Emerald ECU Fuel cut off option

[allegro]

I am running an Emerald 3d mapped system on a 1.8 K and want to know what effect it will have if I de-select the 'cut off all fuel' (over-run) option. At present it is selected to cut off when the throttle pot is almost fully released.

Will I have an uneven tick over or excessive bagging and popping. Thought I'd ask you lot before I started playing.

 

 

Andy Mac C7 GON

😬 Team Langoustine. Hard Core Prawn here 😬

[Jason Plato]

I run with mine switched OFF , I think the settings are "less than 4500 / below throttle pot XXX - about 10 points above idle .

There was no change in behaviour with it off or on , the only difference was that there was more popping and banging on light trailing throttle with it on .

 

Some folk say that with it off , there is a hesitation in response - I have not noticed anything at all .

 

Dave

[Peter Carmichael]

The settings should have it so that fuel is cutoff under circumstances where the engine could not possibly run under power. Unfortunately when you inject fuel, not all of it goes directly into the next firing cycle of the cylinder. A lot hangs around in liquid form in the inlet tract and it evaporates into the airflow from there. Typically 10 times the amount of injected fuel is just kicking around in the inlet tract.

 

When you cut the fuel out on the overrun, this fuel gradually evaporates into the airflow - this causes lean mixtures (pops and bangs) rather than *no fuel*. You also get lean mixtures when the engine slows below the fuel cut-out zone and is approaching idle. This is a characteristic of SLRs which I think pop and bang at 3000rpm on the overrun.

 

When you next open the throttle, there is no established wetted area in the inlet tract; one of the fuel paths into the engine has been removed causing lean mixtures yet again - this results in a stumble as you open the throttle. You can trim the worst of this out with acceleration fuelling settings but it is difficult to get right without causing overfuelling in other snap-open throttle situations.

 

If you just disable the feature you will probably get smoother running, fewer pops and bangs and better off/on throttle transient behaviour.

[Mike Bees]

I run with the fuel cut-off enabled, with no pops & bangs whatsoever. To get the revs to drop quickly in the 2000-3500 rpm range without the fuel cut-off I need to run a less than optimal ignition advance at load site zero, which leads to pops & bangs.

 

Mike

[allegro]

Mine is set 'on' at the moment, with cut off at below 1200RPM and 3 points above idle. I have no pops and bangs and no stumble on acceleration. Sounds like if it aint broke don't fix it. But I was just asking what effect it would have. I was expecting the opposite. That if selected 'off' then unburnt fuel would find it's way to the exhaust and cause excessive bangs and pops. This, depending on your frame of mind might be desirable. Oh and it is an SLR. With the old MEMS it would bang for England. 😬

 

Andy Mac C7 GON

😬 Team Langoustine. Hard Core Prawn here 😬