negotiating the overlap between decel and idle

ochizon · Post by **ochizon** » Thu Feb 16, 2006 6:36 am

In my map, the cell that handles most of the idel fueling is also a point where when decelerating from high rpm/wide throttle goes way lean and stutters. I cant figure out how to negotiate the 2.

I put in a row of lower kpa (down to 15) and a row of lower rpm (down to 400) to richen up when decelerating deep like that, but it still will overlap with that one cell were idle it idles.

Any pointers on how to negotiate the two?

mops · Post by **mops** » Thu Feb 16, 2006 10:46 am

i dont understand the problem.

you are sayin delelerating from high rpm's from wot... but idle is at probably around 800rpm...., to thats very low rpm... you should have no need to go lowet than that....

technically speaking you should not decelerate all the way down to the idle point....

ochizon · Post by **ochizon** » Thu Feb 16, 2006 1:31 pm

What I mean is that when I run the engine high up, and the let go of the throttle, and come out of gear and into neutral (5speed), the engine runs itself down to idle, but drops to a lower kpa before stabilizing back at the idle rpm/kpa.

Does that make any sense now??

mops · Post by **mops** » Thu Feb 16, 2006 1:49 pm

i think i understand....

it's notmal when the engine is decelerating, the map is lower then idle.

idle is the midpoint, i.e. rpms are not rising and not droppping, if the map is lower the rpm's are dropping, if higher the rpm's are incerasing....

when you delelerate from high rpm's you should come up to the idle point from BELOW the idle map...

for what you said in your first post, I unserstand that your decel map is the same as idle map ? sounds not right.... decel map should be lower, so you dont run into porblem that you have.

just thinking.... whats your idle kpa and what are your map bins around idle ? you should normally have 1 to 3 (depending on the engine) map bins below idle map...

e.g. my car idles at 35kpa, but decel is ~15-20 kpa, so I dont really have a problem you are describing....

ochizon · Post by **ochizon** » Thu Feb 16, 2006 3:52 pm

mops wrote: e.g. my car idles at 35kpa, but decel is ~15-20 kpa, so I dont really have a problem you are describing....

mine idles at between 30-35 also, and also decel in the 15-20kpa range. My problem is when it comes back up to idle, its to big a jump, and not enough fuel the moment before it settles, hence the shudder...

Maybe its just a unique quirk...

fscott · Post by **fscott** » Thu Feb 16, 2006 5:48 pm

If the problem is lack of fuel as the MAP rises back to idle, can you solve it by switching to MAPdot acceleration fueling? Then as the MAP rose, accel fueling would kick in and help out your mixture.

Walkinshaw · Post by **Walkinshaw** » Thu Feb 16, 2006 6:44 pm

I'm guessing your issue is on decel in gear. Say @100kmh in 4th gear, then decel to 0kmh and disengage clutch just prior to stall? You're experencing bucking (lean burn issues when under decel just before you disengage the clutch? I had this issue with my stock ECU, but have found that MS2 was able to fix this by doing what others have mentioned.

Richen up your 15kpa bins (decel) to a level above that of your idle bin.

What seems diffrent is your idle MAP and decel MAP values. I see 10-15Kpa decel map values and idle is arround 55kpa.

ochizon · Post by **ochizon** » Thu Feb 16, 2006 8:44 pm

fscott wrote:If the problem is lack of fuel as the MAP rises back to idle, can you solve it by switching to MAPdot acceleration fueling? Then as the MAP rose, accel fueling would kick in and help out your mixture.

That is pretty clever, I will look into that.