[BlackSS/SC]

I have a modded Cobalt SS Supercharged that I'm installing my water injection kit in. I'm going to be running 50/50 meth/water mixture. Right now my a/f ratio is running about 11.5 on my wideband. I'm just wondering if I need to take away fuel when adding the meth kit, and whats the ideal a/f ratiO TO RUN WITH METH?

[pacemkr86]

10.5 with alcohol seems to work well

[pacemkr86]

i beleive 8.1 ratio is perfect when running alcohol only

[kompressor85]

if i'm not mistaken, 14.7:1 is gasoline, 10.5:1 is alcohol, and 6:1 is nitromethane.

but its been years since i've thought up those ratios, double check it.

but the fact that you're running "rich" (for a gasoline engine, anyways) may be good since the way alcohol burns... you need lots of quantity of fuel to cool down the burn so that it doesnt run lean, as it easily does.
my personal opinion:
i beleive in this case, since your engine is supplemented with alcohol/water/whatever, and primarily gasoline powered, it is best to stick with the 14.7:1 fuel ratio. i'm certainly no expert in the ways of alcohol boosting like some of the guys around here most assuredly are, my opinion simply stems from reasoning.

[BlackSS/SC]

I'm talking wide open throttle, not during other driving. My afr is at 11.5 at WOT now. I was just wondering if I should be taking away fuel and adding the meth mix or if I keep the fuel the same. And what would my ideal WOT afr be?

[pacemkr86]

your non alcohol tune should remain the same.. 11.5 is a good a/f ratio without alcohol.

do not remove fuel when adding alcohol

10.5-10.8 a/f with alcohol is a PROVEN combo and it works well

[pacemkr86]

Originally Posted by kompressor85

if i'm not mistaken, 14.7:1 is gasoline, 10.5:1 is alcohol, and 6:1 is nitromethane.

but its been years since i've thought up those ratios, double check it.

but the fact that you're running "rich" (for a gasoline engine, anyways) may be good since the way alcohol burns... you need lots of quantity of fuel to cool down the burn so that it doesnt run lean, as it easily does.
my personal opinion:
i beleive in this case, since your engine is supplemented with alcohol/water/whatever, and primarily gasoline powered, it is best to stick with the 14.7:1 fuel ratio. i'm certainly no expert in the ways of alcohol boosting like some of the guys around here most assuredly are, my opinion simply stems from reasoning.

Alcohol for Motor Fuels
K&N Air/Fuel Ratio Monitors

stioch for alcohol/meth is 6.5

14.7 wot air fuel ratio with meth WILL BE TOOO LEAN

[BlackSS/SC]

Cool, thanks for the help! So I'm running 60/40 Meth to water ratio. Does it make anydifference in the afr I should run?

[pacemkr86]

are you gettin any knock retard?
there isnt a set a/f ratio when tunning for alcohol, it all depends on your combo and what you car wants.

Do you have access to a dyno ?

i normally set my base tune without alcohol for around 11.5- 11.8

then turn the alcohol on and keep cranking it up till the power falls off, then i back it off.

the more boost and timming you run the more alcohol/meth you need

[BlackSS/SC]

Bringing this post back from the dead again. The car is put away for the winter now but I can still get some new info.

I run the M7 nozzle (I think, I know it's the middle one that comes in the kit). So when I run the car without meth, I run 11.5-11.8 afr at 16.5psi and 16 degrees of timing.

With meth added it brings my afr down to the low 10s so I lean my fuel out with my tuner and bring it back up to 11.5 - 11.8 on meth. I'm able to run 23-25 degrees of timing WOT on meth. (50/50)

Does this seem right? Any richer and it seems sluggish. Never went any leaner.