MEGAsquirt A place to collectively sort out this megasquirt gizmo

Nooby Over-run Fuel Cut question

Thread Tools
 
Search this Thread
 
Old 04-24-2017, 06:45 AM
  #1  
Senior Member
Thread Starter
 
poormxdad's Avatar
 
Join Date: Dec 2010
Posts: 1,192
Total Cats: 103
Default Nooby Over-run Fuel Cut question

The MSPNP Pro has had Over-run Fuel Cut OFF since the install and initial tuning. However, if I completely lift off the pedal below 60 mph, the MTX-L quickly reads 22.4. Above 60, it takes a few seconds to kick in, so it seems like there's a related "setting" somewhere that's working. I can't find a field in MegaLog Viewer for Over-run itself. Did I miss something?

Is that how it's supposed to work?
poormxdad is offline  
Old 04-24-2017, 07:58 AM
  #2  
Boost Czar
iTrader: (62)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 79,493
Total Cats: 4,080
Default

here's my question: why is overrun turned off?
Braineack is offline  
Old 04-24-2017, 08:54 AM
  #3  
Junior Member
 
dawson128's Avatar
 
Join Date: Feb 2017
Location: Indiana, a wonderful place to drive your Miata on nothing but oval tracks.
Posts: 72
Total Cats: 0
Default

Originally Posted by poormxdad
The MSPNP Pro has had Over-run Fuel Cut OFF since the install and initial tuning. However, if I completely lift off the pedal below 60 mph, the MTX-L quickly reads 22.4. Above 60, it takes a few seconds to kick in, so it seems like there's a related "setting" somewhere that's working. I can't find a field in MegaLog Viewer for Over-run itself. Did I miss something?

Is that how it's supposed to work?
My overrun was off when I first loaded my basemap as well. IIRC the basemap tune has very lean AFR targets under overrun condition sort of imitating overrun fuel cut but without the setting being on. But I'm also a noob and could be wrong about that, can't look at my tune right now. Post tune if you get a chance.
dawson128 is offline  
Old 04-24-2017, 09:05 AM
  #4  
SADFab Destructive Testing Engineer
iTrader: (5)
 
aidandj's Avatar
 
Join Date: Apr 2014
Location: Beaverton, USA
Posts: 18,642
Total Cats: 1,866
Default

See below
aidandj is offline  
Old 04-24-2017, 09:27 AM
  #5  
Senior Member
Thread Starter
 
poormxdad's Avatar
 
Join Date: Dec 2010
Posts: 1,192
Total Cats: 103
Default

Originally Posted by Braineack
here's my question: why is overrun turned off?
It's just the next thing I plan to deal with. But, since I had that issue with the WOT TPS% in the Alternator Control menu working when it was supposed to be disabled, I wanted to ask whether or not this is how OFC is supposed to look. It certainly is cutting fuel at low loads and TPS%.
poormxdad is offline  
Old 04-26-2017, 09:33 AM
  #6  
Senior Member
Thread Starter
 
poormxdad's Avatar
 
Join Date: Dec 2010
Posts: 1,192
Total Cats: 103
Default

Here's the current tune and a short log I did on I-95 lifting off the throttle. I need to do another log at lower speeds.

Thanks much,
Attached Files
File Type: msq
poormxdad23Apr.msq (274.9 KB, 90 views)
File Type: msl
2017-04-23_16.38.54.msl (563.0 KB, 97 views)
poormxdad is offline  
Old 04-26-2017, 10:24 AM
  #7  
Senior Member
iTrader: (1)
 
acedeuce802's Avatar
 
Join Date: Dec 2010
Location: Farmington Hills, MI
Posts: 1,218
Total Cats: 175
Default

I've seen this as well when tuning with overrun shut off. Even though the VE values in the bottom row seem linearly lower than the rest, it still seems to run very lean under high vacuum. As long as it doesn't run this lean in other conditions, just turn on overrun fuel cut. Your log shows that under decel, you still have an injector pulsewidth, which means that the fuel is not completely shutting off. It'd be much better to not inject any fuel and not have combustion, than having it run very lean like that.
acedeuce802 is offline  
Old 04-26-2017, 12:50 PM
  #8  
Senior Member
Thread Starter
 
poormxdad's Avatar
 
Join Date: Dec 2010
Posts: 1,192
Total Cats: 103
Default

Originally Posted by acedeuce802
I've seen this as well when tuning with overrun shut off.
Thanks much. That's what I wanted to know. Do you have any recommendations for the spark or other options?
poormxdad is offline  




All times are GMT -4. The time now is 03:24 PM.