Air Fuel Ratio
Jun 29, 2006 | 11:12 AM
#21
How do I change this text
iTrader: (26)
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From: Behind the TIG welder
Originally Posted by Yelo
So...what is the min A/F mixture that our engines can safely handle when out of PE mode ??.....I ask because it seems that you could command something like 15.1:1 instead of 14.7:1 to increase fuel mileage while in closed loop mode (kind of a DIY lean cruise mode - just set PE to come in earlier and adjust it to compensate for the leaner mixture), or - getting kind of off-topic here - you could log what MAP ranges you see while athighway RPM's and DECREASE the VE table at those points (therefor decreasing fuel delivery) to again act as a lean-cruise mode.
You can also lean the O2 rich/lean vs. airflow at light throttle
Jun 29, 2006 | 11:17 AM
#22
Originally Posted by BlownChevy
here is one interesting fact that I picked up: 14.7:1 is considered perfect AFR due to the fact that it is as close to a 100% burn of the fuel as you can get.
The only reason our cars run at 14.7 is because it is mandated by the EPA because it is stoich (least hydrocarbon emmisions) but here is a question does it produce less pollution to run at 14.7 or does it produce less to not have to make all the extra billions of gallons of gas that are waisted by running at 14.7. Catalytic converters are in the same boat they produce nitrous oxide a greenhouse gas that is 300x more potent than carbon dioxide. I read an article in the NY times that states the EPA did a study in 89 and realized that late model engines with cats actually produced more greenhouse gases that engines without cats!!!!!
But back on topic 14.7 is far from perfect if you want power you would run richer all the time and bump compression and timing. If you want mileage you would be running in the 15.x-16.x range. Assuming the use of 93 octane.
With higher octane leaner mixtures at wot can net higher HP but increases temperatures and engine wear greatly and sacrifices tq.
Tuners and GM shoot for 12-13.1 NA because of safety and an ability to run more timing on lower octane gases. It depends on what your goals are as too what the "Perfect" AFR is.
Jun 29, 2006 | 11:20 AM
#23
Originally Posted by 04ChargedSS
Now that's a bit (ok, WAY) over my head! 
The only readings I can get on my scanner are MAF, MAP, IAT, and voltages (Mv) for the four O2 sensor points. Oh wait, there are some percentage readings for the fuel banks (short and long term?) How do I convert that to A/F ratio?
Or am I totaly off on one this one?
The only readings I can get on my scanner are MAF, MAP, IAT, and voltages (Mv) for the four O2 sensor points. Oh wait, there are some percentage readings for the fuel banks (short and long term?) How do I convert that to A/F ratio?
Or am I totaly off on one this one?unfortuneatly, you can't. without a wideband, you don't belong in this thread. j/k
you can't convert, it just dosn't work.
i agree that 14.7 is not "perfect" per say. It seems to be the standard though for what everyone uses for a good "middle of the road" a/f ratio. what it boils down to is that each vehicle is different so depending on your goals, you could run richer or leaner at WOT compared to someone else.
Last edited by Holty; Jun 29, 2006 at 11:29 AM.
Jun 29, 2006 | 11:46 AM
#24
Originally Posted by Yelo
So...what is the min A/F mixture that our engines can safely handle when out of PE mode ??.....I ask because it seems that you could command something like 15.1:1 instead of 14.7:1 to increase fuel mileage while in closed loop mode (kind of a DIY lean cruise mode - just set PE to come in earlier and adjust it to compensate for the leaner mixture), or - getting kind of off-topic here - you could log what MAP ranges you see while athighway RPM's and DECREASE the VE table at those points (therefor decreasing fuel delivery) to again act as a lean-cruise mode.
From your smoothing ve thread...
Originally Posted by kbracing96
Actually, I don't use PE or LTFT. I use this.
It's EFILives Custom OS 3 Commanded fuel vs. rpm table. Anywhere that 14.68 is commanded, it uses STFT to correct the fueling. Everything else runs open loop strictly off the VE tables. (Notice the lean cruise in there
)
It's EFILives Custom OS 3 Commanded fuel vs. rpm table. Anywhere that 14.68 is commanded, it uses STFT to correct the fueling. Everything else runs open loop strictly off the VE tables. (Notice the lean cruise in there
)
Jun 29, 2006 | 11:52 AM
#26
Staging Lane
Joined: Jun 2006
Posts: 53
Likes: 0
From: Tri Valley area, NorCal
Originally Posted by Holty
unfortuneatly, you can't. without a wideband, you don't belong in this thread. j/k
you can't convert, it just dosn't work.
you can't convert, it just dosn't work.
I don't belong in this thread, But I have to learn SOMEWHERE and this seems like as good a place as any! 
Thanks for your patience, and please, be gentle with the
LMAO
Jun 29, 2006 | 11:55 AM
#27
Thread Starter
Joined: Mar 1986
Posts: 18,748
Likes: 7
From: Chatsworth, CA
Originally Posted by 02sierraz71_5.3
I dont agree with this 14.7 is perfect for what? Its not perfect for power NA or FI and its far from being perfect for great gas mileage.
The only reason our cars run at 14.7 is because it is mandated by the EPA because it is stoich (least hydrocarbon emmisions) but here is a question does it produce less pollution to run at 14.7 or does it produce less to not have to make all the extra billions of gallons of gas that are waisted by running at 14.7. Catalytic converters are in the same boat they produce nitrous oxide a greenhouse gas that is 300x more potent than carbon dioxide. I read an article in the NY times that states the EPA did a study in 89 and realized that late model engines with cats actually produced more greenhouse gases that engines without cats!!!!!
But back on topic 14.7 is far from perfect if you want power you would run richer all the time and bump compression and timing. If you want mileage you would be running in the 15.x-16.x range. Assuming the use of 93 octane.
With higher octane leaner mixtures at wot can net higher HP but increases temperatures and engine wear greatly and sacrifices tq.
Tuners and GM shoot for 12-13.1 NA because of safety and an ability to run more timing on lower octane gases. It depends on what your goals are as too what the "Perfect" AFR is.
The only reason our cars run at 14.7 is because it is mandated by the EPA because it is stoich (least hydrocarbon emmisions) but here is a question does it produce less pollution to run at 14.7 or does it produce less to not have to make all the extra billions of gallons of gas that are waisted by running at 14.7. Catalytic converters are in the same boat they produce nitrous oxide a greenhouse gas that is 300x more potent than carbon dioxide. I read an article in the NY times that states the EPA did a study in 89 and realized that late model engines with cats actually produced more greenhouse gases that engines without cats!!!!!
But back on topic 14.7 is far from perfect if you want power you would run richer all the time and bump compression and timing. If you want mileage you would be running in the 15.x-16.x range. Assuming the use of 93 octane.
With higher octane leaner mixtures at wot can net higher HP but increases temperatures and engine wear greatly and sacrifices tq.
Tuners and GM shoot for 12-13.1 NA because of safety and an ability to run more timing on lower octane gases. It depends on what your goals are as too what the "Perfect" AFR is.
i think you may have mis-understood the entire theroy......I stated that it is perfect for exactly what you said in the above post.
Catalytic converters are in the same boat they produce nitrous oxide a greenhouse gas that is 300x more potent than carbon dioxide.
Jun 29, 2006 | 12:02 PM
#28
TECH Addict
Joined: Feb 2003
Posts: 2,864
Likes: 1
From: Geneseo, NY
Originally Posted by BlownChevy
Ummmm you might want to rethink that statement.....If a Catalytic converter produces Nitrous Oxide then I am going to re-plumb my exhaust back into my intake.
Jun 29, 2006 | 12:06 PM
#29
Thread Starter
Joined: Mar 1986
Posts: 18,748
Likes: 7
From: Chatsworth, CA
Originally Posted by Yelo
Actually, he's right dude....byproducts of the chemical reaction in the catalytic converter are water vapor and oxides of nitrogen (N20), there's not enough N20 to worry (or care) about though with new catalytic converter technology
Oxides of Nitrogen are actually NOX.
NOX forms when when combustion temps reach 2500*. Modern day cats are designed to reduce NOX.
Jun 29, 2006 | 12:09 PM
#30
TECH Addict
Joined: Feb 2003
Posts: 2,864
Likes: 1
From: Geneseo, NY
Originally Posted by BlownChevy
Oxides of Nitrogen are actualy NOX.
Last edited by Yelo; Jun 29, 2006 at 12:20 PM.