A/F and the effects of meth. - SRT Forums

porksword · 10-03-2009, 01:34 PM

For those of us that are running an A/F ratio guage that doest show lambda. There are alot of us that run meth injection and often times its direct port and a decent amount is injected.

Lets talk about the effects the meth is showing us on the wideband.
A few things we know.

Lambda = TRUE AFR divided by TRUE AFR STOICH.
AFR = Lambda X stoich_ratio
stoich for gas is 14.7:1
stoich for meth is 6.4:1.

As we can see, the stoich for gas and meth are alot different. If you tried to run meth at 14.7:1 it wouldnt last long and gas at 6.4:1 wouldnt work either.

So what we need to know is, when running a straight A/F ratio wideband that dont display lambda, what target A/F ratio should we be looking for? I know this depends on the amount of meth that is flowing so its hard to give an exact # so lets say direct port with 5 M2 nozzles 100% methanol (1 In each port and one in the pipe before the sensor).

On gas I look to stay under 12:1 on a turbo car @ WOT to be safe, Whats the safe target for gas/meth?

Discuss.

nutz · 10-04-2009, 03:07 AM

I posted up the blending calculation for meth as a fuel additive, if the majority is gas i would still shoot for mid 11's now some of the guys using dirrect port meth with 4 nosels will need to run quite a bit lower A/F, it will depend on the percentage of meth to gas and you need to remember that meth has only 43% the densidy (energy content) so when blending 1:1 is realy only (.43:1)

I am still just using meth as an internal innercooler but some of you guys are kinda breaking new ground by switching fuel under boost

lyncoo · 10-04-2009, 03:10 AM

i tuned to a 11.0 with meth and without it was like 11.9 or so

nutz · 10-04-2009, 03:17 AM

Quote: Originally Posted by lyncoo

i tuned to a 11.0 with meth and without it was like 11.9 or so

I use a small nosel and do the oppisit, nine allows me to remove fuel to get a huge boost in power (low 12's) but i use it as a cooler not a fuel

how much are you injecting??

lyncoo · 10-04-2009, 03:19 AM

it was a m7 50/50 mix but i havnt ran meth in about a yr. i plan on getting another kit as soon as i get a dsp and some injectors, and reed is going to do a bottleneck fix for me

sponsorSRT03 · 10-04-2009, 11:41 AM

I try to stay within a solid 11.0 maybe a lil lower. But im using 100% meth and dual nozzles. Total of 550cc meth nozzles.

7055 · 10-04-2009, 02:27 PM

Do widebands measure AFR or Lambda? I know they display AFR but could they be measuring lambda then calculating the AFR based on gasoline's stoich point?

7055 · 10-04-2009, 07:51 PM

Somebody please explain, when injecting meth, why couldn't you just tune using your usual AFRs? I know that meth has a lower stoich point but...

The wideband is measuring the lambda reading, it is then calculating the AFR based on the fact that the stoich point of gasoline is 14.7:1. Therefore even though your WB is displaying AFRs it's actually a lambda reading so you could just tune like normal using your usual AFRs. Am I way off?

Do widebands measure AFR or Lambda? - Innovate Motorsports Forum

duster360 · 10-05-2009, 01:09 PM

Quote: Originally Posted by 7055

Somebody please explain, when injecting meth, why couldn't you just tune using your usual AFRs? I know that meth has a lower stoich point but...

The wideband is measuring the lambda reading, it is then calculating the AFR based on the fact that the stoich point of gasoline is 14.7:1. Therefore even though your WB is displaying AFRs it's actually a lambda reading so you could just tune like normal using your usual AFRs. Am I way off?

Do widebands measure AFR or Lambda? - Innovate Motorsports Forum

Yes, for any mix of fuels, your wideband gauge, if set to display for gasoline, will read 14.7 at the stoich. Propane, keorsene, CNG, E85, ect,,doesn't matter. They all will read 14.7 when lambda = 1.0.

NOTE: A/F for BEST power will be different for different fuels or blends or fuels. Whether or not you'll have more Torque at 11.0, 12.0 or 13.0 is still the question.

When using W/I you still have to strike a ballance of being able to use a Leaner A/F or adding timing. imo always use some water

lyncoo · 10-05-2009, 01:12 PM

Quote: Originally Posted by 7055

Somebody please explain, when injecting meth, why couldn't you just tune using your usual AFRs? I know that meth has a lower stoich point but...

The wideband is measuring the lambda reading, it is then calculating the AFR based on the fact that the stoich point of gasoline is 14.7:1. Therefore even though your WB is displaying AFRs it's actually a lambda reading so you could just tune like normal using your usual AFRs. Am I way off?

Do widebands measure AFR or Lambda? - Innovate Motorsports Forum

i think if your meth ever fails you have time to back out of it.

porksword · 10-05-2009, 09:29 PM

Thanks guys.