best AIR FUEL RATIO
#21
11-14-2011, 11:49 PM
Stellar HDF Member
"[b]est AFR" for what--cruise on flat road, partial acceleration, WOT, etc.????? "Best" for fuel mileage??? "Best" for lower engine temps????
I ask because AFR varies for all of those parameters and, with regard to acceleration and load, there is no single AFR that is "BEST."
I ask because AFR varies for all of those parameters and, with regard to acceleration and load, there is no single AFR that is "BEST."
14.65/1 is the chemically "Ideal" stoichiometric Air Fuel Ratio. Up to a point: Richer (less than 14.65) will get you more power and Leaner (more than 14.65) will result in better MPG. Most dyno tuners I've seen; run things well on the rich side to extract maximum power. Generally doing this at anything less than about 60%-80% Throttle opening is a waste of fuel and washes down the cylinder wall which ultimately shortens engine life over time.
#22
11-15-2011, 12:51 AM
Outstanding HDF Member
Join Date: Aug 2011
Location: Right about the middle
Posts: 3,450
Likes: 0
Received 8 Likes
on
7 Posts
Cruising a/f would get the best mileage at 14.7-1 however it's not that simple. A/f will be different at w.o.t., half and quarter throttle. Thats why a custom dyno tune is best. They will program the ecu for max performance at all the different throttle positions then once you have reached you desired cruising speed a good tuner will lean out the a/f mix for best mileage. If your bike is a 2012 model they come with wideband o2 sensors iirc
#23
11-15-2011, 02:03 PM
With respect to performance, that will have to be determined by you as the definition of a "little" can mean many different things to many different people. And most of those can be done by the DIY'er without major concerns of meltdowns (assuming you're knowledgeable and reasonable in their applications).
I would just caution you to be careful with the information provided here...as I said before, while much of the info is well-meaning, lots of it is just plain wrong or misleading at best.
FWIW, your post count/dated joined suggested you might be a new member and probably relatively new to Harley's so I didn't want to come across the wrong way...so, welcome to the world of Harley.
Last edited by Pine Tree; 11-15-2011 at 02:05 PM.
#24
11-15-2011, 02:10 PM
Tourer
FOR WHAT IT'S WORTH
A stoichiometric mixture is the working point that modern engine management systems employing fuel injection attempt to achieve in light load cruise situations. For gasoline fuel, the stoichiometric air–fuel mixture is approximately 14.7; i.e. the approximate mass of air is 14.7 mass of fuel. Any mixture less than 14.7 to 1 is considered to be a rich mixture; any more than 14.7 to 1 is a lean mixture – given perfect (ideal) "test" fuel (gasoline consisting of solely n-heptane and iso-octane). In reality, most fuels consist of a combination of heptane, octane, a handful of other alkanes, plus additives including detergents, and possibly oxygenators such as MTBE (methyl tert-butyl ether) or ethanol/methanol. These compounds all alter the stoichiometric ratio, with most of the additives pushing the ratio downward (oxygenators bring extra oxygen to the combustion event in liquid form that is released at time of combustions; for MTBE-laden fuel, a stoichiometric ratio can be as low as 14.1:1). Vehicles using an oxygen sensor(s) or other feedback-loop to control fuel to air ratios (usually by controlling fuel volume) will usually compensate automatically for this change in the fuel's stoichiometric rate by measuring the exhaust gas composition, while vehicles without such controls (such as most motorcycles until recently, and cars predating the mid-1980s) may have difficulties running certain boutique blends of fuels (esp. winter fuels used in some areas) and may need to be rejetted (or otherwise have the fueling ratios altered) to compensate for special boutique fuel mixes. Vehicles using oxygen sensors enable the air-fuel ratio to be monitored by means of an air–fuel ratio meter
A stoichiometric mixture is the working point that modern engine management systems employing fuel injection attempt to achieve in light load cruise situations. For gasoline fuel, the stoichiometric air–fuel mixture is approximately 14.7; i.e. the approximate mass of air is 14.7 mass of fuel. Any mixture less than 14.7 to 1 is considered to be a rich mixture; any more than 14.7 to 1 is a lean mixture – given perfect (ideal) "test" fuel (gasoline consisting of solely n-heptane and iso-octane). In reality, most fuels consist of a combination of heptane, octane, a handful of other alkanes, plus additives including detergents, and possibly oxygenators such as MTBE (methyl tert-butyl ether) or ethanol/methanol. These compounds all alter the stoichiometric ratio, with most of the additives pushing the ratio downward (oxygenators bring extra oxygen to the combustion event in liquid form that is released at time of combustions; for MTBE-laden fuel, a stoichiometric ratio can be as low as 14.1:1). Vehicles using an oxygen sensor(s) or other feedback-loop to control fuel to air ratios (usually by controlling fuel volume) will usually compensate automatically for this change in the fuel's stoichiometric rate by measuring the exhaust gas composition, while vehicles without such controls (such as most motorcycles until recently, and cars predating the mid-1980s) may have difficulties running certain boutique blends of fuels (esp. winter fuels used in some areas) and may need to be rejetted (or otherwise have the fueling ratios altered) to compensate for special boutique fuel mixes. Vehicles using oxygen sensors enable the air-fuel ratio to be monitored by means of an air–fuel ratio meter
........and I had a great comprehension of what was being said until I got to the second word.
#25
11-15-2011, 02:17 PM
#26
11-15-2011, 02:21 PM
#27
11-15-2011, 02:57 PM
Tourer
#28
11-15-2011, 04:41 PM
Ultimate HDF Member
What a timely post. I have just spent the last few days building some new maps for my '11 Limited. I'm running a PCV w/AutoTune.
My original map was 13.8/1 in cruise range and 13.0/1 at higher rpm and throttle positions. When hot and cruising at highway speeds up any slight incline I still had a little pinging that I wanted to try to eliminate with the AFR before resorting to backing-out some timing. The timing is at the factory level right now as I have already zeroed out the timing that was bumped-up 2 degrees in my original map.
I richened the AFR targets in my map to 13.4/1 and then took the bike out for a 20-mile test run. Then I checked the adjustments that the AutoTune was making to reach that target. The adjustments from this initial run were primarily in the range of 4%-6%. After hardwiring those changes into the map I did another test run and repeated the process for six or seven iterations. In each subsequent test run the AutoTune adjustments were becoming fewer and smaller. In the end, all adjustments being made by the AutoTune were < 2%. Trying to get any closer than that is like a dog chasing its tail. Up one run, down the next... You have to find a happy median and call it good enough.
I don't know yet if this is going to eliminate my pinging issue as the weather isn't warm enough any longer. I'll need a 85+ degree day to really know. Time will tell. If necessary, I'll try 13.2/1 next, and if that doesn't do it I'll have to back some timing out of it.
After finishing the first 13.4/1 map I changed the mufflers and went through the same process again for the new mufflers. Now I have three maps available. A 13.4/1 and 13.8/1 map for the stock mufflers and a 13.4/1 map for the aftermarket mufflers.
I put about 500 hard miles on my bike building these maps and had fun doing it... It's nice to have time for this kind of stuff - It's nice being retired!
I know a lot of you run leaner maps without any pinging issues, but for my bike, my riding style, and my riding conditions they just don't work for me. When my bike was brand new/stock with the factory 14.6/1 or 14.7/1 AFR I felt like it was going to self-destruct the pinging was so bad. I only rode the bike a week or two before adding the PCV and did that very conservatively. The PCV with the canned map I was running eliminated 90% of my pinging. Now I'm trying to get rid of the last 10%.
Based on my experience with my bike, I think the cruise AFR needs to be in the low to mid 13s to 1.
Good luck with yours.
EDIT: Let me take back my first sentence about this being a timely post... I just realized how old it is LOL. Everything else I wrote still applies!
My original map was 13.8/1 in cruise range and 13.0/1 at higher rpm and throttle positions. When hot and cruising at highway speeds up any slight incline I still had a little pinging that I wanted to try to eliminate with the AFR before resorting to backing-out some timing. The timing is at the factory level right now as I have already zeroed out the timing that was bumped-up 2 degrees in my original map.
I richened the AFR targets in my map to 13.4/1 and then took the bike out for a 20-mile test run. Then I checked the adjustments that the AutoTune was making to reach that target. The adjustments from this initial run were primarily in the range of 4%-6%. After hardwiring those changes into the map I did another test run and repeated the process for six or seven iterations. In each subsequent test run the AutoTune adjustments were becoming fewer and smaller. In the end, all adjustments being made by the AutoTune were < 2%. Trying to get any closer than that is like a dog chasing its tail. Up one run, down the next... You have to find a happy median and call it good enough.
I don't know yet if this is going to eliminate my pinging issue as the weather isn't warm enough any longer. I'll need a 85+ degree day to really know. Time will tell. If necessary, I'll try 13.2/1 next, and if that doesn't do it I'll have to back some timing out of it.
After finishing the first 13.4/1 map I changed the mufflers and went through the same process again for the new mufflers. Now I have three maps available. A 13.4/1 and 13.8/1 map for the stock mufflers and a 13.4/1 map for the aftermarket mufflers.
I put about 500 hard miles on my bike building these maps and had fun doing it... It's nice to have time for this kind of stuff - It's nice being retired!
I know a lot of you run leaner maps without any pinging issues, but for my bike, my riding style, and my riding conditions they just don't work for me. When my bike was brand new/stock with the factory 14.6/1 or 14.7/1 AFR I felt like it was going to self-destruct the pinging was so bad. I only rode the bike a week or two before adding the PCV and did that very conservatively. The PCV with the canned map I was running eliminated 90% of my pinging. Now I'm trying to get rid of the last 10%.
Based on my experience with my bike, I think the cruise AFR needs to be in the low to mid 13s to 1.
Good luck with yours.
EDIT: Let me take back my first sentence about this being a timely post... I just realized how old it is LOL. Everything else I wrote still applies!
If your VEs are correct (and it sounds like they are), then set your target AFR/Lambda between 14.2-14.4 (.977-.981) for your cruise rpm and kPa. Then start targeting the timing. Richer isn't always better, and neither is more timing advance.
Best of luck.
#29
11-15-2011, 05:11 PM
Don't take this as an attack, but you're going about getting rid of your detonation all wrong. If you're at 13.4 in your cruise range and still getting ping, then your timing is too far advanced. I've run for extended periods above 80mph in 100+ degree ambient temperatures at .981 Lambda (14.42 AFR) without a hint of detonation.
If your VEs are correct (and it sounds like they are), then set your target AFR/Lambda between 14.2-14.4 (.977-.981) for your cruise rpm and kPa. Then start targeting the timing. Richer isn't always better, and neither is more timing advance.
Best of luck.
If your VEs are correct (and it sounds like they are), then set your target AFR/Lambda between 14.2-14.4 (.977-.981) for your cruise rpm and kPa. Then start targeting the timing. Richer isn't always better, and neither is more timing advance.
Best of luck.
I don't know if I still have pinging at 13.4/1. As I said I need a warm day to go out and test it. I had a slight ping only under certain conditions at 13.8/1.
I think you have a little better gas in Maryland. You can get 93 octane there, right?
My bike never pings at all with 93 octane but 91 is the best I can get here and then it's borderline. Some tanks, no ping, others a slight ping. I'm real close - just teetering on the edge. That's why I think the slightly richer mixture will help.
If not... backing out some timing is next. Like I said previously, I'm running the factory timing currently so backing out anymore is my last resort.
I appreciate your input.
#30
11-15-2011, 05:19 PM
Ultimate HDF Member
Thanks.
I don't know if I still have pinging at 13.4/1. As I said I need a warm day to go out and test it. I had a slight ping only under certain conditions at 13.8/1.
I think you have a little better gas in Maryland. You can get 93 octane there, right?
My bike never pings at all with 93 octane but 91 is the best I can get here and then it's borderline. Some tanks, no ping, others a slight ping. I'm real close - just teetering on the edge. That's why I think the slightly richer mixture will help.
If not... backing out some timing is next. Like I said previously, I'm running the factory timing currently so backing out anymore is my last resort.
I appreciate your input.
I don't know if I still have pinging at 13.4/1. As I said I need a warm day to go out and test it. I had a slight ping only under certain conditions at 13.8/1.
I think you have a little better gas in Maryland. You can get 93 octane there, right?
My bike never pings at all with 93 octane but 91 is the best I can get here and then it's borderline. Some tanks, no ping, others a slight ping. I'm real close - just teetering on the edge. That's why I think the slightly richer mixture will help.
If not... backing out some timing is next. Like I said previously, I'm running the factory timing currently so backing out anymore is my last resort.
I appreciate your input.
Reason I ask is that the ECM will pull timing even when you can't hear it, and it generally pulls 2-3 times what you actually need pulled. Yanking the timing back will actually give you more power and better mileage since you'll only be pulling what's needed rather than what the ECM pulls in order to keep the engine together.
Also, max timing before ping isn't necessarily where you're going to make the most power.