You are currently viewing our forum as a guest, which gives you limited access
to view most discussions and access our other features. By joining our community, at no cost, you will have access to start new topics, reply to conversations, privately message other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join RX7Club.com today!
it really is pretty simple.... comparing water to alcohol to a mix. all the work has been done, there really isn't any conjecture except in some people's minds. the physical properties differences dictate what each is going to do and not do for you and your motor.
each injectant based on it's properties has it's place. yes, if you are pursuing a particular objective one might be better than the other.
this thread is NOT a place to argue mine is better than yours. it is a place to get the facts and then move forward.
the primary principle of the AI Section is:
run water
run alcohol
run a mix.
but run something or fry your motor.
that said, i will be posting a physical properties comparison during the next week and hope it clears away lots of part truths that fly around out there in cyberspace.
howard coleman
This ad is not displayed to registered or logged-in members. Register your free account today and become a member on RX7Club.com!
Typical gasoline Thermal energy 19,000 BTU/lb max power fuel air mixture 12.5:1
Typical E85 Thermal energy 13,475 BTU/lb max power fuel air mixture 6.975:1
Typical ethanol Thermal energy 12,500 BTU/lb 6.429:1
If you are consuming 100 lbs of air, lets see how much fuel energy you release for each of these fuels.
100/12.5 = 8 lbs of gasoline @ 19,000 BTU/lb = 152,000 BTU
100/6.975 = 14.337 lbs of E85 @ 13,475 BTU/lb = 193,189.9 BTU = 127% more heat energy
100/6.429 = 15.555 lbs of Ethanol @ 12,500 BTU/lb = 194431.5 BTU = 128.9% more heat energy
the primary reason i didn't follow thru was about the time i started the thread the AI wars were escalating and i just decided to let things cool a bit rather than stir the injectant pot.
ideally this thread should not be an either or (water or alcohol) but a resource as to what makes each injectant a bit different.
both have a legitimate place in the AI space.
that said, just a couple of comments...
you really see differing numbers on alcohol's octane. one of the problems is that octane is rated at a specific temperature. alcohol cools so much that there is no way it can be rated at that temperature so we get guesses.
i will say this... it has been my experience thru lots of road testing and 3 dyno sessions that the more alcohol the better. i will be shortly moving from 1200 CC/Min to 1600 CC/Min at peak torque/peak boost.
one of the more interesting considerations is the autoignition temperature of alcohol... to be clear, autoignition is simply the temp where a substance starts burning.
this is highly relevant w the rotary relative to preignition/knock.
gasoline, including racegas, auto-ignites at 660 degrees F.
alcohol, (methanol, ethanol and isopropyl) ignite at 858 degrees F!
that's alot of additional protection against bad things...
i'll be back with more.
any people feel free to add here and that includes the waterites.
"I was tuning a car on the dyno that had high IATs. We sprayed the IC with some nitrous to cool it down, and this dropped the temp 10degF, and the car picked up 14whp!! Same timing, same AF, same boost ,etc (replete with AEM logs to substantiate this claim). This was on a car making mid-high 500s. Quite a significant bump! And this car had about another 30degF left to go before the temps were 'ideal' (i.e. 10degF above ambient)... so in theory it could pick up 45whp from just a better FMIC! Quite significant. So IAT reduction might be a worthwhile point on those of us running undersized FMICs. While the race gas can keep the detonation at bay, the gains from increased air density seem quite significant."
of course we know that the primary deal w lower IATs is more oxygen molecules per volume. and when you are talking oxygen nothing beats alcohol, or methanol specifically.
meth is 49% oxygen by weight
ethanol is 34% oxygen by weight.
gasoline is zero% oxygen.
as to cooling:
meth is 1.154 MJ/Kg
eth is .913
gasoline is .297
Meth is the winner.... lots of oxygen and lots of cooling.
Very similar to that^^^, I read an article where someone was using a dual loop intercooler sprayer that looked like a figure 8 on thier drag civic and it picked up 60 horses. Of course they were also spraying nitrous onto the core. I'll see if I can find it.
i hate to bring this thread back from a few months but it seems that barry is showing the latent heat for vaporization of water is twice that of methanol and second highest enthalpy to ammonia.. which is due to hydrogen bonding.. and i understand that the more oxygen the better for keeping autoignition down but im just wondering the results of water compared to alcohol numbers-wise.. if anyone can show some quantifiable data that would be much appreciated thank you
edit: i realize the ammonia thing isnt in barrys post i was just throwing it out there
I think we're missing the numbers for the specific heat of each fuel in both liquid and air form. I believe latent heat of vaporization numbers are measured at the boiling point, which can skew things if you're spraying a liquid below the boiling point. Then you need to figure out how much energy it takes to heat it up to boiling first, based on the specific heat of the liquid and the change in temperature. And this all might vary with pressure too, I don't remember.
So what we really need is to calculate in then is X kJ of heat absorbed per kg of fuel when the air temperature right outside the intake is 70F, 80F, 90F, 100F, 110F and 120F. That would help provide the most direct comparison between the cooling properties of each. And it would be useful if you're looking to replace x grams of gasoline with y grams of water or with z grams of alcohol and need to get an estimate of what y or z should be. There may be other factors to consider as well, but this should be what matters in terms of preventing detonation.
__________________
1987 white NA RX-7
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
I always wanted to do a 50/50 mix of water and Methanol, but it's too time consuming for me to play chemist and get the mix right every time I fill up. Especially when you drive alot. Rather not worry about it and just use 100% Meth. It smells good too when you smoke the car behind you. *Burning Eyes!*
__________________
- Red 93 FD on MeTh. To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Black 93 FD - 20B - GT42RS
-Red 90 TII w/ LS3
- 02 TDI Jetta - @ 2 bar - 190HP / 350 ft/lbs TRQ- 45+MPG. 170k miles. To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Very similar to that^^^, I read an article where someone was using a dual loop intercooler sprayer that looked like a figure 8 on thier drag civic and it picked up 60 horses. Of course they were also spraying nitrous onto the core. I'll see if I can find it.
EDIT- Here it is http://www.hondatuningmagazine.com/t...est/index.html
__________________ In the middle of difficulty lies opportunity - Albert Einstein
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
OK, my little contribution of what i have managed to glean elsewhere
i fill my rx7 with straight propane
despite the slight BTU losses in volume to blended LPG and petrol
its octane is almost unbeatable, its pound for pound, kilo for kilo comparable in energy to petrol
- and its pump quality/purity assured
-this is an amalgam from my other posts elsewhere-
footnote --
RON or MON or AKI?
in the US ( AKI ) and aus/Europe ( RON ) , different methods are used
what is US 87 octane ( AKI ) is European 91 ( RON )
or aussie normal unleaded
is actually RON 91, 86.75 AKI and 82.5 MON
and conversely ,,
what we in australia call PULP
RON 95 , AKI 91 , MON 85
and PULP 98
RON 98 , AKI 94, MON 88
and blended LPG is
RON 100 , AKI around 97, MON 92
MINIMUM
STILL SLIGHTLY BETTER THAN THE BEST PULP
even at 50% butane blended into 50% propane
and propane is
RON 115 , AKI 110, MON 103
and 91,547 BTUs versus 116,000 BTUs per gallon for gasoline/petroleum
-Methanol contains only 57,000 BTUs per gallon, which is half that of gasoline
( volume comparison)
But on a pound per pound basis, propane delivers almost the same energy as gasoline (21,591 BTUs)
( mass basis )
where-
RON is the knock test at 600 rpm and 40 celcius air temps
MON is a test on same engine at 900 rpm and 150 celsius air temps
BP is the boiling point in celsius
AIT is auto ignition temperature
d is fuel density compared to 1 L/ 1 KG of pure water
--- you can see why in the past i was keen to use toluene and xylene and even acetone as minor fuel additives on drag day
Last edited by bumpstart; 02-18-09 at 09:37 AM.
Reason: typo corrected
Linear Mode
