT gear would have those settings mapped out too.

The stock settings are around 2500rpm enable 2000 disable which as you say wastes fuel and brake pads. I have mine set to cut down to about 1300, I have tried going lower but it causes clunking when the injectors turn back on. There is also a "DFCO min speed" which you can tweak to prevent it coming on in lower gears, and a few time delays (you need about 1 second delay after lifting off the throttle or it will activate during gear changes which is annoying).

Best to find a tuner who is willing to fiddle, or look into Moates quaterhorse or J3 chips and TunerPro or Binary Editor. I've put together a pretty complete TunerPro definition for the AUII 200kw motor and have a done a partial one for the AUIII (both manuals only, no interest in autos) and can provide these if you're interested

[madmelon]

Undertow, this is excellent information- much appreciated. The car has already been tuned using an SCT X3 by Spiro at Autotech. I did specifically ask for this change and I was told yes but as I mentioned, it was 'overlooked' - possibly he was unaware of if it was possible or which parameters to change.

DFCO min speed is a parameter I was really hoping would exist too. Means you can get the burble at low speed still!

Can you list the parameter names (and the units- sec, rpm, revs, etc) so I know exactly what to ask for next time?


Thanks in advance!

[madmelon]

It's interesting you mention activation during gear changes being annoying- this is exactly the sort of strategy apparently now used to really minimise fuel consumption. I think it was a Coyote/Mustang article I was reading where the calibration engineers talk about it.

[undertow]

If you want PM me your email and I can send you a tunerpro definition and stock tune so you can see what the parameters do. Tunerpro is free to download, you just load the definition and the tune (bin file) then can look through the parameters and their descriptions

I think the SCT gear actually replaces the whole program with its own simplified version so I'm not sure if it works in the same way.

[madmelon]

Originally Posted by undertow

If you want PM me your email and I can send you a tunerpro definition and stock tune so you can see what the parameters do. Tunerpro is free to download, you just load the definition and the tune (bin file) then can look through the parameters and their descriptions

I think the SCT gear actually replaces the whole program with its own simplified version so I'm not sure if it works in the same way.

I was under the impression the SCT tune simply replaced the program with something that had updated parameters- not a whole new program. I will investigate this further.

[NCII40]

This is what i been looking for too, Thanks for the post
a tuner i spoke too referred to this issue as setting the AFR's high at cruise ?
I might be getting confused here, but anything to reduce my 17.5L/100 would be great!
Tuner also told me, AU2 will only accept SCT 2 Blue screen or J3 chip for tuning

[mcfly94]

Originally Posted by NCII40

This is what i been looking for too, Thanks for the post
a tuner i spoke too referred to this issue as setting the AFR's high at cruise ?
I might be getting confused here, but anything to reduce my 17.5L/100 would be great!
Tuner also told me, AU2 will only accept SCT 2 Blue screen or J3 chip for tuning

17.5L not too bad, mine does 17l 100km but that's because how i drive it.

Tuner is wrong, AU2/3 will take SCT2/3, J3 Chip (in form of T.I or Quarterhorse)

[NCII40]

Thanks for clearing that up!

I couldn't understand why the SCT 3 wouldn't work ?