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Discussion Starter #1
Finally got the mustang inspected and on the road. During deceleration the car goes super lean 9.0-10 when the TPS is at zero. Once i give it gas and the TPS is anything above zero the AFR's come back up to 14.5 as i have it set in the programming. Self learning status and CL status goes from green to blue as soon as the TPS is at zero. What do i need to adjust to fix this so the car doesn't stay lean during the entire time of decel? I have a Pro Comp C4 3 speed automatic in the car. When im in decel and above say 30 MPH the car does this. Once i slow down and the converter isn't locked the car will idle at 14.5. Only at slow speeds. If i do pull to 100 mph the status goes blue and AFR's go down in the 9's until i'm under say 30 mph. I dont want to burn up my new build. Please let me know what i need to adjust! Thank you guys! - Gene
 

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9.0 to 10.0 is really rich, not lean.

It's normal to see a lean condition on decel. Depending on your settings, you may have the fuel commanded to shut off on decel.
 

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Discussion Starter #3
9.0 to 10.0 is really rich, not lean.

It's normal to see a lean condition on decel. Depending on your settings, you may have the fuel commanded to shut off on decel.


Thanks. What AFR is normal on decel? I know my WOT target AFR should be 11.5, and idle should be 14.5. Im boosted running about 12-15 psi. Do you think seeing 9's on decel is a bad thing? Trying to get the old girl tuned so i can take it to the track. Any suggestions guys?
 

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You can turn fuel off on decel... Decel afr are not that accurate I'd lean it up on decel until it starts to run bad then add just a little back. This will help with fuel mileage.
 

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Discussion Starter #8
You can turn fuel off on decel... Decel afr are not that accurate I'd lean it up on decel until it starts to run bad then add just a little back. This will help with fuel mileage.
How do i adjust that. Thanks for helping me out!
 

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Thanks. What AFR is normal on decel? I know my WOT target AFR should be 11.5, and idle should be 14.5. Im boosted running about 12-15 psi. Do you think seeing 9's on decel is a bad thing? Trying to get the old girl tuned so i can take it to the track. Any suggestions guys?
For idle and cruise LEAN THAT BITCH OUT until it misfires. I target idle for 15.2 and cruise down the highway as high as 15.9. Keeps the plugs clean and saves fuel.
 

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Some say rich on decels helps cool, but destroys economy. On a friends bike with power commander. We added 10% fuel at throttle closed at high rpm just because he wanted flames.

9-10 on decel isnt too bad, does it backfire or pop in the exhaust. The worst case is you will not get a great plug read after a run.
 

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Some say rich on decels helps cool, but destroys economy. On a friends bike with power commander. We added 10% fuel at throttle closed at high rpm just because he wanted flames.

9-10 on decel isnt too bad, does it backfire or pop in the exhaust. The worst case is you will not get a great plug read after a run.
If someone wants cooling on decel, TURN THE FUEL INJECTORS OFF until it needs to be restored to keep the engine from stalling.

Raw air with no fuel to ignite is certainly cooler than combustion gases, even if those gases are from a rich mixture. ;)

NOTE - I do not let the fuel injectors turn off during a run. If you are running at high power, especially high boost and lift momentarily, you don't want to stop the fuel flow totally, it will make the engine even leaner when you get back into the throttle. Most ECUs can be programmed with a delay to prevent them from turning off during a momentary lift.

That's why I like traction control so much, you don't have to lift in most cases and the air/fuel keeps flowing.
 

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Discussion Starter #15
fuel> fuel modifiers> fuel control



My decell fuel cut off is not enabled. Should i enable it?

AE vs TPS RoC blanking is set at 7
AE vs MAP RoC blanking is set at 7


What do i need to adjust to make it leaner on decel?



Car does not pop or misfire during decel, RPM's drop to idle and AFR is pegged in the 10's.


Thank you for all of the help guys its a learning curve for me.
 

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Discussion Starter #16
Keep in mind i have an automatic not standard so RPM drops to idle it doesn't rev down in the RPM.
 

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Holleys fuel model will not allow you to dial in decel fuel perfectly. It just doesn't work. To do that you need something like the x-tau model from megasquirt. It has to do with what's called the 'fuel puddle':


http://www.megamanual.com/ms2/xtau.htm


http://video.google.com/videoplay?docid=-1671092540772647555&hl=en


It's simply impossible to do that with Holleys fuel model. However we have a few things we can do to alleviate the issue. First is turn on decel fuel cutoff. Make it active no shorter than 0.8 seconds. Second is we can lean out the VE table in areas that are deceleration only. Third we can use an 'advanced table' to pull fuel in areas when TPS is 0%.



All other times actual AFR should follow target AFR pretty well. There will also always be a lag, maybe half a tenth at high rpm and two tenths at lower rpm. Depends on where the wideband is located too of course. But on deceleration it will always be richer than what we want. Closed loop is also shut off on deceleration.
 
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