AIR/FUEL ratio
Extreme HDF Member
Joined: Apr 2006
Posts: 10,449
Likes: 46
From: Roswell, GA
Streetrunner: What is your fuel milleage? I ask because that will be a good indicator of whether your bike is rich. If your mpg is 40+, and your engine temps suggest that it is, the exhaust smell is probably the result of the denser air supporting more fuel for the same AFR, so the exhaust has more unburned fuel though the AFR remains the same.
As for a dyno AFR trace going below 13, that's common--at WOT an excess amount of fuel is added to compensate for the relatively inefficient burn of the fuel, especially with carbed bikes which don't atomize fuel as well as EFI bikes. However, as the rpms increase the mixture should be leaned out even at WOT.
As for a dyno AFR trace going below 13, that's common--at WOT an excess amount of fuel is added to compensate for the relatively inefficient burn of the fuel, especially with carbed bikes which don't atomize fuel as well as EFI bikes. However, as the rpms increase the mixture should be leaned out even at WOT.
Last edited by Harleypingman; Nov 8, 2008 at 06:33 AM.
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Stellar HDF Member
Joined: Dec 2005
Posts: 2,598
Likes: 52
From: South Jersey
That sig pic is old and my SG have gone through a few cosmetic changes since that was taken. I'm to lazy to figure out how to get a new pic on this site. It took me a lot of time to get this one posted.
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Stellar HDF Member
Joined: Dec 2005
Posts: 2,598
Likes: 52
From: South Jersey
When I brought it back to the tuner that was the first thing he attempted to change. It didn't change things. Of course it could be him, I don't know.
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Stellar HDF Member
Joined: Dec 2005
Posts: 2,598
Likes: 52
From: South Jersey
Here's the funny thing; in the summer I get 41 - 45 and when the weather gets a little cooler I get anywhere from 32 -36. So, yes, the smell = richness. The real question is, "why does it change so dramatically?"
Cruiser
Joined: Feb 2007
Posts: 115
Likes: 34
From:
Perhaps it's a problem with the intake air temp reading- faulty sensor or corrupt tables in the tuning file....
Tourer
Joined: Aug 2007
Posts: 250
Likes: 0
From: Jackson, MI
I assume you are running true duals? From what I have read, it's the result of exhaust reversion due to the 2 into 2 and the bike will run rich around 2500-3000. It needs to be leaned out in that area, by way of tuning.
Road Warrior
Joined: Nov 2008
Posts: 1,955
Likes: 7
From: The Great Northwest
My vote would be for the PCIII. Probably because I have a PCIII and as we all know, humans will usually claim that whatever they bought is the best. I have a few different custom maps on my laptop.
1) Local Map
2) Long Cruise Map
3) Altitude Map
I takes about 3 minutes for me to change maps according to my trip plans or my mood. Hook up the USB cable, highlight my map, and click on send map. So easy even I can do it. I don't have ABS so the PCIII is easily accessible and located under my starboard side cover. That's my .02.
1) Local Map
2) Long Cruise Map
3) Altitude Map
I takes about 3 minutes for me to change maps according to my trip plans or my mood. Hook up the USB cable, highlight my map, and click on send map. So easy even I can do it. I don't have ABS so the PCIII is easily accessible and located under my starboard side cover. That's my .02.
6th Gear
Joined: Aug 2025
Posts: 14
Likes: 1
From: USA
I don't know what tuner was used? SE Pro Tuner to maintain warranty? At any rate, I have never tuned a bike but am under the impression the SE Tuner is very limited on adjusting fuel/air mixture. This is based on the narrow band sensors and EPA requirements. SE tuner tends to run the bike lean. The system operates in two primary modes: "Closed Loop" and "Open Loop." During steady cruise at part throttle, the system uses the O2 sensor to maintain a near-ideal air-fuel ratio of approximately 14.6, which is considered stoichiometric for efficient combustion and emissions control. When the throttle is opened significantly (e.g., during acceleration or wide-open throttle), the system switches to "Open Loop" mode, where it relies on pre-programmed fuel maps based on engine load and RPM, typically running richer (e.g., 12.5 to 13.5) to protect the engine from overheating and provide adequate cooling. The system automatically compensates for changes in air density, such as cooler, denser air in colder weather, which can naturally lean the mixture, by adjusting fuel delivery to maintain the desired ratio. I wonder if your intake manifold is leaking? MAP and IAT is critical for correct mixture ratios. During deceleration, your manifold should have high pressure. If the MAP senses low pressure (leak) it may be adjusting fuel ratios thinking you are running at more open throttle. So perhaps the original tune is not representative due to leaking. Remember the IAT is probably located in the intake manifold along with the MAP and this manifold connects to the input ports on the engine. And the miserable intake is made of plastic which tends to warp with high temperatures. I know when my friend and I build my shovel head back in the day, he was always concerned with intake air leakage. He was a wiz on carb adjustment and operation.
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Seasoned HDF Member
Joined: Sep 2009
Posts: 17,149
Likes: 6,173
From: SE Michigan
I don't know what tuner was used? SE Pro Tuner to maintain warranty? At any rate, I have never tuned a bike but am under the impression the SE Tuner is very limited on adjusting fuel/air mixture. This is based on the narrow band sensors and EPA requirements. SE tuner tends to run the bike lean. The system operates in two primary modes: "Closed Loop" and "Open Loop." During steady cruise at part throttle, the system uses the O2 sensor to maintain a near-ideal air-fuel ratio of approximately 14.6, which is considered stoichiometric for efficient combustion and emissions control. When the throttle is opened significantly (e.g., during acceleration or wide-open throttle), the system switches to "Open Loop" mode, where it relies on pre-programmed fuel maps based on engine load and RPM, typically running richer (e.g., 12.5 to 13.5) to protect the engine from overheating and provide adequate cooling. The system automatically compensates for changes in air density, such as cooler, denser air in colder weather, which can naturally lean the mixture, by adjusting fuel delivery to maintain the desired ratio. I wonder if your intake manifold is leaking? MAP and IAT is critical for correct mixture ratios. During deceleration, your manifold should have high pressure. If the MAP senses low pressure (leak) it may be adjusting fuel ratios thinking you are running at more open throttle. So perhaps the original tune is not representative due to leaking. Remember the IAT is probably located in the intake manifold along with the MAP and this manifold connects to the input ports on the engine. And the miserable intake is made of plastic which tends to warp with high temperatures. I know when my friend and I build my shovel head back in the day, he was always concerned with intake air leakage. He was a wiz on carb adjustment and operation.
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