EvoLutionized8

iTrader: (62)

Let me first say that I am no Chemist, and I will definitely try not to come off as if I were.. but I was wondering if anyone knew if it were possible to mix Isoproponal with the fuel to gain points, just the same that most use Methanol??

I talked to a few individuals who use ISO-HEET as an additive to their tanks.. and I know what it is meant to do to the water content in the fuel line and tank, but they also use it as an enhancer of sorts for their fuel..

Does anyone have the simple version as to why this can / cannot be done?? Any information would be greatly appreciated..

LivingWeapon

Chemistry aside, tell your friends M1 alky can be had for $4-$5/Gallon bulk, or your regional track price, vs. $3-$4 for a tiny bottle of ISO-HEET

There are entire books & web sites dedicating to mixing gas for racing, and plenty of word-of-mouth wisdom as well. Injection based systems work on a different mechanism vs. mixing a batch of race gas for a single fuel delivery system ...but both have the same goal: delay onset of detonation, so you can advance ignition timing and/or run higher compression. For turbo engines, where you can effectively dial in additional compression by running higher boost, it is (relatively) easy to to tune both these parameters (within a given turbo's efficiency due to pressure ratio).

With added alky or nitromethane in the gas tank, an engine actually needs more fuel to maintain the same A/F ratio. That's because alky is a shorter carbon chain than gas (fewer carbon/carbon bonds per gallon), and nitromethane is a completely different chemistry all together (it is an oxidizer as well as a fuel). EMS, the fuel pump, and injectors need to compensate for that or the engine will run lean. On a factory tune 10% methanol in the gas tank is something the factory fuel delivery system can compensate for, but under higher boost you'll need an upgraded fuel system to run alcohol in the gas tank without risk of leaning out. Did I mention being careful not to lean out?

Anecdotally, you may have noticed about 5% less gas mileage on 10% methanol gas sold at the pump. Again, that's because the EMS calls for a greater volume of gas to balance the A/F, so you go through a tank quicker.

With alky injection, the engine gets a 2nd fuel system adding additional fuel to the mix, but (unlike staged injection adding more of what's in the gas tank), the intent is usually not to enrich the mixture. Rather, the intent is to cool the air charge, much like the intercooler does, so more (denser) charge will fit into the cylinders each time an intake valve opens. The phase change from liquid to vapor (evaporation) of alcohol or water in the intake cools the mixture. Then the primary fuel system adds an appropriate amount of gas to meet the desired A/F ...not much gas if the injection system is fogging tons of alky, or more gas if the injection system is increasing the charge density enough to improve the volumetric efficiency of the intake stroke.

Injecting water alone provides intake cooling and some negligible "bonus" steam pressure, without complicating the A/F ratio (other than the additional fuel needed to maintain A/F ratio of a denser charge, which gets more air into each cylinder). However, water evaporates slower, so a set up with long intake runners or a very hot charge (e.g. a supercharged V8 with no intercooler) could see a lot of improvement with just water. Otherwise, misting alky is much better.

For a given boost pressure, cooling the intake charge should produce a higher lbs/min of flow through the engine, so long as the plumbing is "open" enough to support the increased flow. Of course, the goal of any engine is moving more CFM or lbs of air, so the engine can turn more fuel into power. The actual intake pressure required to move the air is anecdotal, but easier to directly measure.

In terms of which alcohol to inject: methanol, with the highest vapor pressure, evaporates quickest. This results in the most effective intake cooling, densest charge, and best volumetric efficiency for the cylinders.

C6C6CH3vo

iTrader: (9)

Isopropyl sucks

Methanol is best, even though water has better latent heat value, methanol evap rate is so much faster making waters latent heat values useless

SlowCar

iTrader: (4)

methanol is good for cooling air charge, water excel in in-cylinder cooling

RenoEvo

iTrader: (43)

not to hijack, but Isn't pure meth too corrosive to run straight for extended periods of time? I think it would eat through a lot of your fuel components eventually. A 50/50 mix of dentaured alky and water is the best combo from what I've heard.

Richard L

iTrader: (5)

On this article below, there is definitely no go for isopropyl ...

http://enginehistory.org/Frank%20WalkerWeb1.pdf

94AWDcoupe

iTrader: (125)

I had a similiar experience. Ran out of meth one weekend. Tryed isopropol in its place. car picked up detonation like the injection wasn't even working.

LivingWeapon

Wow, 150" Hg manifold pressure on the R-2800 = 78 PSI

I wonder if that was +78 above ambient, or 78 absolute ...either way, that's a pantload of boost.

Really cool link Richard. Bizarre how those old aircraft engines ran at such low compression the "drowning test" didn't cause hydraulic lock.

So, back to the topic at hand: isopropyl has an aggressive LEL (Lower Explosive Limit) of only 2%, so in concentrations suitable for intake charge cooling it becomes a combustion product. Methanol will not burn at all in concentrations below 6.7%. I found a nice table here.

So I was a bit misleading when I said that the EMS would need to account for the presence of methanol in the mix when adjusting A/F. The EMS will only need to add more fuel to take advantage of the denser charge and higher boost levels, and avoid leaning out. Injected methanol should pass through the engine unburned, just like injected water, so long as the concentration remains lower than 6.7% of the cylinder contents.

I was a bit perplexed to see a 3.3% LEL for etheyl alcohol ...sounds dangerously close to isoproply's limit, at less than half methanol's comparatively safe limit

Richard L

iTrader: (5)

LEL figure is a good find. I wonder if the chart can be extend to higher operating conditions such as the cylinder pressure and temperature just before or just after ignition. I suppose this is getting towards octnae numbers.

C6C6CH3vo

iTrader: (9)

Also, I truely believe that methanol concentrations higher than 75% in water decreases overall effectiveness.

Ever mix anhydrous methanol with H2O, if so, notice the liberated heat?

Now think off what happens as the two in solution vaporize - ice. I'm claiming that 75% methanol absorbes more heat than 100% methanol during vaporization, furthermore the remaining water vapor (vapour UK) still contains a laten thermal potential for even more cooling.

Don't forget 100% methanol can boil at room temperature under mild vacume (vacuum UK )

SlowCar

iTrader: (4)

is methanol + water really exothermic?? Will try this out in the morning!

SlowCar

iTrader: (4)

50cc deionized water @23.6C
50cc HPLC grade methanol @21.7C

water + methanol = 32.6C - its exothermic!

experiment was done in a foam cup with type K exposed thermocouple

donperry

Don't like to create new threads so i'm bumping this one.

Ran out of methanol and had to used 70% isopropyl bottles. As i was challenged to a race. I used 1 gallon to half gallon isopropyl, which prob would be 65/35 water alcohol ratio

(had more water per volume than the isopropyl) and reduced my AFR from 11.7 to 11.3. I cut my flow a little and I come out with more power 269hp/240tq vs 263/225 . But what is weird is when i lean out the 50/50 methanol anymore than 11.7 i would get knock in the high gears near redline, not so with this isoprop and water mix. At most i'e seen only 1.4 degrees pulled at 6800rpm.

I believe i have some more tweaking to do with the meth mix as that's not supposed to happen