MAP under fuel decel
#3
Boost Pope
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Yeah, just checked some old logs and saw 12-14 kPa.
Sidebar: I just realized that it's been just about two years at this point since I've datalogged a car. Been driving on a stock ECU for that whole time. Something must be done to change this...
Sidebar: I just realized that it's been just about two years at this point since I've datalogged a car. Been driving on a stock ECU for that whole time. Something must be done to change this...
#5
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Also does it hold down at those areas though out the area when coming down until fuel cuts back in.
Here's a little snapshot of a log:
At the left, I've just taken my foot off the pedal after some full-throttle acceleration. TPS and MAP both fall to the bottom of the scale immediately, while RPM begins to decrease gradually. You can see that as RPM falls, MAP eventually begins to increase slightly. Then I push in the clutch and shift into neutral, allowing RPM to fall faster, and MAP to rise slightly faster. Then there's a sort of hump where you can see the idle valve starting to do its thing, (RPM fell a bit too much here, suggesting that this log was taken from before I sorted that all out) at which point RPM rises, followed by a slight drop in MAP as the idle valve closes a bit, and things then stabilize.
Last edited by Joe Perez; 01-16-2012 at 01:29 AM.
#6
Ive got mine much higher, arround 24kpa. I dont see any ill effects but im very new to this. I recall reading somewhere that it should be set 4-5kpa below the lowest u see at idle ( could be from when i had a Miata link ecu). Feel free to enlighten me if 24 is stupid / could be causing issues.
Cheers
Cheers
#7
Boost Pope
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Boy, did I misinterpret the meaning of this thread the first time around. OP was asking what value we had specified under "Over Run Fuel Cut." I thought he was asking what actual MAP values we were observing under deceleration.
The exact number used is not critical; it just needs to be lower than the lowest value you expect to see under sustained light-load cruise, yet slightly higher than the actual MAP values observed during deceleration. I set mine to 20.
The exact number used is not critical; it just needs to be lower than the lowest value you expect to see under sustained light-load cruise, yet slightly higher than the actual MAP values observed during deceleration. I set mine to 20.
#9
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It varies with RPM and compression, but 12-15kpa. Fresh motors are 16-17kpa, and I consider them "broken in" when I see 13-14kpa. I typically set overrun at 20-22kpa - the slightest crack in the throttle will typically bring it up to around 25-28kpa.
#11
I see a difference. Before with the IAC enabled and working usually it would hover around 20s coming though decel fuel cut.
With closed loop idle turned off and a cap over the IAC opening I pull all the way to 13s, probably lower then 13s considering that 13 is the limit of the map sensor iirc.
Just trying to check all the variables.
With closed loop idle turned off and a cap over the IAC opening I pull all the way to 13s, probably lower then 13s considering that 13 is the limit of the map sensor iirc.
Just trying to check all the variables.
#12
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I'm struggling to understand why you keep mentioning the decel fuel cut function. Are you positing that one is likely to observe different MAP values while decelerating in gear with the throttle closed based on the setting of that particular software variable?
#14
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I see a difference. Before with the IAC enabled and working usually it would hover around 20s coming though decel fuel cut.
With closed loop idle turned off and a cap over the IAC opening I pull all the way to 13s, probably lower then 13s considering that 13 is the limit of the map sensor iirc.
Just trying to check all the variables.
With closed loop idle turned off and a cap over the IAC opening I pull all the way to 13s, probably lower then 13s considering that 13 is the limit of the map sensor iirc.
Just trying to check all the variables.
#17
so far yes it seems to be so, though with it disabled it seems on my car atleast I can pull map down further on decel.
That and I can idle better so far around 15.2+-2 at 900rpms and 27kpa. Just research. Thinking my megasquirt isn't doing a great job with the idle valve.
I did notice with it open to atmo compared to connected to the intract tract that the car rev up better from idle.
That and I can idle better so far around 15.2+-2 at 900rpms and 27kpa. Just research. Thinking my megasquirt isn't doing a great job with the idle valve.
I did notice with it open to atmo compared to connected to the intract tract that the car rev up better from idle.
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