How much octane does methanol injection really add?

[2gGSX]

I propose that meth injection is not enough to significantly alter your octane rating as it's done by most people (e.g. M12 nozzle, delivering 750 cc/min). With dual M12's and 100% methanol, you'd get 2.61 lbs/min mass flow, or 1.137 lbs/min effective flow (flow in terms of gasoline, which is raw mass flow multiplied by 6.4/14.7). In a typical 450-500 lbs/min setup with 50 lbs/min airflow and an 11.5:1 AFR (4.34 lbs/min total fuel, assumed to be 93 octane), you'd end up with 98 octane [113*1.137/4.34 + 93*(4.34-1.137)/4.34]--and that's with 26% of your fuel coming pre-injector/intake manifold.

Stemming from this post: http://www.dsmtuners.com/forums/151401871-post32.html

While I agree that that is really rich (even more so with the 12 GPH, or 757 cc/min M12 nozzle spewing more fuel in), it seems to get rid of knock, which is always my first priority.

In my opinion you're just at the limits of your fuel, meth and all. Even after the meth injection, I'd put you between 92-94 octane.

Highlight this if you really want to see the fuzzy logic calculations
Assuming you *are* at 9.5:1, you'd be running about 4.63 lbs/min of fuel total. The 50/50 meth being injected gives ~380 cc/min, or .659 lbs/min of meth. Your effective octane rating would be 113*(.659*6.4/14.7[to factor in the lower energy content of methanol]/4.63)+91*(1-.659*6.4/14.7/4.63) = 92.36. That's not 100% accurate, but I'd put you right around there (within 1 or 2 points at most).

If you were to lean your AFR out, you'd have to either lower timing or drop boost. At this point, your only option would be to lower boost and thus some airflow. Your best way of figuring out which nets you more power would be on a dyno, although something like a 70-90 mph 3rd gear pull time comparison may work as well.

I'm actually just ranting now.

Ignoring the fact that I just quoted myself...

The problem I have with that calculation is that it seems to decrease the effective octane of the original gas, which makes no sense. Furthermore, the octane properties of methanol should come from mass-flow, not the converted flow. When I try to do anything like that though, I end up with a total octane value of 110+ which makes even less sense. In the end, I think that it's just the nature of how the equation works.

THE BIG QUESTION IS: how much octane does injecting methanol actually add?

 

[assault187]

I dont really understand the calculations, but from what I have read up on in the past prior to buying and installing a meth kit in my own car, is that with 93 octane pump with meth you should see the 110 octane #'s as you stated.

 

[2gGSX]

The value I used for the octane value of methanol was 113, from (RON+MON)/2, or the AKI value, as used generally in the U.S./Canada. With that said, I don't see how injecting even 25% of the total fuel as 113 octane methanol puts you anywhere near 110+ overall octane.

 

[Defiant]

The benefits of injecting water or alcohol aren't from any real, imagined, dreamed or fantasized octane alteration. I've still not run across a satisfying explanation of why it helps, but I've heard a lot of theories ranging from "quenching" (whatever the proponent thinks that is), to "charge dillution", "molecular dissociation", "fuel dispersal", "steam expansion" (oh, look, a magical leak that's letting calories seep into the process), and the much-loved "octane boost" are bandied about.
Water/propane/methanol/windshield washer fluid/acetone/bat urine in some way stabilizes and "calms" combustion, giving a ballpark 5% buffer area to enable an engine's tune to be optimized further than a system without it. It may be as simple as the result of having the combustion chambers and valves being continuously cleaned of carbon and that "gunky engine buildup" that Shell Oil wants you to be terrified of, whateverthefcuk it is in the first place.
IF there's any effective change to the "octane rating" (which in scientific terms is quantified as being as Wild-Assed Guess) it won't be more than a point or two.

 

[Nvisabl]

Let's no forget the cooling effect of the water in the 50/50 mix. We have run cars on both 100% and 50% on a gt3076 running 37psi we got more timing on the 50/50 mix then the 100% both tuned to no knock and air flow according to DSM link in the 59lbs/ min range. I personally believe the 50/50 is the better mix if you need 100% meth you need more fuel. We have a 2g running a 50/50 as I said on a gt3076 w/ aprox 37psi on pump no knock. 3000gt vr4 with dr650's running 23psi no knock ( and if you have tuned a 3si knock is tough )
and a ford focus gt2852 running 15psi on stock motor no knock. as we say "Our Meth won't rot your teeth" So I pay no attention to what octane should be and tune to what works.

 

[2gGSX]

The benefits of injecting water or alcohol aren't from any real, imagined, dreamed or fantasized octane alteration. I've still not run across a satisfying explanation of why it helps, but I've heard a lot of theories ranging from "quenching" (whatever the proponent thinks that is), to "charge dillution", "molecular dissociation", "fuel dispersal", "steam expansion" (oh, look, a magical leak that's letting calories seep into the process), and the much-loved "octane boost" are bandied about.
Water/propane/methanol/windshield washer fluid/acetone/bat urine in some way stabilizes and "calms" combustion, giving a ballpark 5% buffer area to enable an engine's tune to be optimized further than a system without it. It may be as simple as the result of having the combustion chambers and valves being continuously cleaned of carbon and that "gunky engine buildup" that Shell Oil wants you to be terrified of, whateverthefcuk it is in the first place.
IF there's any effective change to the "octane rating" (which in scientific terms is quantified as being as Wild-Assed Guess) it won't be more than a point or two.

I agree wholeheartedly.

 

[turboglenn]

It's all voodoo, now that i've got a shrunken head in my meth tank i'm getting no knock at all

 

[Defiant]

You should zip-tie a couple of cow magnets to it

 

[2gGSX]

Tom,
Think I have the definitive answer here.
First off, R+M/2 octane of pure methanol is only 101.
Homebrew Octane Boosters Look at "Formula 4"

Secondly, I've been playing around with the "Octane Boost Wizard" (which agees with the link above) here:
Octane_Boost_Wizard

This is cool that you've got the flow rates all calculated, which lets you figure your gas/alky mix just as if you were pouring the meth into your tank, which is what this wizard is assuming. Only you would need volume flow rate, not mass flow rate. The wizard uses volume of gas + volume of octane booster for the input. Use the first wizard called "Single Component Octane Booster Calculator". Every time you want to change a number in the wizard hit the "clear" button first and start all over, otherwise it gets cranky and doesn't want to do anything. Pick "Methanol" from the drop-down list for "octane booster". The wizard will give you the resulting octane of whatever mix you have.
Notice that if you put in "0" gallons of 93 octane + 1 gallon of Methanol it will give you resulting octane of 101, which agrees with the first link.
Or go with the shrunken head.

If you don't mind, copy and paste this into your thread. I can't post it there, still a friggin Newbie!

Gary
We're on Boost

Oh yeah, here's the real voodoo.
Heat of vaporization:
gasoline ~ 900 BTU per gallon
methanol ~ 3340 BTU per gallon
water ~~~7000 BTU per gallon!

That's why spraying water and alky works better than spraying just alky. Anyway, they both do a lot more cooling than gasoline so you can advance timing some without knock.
Post this too, ok?

Thanks,

Gary
We're on Boost

Forwarding the message.

 

[dsm-onster]

Yea, just ask Turboglenn. After he played with his shrunken head diameters, his zombie car started eating metal .

I didn't really follow your formula. But you highlighted that if 26% of the total fuel in the combustion chamber is methenol, then you have an octane of 98. That is correct by my calculations. I've understood meth octane to be 113-114, as well. Which doesn't go along with Gary. . .He's likely correct.

Now, if you can alter the characteristics of the fuel once it get into the combustion chamber, then you raise the "effective octane". Effective octane is the result of an octane rating, though the fuel doesn't display that rating in the lab. Altering effective octane is the benefit of adding water to the mix. Water can absorb more heat, as you quoted above. But it does it at a slower rate than alcohol, because it is difficult to achieve the surface area in the spray that would be remotely close to any alcohol. Alcohol spray actually removes more btus per unit time than same flow (same volume) water spray. Water has much stronger surface tension. That's why Isopropynol cools our cuts. Water therefore stays in the aircharge in a "droplet state" long enough to get into the combustion chamber. There, as the energy of the combustion process is released, the water vaporizes and it's ability to absorb lots of heat shows itself by doing it at a VERY fast rate. This "slowing the burn" causes the fuel not to want to detonate. The burn rate can be brought down to 110 octane rates.

SOO, less meth than 26% of the fuel demand, but a higher octane result. Not as cold an aircharge in the intake manifold, though.

 

[Devilsown]

The amount of real world octane increase is very small. Remember you usually injection aprox 15% water/meth at a 50/50 mix. So lets say 7% of what your injecting is meth and this is what going in the motor. Now usually 10% of the whole amount is going to dis pate in the intake track. So your going to end up with aprox 2.5% of your fuel as 116 methanol. Now this can greatly vary depending on setups. How much heats in the intake track etc. The majority of the kr resistance and power thats achieved from the alcohol injection kits is the cooler intake air temps.

 

[dsm-onster]

The methenol molecules are still in the intake track no matter the state of matter in which they are. From my understanding, if it's injected and there's no boost leaks, all of the meth injected ends up in the combustion chambers.

But, I do agree that most of the knock resistance with meth injection comes from cooler intake aircharge. However, that's because most run too little a nozzle with too high of a methenol mix. It is proven that pure h2o injection does great in supressing knock but doesn't cool the aircharge nearly as well as much less meth. So there's minimal hp benefits other than a more aggresive tune. Injecting pure meth as the op mentions at the rate the op mentions (much more nozzle than most do, dual m12s with pure meth) will yield around 97-98 octane. . . Which is OK. But yes, probable not enough for an aggressive race gas tune except for the excellent aftercooling you brought up.