Deceleration Lean Issue - Help!

[brockbenson]

Hi All,

I have been having some problems with a deceleration issue since getting my megasquirt up and running. When I come of the gas the engine leans out off the scale, stumbles and sometimes recovers and sometimes stalls. If it doesn't stall the engine then comes back to an AFR around 13-14 and continues on fine without issue. But this happens every time I come to a stop. The car is a manual gearbox, and it makes no difference if I'm gearing down or coasting in neutral to a stop, once I come off the gas it leans out. It does it occasionally even if I rev the engine while sitting stationary.

I have tried the DECEL FUEL AMOUNT setting it anywhere from 80 - 100 made no difference. I have run a log and tried to mark the places where this happened, but interogating the data has confused my further. Can anyone shed some light on this annoying issue?

I am running MSII v3.0 with code 2.920. I am only running fuel at the moment.

I have attached my tune and the datalog.

Some assistance would be greatly appreciated

BB

[Matt Cramer]

Decel fuel amount only applies for less than a second on lifting the throttle. What you need to do is tune the VE in the low MAP area that you land in on deceleration.

[brockbenson]

Matt,

Thanks for the response. I adjusted the low pressure area of the map and that seems to have cured my decel lean issue.

Thank you,

BB

[brockbenson]

Hi Matt and fellow MSer's

Well I thought tuning the lower end on the map would solve my off deceleration issue, and for a time it seemed so. But after a proper long drive over the past weekend i found that she is still leaning right off the gauge and stalling (or almost stalling) whenever i come off the accelerator.

To my mind something seems odd, as i added up to 20% more fuel to the low map area where it lands when i come off the accelerator. The more i added, the less it made any difference. The attached image is before i started adding fuel to the 500rpm fuel map column. You can see on it where the point is landing on the off accelerator phase.

I have also attached another data log i did after upping the fuel. I have marked the points where this is happening, but unfortantely a couple of time i hit the accelerator (old habbit from my carby days trying the pump the accelerator to stop it stalling).

Am i missing something here? Any assistance would be fantastic.

Cheers, BB

[Matt Cramer]

That idle is going WAY low. Try adding a bin at 500 RPM with about 18 degrees of timing to help "catch" the idle when it falls, and possibly even a 300 RPM VE row for adding more fuel. I think you're landing in a bad cell of the map.