Ted,

here is my particular situation. i tune the car on the meth, never tuned it on pump gas alone before starting to spray meth.

basically, im running an 11.2:1 a/f going into the high 10s up top. dunno HP yet, but im running a 35r on about 26psi at this point, ill be getting on the dyno on wed so ill have power numbers then. i run 880cc injectors. i have the SMC evo kit with the standard size jet(the one Steve sends in the kit). the pump is at full blast at about 14psi and spraying 100% meth.

i would guess im somewhere around 475whp right now....give or take. i know the SMC kit maxxes out at a certain point(14psi in my case) and the fuel pressure raises with boost pressure, so at say 28psi and an 11:1 a/f ratio shouldn't you be able to calculate the effective octane of my mixture?

thanks,

Jeff

 

Can you clear your PM box please (I emailed you as well)? I had a question regarding the stock airbox with the gt35r. Thank you.

 

Cleared PM box and returned email

BUMP FOR TED's RESPONSE

 

I'll keep the numbers conservative . . .

At a relatively rich 11:1 AFR or thereabouts, we'll call the BSFC 0.6 lbs/hr/bhp

At 475 bhp, that equates to a fuel demand of 285 lbs/hr, or, 4.75 lbs/min.

A standard M7 nozzle at 100psi (I believe) gives 7 gph of methanol. The specific gravity of methanol is 0.79, which equates to ~6.6 lbs/gal. This equates to an injection rate of 0.77 lbs/min.

It requires approximately 2.28 times the mass of methanol to equate the stoichiometry of gasoline (6.4 vs. 14.57 respectively), so 0.77 lbs/min methanol replaces around 0.34 lbs/min of gasoline if we keep the AFR straight.

That leaves us with 0.77 lbs/min methanol and 4.41 lbs/min gasoline, which equates to ~17.5% of the fuel charge being methanol at the point in time when the engine is delivering 475 bhp.

As far as how to calculate the octane rating of a mixture of 82.5% 93 oct and 17.5% methanol, you may be able to find an online resource to do that.

 

Or maybe we could just get one of these and make it easy:

http://www.shatox.com/octanemeter.html

 

damn Ted, you are out of my league.

 

lol....

 

For the lazy... assuming pure Methanol has an octane rating of ~ 140 (if this figure is wrong, please correct me), we have

((93 * 82.5) + (140 * 17.5)) / 100 = 101.225

 

wow, thought it was more like 105.

i wonder though, at 100 octane WITH methanol in it....how does that mixture compare to 110 leaded as far as being detonation prone.

i wonder if that small mixture of methanol in the gasoline makes the mixture as detonation proof as higher octane leaded race fuels.

any thoughts?

 

I would hope it would be a lil higher then that. I though it was around 108 octane?

 

well, the higher amount of power and higher amount of boost brings the effective octane of meth injection down.

think of it this way, at 50% duty cylce of the injectors and say 60psi fuel pressure the meth kit is spraying the same amount as it is when the injectors are at 90% duty cycle and 80psi of fuel pressure.(these are just arbitrary numbers, but you get the point)

 

My number above is based on Ted B's math (post #19), which is probably better than anything I could come up with.

I like this idea too.

Well, the alcohol does cool the intake charge, which would decrease the likelyhood of detonation, giving it a higher "effective" octane. It seems to me though, that the octane rating of a fuel is only a guide, and what actually matters is what kind of knock activity you're seeing.

 

to anwser your question. you can run methanol and 93 octane to run 40 psi on the gt35r but you should not run 40 psi on the gt35r because it is way out of its efficiency range. Keep it around 35 psi and it will be happy with the methanol. make sure you get a kit with a static state relay that is stand alone or built into the controller. this will raise the voltage going to the pump as your rpms increase, thus increasing the pressure as the rpms increase. make sure you get a pump with an adjustable pressure setting on the pump, most high end pumps have them. Also, be sure you place your nozzle very carefully, when you run 93 and methanol and high boost you have to be sure to get equal amounts of methanol to each cylinder. Remember to dial in the methanol max pressure for the maximum amount of boost you will be running. the pump i use can make 150 psi at the nozzle. I dont use near that much pressure so dont get crazy with it. If you really want to you can run a huge nozzle and cut the fuel down to nothing and in effect be running on close to all methanol and no 93. Im just having fun with you there, you have to do a lot more to your motor to run that much methanol. lol. Hope that helps.