methanol a/f ratio's

[zross1]

For those of you running methenol what type of a/f's are you seeing or do you shoot for?

 

[andymoraitis]

Try this for reference:

http://www.smokemup.com/tech/fuels.php

Performance based site or not, you won't find too many people running straight methanol here, but a few do run straight E85.

Hope that helps,

Andy

 

[MMM]

Are you refering to meth injection? or running straight meth (gas substitue)?

 

[NitrousBob]

Tune using lambda. Most, if not all the afr guages right now only show from 10-20afr. Most of them have leds that are a graduated lambda scale above the calculated one. I have tried this a few times when Im mixing fuels and found lambda is easier to tune with personally.

afr for meth is around 6:1, afr for gasoline 14.7:1. Nice thing is lambda is 1 in both cases so <1 is rich and >1 is lean regardless of fuel type. This is a generalization, actual fuel requirements or fuels will require proper tuning of course.

 

[zross1]

Sorry, I mean methenol injection. Sorry again.

 

[tstkl]

yeah, you can't use lamda any better when your injecting meth, I think it depends on how much your injecting in relation to how much fuel your injecting, and what percent your using.

I know paul (newlogics) told me hes running 100/0 meth and he took 30% out on his afc, but I dunno how much fuel or meth hes flowing. All he could remember was that the meth nozzel was "stage 3", which means nothing to me, and he has a 60 trim (I believe) at ~27 lbs.

I'll ask him more about it tomorrow, or if he sees this and posts, I'll let him do the talking, but as far as a givin afr goes, I don't think you can really have a set afr for people injecting meth and running gasoline. Some people run 50/50 meth, some run 75/25, some run 100/0, which is a huge factor on this as well.

I think watching knock, timing, and getting the car dyno tuned is your best bet. Its like adjusting your cams, every car has a different set up, and there isn't a definit max power sweet spot you can just set them to and the car will have the peak hp its capable of.

 

[andymoraitis]

Running straight methanol injection would be similar to the A/F's you can run on race gas. 12:1 or 12.5:1 with strong timing (18-24 degrees) is more than doable depending on the setup. The more diluted the methanol solution is, the less you'll be able to get away with.

 

[scottsee]

I've been reading & searching all over the internet on a good discriptive artical on tuning with Meth/AFR.. I've kind of peiced some info together from the Dsmlink forum, I'm running 450cc @ 92% IDC and want to run 50/50 h20/meth through my m7. I'm trying to figure out how to tune my PLX to get Actual AFR without running to rich/lean.. Aside from what I've provided am I missing anything?

Stoich Values:
Gasoline = 14.7
Methanol = 6.40

Weight:
Water = 8.33lbs/gal
Methanol = 6.59lbs/gal

Specific Gravity:
Gasoline = .737
Methanol = .791

Specific Gravity Differences:
Gasoline = 1.07 more dense than methanol
methanol = .93 less dense than gasoline

Equation to get Percent Methanol to Water Injection by Mass:
(Methanol Weight per Gallon)(Volume of Methanol in Mixture) = Methanol Total Mass
(Water Weight per Gallon)(Volume of Water in Mixture) = Water Total Mass

(Methanol Total Mass)(100)
(Meth Total Mass) + (Water Total Mass) = Methanol Percent by Mass

Equation to get Actual Percent of Methanol Injected:
(Methanol Percent by Mass)(Total Percent of Water Injection Mixture) = Methanol Percent Injected

Equation to get Mixture Stoich Value:
(Meth % by Mass)(Meth S.G. Difference)(Meth Stoich) + (gas %)(gas S.G. Difference)(gas Stoich) = Mixture Stoich Value

Equation to get REAL AFR:
(Mixture Stoich Value/WBO2 reading) x 14.7 = REAL AFR


Example:
75% meth injection to 25% water by volume at 20% of fuel delivery and a WBO2 reading of 11.2:1AFR.

Percent Methanol in Water Injection Mixture by Mass:
(6.59lbs/gal)(.75) = 4.9425

(4.9425)(100)
4.9425 + 2.0825 = 70% Methanol by Mass of 20% Water/Methanol Injected

Equation to get Actual Percent of Methanol Injected:
(70%)(20%) = 14% Methanol injected to Fuel

Mixture Stoich Value: (.14)(.93)(6.4) + (.86)(1.07)(14.7) = 14.36

Real AFR: (11.2/14.36) x 14.7 = 11.47 REAL AFR

There's most definitely a method to the madness of choosing a nozzle(s) size for a meth injection kit. And no, it's not a "go big or go home" mindset. Depending upon your power level and the availability of methanol, you want to inject 30%-50% methanol in relation to your total fuel consumption (water injection is ~15%-25%).

Example:
720cc injectors running @ 90% duty cycle while under max boost.
720cc x .9 (90%) = 648cc
648cc x 4 injectors = 2592cc/min total fuel consumption
2592cc x .3 (30%) = 778cc/min total meth injected

 

[GVR4592]

I didn't read it in detail but it looks really close, if not right on. Keep in mind that with methanol, or any alcohol, you don't want to run it to lean. In most cases you should be a little richer than what you started with on pump gas. Here's a link I found that give an idea of how to do the math for calculating what your A/F should be while injecting methanol.

http://www.ls1tech.com/forums/showthread.php?t=263724&page=1&pp=20

 

[donmagicjuan]

I didn't read it in detail but it looks really close, if not right on. Keep in mind that with methanol, or any alcohol, you don't want to run it to lean. In most cases you should be a little richer than what you started with on pump gas. Here's a link I found that give an idea of how to do the math for calculating what your A/F should be while injecting methanol.

http://www.ls1tech.com/forums/showthread.php?t=263724&page=1&pp=20

I don't disagree with the first post (very well presented, scottsee), but that link has me scratching my head at the moment. In his calculation of the optimum AFR for a meth injection setup, he assumes that the ideal AFR for the gasoline portion of the mixture is 11.5:1 (for an FI engine). However, isn't this normally because the extra heat added by the compression of the air and as a result of the turbo's <100% efficiency prevents safely running leaner AFRs? I thought the ideal AFR for gasoline was 12.5-12.8:1. If the primary benefit of running meth/water injection is the cooling of the intake charge, shouldn't this value be higher in the calculation?

For my setup with a 50/50 mix, I run an indicated AFR of 11.5:1, meaning that in actuality (according the the original post), my AFR is leaner than this. I don't experience any knock when logging 4th gear pulls, but am I sitting on a ticking time bomb?

 

[scottsee]

I converted all of that into an excel program. I'm trying to figure out how to make a displayed list of shown afr's to actual afr's via % of water/meth, injection rate, psi & gas type. shouldn't take to long..

 

[RavenX]

Am using a M7 nozzle with my meth injection kit. Right now am at 75/25 meth to water. Am going up to a M10 nozzle because its not injecting enough for me to get away with the air fuels i want 11.0-and up at 25psi and up.

 

[scottsee]

Here is a rough sheet from what was posted. No cells are protected, so be carefull.. I'm pretty sure the math is correct for caculating actual AFR with % of meth injection based on the GPH/CC nozzel size..

http://www.box.net/public/ard230muhd

 

[scottsee]

Are you accounting for the correction factor in AFR's. 11:1 on a wideband DOES NOT mean you're running 11:1 when injecting meth... On my M7/600cc/8.4gph nozzle, 450'cc injectors at 90%IDC running 75/25 meth/h20 the correction factor from my PLX value of 11.1:1 (seen) are 12.4 (actual).

What is your IDC at WOT?

Just guessing here. Assuming about 44lb/min airflow through your 57trim you would be seeing around 55%IDC. That should be giving you an actual AFR of 11:8:1 if you seeing 11:1 AFR on your wideband. Tunning for 12.5:1 you will need to see 11.7:1 on your wideband. Upping the injector to an m10 will only make you have to lean out your seen AFR even more....


Edit: had to correct some math..

 

[tstkl]

this might be completely ignorant, but....

doesn't it not matter what your afr is as long as you don't knock (as far as ruining your engine goes), and if the most efficent afr is 12.5ish:1 for a FI engine, then him running at a displayed 11:1 is just about right on then. If you tune the knock out, there shouldn't really be a problem, should there?

 

[scottsee]

It matters if you are searching for that perpetual, elusive perfect tune at the track. every day driving, no, not really as long as your knock sum is below your wanted values. 11.1 is simply the fastest flame speed in the combustion chamber. Best torque is more around the 12.5-13.1 range so tuning for effency is entirely up to the individual.

Tuning for knock is obviously the most important value to be concerned with. Controlling detonation is how you keep engines together without wearing out piston rings, gaskets, burning valves exc. It's more the threshold of a tune. Honestly it's really hard to tell what is going to happen with boost/tuning manipulation or what positive or detrimental effect it will have on your performance unless your sitting on a dyno... Just one of those things ming!

 

[donmagicjuan]

11.1 is simply the fastest flame speed in the combustion chamber. Best torque is more around the 12.5-13.1 range so tuning for effency is entirely up to the individual.

How can the fastest flame speed AFR value and the maximum torque AFR value be different for a given fuel? Assuming ignition timing is continuously optimized for each AFR, doesn't a faster burning flame front produce higher peak cylinder pressures, which in turn are responsible for generating torque?

 

[scottsee]

I'm really not sure.. Good question... Just what I've read in "How to tune & modify engine mangment systems" by Jeff Hartman... Has a very good ecu tuning 101 section... I highly recomend it for a good falling asleep meteraial. Works for me every time..

 

[RavenX]

Are you accounting for the correction factor in AFR's. 11:1 on a wideband DOES NOT mean you're running 11:1 when injecting meth... On my M7/600cc/8.4gph nozzle, 450'cc injectors at 90%IDC running 75/25 meth/h20 the correction factor from my PLX value of 11.1:1 (seen) are 12.4 (actual).

What is your IDC at WOT?

Just guessing here. Assuming about 44lb/min airflow through your 57trim you would be seeing around 55%IDC. That should be giving you an actual AFR of 11:8:1 if you seeing 11:1 AFR on your wideband. Tunning for 12.5:1 you will need to see 11.7:1 on your wideband. Upping the injector to an m10 will only make you have to lean out your seen AFR even more....


Edit: had to correct some math..

Interesting thats pretty much what i see . So what do you think would it be better to just stay with a single M7 or would it be better to have say a M2 and a M5 spraying at different boost points. I used to have the dual setup but i switched over to the check valve and could only use one nozzle. Am not having as much luck with a single in terms of knock and what not than what i did with the duals.

 

[Maglin]

You have to remember that with a wide band and it's gauge is relitive to lamba. So if your gauge is setup for a 14.7:1 stoich then even when you run say meth through it .85 lamba will still be around 12.5:1 AFR displayed on the gauge. Actual AFR might be different because of gauge calibration for the fuel being used but you are still seeing .85 lamba at 12.5:1 even though in fact it might be more like 10:1 AFR.

I have a inovate WB and when I switched to E85 I didn't want to recal my gague (actually I didn't have the software handy to do it) so I just kept going off of gasoline AFR's to tune. Still had a perfect tune once I got it all dialed in. My exhaust manifold and plugs told me that when I pulled them recently. Finally got my new internals to install.

 

[99EclipseX]

How long does a 2qt bottle of methanol last if you are running it all the time?

 

[donmagicjuan]

That's a very relative and subjective question. It depends on your nozzle size and your type of control system. I have a 7gph nozzle and a 1 gallon tank, and it supplies me with enough alcohol for approximately one tank of fuel. This is with normal, "spirited" driving on the street. If you wanted to know how long it would last for continuous operation at WOT, I suppose you could just do the calculation based on your nozzle size and IDC. Just keep in mind there are far too many variables to predict this with any real precision.

 

[andymoraitis]

For my setup with a 50/50 mix, I run an indicated AFR of 11.5:1, meaning that in actuality (according the the original post), my AFR is leaner than this. I don't experience any knock when logging 4th gear pulls, but am I sitting on a ticking time bomb?

Don,

I wouldn't think so based on the fact that the motor's not knocking. While this may seem arcane, I use a limit of 2-3 counts of knock to tell me where the tuning edge is with respect to A/F and timing. Once I see that 2-3 counts, I either raise fuel pressure or octane to compensate. If you're not seeing knock, I wouldn't be overly concerned and I don't see how this would change irrespective of whether one runs methanol or not.

Someone please let me know if I'm off base here.

Andy

 

[donmagicjuan]

Thanks for the reassurance, Andy. After giving it some more thought and looking at my experimental data, I would say that I can't really subscribe to the assumptions in the calculations for ideal AFR. I'm sure the principle is applicable, but I'm still not sold on the notion that 11.5:1 is ideal for FI engines in the presence of methanol injection. Of course, I don't really have the means to experiment with various AFRs to suggest otherwise, but I think I can rest assured that I'm not risking any damage to the motor.

 

[andymoraitis]

As Scott mentioned, perhaps the best way is to get the car on a load holding dyno and see how it responds to changes. I don't know that it will establish an optimal A/F for every FI motor out there, but it would at least identify the sweet spot for yours.