arghx

iTrader: (3)

I don't want to get too deep into this here, but to summarize the Honda study (Toshiyuki, "Pre-ignition Phenomena of Methanol Fuel (M85) by the Post-Ignition Technique," 1989) found that

1) Due to chemical reactions, methanol fuel preignites at lower temperatures and with greater severity inside an actual engine compared to premium pump fuel.



Note that in this study, the methanol-fueled engine runs a colder plug and still preignites at a lower temperature than premium gasoline

2) Methanol is particularly prone to preignition when the spark plug uses noble metals (platinum), such as what you find in typical race plugs and even regular spark plugs today





So In this study, the methanol-fueled engine with platinum plug (plug A) had extra sensitivity to preignition. This is because noble metals help set off the very chemical reactions that cause preignition with methanol fuel.

in the study they didn't test irridium (which is also a noble metal) plugs but I presume the overall trend holds.

3) higher rpm and richer mixtures mitigate the pre-ignition tendency of methanol, which would explain how people have gotten away with it



PM me if you are interested in reading the whole study. I haven't seen such issues arise in ethanol studies, although I won't claim to have read everything out there. Howard, if you want to we could take a discussion on this issue to a dedicated thread in the AI section.

Barry Bordes

This is what auto-ignition or pre-ignition looks like on a rotary.
Normally the pressure from the growing kernel would not start till after TDC if ignition was say 15 degrees BTDC.
This test is running 50/50 meth/water and 12 lbs boost.
Peak pressure has moved to 40 deg ATDC.
Interesting but scary when we are not in control of the timing.

smg944

iTrader: (34)

dam went to edit lost what i had said.

easy2speed

Nice!

Mr rx-7 tt

iTrader: (5)

I take it you aren't a methanol/water inj fan? Do you like lower ratios of water to methanol under 50/50?

Liborek

I´m big fan of water injection. But I´m just proposing what I learned from various research studies. Theoretically, 100% methanol is extremely good charge coolant, but due to its preignition properties (examined above) it simply doesn´t work as someone wants to think. 50:50 water/methanol by mass is vastly superior, any more methanol in mix increases preignition chance and lowers permissible power level.

I asked very simple question, why methanol fueled engine, even with its huge cooling properties, has to be run so rich on lambda scale compared to gasoline? Assuming that both fuels are run at same lambda, methanol fueled one will have 8 times higher cooling effect due to evaporation. So why run it even richer? As chart above indicates, its done due to preignition tendencies of this very sensitive fuel.

Howard Coleman

iTrader: (6)

"Due to chemical reactions, methanol fuel preignites at lower temperatures"

thanks all for the excellent content. it does have me reconsidering my AI injectant. i will say i am scratching my head re the "chemical reactions" aspect of meth in the combustion chamber. it certainly is opposite of what i would expect given methanol's approx 850 F autoignition temperature V gasoline around 450. of course chemical reactions can change things and i still have lots of gasoline in the chamber to start the burn process...

i am thinking i may consider going to a 50/50 meth distilled water mix and see where that leads. w a few of the turbos in my stable we will be reaching for 600 and it will be interesting to see if 93 pump can hold together. i need 600 for my Texas Mile run and was planning to switch over to 100% meth for that particular event. maybe it can be done w pump and a mix. it certainly would be easier than setting up about 12,000 CC/min (Gross) w straight meth.

i did speak briefly w my 100% meth drag race 1000 rwhp+ 2 rotor guy over the weekend. our conversation was unfortunately short due to our schedules.

he indicated that Lambda generally run by his meth burning competitors is generally between .76 and .81.

that is 11.17-11.91 gas and 4.88 to 5.21 meth.

which means by weight 5 parts air and one part meth.

while gasoline is 11.5 parts air and one part gasoline

2.3 times (weight) meth to gas.

you need a 2.02 ratio to get equal BTUs so they are running another 14% richer.

the only conclusion fits exactly in line w Liborek. they run that ratio because they have to.

very interesting.

hc

rxspeed7

iTrader: (5)

That's exactly like our drag or any all meth car. You have to run twice as much fuel as you would with pump but the advantages are still worth it to run it. Albeit it takes twice as much. Lol. I really wish I could tell you what Afr we run on it but the car is tuned solely off egt and sound(carlosmis super old school) but I will admit, it works flawlessly and has worked for many years for him. Even his NHRA sport compact car he won the championship with was set up exactly as this car and tuned the same way with a mechanical injection setup.

j9fd3s

iTrader: (3)

just a thought, but is the gas tank big enough to do the texas mile with that kind of fuel flow?

12,000cc/min = 3.17 gallons/min. tank is 18 gallons/3.17 = 5.67minutes of run time full out. @150mph (150/60=2.5 miles/min 2.5miles a minute X 5.67 minutes) that is 14 miles, should be enough.

14 miles ought to be less than one mile even in texas!

rxspeed7

iTrader: (5)

Our drag car has a 5gal cell on it. That is enough fuel for the burnout,staging,the run, and sometimes the trip back to the pits.

arghx

iTrader: (3)

Howard,

I have had friends run denatured alcohol from the hardware store with some success, although not at the power levels you are talking about. I'm pretty sure that's just grain ethanol + something to make it unfit for human consumption.

I wish I had some data directly comparing methanol vs ethanol in terms of preignition tendencies (as a result of these chemical reactions). The sense I get is that whatever seems to make methanol preignite more than gasoline (on paper at least) is still present in ethanol, but to a significant degree less. So the autoignition temperatures and whatever is happening on the chemical level could be two separate but related things.

Theoretically then, in my mind it goes like this

1. premium gasoline --> lowest octane, least cooling effect, least tendency to preignite (?!)

2. ethanol --> higher octane, greater cooling effect than gasoline, higher autoignition temperature than gasoline, higher tendency to preignite (?!)

3. methanol --> highest octane, greatest cooling effect, highest autoignition temperature, highest tendency to preignite (?!)


Now to murky the waters further, I recently read a Bosch study where they converted a Pontiac Solstice turbo engine (GM LNF motor, 2.0 direct injected) to E85.



E85-->autoignition temperature is much higher than gasoline, but surface ignition temperature is lower ?? What the heck does that mean?

"Fueling levels change as stoichiometric ratio changes as
a function of the alcohol concentration. Spark timing
requirement changes due to the difference in flame
speed with alcohol concentration. There are additional
issues to consider with spark timing. With E85 there is a
much greater propensity for pre-ignition to occur due to
the lower surface ignition temperature. In some cases
spark advance has to be limited even though the spark
advance is not limited by knock. Spark plug fouling
during cold start is also an issue on E85 often requiring
compromise between spark plug heat range selection for
cold start and that required to avoid pre-ignition. "

Call me confused, or at least a little unsure. I suppose trying to glean a lot of information out of journals and lab tests can be just as confusing and contradictory as talking to race teams or people on the internet. I doubt there is much work being done about methanol, considering all the infrastructure is built around ethanol today.

For reference here are specs on the fuel Honda used in their study of the naturally aspirated M85 engine I was talking about earlier. It's not presented in the same way as the chart above.



I'm not positive on how all the effects relate to each other, but it still seems to me that ethanol/denatured alcohol could potentially be a better fuel than methanol for resisting all the various forms of knock.

madbouncy

So by being worried about pre-ignition but not worried about knock then that should just mean that, like it said, you have more to worry about before TDC than after. Essentially the residual heat left over in all your metals is your biggest concern since after the kernel is formed and the pressure and temperature start to rise, ethanol is able to handle it due to having a higher auto-ignition temperature for the fuel itself. Do you think this is mostly due to the evaprative nature of alcohols since they are far more likely to turn to vapor near a hot surface than gasoline? Would go along with what has been said by others about cooling the intake manifold itself more than the actual air since the alcohol is having the greatest heat rise by pulling heat from the engine itself before combustion ever starts.

arghx

iTrader: (3)

^ there may be different perspectives on this, but I think we're reaching the limits of my chemistry knowledge and the limits of what I've been able to find so far in the literature. It would be nice if we had better resources to study how all these fuels work inside a rotary engine specifically. You really need an engine dyno for that, or even better an optical engine. Just having combustion analysis equipment on an engine dyno would help us understand combustion chamber pressure, heat release, combustion phasing, etc so much better. Then we could get a better idea of spark timing and fuel under controlled conditions.

What happens if we crank up the intake temps? Does methanol and ethanol give us more marginal safety then? Are either of them more sensitive to some other factor of preignition, like carbon deposits inside the engine? How about premix or lubrication in general? Are there interactions between that and whatever else you are injecting? There's been some studies of carbon deposits and oil mists in piston engines regarding how they affect preignition tendencies.

Clearly cooling is good for our purposes. But there's something else at work on a chemical level regarding the preignition tendencies mentioned here that I think perhaps only a few researchers would understand fully as it applies to an actual engine. And making the leap from this mostly academic and theoretical discussion to a practical setup meant to achieve real world goals is tricky.

It kind of makes you want to go with 100% water (except in winter maybe) not necessarily because it's "better" but just because it's less complicated in a way.

rxspeed7

iTrader: (5)

That's why the majority of people who have tested with diff injectants through the ages have either went with straight water or 50/50 by mass. its been proven for years to make the most power while detterring preignition.
http://www.aquamist.co.uk/vbulletin/index.php

endless amounts of info you are looking for can be found there.

Liborek

When you do some simple math with ideal gas law and apply common sense, you will see that theoretically every engine, even naturally aspirated, should preignite to death just from final temperature after compression stroke, at least on gasoline. We know it doesn't happen. When you combine this fact with one of the charts above, which indicates that higher engine speed pushes surface preignition temperature higher, its obvious that this destructive phenomena takes certain amount of time to occur. So far it seems that autoignition temperature is meaningless parameter for internal combustion engines - IMO.

Surface ignition temperature is different story. Its obvious that alcohol fuels due to certain chemical reactions are very sensitive in this regard but as above, rich mixtures and higher engine speeds are somewhat helpful in this regard.

Forget about engine parts, actual cycle happens so fast, that it can be considered as adiabatic. My point was, that measuring temperature in intake manifold is meaningless when we doesn't know what happens inside the engine and also the fact, that condensed fuel doesn't burn, it just washes away oil film and contributes to irregularities of combustion.

You don't wanna cool engine parts, but whole charge itself as one of the main determining factors if the engine will or won't knock is charge temperature after compression - obviously lower initial T means lower final T.
Charge is composed from air, fuel and residual exhaust gas. Residual amount is very small but very hot and contains partialy burned HC which is very prone to detonation. What you can do with charge coolant (water, ethanol, methanol) is to cool whole charge to bring whole bulk temperature as low as possible.
In one study of direct injection of E85/Methanol, they go so far, that injection pattern is designed to inject towards residual gasses. Proof of concept is that they used less charge coolant for same permissible power. Minimizing residual gas content and temperature is very vital for power and reliability.

arghx

iTrader: (3)

If 50/50 water/methanol has been known to work, does 50/50 water-ethanol actually work better in a test lab and in the real world? I know people who do that instead of methanol, as I mentioned before. They use denatured alcohol from the hardware store + distilled water.

bumpstart

methyl, ethyl and propyl alcohol
1, 2 and 3 carbon chains
,, denatured stuff from the chemist over here is iso-propanol

things to note that are going undiscussed but factor in the equation -

A-not all fuels have the same explosive range
hydrogen being the widest explosive range , and petrol being fairly narrow

the implications when you mix two differing fuels ( alcohol and hydrocarbon ) are at the moment largely unknown in the mainstream
they may be benificial in raising the preigintion point
,, but they also quite likely may lower the potential to resist pre-ignition to the lowest denominater
they may also under go chemical or catylitic reactions that may prove to lower the preigintion threshold ,, as is hinted with methanol

B-not all fuels stratify the same
and this has implications in judging the ideal no - det and no- ping mixture if fundemental mixture stratifcation is not consistant , or changes with rpm

C- charge dilution with EGR or unburned HC fractions
and their role in the mixture in relation to detonation and preignition is often discussed but very difficult to quantify

D interactions of all of the above points


in some other topics on this forum we can see the effect of the peripheral exhaust port and its charge dilution
compared to that of the side exhaust engine
and the charts show the ideal idle mixes to achieve consisitant and steady combustion at idle rpms
its demonstrated that the rx8 can do so at much closer to stoich due to less internal EGR

now,, i have the opposite ,, an engine with peripheral exhaust and slightly more than stock overlaps,, and late close ( 6p ) inlet timing
ie,, reasonable amounts of internal EGR ,, and some reversion and compression heating back into the inlet manifold from the late close inlet timing

( from the chart ) you would expect that i need to keep my idle mixes reasonably rich to keep idle stable
i idle at lambda 1 ,, 15.5:1 to be exact,, and the fuel is hydrocarbon LPG
the factor that makes all the changes here is purely the inherently good stratifcation of this particular fuel






also -
i think what people are missing when they see auto ignition point
is the explosive range of the air fuel mix under pressure and in proximity to the ( auto ) ignition source

IE
they are not seeing that the auto ignition number is for an ideal air fuel ratio at standard pressure
,, and this is not what is happening under compression and stratification
( which is possibly why we see a "surface ignition temp" number to reflect this a little better )

bumpstart

back in the 40's when the real work was done on this stuff they initially added the alcohol for antifreeze due to the altitudes they had to run
the germans had MW30 and MW50 and even EW30 and EW50
and never twigged that they didnt get duration in the inlet tract to cool like carbed systems the allies used
( the pre turbo V cylinder direct argument !! )

both of these fuels ( methyl and ethyl ) are below the LEL ( lower explosive limit ) when at 50 -50 mixes

-but may not be when above that concentration-

both germans and allies realised at some point that higher than 50 % meth / eth ratio had negative effect on detonation limits
the allies also found out that the ideal ratio for propyl was much lower,, below that required to have its necessary antifreeze property

case in point -
in 45 the US inadvertantly used propyl alochol at the normal ( meth ) 50-50 mix
( to prevent freezing at altitude )
and found the detonation threshold was significantly lowered for the worse, costing a spate of engines

- they had crossed over the LEL threshold and the propyl alcohol was preigniting before the ( very high octane , PN -130 ) fuel

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

BDC

That someone was probably me. I'm beginning to wonder if there's something unsuitable about it as during my hot-air experiment, over the course of about 2 years, I've cracked three plates. So some sort of knock happened although, according to the numbers, everything looked just fine. The setup was injecting about ~1600cc/min in at top load point. Highest boost achieved through a full 4th gear run up just past 120mph was 27psi. AFR's parked in the low 10's:1 with base fuel (93 octane pump) consisting of about 65% of total fuel delivery. The ambient temps out that day were in the high 70*F's if I recall correctly and from memory the highest air temp I datalogged was 127*F at the inlet just in front of the throttle body. I never could pinpoint exactly what's done it but something odd did. I've changed plugs, run leaner and richer, and seemingly no change. It would run terrific for days on end, beating the crap out of the car, then wham out of nowhere, a lower boost run and a broken plate; no misfire, no hint of anything else.

I can say however with a measure of confidence that I think using 100% methyl alcohol as a charge cooler does work and work very well. I've seen it on a number of vehicles including my own which has no intercooler. But past that, I wonder if it's not enough.

^^^ That's what I wonder too. Is there something going on in the chamber that's "outside" of all of the numbers that some of us (myself included) have assumed are what determine it to be of "acceptable" use as an auxiliary injectant?

B

BDC

Was talking to Howard about this last night. On the next go-round of my hot-air experiment, assuming I change the EFI system (my E6K ECU is finally going bad; temperature and MAP Sensor readings are going askew when engine is at rest), I'm considering trying a 50/50 water to methyl alcohol and even perhaps a 50/50 water to ethyl alcohol and see what happens. Probably will not change the total output volume of 1200-1600cc/min at higher loads. I'm curious to see what the introduction of water does in the current spots on the hot-air pipe (one M10 nozzle about 8" post turbo discharge and the other M10 nozzle about 10" past that) with respect to air temps. Also considering adding an additional nozzle pre-turbo or just moving the whole setup over there.

B

Turbo II Rotor

iTrader: (2)

Have you considered purchasing Rice Racing's kit? He seems to know his **** on this topic.

rxspeed7

iTrader: (5)

^1

BDC

If I did it'd be in the future somewhere after I exhaust using the Alkycontrol setup. It's not mega-ultra precise like Howard's setup with the precision injector control but it seems to work. I'm not against changing the setup, though. Regardless of all the Internet forum bickering and arguments, I'm a pragmatist when it comes to car stuff and tend towards simply whatever works. If his works best, so be it!

Back to the methyl alcohol chemical reaction thing - Does anybody else have any other info on this?

B

arghx

iTrader: (3)

^ shoot me a PM and I'll send you some literature. You can use it to form your own opinion.

Rx7Turbologic

I'm with him. Whatever works best and givem me the result that I want that works for me.