E15

Dave R · 03-16-2011, 02:24 PM

Plain old gasoline needs a 14.7:1 air to fuel ratio (by mass) in our engines. Ethanol contains some oxygen and requires less air so the proper air to fuel ratio for ethanol is 9:1. If my math is correct, you'd need 6% more fuel to get to the proper air to fuel ratio with E10, and 9% for E15.

Modern car engines have closed loop fuel injection and will adjust the air to fuel ratio on-the-fly based on the oxygen content in the exhaust. Boats engines, even those with fuel injection (except the catalyst equipped models, as far as I know) don't have the ability to adjust air to fuel ratio automatically. They run open loop and simply calculate the ratio with a fixed table that injects a specifica mount of fuel for a specific amount of air. What this means is that on E10, we are running 6% lean and on E15 we'd be running 9% lean. This is going to affect HP for sure, and potentially engine longevity since lean conditions cause excessive heat.

Has anyone ever had a ECM re-programmed with a richer air to fuel mixture? I'm thinking I'd like to do this on my Mercruiser 7.4 MPI engine, if we get stuck with E15.

MDoug · 03-16-2011, 03:08 PM

Last season a fuel line burst inside the engine cowl of my outboard. First time that happened to me. A few friends have suggested that ethanol mix may have deteriorated the line. Several say they replace fuel lines every couple of years now.

robmac · 03-16-2011, 04:51 PM

I am going to call Arizona Speed & Marine and see if they can do that for my PCM.

Dave R · 03-16-2011, 07:23 PM

Quote:

Originally Posted by robmac

I am going to call Arizona Speed & Marine and see if they can do that for my PCM.

Please post the details when you know them.

03-16-2011, 03:08 PM	#2
MDoug Senior Member Join Date: Dec 2006 Posts: 342 Thanks: 116 Thanked 42 Times in 39 Posts	Ethanol Mix Last season a fuel line burst inside the engine cowl of my outboard. First time that happened to me. A few friends have suggested that ethanol mix may have deteriorated the line. Several say they replace fuel lines every couple of years now.

03-16-2011, 02:24 PM	#1
Dave R Senior Member Join Date: Jul 2004 Posts: 2,985 Thanks: 246 Thanked 744 Times in 444 Posts	Plain old gasoline needs a 14.7:1 air to fuel ratio (by mass) in our engines. Ethanol contains some oxygen and requires less air so the proper air to fuel ratio for ethanol is 9:1. If my math is correct, you'd need 6% more fuel to get to the proper air to fuel ratio with E10, and 9% for E15. Modern car engines have closed loop fuel injection and will adjust the air to fuel ratio on-the-fly based on the oxygen content in the exhaust. Boats engines, even those with fuel injection (except the catalyst equipped models, as far as I know) don't have the ability to adjust air to fuel ratio automatically. They run open loop and simply calculate the ratio with a fixed table that injects a specifica mount of fuel for a specific amount of air. What this means is that on E10, we are running 6% lean and on E15 we'd be running 9% lean. This is going to affect HP for sure, and potentially engine longevity since lean conditions cause excessive heat. Has anyone ever had a ECM re-programmed with a richer air to fuel mixture? I'm thinking I'd like to do this on my Mercruiser 7.4 MPI engine, if we get stuck with E15.

The Following 2 Users Say Thank You to Dave R For This Useful Post:
NoBozo (03-16-2011), NoRegrets (03-17-2011)

03-16-2011, 04:51 PM	#3
robmac Senior Member Join Date: Jan 2005 Location: Nashua,Meredith Posts: 951 Thanks: 213 Thanked 106 Times in 81 Posts	I am going to call Arizona Speed & Marine and see if they can do that for my PCM.