akunochi

iTrader: (7)

Hey guys I was wondering if anyone had some insight into tuning for water/meth. I am tuning several cars here in Japan and there are a couple guys coming with water/meth systems that I have previously tuned. Their AFR is pretty solid across the map since I have previously tuned them, but I don't know what I am targeting when I start adding additional fuel in the form of meth. I know meth has a different stoich afr than gasoline and have seen some notes about tuning to the same AFR when Meth is being injected as I would for a system without meth.

I just wanted to get some insight in how you guys have gone about tuning etc since there is more experience here.

Thanks ahead of time.

Seth

Sgtblue

iTrader: (16)

Not a big brain here, but personally my car isn't tuned with AI/WI. It's there as a safety...to lower IATs a little, and control knock and carbon. Seems like if you tune with it, the system would have to be progressive and probably with multiple nozzles and have a large reservoir. And it would have to be rock solid reliable. Mine is only the latter.

Howard Coleman

iTrader: (6)

i generally agree w Post 2.

most people use water/water-meth/meth to cool intake air temps and quell detonation.

you haven't given much info on the power levels of the cars on which you will be working...

let's assume 500 rwhp rotary. you can then modify to your specific level.

500 rotary is 960 CFM and 66 pounds per minute of air.

let's assume a 10.0 AFR so that would be 6.6 pounds of fuel per minute.

that would be 1.04 US gallons per minute.

or... 3937 CC Per minute.

1.04 X 116,090 (BTUs in a gallon of gas) = 120,733 BTUs to make 500 rotary rwhp

normally you are injecting 630 CC per minute w a M10 nozzle or
945 w a M15 nozzle.

if it is 100% meth...

630/3785 (CC in a gallon) = 16.6%

meth has 49% of the BTUs of gas...

16.6% X 49% = 8.1%

if you on straight meth you are adding 8% to your fuel using a M10/630 CC nozzle.

if you do water meth...

water has negative BTUs and will obviate the need to change the tune as it offsets the meth positive BTUs.

generally if you just run water somewhere between 400 CC and 600 CC works in most cases.

keep an eye on misfires w water. set the dyno on zero smoothing and look for jagged plotting around peak torque and beyond... maybe tighten the spark plug gap if necessary... .023.

Howard

akunochi

iTrader: (7)

Both,

Thank you for the replies.

Howard,

As always your reply was very thorough. Like they say tuning is math not magic.

briansfd

iTrader: (4)

@Howard Coleman CPR Do you know of any test data that shows the difference in IAT/Knock/Ect. vs Methanol content (straight water/washer fluid/boost juice) for our cars?