Octane Rating of Methanol?

[JonKBmw]

Hey guys - building a high horsepower turbo BMW and I have a few tricks up my sleeve to help spool the large turbo. I am about 8/10 finished my project, and have a full tubular manifold (inline 6), 76mm turbo, nitrous, and methanol injection. I intend to spray about 100 hp worth of nitrous (wet kit, so fuel as well) into the engine, 30 - 35 psi on turbo, and cover myself with methanol injection.

I am not willing to run straight methanol injection because of the low flash temperature as well as fumes and overall safety as this is a street car. So I am looking to go between 30 - 50% water (I currently use 50% water 50% methanol) to help with cooling the charge and increasing fuel octane.

What octane is methanol, generally? Meaning, if I were to run the car on pure methanol, which I can't due to injector size, what effective octane results? And as such, is it easy to calculate effective octane when using 93 octane gasoline, 50% water, and 50% methanol injected at a known rate (or any combination thereof)?

I am primarily concerned with the octane rating of Methanol itself, however.

Thanks!

 

[patprimmer]

It depends a lot on how it is measured and various reports give different values, but 115 octane seems about typical.

As methanol will burn with a VERY rich mixture, going rich can support higher effective or total compression than the octane rating would suggest.

Pure methanol at about 5.5:1 A/F ratio will suport a total compression ratio of about 20:1.

The nitrous will reduce the boost or compression you can run.

To much fuel and water can lead to hydraulic lock, but you need to be really over the top for that to be a real risk.

To much nitrous and methanol can put in enough fuel to cause so much evaporative cooling that it gets real hard to light the mixture.

Regards

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[JonKBmw]

Thanks - I understand the points about fueling, and locking, and ignition. It would take a ton of water/fuel to lock this guy up, especially considering the flow is controlled by nozzle diameter. As for igniting the mixture, I have a capacitive discharge ignition system I'll be implementing to make it all happy. I have run over 20:1 dynamic compression on just pump fuel and 50/50 water:methanol injection. Its all about injecting enough based on how much air (and is usually calculated on horsepower) you flow. Thanks - I've heard 116 - 126 octane on methanol and its just confusing.

 

[carnage1]

as a note the last e-85 specs I saw required the blend to have an octane rating of 100 to 105. and winter e-85 can have up to 30% gasoline to improve starting.

 

[JonKBmw]

Thanks but understand I am not trying to run the car on methanol. It will be run on 93 fuel on the street and prob ~110 octane on the track, with methanol/water injection supplementary to the primary fuel.