I wish i could answer that question for you.

If i were in your shoes i would see how much power difference there is in leaning the car out(on a dyno). I would not risk running lean for 20hp, but this is jmho

 

I would not risk lean for any given HP level. It makes whatever it makes, as long as its safe and efficient. Given that variable, I think mid 10's on the AFR side of things is WAY overkill on the safe side. You can be too rich and have other issues also (not that mid 10's are that bad). Again, ideally I am aiming for 11.0 (hoping that the meth isn't skewing the wideband more than .5-1).

 

Meth/water and pump gas with 10% ethanol will all have a different stoich and you can adjust the wide band table to that stoich if you can do the math, then tune to some number based on that fuel mixture which makes good power, or you can just leave it alone and tune to the gasoline stoich conversion table which a lot of people in the states do, it really doesn't matter. Just look at Lambda and whatever that gets converted to based on the stoich number for the given fuel is just a number. People get all hung up on that because they dont understand it. Only the dyno or track testing with careful data logging will really tell you where you are making lots of power and what number on your wideband you need to tune to, whatever table you are using. Most people are afraid to use meth injection correctly by leaning out the fuel and bringing back the timing, and they lose power over not injecting it at all because they are running too rich. Sure, it's safe, other than washing your cylinders down while it is activated. Hell, my engine went 14:1 on a run and still went 126 mph before by accident of the fuel system not keeping up, but it didn't fry the pistons because the effect of the meth/water injection keeping everything cool. I hope to not have that ever happen again, but it will hold together if it does unless the spray doesn't activate. Meth injection is great, but it doesn't do much good to inject it on top of an already rich fuel mixture and retarded timing. If you tune rich and safe so that in case the spray doesn't activate and you stay out of trouble, that is understandable, but it's better to use a flow meter as a failsafe to drop the timing back if that happens. In the meantime, make more power. Just my ho.

 

I have ran well over 100 gallons of methanol over the years on my GN. BTW, you will have alot more success with straight over water/meth. Where brian has your tune is perfect, you need to keep in mind the different stoich ratios for the different fuels and the % of meth you are spraying. I used to spray around 35-45% of my fueling as methanol. As it is added the AFRs are going to go down, thats just the way it is. Its trying to get down to 7:1 and you need to calculate the AFR you should be seeing based on the % of fuel you are using. once i maxxed out my 36lb injectors at around 360whp, i started adding more and more meth and timing. I ended up pretty much maxxing out dual m10 nozzles at 150psi of head pressure.
I also found that i made the most power on gasoline around 11.8, and by adding to keep knock away i was around 10.2-10.4, and went from 17psi/16* timing at 360whp/410tq to 30-32psi and 26* with no other changes other than spraying meth, to the tune of 460whp/540wtq

So i would leave it as is, obviously your straight fuel tune is right where you want it, so adding the methanol would richen it. You can take advantage of this by adding even more timing though.
Gary

 

Why do you use AFR ? If ju talk/think Lambda you dont have to worrie aboute different Stoich numbers for every fuel mix.
We have used lambda 0.80 as target widh E85 and water/meth injection and also works for pump gas.

 

Sorry you misunderstood me. The worst case scenario for a kit corrossion wise is straight methanol, the least is straight water. Tuning worst is water, easiest is methanol. Water, water alcohol, alcohol all work. It just depends on goals and ability to tune. And then what keeps the most stable tuneup.

If you get aggressive with water, you get will get a loss of power, have popping/sputtering, and run the chance of breaking pistons(hydro). The water mix is the next best.. its better than water, but on low boost applications there typically isnt a lot of heat available and that cuases a lot of distribution issues. This leads to tuning issues. Then you get into alcohol.. its easier to tune becuase as its not as temperature dependant as water. Meaning alcohol flashes at 70 degree's. Water is 180 degree's. Meaning if you dont have enough temp, it doesnt flash and distribute.

With the cost of dyno time at most shops, most want to be on/off the rollers as soon as possible $$$. If you get into tuning issues on the rollers.. its going to cost you $$$. That is why the majority of shops I deal with use straight methanol(alcohol) as a few pulls.. the motor is dialed in.. away you go.

Air fuel wise, the majority of shops I speak to/deal with use the 11.5:1 AFR as the rule of thumb number on forced induction using pump gas. When you inject straight methanol as the volume of it increases you decrease the target(ie 11.5:1). Rule of thumb on a single nozzle system is .5 decrease in AFR target. The twin nozzle systems will be a point lower.. and on some apps.. even more.

http://www.campbellautomotive.com/1000hpv6.wmv

This was done on 91 octane, straight methanol injection, at 10.0:1 air fuel.

Use Lambda if you wish. Its all about keeping the engine together.. and stopping the knock

Hope this helps

 

I have a little disagreement with the concept of tuning to a predetermined AF ratio. It's good to know what generally works to get you in the ballpark. But a particular combo may want to be a full ratio richer or leaner. My own approach is to start around 10.5:1, as I have never seen one want more fuel than that and lean it out until the power drops, then go back to max power.

Depending on the conditions of the test, it may sometimes be best for it to go out a bit too rich. The most common scenario for this is poor air on the day of the tune. If you can assume it's usually going to be leaner (based on better air) you may want to make it a little rich so it is closer to optimal under typical driving conditions. Also, if the owner is kind of person who doesn't have much "engine sense" and is likely to abuse the crap out if it, put in bad gas, etc. making it a bit too rich may be a safety margin.

In an ideal world, you would also have time and money to experiment with different proportions of water/methanol. But I think 50/50 is the best compromise. Interesting points about tuning issues with different mixtures.

Rich

 

You'll have to excuse my lack of knowledge on Lambda. I have a Lambda readout on my digital wideband display, but honestly never understood what Lambda was/is.

You are saying that .80 Lambda is ideal. I am assuming this is at WOT with meth? And if so, is it just a different way of reading rich to lean? How do you adjust the car so the Lambda is idea?

 

BTW, thanks Julio for the specific info on meth and AFR, and thanks Rich for your input as well. I agree this is interesting on the different tuning points with different mixtures of meth.

 

Hope this helps, but, this was my experience...

I installed a Snow (stage 2) kit on my app. (App... 97ss M6 383 D1 AFR heads Acceleronics driver with 72# Seimens peak/ hold Injectors.) I also run a large Spearco air-air intercooler heat exchanger, with, the 70%/ 30% Methanol/ H2o mix (4 psi on 12 psi max setting.) Since playing with this system, it works best on hot days then the IAT is high from 125 to 150+*F. On cold days (it gets cold here) the IAT does not have sufficient temp to flash the mixture to a vapor (ie... Latent heat of vaporization cools the air charge by phase change). Low (insufficient temp) IAT allows the mix to travel wet into the cylinders and results in, in-complete combustion driving the O2 to read rich (I normally run 12.8"1 AFR under WOT full load mode). So, I have a switch to disable the Meth/ H2o injection in cold weather, and, runs much stronger in cold weather since it is not necessary with colder IAT (I also run an MSD6 with 8202 coil and Zex plugs).

The second problem I had was with the fuel regulator. The typical gm (end of raill type) regulator usually has a very limited life (ie... Aeromotive - I've been thru 2 and I think they are junk). With the reg leaking @ the diaphram, it will not allow the MAP (boost pressure) to trigger the Snow controller to turn-on the pump. I machined the fuel rails and re-plumbed with a larger regulator which works much better. The Snow unit triggers ON and functons as expected.

Hope this helps. B.

 

Don't most widebands read lambda and convert it to AFR for pump gas? If this is true then why would everybody be shooting for lower indicated AFR (when running meth) when the wideband doesn't know the difference whether you are running straight meth, straight pump gas, or a mix of the two.