A/F ratio with alky?

[edmundu]

I have a question....

What method are you guys using to measure the afr's at 10.5 w/meth, and 11.5 w/o?

Because even though Meth is 6.5 stoich, and gas is 14.7, you still look to hit .80 lambda regardless of which fuel is used. Furthermore a wideband only measure's oxygen content, it is not privy to what fuel is being utilized. So it appears that you guys are running excessively rich, no? I know that with alky, you can run too rich, and not have the power dropoff as sharp as it does with gasoline.

I do understand that the "actual" air to fuel mass being injected is closer to 10.5:1, but that is not what a wideband measures. I have searched around on many, many performance forums, and only the Buick boy's run such rich afr's on alky injection, hence why I question the reasons for running that way....

[Steve Wood]

Because it makes the most power for us...we are running wb's with stoch set for gasoline.

Many have systems that are able to produce high volumes of methanol flow and we are using the meth as much for fuel, as for charge cooling. I think many are running 20%, and sometimes more, meth versus ~80% gasoline.

It is not excessively rich if the car is making more power. It is what works for many of us...but, few of us would be held to any magic number...just what works for each car.

[edmundu]

Thanks for elaborating a bit....

So on the Buick GN's you have found that 0.7-.71 lambda works best for max power?

[Steve Wood]

Even tho lambda is 1 as you point out, I hesitate to use it as we are mixing fuels without a consistent ratio to the mix. As we have our choice of using either gasoline or methanol when setting up our wb's...most use gasoline with the corresponding stoch so the a/fs displayed are relative to that.

Using gasoline computed a/fs, the fastest guys seem to be around 10.5 to 10.6 from what I haves seen. These are the guys knocking on the 10.0 ets. Guys in the 11.0s are probably closer to 11-1.

Combination has much to do with it.

Again, it is probably because we are relying upon the detonation resistance of methanol when we use it as fuel...(and hoping preignition does not bite us)

Charge cooling is secondardy, I think, on the really quick cars.

On street cars that are running less alky, charge cooling is probably a bigger factor.

[John Lindsay]

I tuned my datsun with a EGT befor the turbo and found that 1550 deg. of temp. was a good number evan at 29# of boost and 29 deg. of timming but I was using alot corn ethanal and I think it runs alot better than denature from the paint store. so the AFR could be any where. I would like to know if any one else used a EGTand if it help. I was lost with out it.

[Steve Wood]

I use an egt....typically around 1600 on methanol.