[dzenno]

When I run with just pump gas the car is tuned to hit low 12s high 11s under WOT...when meth turns on (80/20 meth/water mix with two CM7 nozzles and a 200psi pump from coolingmist) this should inject about 900cc/min given pressure back on the nozzles with boost and the fact there are two nozzles to push liquid out of.

At the time it starts spraying I see the AFR reported on the widebands (I have two of them) 1-1.5 points leaner than when running just pump gas. I then went on and tuned the car to run 11.8-11.9 AFR with meth running and that was fine, I was happily hitting 11.8-11.9.

Then I switched meth off and did a run and I see AFR richer at 10.5-10.8 running just pump gas. Why does this happen? Is the LC-1 giving me false lean readings on meth somehow? Which should I take for reference? Could it be that LC-1 is being thrown off somehow by introducing meth?

I know that the sensor is fine, new kit installed 4 months ago and I've done tons of logging/tuning with it on pump gas...only when introducing meth in the mix and keeping all the other tuning parameters the same does it start to read leaner on meth than on pump

Given everything I've read so far, if you don't touch the stoich settings on the wideband and leave them at gasoline 14.7 settings and then add meth to the mix, what "should" happen is that the wideband should report richer not leaner...what gives?

Same exact thing happens with 50/50 washer fluid mix...weird

[Clap135]

What do the stock widebands report?

[Joshboody]

Just guessing but if you are adding AFR ratios while tuning instead of lambda value then the back calc to lamdba would be leaner. Meth is like 9:1.

You can check this by logging fuel volume to see your apprx meth %.

Not sure though.

[dzenno]

Originally Posted by Clap135

What do the stock widebands report?

Haven't checked yet but I'll do that next...any reason why stock would report differently? LC-1s that I have also use Bosch sensors

[Clap135]

Originally Posted by dzenno

Haven't checked yet but I'll do that next...any reason why stock would report differently? LC-1s that I have also use Bosch sensors

The sensors might be from the same company, but the software that runs them is different. Id have to think about it some more, but Josh is on the right path.

[dzenno]

Originally Posted by Joshboody

Just guessing but if you are adding AFR ratios while tuning instead of lambda value then the back calc to lamdba would be leaner. Meth is like 9:1.

You can check this by logging fuel volume to see your apprx meth %.

Not sure though.

meth is actually around 6.5AFR ... logging and figuring out fuel volume to meth would be a bit tough, no? How would you do it best on this car/tools?

Most online info indicates that the expectation is that the mixture will go richer on a 50/50 mix. But there's quite a few posts out there indicating that some ppl observe the same readings as I did (i.e. going leaner when meth/water turns on...and that the more water is introduced the leaner the mix that's logged)

In any case, I'll try to see how stock widebands compare, easy enough to log both at the same time

[Joshboody]

yeah, I'm not sure now. Entering 12:1 is .81 volts which would be constant. this is hurting my brain. Water shouldn't make much (or any) difference as the molecules do not separate.

[dzenno]

Funny thing is most posts I found about ppl reporting leaner on the widebands with meth than without it, all seem related to Innovate's widebands...interesting..

[Jeffman]

Originally Posted by dzenno

Funny thing is most posts I found about ppl reporting leaner on the widebands with meth than without it, all seem related to Innovate's widebands...interesting..

Isn't one of the reasons to run richer (AFR < 14.7, or lambda < 1) at WOT is to allow the extra unburnt fuel to soak up some of the heat to prevent knocking? If so, then the meth (and/or 50:50 methanol:water) serves that function to soak up the heat. Hence, less fuel is needed so you end up running leaner with meth and/or meth mixtures.

[dzenno]

Originally Posted by JHR

Isn't one of the reasons to run richer (AFR < 14.7, or lambda < 1) at WOT is to allow the extra unburnt fuel to soak up some of the heat to prevent knocking? If so, then the meth (and/or 50:50 methanol:water) serves that function to soak up the heat. Hence, less fuel is needed so you end up running leaner with meth and/or meth mixtures.

Those are good reasons but have nothing to do with what a wideband should report in terms of lambda/AFR

[Clap135]

Originally Posted by dzenno

Those are good reasons but have nothing to do with what a wideband should report in terms of lambda/AFR

It does if you think about it.
Gasoline is replaced with your meth mixture. Being that the widebands are calibrated to read 14.7 stoic vs whatever 6.5/14.7 mixture you got in there.

[dzenno]

right ok, but the point is it should go richer if anything, not leaner, when on meth

[Clap135]

Originally Posted by dzenno

right ok, but the point is it should go richer if anything, not leaner, when on meth

What makes you think it should be richer on meth? Meth is partially replacing the gasoline. Being that anything over 6.5 is considered lean on meth it would technically report leaner readings if calibrated for straight gasoline. I could be way off here, but thats how it makes sense to me in my head lol

[Joshboody]

Originally Posted by Clap135

What makes you think it should be richer on meth? Meth is partially replacing the gasoline. Being that anything over 6.5 is considered lean on meth it would technically report leaner readings if calibrated for straight gasoline. I could be way off here, but thats how it makes sense to me in my head lol

Think in lambda. If enter an AFR target of 12:1 this would mean the wideband is looking for .81 volts. It doesn't matter the fuel, only the oxygen present. stoic of 14.7 or 6.5 just means the amount of air to have a complete burn of the fuel. So the DME will adjust fuel to see the .81 volts... corresponding quantity of oxygen. Theoretically I don't think there should be a difference in the reading no matter the fuel if the hardware can adjust appropriately.

EDIT: it would NOT be .81 volts but instead this is multiplier to the stoic voltage, which I don't know what this is.

[Clap135]

Originally Posted by Joshboody

Think in lambda. If enter an AFR target of 12:1 this would mean the wideband is looking for .81 volts. It doesn't matter the fuel, only the oxygen present. stoic of 14.7 or 6.5 just means the amount of air to have a complete burn of the fuel. So the DME will adjust fuel to see the .81 volts... corresponding quantity of oxygen. Theoretically I don't think there should be a difference in the reading no matter the fuel if the hardware can adjust appropriately.

But the hardware can't adjust to different fuels. Thats the whole point.

Say 50 percent of your lambda is gasoline and the other 50 is meth.
The computer is programmed for gasoline so you divide whatever number you get by 14.7 to get your a/f ratio right? Being that meth is 6.5, dividing the whole thing by 14.7 is inaccurate.

14.7 plus 6.5 is 21.2, divide that by 2 is 10.6 is stoich assuming equal burn.

1.00 lambda divided by 14.7 is 14.7 af
1.00 lambda divided by 10.6 is 10.6 af for that mix.
Being that the computer is set to use 14.7 as stoich when actual is 10.6, it would show leaner readings.

You can't think of lambda cause lambda and af are tied in, they rely on each other. If i request .81 lambda it will spit out a 12.1 af ratio, however that .81 also depends on what type of fuel your are using.

[Overboost]

This may help a little

Race Gas Stoich Rating Tuning Considerations

Well I have seen questions from time to time about adding race gas without tuning which can be a very expensive experiment. I am going to explain how stoich effects AFR. Hopefully in simple format.

I am not going to get into MAF transfer functions or other tuning functions.This is just about fuel.

First lets define a few terms:

AFR: Air Fuel Ratio

Stoich Rating: In simple terms is the AFR to have chemically complete combustion that is neither rich or lean. For Example most pump gasoline is about 14.64 to 1. Which means 14.7 parts of air to 1 part of fuel.

Lambda: Is a term that is utilized when tuning. In basic terms think of it as an adjustment to your stoich rating when tuning AFR. For example with pump gas tuning .80 lambda, 14.7 x .80 = 11.76 AFR target.

Lets assume your car blower car has a nice tune that gives a perfect 11.8 AFR under WOT with pump gas.

So now it is race day. We add some timing to our tune, drain the fuel tank, and fill up with some high octane unleaded VP109.

We go for a blast down the 1/4 mile while datalogging and see the A/F is reading 12.8 then make a quick trip to the bathroom only to find out they are out of toilet paper.

There are a few factors here to consider.

The stoich rating of VP109 is 13.41.
Most wideband A/F modules are calibrated to 14.7 pump gas stoich.

So this is the formula to determine the true A/F for the run.
AFR/Wideband Stoich x Race Gas Stoich
12.8/14.7*13.41= 11.7 AFR on Race Gas

So you may think 11.7 sounds safe but we must remember the VP109 stoich is 13.41. So 11.7 AFR = .87 lambda. For the most part a safe lambda value is .80 to .82 for a forced induction mustang. I prefer .80

So we take VP109 stoich of 13.41 x .80 lambda = 10.73 AFR
This is the AFR (10.73) I am tuning for.

Keep in mind this is not what will display on your wide band as it is programmed to 14.7 stoich. You must convert the AFR.

AFR/Race Gas Stoich*Wide Band Stoich

10.73/13.41*14.7 = 11.76 AFR is what I want to see on my wideband when running VP109.

Just to reiterate 11.7 on the AFR display with VP 109 is really a 10.7 AFR.

Ok so hopefully you are not totally confused.

There is a simple solution to all of this madness. The SCT Advantage software has a Scalar for Stoichiometric Air Fuel Ratio. You simply enter the correct value for the fuel you are using and all lambda fuel calculations will be based on this value. Then just do the first formula conversion to determine what you should be reading on the AFR display. Some AFR modules may be able to be programed to the correct stoich.

Or leave the stoich in the tune and wideband at 14.64 and calcualte what AFR you need to read on the wideband for the fuel that is used. (This is how I did it in the past, but I find it easier to change the stoich scalar)

This is why you have to exercise caution when mixing race gas and pump gas as you do not know the true stoich of the mixture. The leaded race fuels have a stoich that is closest to pump gas. I always drain my tank before putting in the race gas. When I mixed fuels in the past I didn't notice a drastic change in AFR, but when I have 100% unleaded race gas it really leans out with a 14.64 stoich scalar in the tune.

The other caution is the winter (oxgenated) gas we get in Arizona. I noticed the car leaned out in the winter when it was tuned on the better summer blend. A 14.1 stoich scalar works for the AZ winter gas if your initial tune was based on the summer blend.




Race Gas Stoich Ratings

Sunoco MO2X UL – 14.5
Sunoco 260 GTX – 14.4
Sunoco 260 GT – 13.9
Sunoco 260 GT Plus – 13.7
Sunoco Standard – 14.8
Sunoco Supreme – 14.9
Sunoco MO2X – 14.5
Sunoco HCR Plus – 14.8
Sunoco Maximal – 15.0
Sunoco MaxNOS – 14.9

Turbo Blue Unleaded (100 octane) -13.9
Turbo Blue Unleaded Plus (104 octane) - 13.7
Turbo Blue 110 - 14.7
Turbo Blue Advantage - 14.9
Turbo Blue Extreme - 15.0

VP Street Blaze 100 - 14.16
VP C10 -14.53
VP C16 - 14.77
VP 110 - 15.09
VP MS109 - 13.41

[Joshboody]

Originally Posted by Clap135

But the hardware can't adjust to different fuels. Thats the whole point.

Say 50 percent of your lambda is gasoline and the other 50 is meth.
The computer is programmed for gasoline so you divide whatever number you get by 14.7 to get your a/f ratio right? Being that meth is 6.5, dividing the whole thing by 14.7 is inaccurate.

14.7 plus 6.5 is 21.2, divide that by 2 is 10.6 is stoich assuming equal burn.

1.00 lambda divided by 14.7 is 14.7 af
1.00 lambda divided by 10.6 is 10.6 af for that mix.
Being that the computer is set to use 14.7 as stoich when actual is 10.6, it would show leaner readings.

You can't think of lambda cause lambda and af are tied in, they rely on each other. If i request .81 lambda it will spit out a 12.1 af ratio, however that .81 also depends on what type of fuel your are using.

You enter 12:1 into the tune. This converts to .81 multiplier to stoic voltage in the wideband. So it is looking for .81 ratio of air basically. This will be 81% of 6.5 and 14.7 (at whatever combination) which will be rich. The DME adjusts fuel to reach .81 ratio which will always be rich.

[dzenno]

Originally Posted by Clap135

But the hardware can't adjust to different fuels. Thats the whole point.

Say 50 percent of your lambda is gasoline and the other 50 is meth.
The computer is programmed for gasoline so you divide whatever number you get by 14.7 to get your a/f ratio right? Being that meth is 6.5, dividing the whole thing by 14.7 is inaccurate.

14.7 plus 6.5 is 21.2, divide that by 2 is 10.6 is stoich assuming equal burn.

1.00 lambda divided by 14.7 is 14.7 af
1.00 lambda divided by 10.6 is 10.6 af for that mix.
Being that the computer is set to use 14.7 as stoich when actual is 10.6, it would show leaner readings.

You can't think of lambda cause lambda and af are tied in, they rely on each other. If i request .81 lambda it will spit out a 12.1 af ratio, however that .81 also depends on what type of fuel your are using.

Ok, so how do you tune the car in that case is what I don't understand? On pump gas I'll tune it say at 15psi for a nice 11.8-12.0 AFR..then introduce meth and I see its showing 12.8..what number do you go by and do you retune then when on meth to get it down to 11.8-12 again?

[dzenno]

Overboost, that's actually a great post! So it seems that the LC-1 is actually doing what its supposed to do, i.e. reading leaner than it really is as it is calibrated to pump gas at 14.7 stoich...the question is how to figure out the "right" AFR given a meth/water mix, amount of meth/water injected and the amount of gasoline injected...fu*king headache!

and then ALL that changes winter to summer with different "blends" and then yet again when running race gas such as MS109 that burns at 13.4 stoich, geez, i never knew this would be that complicated when mixing fuels...

no wonder I'm getting backfires when on meth from running too rich (between shifts) as I've been adding more fuel to fight the perceived lean runs when in fact when you take into account what Overboost quoted above it might be actually too rich after re-tuning...

i think the best approach, to make it easy, might actually be to tune it on pump gas for X AFR and then just run meth on top as it can't be leaner only richer and more safe than on just pump gas...the issue is monitoring/logging are all off, damn it

It'll be interesting to see how the stock widebands log on/off meth

[Joshboody]

I think everyone is getting confused. If you tune for 12:1 with gas your wideband will target the ratio, so you do not have to change anything to keep this ratio no matter the fuel used. If you want to know the actual AFR of the fuel used then you have to do some calcs. BUT the ratio of air to fuel will stay constant.

[dzenno]

Originally Posted by Joshboody

I think everyone is getting confused. If you tune for 12:1 with gas your wideband will target the ratio, so you do not have to change anything to keep this ratio no matter the fuel used. If you want to know the actual AFR of the fuel used then you have to do some calcs. BUT the ratio of air to fuel will stay constant.

Wideband doesn't target anything, i'm sure you know that just wanted to clarify its obviously the DME that's doing the targetting and in my case with the JB4 at the moment JB4 is applying a voltage bias to the stock widebands to add fuel and that's why I'm not reading the stock widebands when JB4 is plugged in as they'd be off or at best calculated in the jb4 logs which I wasn't happy using and felt it was better to use an external wideband..RUN ON SENTENCE FULL STOP lol

I did tune 12:1 on pump gas so I expected AFR to stay the same...turned on meth, the gauge in the "instant" meth starts flowing goes leaner than what was setup on pump (lambda goes higher than on pump gas), and in the "instant" meth turns off it goes back to where it was tuned for on pump gas

[Joshboody]

Did you turn on/off meth manually or through the JB also? Try all the same settings with JB constant and turn on/off meth manually.