Air/Fuel ratio ?
- Thread starter mrose
- Start date
ALVAROG1983
EVIL GN
- Joined
- Mar 27, 2007
How about 12.00 or little higher with alky.
slimtastic
yea dude...I rock
- Joined
- Aug 9, 2002
ive found on the dyno that with iron headed cars the AFR that produces the most power is right around 11to1 afr. any leaner and your loosing power. with alky id stay right in that same afr or go just a tad richer.. stock iron heads and dish pistons have horrid "quench" with basicly means that you have to throw more fuel at is to get all the oxygen to burn as the air/fuel doesnt mix very well
with a aluminum headed car you can make more power going leaner....even more so if you have a set of pistons that match the quench pads in the aluminum heads
with a aluminum headed car you can make more power going leaner....even more so if you have a set of pistons that match the quench pads in the aluminum heads
slimtastic
yea dude...I rock
- Joined
- Aug 9, 2002
that will break everything under the hood (over 16 lbs) lol
You really tune it that fat on alky? This is really confusing to me. I would think with the cooling effects of alcohol that you would be tuning for numbers more similar to race gas.
The non alky numbers are what I would tune for, just surprised by the others.
You really tune it that fat on alky? This is really confusing to me. I would think with the cooling effects of alcohol that you would be tuning for numbers more similar to race gas.
The non alky numbers are what I would tune for, just surprised by the others.
I personally am not an alky user. I deffered to the experts on the numbers, and they tell me 10.8-10.9 on alky.
RmvBfrFlght
Well-Known Member
- Joined
- Sep 28, 2007
You really tune it that fat on alky? This is really confusing to me. I would think with the cooling effects of alcohol that you would be tuning for numbers more similar to race gas.
The non alky numbers are what I would tune for, just surprised by the others.
Adding alcohol skews the WB reading. For a WB to be truly accurate in reporting AFR, the ratios of hydrogen to carbon (H/C) and oxygen to carbon (O/C) ratios of the fuel are required.
The WB controller needs this information to correctly convert the sensor reading into an AFR. Even a Lambda value would need to be corrected once off of stoich.
Adding alcohol to gasoline changes the H/C and O/C ratios. Thus skewing the reading.
RemoveBeforeFlight
The more power and more alky injected the richer it should be. Under 500whp 10.8-11.0.1 is fine. it will make more power being leaner until it's starts melting stuff. There is not much to be gained going a little leaner. Maybe a few hp. It will easily tolerate being a lot leaner on a dyno because the time under power and load is not like making a full pass through third on the pavement. I run 10.4-10.6 for 650whp.
If you go leaner and are making any power you will soon find out how to replace pistons and repair burned decks/ melted heads and pistons. Non oxygenated race fuel can be run much leaner. Pump gas is oxygenated and you are replacing part of if with methanol which will further require richening.You really tune it that fat on alky? This is really confusing to me. I would think with the cooling effects of alcohol that you would be tuning for numbers more similar to race gas.
The non alky numbers are what I would tune for, just surprised by the others.
- Joined
- Feb 18, 2006
and thats the bottom line right there.............
Unfortunately you can't be sure what% of pump gas is co-solvent so your stoic will be varying every tank of fuel. It's easier to use the gasoline table and just shoot for conservatively richer targets.
Bison, are these AFR numbers for an alky and 93 octane? What would you look for with say a 50/50 mix of 93 and 110 with a dual nozzle alky kit?
Pat
RmvBfrFlght
Well-Known Member
- Joined
- Sep 28, 2007
Absolutely in agreement. Although to an O2 sensor, stoich is stoich (NB or WB). If the WB controller is set up to report 14.7:1 (Lambda = 1) for stoich, it doesn't matter what fuel is used. Even straight methanol will report 14.7:1 when run at stoich with that controller set up.
This is important to understand when using a WB setup. With any fuel the reported AFR at stoich will always be the same. This will be whatever the controller is set for, AFR wise, for Lambda = 1.
Once the AFR moves away from stoich the reading then depends upon the composition of the fuel. More so as one moves richer then leaner.
This helps explain why we are running such rich AFRs as reported by the WB.
RemoveBeforeFlight
Burning pure methanol, I get best power at 1.1 -1.2 volts on the wideband. The gasoline based readout would be 11.0-11.2:1. This is at 31 PSI boost and a BHP level of 1180-1230. Power drops off fast rich or lean of these numbers. The plugs look very safe with these numbers.
The plan is to use 10.8:1 as I test boost levels beyond 31 PSI. If the plugs show me that I can move leaner, then I'm sure I can find more power there. Reading the plugs will let me know.
Each case can be different, so stay on the rich side until you can check things out to judge whether or not you can get away with going leaner. Reading the plugs will be very important in making that decision.
If you want to stay safe and give yourself some safety margin, shoot for 10.8:1.
The plan is to use 10.8:1 as I test boost levels beyond 31 PSI. If the plugs show me that I can move leaner, then I'm sure I can find more power there. Reading the plugs will let me know.
Each case can be different, so stay on the rich side until you can check things out to judge whether or not you can get away with going leaner. Reading the plugs will be very important in making that decision.
If you want to stay safe and give yourself some safety margin, shoot for 10.8:1.
