Do we really need methanol?

[bmw5002]

First I'd like to say happy holidays to all. Second, I'm a new member. :smile: Third, my first question for all of you would be, do we really need to use methanol with our WI setups? Besides a little bit added so the water does not freeze in cold temps, what is the benefit of adding more than say, 30% methanol to the water? Ive seen charts showing how the latent heat capacity of the mixture goes down as more methanol is added. It is well known that water injection will cool the air charge going into the engine best. It is also known that heat causes detonation. The water injection is able to combat detonation or pre-ignition by cooling the air charge. A leaner A/F mixture raises the temps as well. The WI will allow us to lean out the A/F ratio without adding additional heat to the combustion chamber. We all know this stuff. I have seen on many sites that adding methanol to the mix will increase the octane of the A/F mixture, allowing leaner A/F ratios and advanced timing. I am wondering why one would need a higher octane in the first place, if the cooling effect of the water is able to prevent the very detonation that raising the octane also prevents. So I ask, what is the point of injecting more than 50% methanol?

[keithmac]

I inject 75% methanol, I got this mix by trial and error through logging knock at higher boost settings. If your car is octane limited and this is the main cause of knock then running methanol is a good way to fortify the fuel. I inject nearly as much water/methanol by volume as I do fuel on full boost, just water at these quantities would bog the engine badly.

It all depends what your engine and setup wants, and you have to work from there.

My cars a JDM so requires a higher grade fuel than is normally available in the UK, add on top of this more boost and more timing and
the need for higher qantities of methanol arises.