Some interesting A/F info for all us midwesterners
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From: 41° 59' N, 87° 54' W
Some interesting A/F info for all us midwesterners
Found this info in the latest newsletter from Innovate Motorsports (http://www.innovatemotorsports.com/resources/news6.php) makers of the LM-1 AFR gauge...
Since most of the midwest mandates 10% ethanol on pump gas (for sure IL does), this is pretty helpful info, especially for those passing through from out-of-state with aggressively tuned cars.
l8r)
Originally Posted by IM Newsletter #6
Tuning Tip: Ethanol Content
We've had a few reports where users could not “nail down” their tune on the street with the LM-1. The AFR's would jump about 0.5 AFR across the WOT band even in the same weather conditions in the space of a few days. Instead of holding a tune, the engine seemed to slowly “yodel.”
Naturally the first thing to blame was the LM-1. But it turned out that the users filled up at different gas stations, sometimes filling up on gas that had 10% ethanol mixed in. As expected, when Schnapps is mixed with cars, things get a little complicated.
If ethanol (stoich AFR of 9) is mixed with gasoline (stoich AFR of 14.7) the resulting gas has a lower stoich AFR than 'pure' gasoline. As the fuel injection is tuned to mix a certain amount of fuel for a given amount of air, the resulting mixture would be leaner when using a fuel with lower stoich AFR.
This can be calculated:
sAFR = (%ofAdditive * sAFRadditive + (90-%ofAdditive) * sAFRgas) /100
where:
sAFR is resulting stoich AFR
%ofAdditive is amount in % of mass of additive (ethanol) mixed in
sAFRadditive is stoich AFR of additive (9 for ethanol)
sAFRgas is stoich AFR of base gasoline (14.7)
For a 10% mixture of ethanol to gasoline by mass the resulting stoich AFR is 14.13
So, for an engine that's tuned to certain AFR at a certain load and RPM on straight gas, the resulting (gasoline equivalent) AFR when running the mixture can be calculated as:
new AFR = tuned gas AFR * (gasoline stoich ratio) / blend stoich ratio
An engine tuned to 12.5 gas AFR will run at the equivalent of 13 gas AFR with a 10% ethanol blend. This is what these people were seeing.
Of course, when running in closed loop, the engine will run at 14.13 AFR instead of 14.7. O2 sensors (incl. widebands) don’t measure AFR, but Lambda. Lambda is defined as actual AFR/stoich AFR. It's a ratio. In closed loop part throttle the engine is just running at Lambda 1.0, regardless of fuel. The same would be true for other Lambda values when running closed loop at WOT using a wideband. The engine would run at the tuned Lambda and everything would be fine. Open loop systems would need to be retuned for alcohol blends though.
Until next time... Keep On Tuning!
We've had a few reports where users could not “nail down” their tune on the street with the LM-1. The AFR's would jump about 0.5 AFR across the WOT band even in the same weather conditions in the space of a few days. Instead of holding a tune, the engine seemed to slowly “yodel.”
Naturally the first thing to blame was the LM-1. But it turned out that the users filled up at different gas stations, sometimes filling up on gas that had 10% ethanol mixed in. As expected, when Schnapps is mixed with cars, things get a little complicated.
If ethanol (stoich AFR of 9) is mixed with gasoline (stoich AFR of 14.7) the resulting gas has a lower stoich AFR than 'pure' gasoline. As the fuel injection is tuned to mix a certain amount of fuel for a given amount of air, the resulting mixture would be leaner when using a fuel with lower stoich AFR.
This can be calculated:
sAFR = (%ofAdditive * sAFRadditive + (90-%ofAdditive) * sAFRgas) /100
where:
sAFR is resulting stoich AFR
%ofAdditive is amount in % of mass of additive (ethanol) mixed in
sAFRadditive is stoich AFR of additive (9 for ethanol)
sAFRgas is stoich AFR of base gasoline (14.7)
For a 10% mixture of ethanol to gasoline by mass the resulting stoich AFR is 14.13
So, for an engine that's tuned to certain AFR at a certain load and RPM on straight gas, the resulting (gasoline equivalent) AFR when running the mixture can be calculated as:
new AFR = tuned gas AFR * (gasoline stoich ratio) / blend stoich ratio
An engine tuned to 12.5 gas AFR will run at the equivalent of 13 gas AFR with a 10% ethanol blend. This is what these people were seeing.
Of course, when running in closed loop, the engine will run at 14.13 AFR instead of 14.7. O2 sensors (incl. widebands) don’t measure AFR, but Lambda. Lambda is defined as actual AFR/stoich AFR. It's a ratio. In closed loop part throttle the engine is just running at Lambda 1.0, regardless of fuel. The same would be true for other Lambda values when running closed loop at WOT using a wideband. The engine would run at the tuned Lambda and everything would be fine. Open loop systems would need to be retuned for alcohol blends though.
Until next time... Keep On Tuning!
l8r)
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From: high up in the mountains!!
Toluene kicks ***..
sunoco, i think, has it as the main octane booster in some of their race gases.
I have had *****in' results with it.!!!!
hardware store race gas kicks ***!! but make sure you pay attention to the ratio you mix it as
sunoco, i think, has it as the main octane booster in some of their race gases.
I have had *****in' results with it.!!!!
hardware store race gas kicks ***!! but make sure you pay attention to the ratio you mix it as