Desired AFR at W.O.T.

StangD · Post by **StangD** » Sun Aug 16, 2015 4:57 pm

94 Mustang with a 347. There is a big penalty for detonation on the stock block. Anyone have a suggestion you are confident with over the long term? Mostly a strip car that sees 6500 RPM. I promise not to sue you for commenting. :)

Mitchb · Post by **Mitchb** » Mon Aug 17, 2015 4:15 pm

You are probably going to want 12.8 - 13.0:1, but the spark you run will be more critical.
What is the stoich of the fuel you are using? You must factor this in to your desired AFR.

Mitch

StangD · Post by **StangD** » Mon Aug 17, 2015 4:41 pm

I was using 14.7, but I doubt I will be able to find 100% gasoline this year in 91-92 Octane. It will be E10 Premium more than likely. I'm not certain what the stoic would be for E10 off the top of my head. I gave the car a few shakedown runs on a base tune last year. If i remember correctly I was running about 12.3 AFR at WOT last year. I didn't mess with the stock timing much other than eliminating the tip in shift retard so it was conservative. 11-1 CR and aluminum heads of course. Everything seemed fine though I think I could lean it a bit for better performance. Car is a few tenths slower than I think it should be. Lost my laptop and some data. Starting over on the tune tonight while I wait for a new Quarterhorse to arrive.

Mitchb · Post by **Mitchb** » Tue Aug 18, 2015 12:40 pm

10% ethanol has a stoich of around 14.07.

Mitch

StangD · Post by **StangD** » Tue Aug 18, 2015 1:16 pm

Thanks Mitch.

85GT · Post by **85GT** » Wed Aug 19, 2015 11:58 am

Just don't target 14.07 on your WB for stoich. unless you recal'd it for E10 too...

StangD · Post by **StangD** » Wed Aug 19, 2015 12:21 pm

Thanks, I found my backup CD which has my Lasota tuning book and some other info I gleaned from this site a year or so ago. I'll be careful to ensure my tune and Innovate WB software are all reading E10. I'd like to stay 100% gasoline but I know I will just end up having a problem getting fuel when I want to race. Better to just accept the reality and tune properly for it.

JohnnyK · Post by **JohnnyK** » Wed Aug 19, 2015 2:27 pm

85GT wrote:Just don't target 14.07 on your WB for stoich. unless you recal'd it for E10 too...

What do you mean by this exactly? The WB is just reporting what it sees, no? The ECM is looking for 14.07, so shouldn't we be seeing that on the wb as well?

StangD · Post by **StangD** » Wed Aug 19, 2015 2:40 pm

Non-specific answer I know but you need to tell your WB software what is in the fuel tank. Gasoline-E10-E85-Racing fuel all have a different stoic. Lambda is 1.0. You have to tell it what 1.0 is. Somebody smarter than me feel free to explain it more thoroughly.

85GT · Post by **85GT** » Wed Aug 19, 2015 5:41 pm

JohnnyK wrote:
85GT wrote:Just don't target 14.07 on your WB for stoich. unless you recal'd it for E10 too...
What do you mean by this exactly? The WB is just reporting what it sees, no? The ECM is looking for 14.07, so shouldn't we be seeing that on the wb as well?

WB knows lambda, then converts to an AFR ratio for the fuel it thinks you have. If it's set for gas, and it displays 14.07, it's seeing a lambda less than 1. So an E10 fuel would be richer that stoich with that display rather then what you would think is stoich.

StangD · Post by **StangD** » Wed Aug 19, 2015 7:37 pm

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