I've known some thermodynamics for years, but I only recently grasped exactly why spraying a liquid cools the surrounding air. A lot of the real explanations for things like that just aren't given in the textbooks.
I overlooked that about the decreased temperature not resulting in lowered pressure due to the introduction of more gas. I was going to say that if the pressure was lowered than one would think that water injection alone with no other changes would increase power.

 

Wow, are you guys lucky I found your thread so I could explain yourselves to one another.

First off, Julio (the Buick V6) guy is most likely using Methanol injection not just for detonation prevention, but for FUELING at least part of his combustion. So yes, replacing his fuel with water, in any ratio, will cause a drop in power as he notes.

The LSx guys are talking about water/methanol injection for a car that is already adequately fueled, but without enough octane to support the heat and pressure.

In the case where you're adequately fueled, water is preferred. In the case where you're actually injecting something to support combustion, something flammable (ie: methanol) is preferred.

It really took 9 pages of this thread to get here?

When you're doing it for combustion, call it methanol injection. When you're doing it to reduce temperatures, call it water injection. I have spoken.

 

Yes, thanks for educating us

 

We understand the difference between the two. We were arguing the merits of each.

 

I'd like to better understand which setup (straight water, mix, straight meth) has potential to make the most power on pumpgas-93.

If you were to build a combo from scratch to get the most out of FI on pump, which fluid do you pursue?

What are most high horsepower pumpgas guys running?

Thanks,
Scott.

 

Well, your post opens up the same debate people have already expressed opinions on. I think I stated mine pretty clearly. Straight water and mixtures of water:methanol or even straight methanol significantly lower combustion temperature and allow either more boost or higher compression. Straight water has the greatest effect on combustion temperature/volume injected. Mixtures of up to 50% methanol provide most of the benefits of straight water in terms of reducing temperature and also have a much lower freezing point in addition to allowing larger volumes to be injected (because the methanol burns as a fuel). As the methanol:water ratio rises over 1:1, the loss of cooling effect offsets the greater volume you can inject without excessively inhibiting combustion. Therefore the ideal mixture is ~1:1 water:methanol. Also, it's really best to think of it as a mixture of gasoline, methanol, and water. The ideal combination for a particular gasoline is going to differ. Of course, what works best is setting up to car to run on straight methanol. This is not practical for a street car though

IMHO.

Rich

 

Thanks Rich,

I didn't realize (or maybe I had forgotten) there were so many good posts leading up to the current to which I replied.

Thanks again for your support!

-Scott.

 

An excellent read. I really appreciate threads where informed people engage in intelligent discussions while having differing viewpoints.
I'm a 50/50 person myself b/c I use the injection (with appropriate warnings) rather than an intercooler to cool my IATs .

 

Saw this article recently and it reminded me of this thread.

Get Schooled: Water Methanol Injection 101 - Dragzine