Methanol mix A/F ratio code CRACKED!
I thought I read somewhere that meth injection only increases octane by 10%, I forget where. I could be wrong. But the goal you have is to really validate there is a meth injection level/formula that is as safe, reliable and attainable as using straight C16.
I was told by a few people using the SMC kit including Steve that with the 93 and the meth, effective octane is around 104. But of course it depends on a lot of things.
I always thought meth had an octane rating of 120.
I always thought meth had an octane rating of 120.
On The Tree
Joined: Jul 2002
Posts: 109
Likes: 0
From: Edmonton, Alberta
The way I understand methanol and nitro-methane to be such effictive horsepower adders is that there is such a large amount of fuel entering the cylinders, the fuel absorbs excess heat from the cylinder, keeping you out of detonation. The methanol may only have an octane rating of 100 (it's resistance to detonate) but because you need a relatively large amount of it, it cools the cylinder and is equivalent to a higher octane gasoline in that respect. Methanol has a smaller BTU than gasoline, and Nitro-methane even a smaller BTU. The larger amounts of fuel required keep the cylinders cool so that you can run more boost, and therefore more fuel, and more boost, and so on... Until you end up with a 5000 horspower engine running nitro-methane... something like that...
Nitro is a great power producer because it brings liquid oxygen with it. You can only flow so much ox through an intake at reasonable pressures and then you're choked. Bringing ox with the fuel greatly adds power over that choke point.
TECH Enthusiast
Joined: Aug 2003
Posts: 596
Likes: 0
From: Downers Grove,IL
sjh, i have been reading all afternoon.. i see your point about just shooting for say a .8 rich lambda for either fuel and that 5.0 afr of methanol will show up as 11.5 afr of gasoline (on a gasoline scale)
that would mean all my work was a waste of time.
what i cannot figure is how the best running/longest lasting alky/pump gas cars that i know of have air fuel ratios that dip into the low 10's.. (i thought my calculation was right based on that sotp measurement and comparison)
by the lambda rule the should be able to safely run the same afr with methanol as without it. and that just seems too easy for all the hard time and no answers i've seen on the net and on this board in the past..and then you just throw in a 1-liner here
after i spent all last night trying to find it my own way
that would mean all my work was a waste of time.
what i cannot figure is how the best running/longest lasting alky/pump gas cars that i know of have air fuel ratios that dip into the low 10's.. (i thought my calculation was right based on that sotp measurement and comparison)
by the lambda rule the should be able to safely run the same afr with methanol as without it. and that just seems too easy for all the hard time and no answers i've seen on the net and on this board in the past..and then you just throw in a 1-liner here
after i spent all last night trying to find it my own way
Most guys run the motors very rich into the low 10-1 A-F range with the alky kits and I did the same when I ran alcohol.And many don't even have a clue as to what the a-f ratio is because they don't have a in car wideband. This is one big reason the relatively small amounts of alcohol used in the kits help stop detonation. If you dial back the gasoline to get A-F ratios of 11.5 or so, you'll find the alky kits are not as effective at stopping detonation with pump gas.
I used to run no leaner than a 10.8-1 A-F with 15-20 gph alcohol flow rates and pump gas with 10-12psi boost. I make much less power than you do so the alky % to pump gas is even lower for you. But I was non intercooled back then also.I would think with a good intercooler 11.5-1 alky/pump gas combos would work well but always good idea to start our rich.
Here's some good info on race fuels, Methanol and even Nitromethane.
http://www.turbofast.com.au/racefuel.html
Steve
On The Tree
Joined: Jul 2002
Posts: 109
Likes: 0
From: Edmonton, Alberta
Originally Posted by onfire
Nitro is a great power producer because it brings liquid oxygen with it. You can only flow so much ox through an intake at reasonable pressures and then you're choked. Bringing ox with the fuel greatly adds power over that choke point.
From http://www.jagweb.com/aj6eng/superchargers.html
Still more extreme is Nitromethane. Most people know that "nitro" is some sort of "super-fuel" but not so many know why, so perhaps a brief explanation is called for. It is an oxygen bearing compound with an energy content (specific energy) 2.3 times that of gasoline. Not only that but its stoichiometric A/F ratio is 1.7:1. What this means is that a charge of nitromethane mixed with air in the perfect ratio contains about 20 times as much energy as a comparable gasoline charge. Best power is at richer A/F ratios than stoichiometric, as with gasoline and methanol, so a nitro burning dragster engine might run at an A/F ratio of around 1:1. Detonation resistance is not particularly good but is offset by the extremely rich A/F ratios.
Nitromethane can even be used as what scientists call a "monopropellant" - which means it will combust without need of any air at all but for practical reasons it is usually blended with about 10% methanol for use at a unity A/F ratio as stated. A useful side effect of introducing liquid fuel in these vast quantities is the cooling effect on the engine internally through evaporation - but just one misfire can mean a hydraulic lock and a wrecked engine in an instant.
Thread Starter
Joined: Nov 2001
Posts: 10,018
Likes: 51
From: Virginia
ok guys.. i just read that while all of my calcs were made for .6bsfc
if i was running 100% alcohol the new bsfc would be 1.2
this would make a big difference.. is this the missing link between why we think the a/f needs to be fatter but (by lambda) it should be ok to stay the same?
if i was running 100% alcohol the new bsfc would be 1.2
this would make a big difference.. is this the missing link between why we think the a/f needs to be fatter but (by lambda) it should be ok to stay the same?
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dang it, need to figure this out soon cause I want to start "playing" soon...
Im kinda confused on where we understand things are now... Is the AFR not gonna change with MEOH injection?
Im kinda confused on where we understand things are now... Is the AFR not gonna change with MEOH injection?
TECH Fanatic
Joined: Nov 2001
Posts: 1,986
Likes: 1
From: Centrifugal City
Ripped from C5 Forum.
Twin Turbo, No I/C, Straight Methanol, 44psi, 10:1, 2900HP.
http://www.highperformancepontiac.co...410pon_butler/
Twin Turbo, No I/C, Straight Methanol, 44psi, 10:1, 2900HP.
http://www.highperformancepontiac.co...410pon_butler/
Thread Starter
Joined: Nov 2001
Posts: 10,018
Likes: 51
From: Virginia
have seen that, good reading. i think if you are running 100% of either fuel like was said above just keep the lambda under 1.. like .8 so if you are using a gasoline meter make the a/f 11.5ish and if you're using an alcohol scaled meter keep it 5.xish.
that is because the bsfc for each is different, when you mix them i 'think' you need to make an adjustment to the target. havent spent any time on it yet.. it will probably come out the same as my first calculator.
that is because the bsfc for each is different, when you mix them i 'think' you need to make an adjustment to the target. havent spent any time on it yet.. it will probably come out the same as my first calculator.
Teching In
Joined: Feb 2004
Posts: 19
Likes: 0
Just to add a little to what others have said. Octane rating is calculated by increasing or decreasing the compression ratio of a test engine and detecting the knock point. The air temp is constant on the test bench.
In a turbo application where the boost goes up to get more power the intale temp increases. A fuel that cools the charge and stops detonation, while having a similar octane rating on the test bench performs much better on the track.
In a turbo application where the boost goes up to get more power the intale temp increases. A fuel that cools the charge and stops detonation, while having a similar octane rating on the test bench performs much better on the track.
Originally Posted by MIGHTYMOUSE
ok, putting my assumptions up front.
methanol burns appropriately for FI at 5.5:1 (most scientifically backed figure found on google)
gasoline burns appropriately for FI at 11.5:1 (from experience on here)
the weight of gasoline is 6.25 lb/gal (most scientifically backed figure found on google)
my bsfc is .6 (from Kurt Urban)
my (future) flywheel horsepower will be 1200
I have calculated earlier that I move 22.2 gal/hr methanol
(375 ml/min nozzle + 625 ml/min nozzle at 220 psi pressure) (from Matt Snow)
the rest is math. here we go.. this took 6 post-it-notes to get right.
Total Fuel Flow = hp * bsfc = 1200 * .6 = 720 lb/hr
720 lb/hr * 6.25 #/gal = 115.2 gal/hr
11.5 parts air to 1 part gasoline = 12.5 parts total
total flow through the engine (air + fuel) = 12.5 * 115.2 gal/hr = 1440 gal/hr
% of total flow that is gasoline = 1 / 12.5 = .08 = 8%
now here is the addition of methanol to the flow
1440 gal/hr + 22.2 gal/hr = 1462.2 gal/hr (total flow of air + gas + methanol)
% of total flow that is methanol = 22.2 / 1462.2 = .01518 = 1.518%
the ratio of methanol % flow to fuel % flow = 1.518 / 8 = .18975
this .18975 is the methanol part of the 1 fuel part (in the X:1) a/f ratio
the gasoline part is what is left over (1 - .18975) = .81025
the new combined air/fuel rato is...
gasoline factor + methanol factor = new appropriate mixture a/f ratio
(11.5 * .81025) + (5.5 * .18975) = 10.3615
you can also calculate your new octane rating with the same factors
(93 * .81025) + (126 * .18975) = 99.26 (a close guess on the meth octane)
whew!
*remember you have to calculate your OWN methanol flow and use your own flywheel horsepower..
*this is only my effort at the calculation, I certainly cannot gauantee it is 100% correct.
questions / comments please!
methanol burns appropriately for FI at 5.5:1 (most scientifically backed figure found on google)
gasoline burns appropriately for FI at 11.5:1 (from experience on here)
the weight of gasoline is 6.25 lb/gal (most scientifically backed figure found on google)
my bsfc is .6 (from Kurt Urban)
my (future) flywheel horsepower will be 1200
I have calculated earlier that I move 22.2 gal/hr methanol
(375 ml/min nozzle + 625 ml/min nozzle at 220 psi pressure) (from Matt Snow)
the rest is math. here we go.. this took 6 post-it-notes to get right.
Total Fuel Flow = hp * bsfc = 1200 * .6 = 720 lb/hr
720 lb/hr * 6.25 #/gal = 115.2 gal/hr
11.5 parts air to 1 part gasoline = 12.5 parts total
total flow through the engine (air + fuel) = 12.5 * 115.2 gal/hr = 1440 gal/hr
% of total flow that is gasoline = 1 / 12.5 = .08 = 8%
now here is the addition of methanol to the flow
1440 gal/hr + 22.2 gal/hr = 1462.2 gal/hr (total flow of air + gas + methanol)
% of total flow that is methanol = 22.2 / 1462.2 = .01518 = 1.518%
the ratio of methanol % flow to fuel % flow = 1.518 / 8 = .18975
this .18975 is the methanol part of the 1 fuel part (in the X:1) a/f ratio
the gasoline part is what is left over (1 - .18975) = .81025
the new combined air/fuel rato is...
gasoline factor + methanol factor = new appropriate mixture a/f ratio
(11.5 * .81025) + (5.5 * .18975) = 10.3615
you can also calculate your new octane rating with the same factors
(93 * .81025) + (126 * .18975) = 99.26 (a close guess on the meth octane)
whew!
*remember you have to calculate your OWN methanol flow and use your own flywheel horsepower..
*this is only my effort at the calculation, I certainly cannot gauantee it is 100% correct.
questions / comments please!
MAN what a super old, but super informative thread. I don't care...I'm posting anyways(unless I'm breaking a rule). I find it relative today and others may as well. Awesome formula OP. I entered my data, keeping 0.6 as my bsfc, using 700 as my flywheel hp, and using 10, 11, & 12 as my methanol gph(gph numbers per DevilsOwn website calculator).
For 10 gph my final combined afr is 10.6
For 11 gph it is 10.5
For 12 gph it is 10.4
Even if your formula is flawed, I'd think a mid 10 afr would be a pretty reasonable expectation.
But should you leave it at 10.5? Or do you tune it back to 11.5? Haha that's a question for a whole other thread.
For 10 gph my final combined afr is 10.6
For 11 gph it is 10.5
For 12 gph it is 10.4
Even if your formula is flawed, I'd think a mid 10 afr would be a pretty reasonable expectation.
But should you leave it at 10.5? Or do you tune it back to 11.5? Haha that's a question for a whole other thread.
Thread Starter
Joined: Nov 2001
Posts: 10,018
Likes: 51
From: Virginia
back from the dead wowow.
once i started using this a/f adjustment 'idea' (wrong or right) I went from melting pistons to... NOT! lol Haven't melted one since... won a bunch of races, and kept the thing running
very happy me.
interesting enough my best pass on my t/a on pump/race gas mix and methanol (same nozzles in my post calculations) and my targeted hp achieved (1200 crank) last pass ever under my ownership was a 8.49 at 162 364ci, 26# boost at 3775# weight and drove it home. (10.3 A/F)
sorry that my spreadsheet links are dead, ill see if i have them at home.
once i started using this a/f adjustment 'idea' (wrong or right) I went from melting pistons to... NOT! lol Haven't melted one since... won a bunch of races, and kept the thing running
very happy me.interesting enough my best pass on my t/a on pump/race gas mix and methanol (same nozzles in my post calculations) and my targeted hp achieved (1200 crank) last pass ever under my ownership was a 8.49 at 162 364ci, 26# boost at 3775# weight and drove it home. (10.3 A/F)
sorry that my spreadsheet links are dead, ill see if i have them at home.
Thread Starter
Joined: Nov 2001
Posts: 10,018
Likes: 51
From: Virginia
I found it and re-uploaded it to google to share again for what its worth.
Link to Calculator Spreadsheet
Link to Calculator Spreadsheet