Now you've added a twist because you want to mix E85 and gasoline together. First off, mixing 50/50 E85 and gasoline is not truly a 50/50 solution of ethanol and gasoline because there is 15 percent gasoline mixed with the E85. To produce a true 50/50 ratio, you will have to mix 5.88 gallons of E85 with 4.12 gallons of race gasoline to make 10 gallons of that 50/50 brew. This makes the math much simpler in Klaus' next equation. Plus, mixing 105-octane E85 with 110-octane race gas in the 5.88 + 4.22 ratio will produce roughly an octane rating of 108. To come up with an air/fuel ratio, Klaus suggests using a simple equation that will produce an air/fuel ratio you can shoot for with this mixture. Basically, we're multiplying the stoich A/F ratio of gasoline times the amount of fuel mixed, then doing the same with E85, and then adding those two together. With a true 50/50 mix, it looks like this: (0.50 x 14.7) + (0.50 x 9) = stoich A/F for this mixture of fuel. Doing the math gives us 7.35 + 4.5 = 11.85 stoich A/F. Warning: This is the stoichiometric ratio-NOT the maximum power air/fuel ratio. When you mix the fuel is when you would apply the jetting conversion calculated above. The ideal max-power A/F ratio will be roughly 10.:1. We shoot for a max-power A/F ratio using Innovate's meter in the lambda scale. Ken Duttweiler has been beating this into us for the last couple of years, since we started working with E85. His point is that max power occurs with a lambda reading (regardless of fuel used) of around 0.85-or 15 percent richer than 1.0 (lambda) with fuels like gasoline, methanol, or alcohol, or any mixture of the above since the number is the same. So with a calculated A/F for the 50/50 fuel mix of 11.85:1 (1.0 lambda), multiply by 0.85 (best power in lambda), and we come up with a 10.0:1 A/F ratio as what you should target. Interestingly, the baseline test for this thought process is simply to take the gasoline stoich A/F of 14.7 and multiply times 0.85 (lambda), and you get 12.49:1 A/F. Amazing how all this ties together, isn't it?
If we haven't totally confused you, I think this is a great way to approach what you want to do, and working through this will help you with other mixture calculations that you might want to try such as E75 or E90. I'd like to thank Klaus Allmendinger and Innovate Motorsports for enduring several rounds of my questions about this issue. If this subject intrigues you, Innovate Motorsports has a great forum full of interesting questions, and Klaus is a frequent contributor who can produce laser-beam answers.
More Info
Innovate Motorsports; Irvine, CA; 949/502-8400; innovatemotorsports.com
Olds Dilemma
Oldsguy, via CarCraft.com tech forum: I have an '84 Olds Cutlass with a 403ci with pocket-ported heads, an Edelbrock RPM intake, and an RPM camshaft. The cam is 2 degrees retarded from the spec card, so I advanced it 4 degrees. This combo in a street car with open headers ran an 8.19 in the eighth-mile with a Q-jet and a 1-inch spacer. After that I began having trouble with the idle. I had a new Holley 830 for another car that is not done yet, so I put it on with a new 50cc rear accelerator pump and cams to eliminate a flat spot on the launch. I lost 0.30 second and can't seem to get it back. I replaced the front power valve with a plug and raised the jets the recommended amount from 78 to 85-still no help. I had to put on some collectors with short 3-inch turndowns because it burned my shifter cable. This cost more time, and now we are at 8.7s. I put on an NX Hitman with 150hp jets to get back to 8.20s. I spent over $1,000 to get the same time again. The plugs are black, so I'm thinking I should lean out the air/fuel mix, replace the 1-inch spacer, remove the collectors, leaving the shield in, or just burn the whole car and start over since I bent the butterflies. As you can see, I need help. It seems every way I go costs more money. I am still having a good time, but it would be better to get back to the 8.19s without the nitrous. Then the real fun can begin.
Quadrajets have an undeserved reputation as a Quadra-bog. Secondary hesitations can be largely eliminated by adjusting the secondary air-valve door spring to delay the opening until there is sufficient air velocity to pull fuel out of the secondary metering circuit.>>>