high idle and overrun issues

[Cropduster]

Hi All,
I have a Ducati with an M400 to control a single shower injector per cylinder, i use IWP189 12 port injectors rated at 510cc. the original single port injector (IWP069) is rated at 491cc so i don't think the injectors are too large, or are they?

Unfortunately the guy who originally tuned it took a file from a much larger race bike and loaded it into mine and that's all, it's had a proper dyno set up since then and on acceleration it's very good but while this guy is much more trustworthy he isn't a motec specialist. the idle is too high, given the injector size i don't see why i can't limit the duty cycle of the injector at idle? how do i find it in the map table please? I have set the throttle butterflies as close to closed as i can get them with the stops on both cylinders touching to eliminate the throttle sucking shut completely which makes it very snatchy off a closed throttle as the twist grip input to overcome this is too great.

also on overrun it seems to be loading up on fuel if i coast then blip to down change, if i roll off the throttle and blip/downchange immediately it's clean and works well, if i coast it loads up so i believe the injectors are still feeding while the throttle is closed? is there a decal map or setting i can look at to alter this?

Thanks for the help.
Paul.

[Sean]

What sort of Ducati Paul? Idle speed is a function of airflow more or less, reducing fuel at idle will make it leaner and harder still to pick up the throttle. Unless overrun fuel cut is active or the main fuel table is 0 in that area it will still inject on the over run.

[Cropduster]

It's an 888 with 748R Throttle bodies, the 44mm restrictors have been milled out so they're now 50mm with 54mm butterflies.
I understand the idle speed is controlled primarily by air speed, as i said i've got them as closed as possible. The 12 port injectors are only 6% larger in flow over the originals so with the bike mapped i expected it to idle at close to the same speed as a std bike. maybe the larger chokes are having an effect? i'm hoping the 12 port design is much more efficient than the single port and i can lean it out below say 1800rpm to slow it?

Picking up the throttle shouldn't be an issue, it rarely if ever falls below 2000 while being ridden, because of the overhead shower injectors it's habit to give it a quick blip to clear the pooling fuel off the butterflies before riding off from a standing start.

Overrun fuel cut? can you explain that further please? where can i find that to activate it?

[Sean]

The larger throttle bodies will naturally flow more air than the smaller ones at the same idle throttle percentage.

Have you log files from the ecu or a data logger? Do you have a wideband O2 sensor connected to the ecu?
What tracks do you run at?

Overrun fuel cut is under the menu Adjust> Functions> Overrun fuel cut
I have not used it, so cannot advise you on the best setting. I would have thought that with the ECU
set up well overrun fuel cut would not be needed.

[Cropduster]

i've watched a webinar and i'll retard the timing in the rpms i need to pull the idle down into, i'll also target the rpm 100 lower than optimum so i can open the butterflies slightly to reduce pooling and stop it loading up while idling for extended periods, that should sort it.

Thanks for the location on the overrun cut, my ECU has been mapped very well, the low speed running is very responsive and the A/F is pretty well spot on so i'm glad i don't need to adjust the fuel map or injector open time.

It's a road bike so rideability is important and there's no need for fuel to be fed in on overrun, the issue i have is when i coast on a closed throttle then blip to rev match on a down change it's loaded up and i need it to be crisp and responsive, turning the overrun fuel cut to on will definitely improve rideability, so thanks mate.

[Sean]

Let us know when you have tried it, I'm interested to know.

[Cropduster]

OK, so i retarded the timing below where it was idling to bring the idle down, that has worked, however the ignition map is in 500 rpm increments, can i increase the resolution to say 250rpm increments because where the bike should idle it hangs when i rev it and then slows to almost stalling and then picks up again, if i could increase the resolution i could adjust the timing before the idle up a degree or so to stop it wanting to stall and in front of the idle retard the ignition by a degree or so to stop it hanging up? It's definitely not lean BTW!

The over run cut is set to zero so i think i need to lean off the function that controls the "blip" of the throttle between down changes but i can't remember where it is, i seem to remember it might be the accelerator pump feature but i can't find where to adjust it, anyone know?

cheers
Paul.

[Sean]

You can go 100 rpm increments if you want in that area. Right click on the ignition table and go axis setup.

Accelerator pump function can just end up pumping excess fuel in on the throttle blip if it's set sensitive enough to do anything. Adjust>Fuel>Accel Enrichment Try it turned off.

Have you got an oxygen sensor wired to the ecu and are you logging it? I assume you are logging in the ecu?

[CPL Racing]

You could control the idle better by using one of the ign comp tables.
Set your desired rpm with no comp and then retard ign above the desired rpm to bring the idle down and add ign below the desired rpm to raise the rpm. if you do this in say 200rpm increments you should get the idle just where you want it.