I was bored in class and figured I'd figure out the stoich ratios for mixed meth/gas

100% gas.......................14.7
90% gas, 10% meth.......13.87
80% gas, 20% meth.......13.04
70% gas, 30% meth.......12.21
60% gas, 40% meth.......11.38
50% gas, 50% meth.......10.55
40% gas, 60% meth.......9.72
30% gas, 70% meth.......8.89
20% gas, 80% meth.......8.06
10% gas, 90% meth.......7.23
100% meth.....................6.4

Hope this helps someone

 

Waste of time. you should be paying attention in school.
Stoich is always 1 lambda no matter what fuel you use.

 

Well yes stoich is always 1 lambda... but who tunes with lambda? these are AFR readouts.

 

I shouldve known responding to this would be wasting my time.

 

Nowhere in the post did I say I was the God of EMS tuning... tell me why the information is useless, don't just insult me.

 

who doesnt tune in lambda is the proper qustion.

lambda is soo easy to figure out and tune, i dont even use anything else besides lambda any more.

 

Once you start tuning for different fuels and so on, lambada is easier.

and none of the stoich **** means anything in real world tuning.

 

I fully agree with what SirCygnus & rx72c said. Also please understand that people don't like insinuations that they're inferior to you. I think you've intimated that you're a student; as a student you might want to consider that building bridges is typically far more useful then destroying them. Personally I think it's great that you took the initiative to and have the desire to do blended fuel calculations; constructively and politely channeling your talent and desire will serve you well.

-Mike

PS: I'm fluent in A/F & lambda, prefer lambda for computational ease. I also own both an RX7 and an RX8, neither is better than the other. Apples != oranges. They're both engineering marvels in their own right. Peace.

 

Thanks guys... Why lambda though? Is it that .85 lambda is max power? The few people who have done EMS tuning around here (In Indianola, Nebraska XD) have always tuned with AFR's... I'm sorry I just thought wideband logging was how you do it? Thanks again.

 

their is no perfect afr or lambada. People have to get this crap out of their head.

Every tuner has their method. I like to tune to the safest possible mixture without loosing too much hp.

 

There goes everything I know.... I have heard of people making the mixture "LEANER" not leaned out to the point of detonation. before turbo spool to help it spool faster... But surely theres a nice midpoint before leaning out to detonation and getting so rich its boggy...

 

If the car starts to loose power when going rich its cause your ignition is crappy.

 

Even under stupid rich conditions? like under 7:1?

 

dont get cocky.

what we are saying... is that most tuners can tune in lambda. lambda is the same no matter what concentration of fuel or what kind of fuel you use.

also, some tuners tune for safety, and not for power. visa versa.

thanks for the calculations, its not like we needed it. however, you should be paying attention in school.

 

I have a related question please

I understand that if you have an AFR meter that is calibrated for gas, 14.7 stoich., then if you add methanol or whatever, you would then still target the same AFR as if it was 100% gas.

This is well explained e.g. in the RICE RACING sticky thread https://www.rx7club.com/auxiliary-injection-173/ai-tuning-afr-important-582856/

But what do these WBO2 sensors actually read to calculate Lambda? "excess" oxygen reading works for lean mixtures, but what if the mixture is reach?

In one of the posts referred to by RICE RACING, Innovate says
"Widebands (and 5-gas analyzers) do NOT measure some magical AFR. They measure Lamda. There is a second way to calculate Lambda aside from the familiar actual_AFR/stoich_AFR. It's
Lambda = %O2_of_air / (%O2_of_air - %O2_of_exhaust) This is how a wideband measures Lambda."
and then adds
"The term %O2_of_exhaust can go negative if the gas is rich. In that case it means the amount of additional O2 needed to get the gas to stoich." ?!?
http://www.innovatemotorsports.com/f...2&postcount=12

OK, the first part makes sense. With my AFX meter, I calibrate it first to read air, so that the meter learns what the term "%O2_of_air" is.

Then, if I am stoich. all O2 must have been consumed in the combustion.
The sensor read no O2 present, the denominator in the fraction becomes "%O2_of_air-zero" and Lambda=1 (i.e. 14.7 AFR reading)
If I am lean, there is still O2 in the exhaust, the denominator becomes larger than the numerator and Lambda>1 fine...

But what does the sensor read if I am rich? I still have consumed all the O2. How can the denominator become larger (i.e. negative O2 at the exhaust?). Evidently, the sensor must measure something else beyond O2, like excess hydrocarbons and the formula must include those.

I realize this is just an academic question, with no practical application on tuning and I don't want to waste anyone's time.

Just curious to know.

Thanks,

Sandro

 

The theory and physics behind WBO2 sensing is described fairly well at http://www.megamanual.com/PWC/ . The sensor does indeed measure HC at richer than stoich, details are in the link. I would have to respectfully disagree with your statement "I realize this is just an academic question, with no practical application on tuning and I don't want to waste anyone's time.". It is in fact very important to understand the physics behind an ICE. This comprehension is fundamental in understanding why strapping a fart can on a 96 Civic does not in fact help performance, as an example.

 

Very exhaustive and interesting information. Now I feel better

Thanks a lot!

- Sandro

 

Thanks everyone... gotta start somewhere and thanks for all the additional info.

 

How did you miss this sticky: https://www.rx7club.com/showthread.php?t=582856

Edit: I see Sandro got to it first.

Read it and THINK about it. It all makes sense. The wideband outputs lamba and uses the stoich value of a fuel to report an AFR. The stoich value is just a "conversion" factor and is irrelevant. Keep tuning to your standard AFRs regardless of your combined fuel's stoich.

Say you tune for an AFR of 12.0 on gas. That is 0.82 lamba. Now, assume that you want to tune to 0.82 lamba on your 50/50 mix of meth and gas. Guess what, it is 12.0 AFR on a gas and you can tune to 12.0 because it is the same as 0.82 lamba. Again, the wideband outputs lamba, not an AFR. The AFR is calculated based on a stoich value you select. That's it.

 

That's exactly why utilizing lambda as a term, spoken and written, is far preferable to "AFR". The 12.0 reported on your hypothetical 50/50 mix isn;t really 12.0 - it's what the wideband processor, knowing only of straight gasoline, is converting the real lambda number to. KTM, I understand you said the exact same thing, I'm just trying to make it a bit clearer.

 

And I appreciate the help.

 

This topic always comes up and people get confused. It's actually very simple, but some how people have a hard time wrapping their brain around it. And while it is true that a 50/50 mix is no longer 12:1, it also doesn't matter. It's still relative richness or leaness compared to stoich.

I made a calculator that "should" help people understand this. I'd like to add more fuels to the calculator, but my limited java scripting is holding me back. The calculator is at www.wannaspeed.com/lambda.html

Using the calculator you can see the correlation between lambda, gasoline afrs, and meth AFR's don't change. 1 lambda IS 14.7:1 gasoline AFR, 1 lambda is ALSO 6.4:1 Methanol AFR. So if I switch to straight methanol and tune to 10.8:1, thats a lambda of 0.73, and the true Air/ fuel ratio that we need not ever even know is 4.7:1.

For me it's far easier to see 10.8 - 11.5 and know where I'm at, then to see 0.73 - 0.78 Lambda or to switch to true methanol afrs and see 4.7 - 5.0 AFRS. Not to mention you would also have to change all the settings in your wideband to read either of them.

 

Whatever the individual feels comfortable with is fine especially with your observation that the user needs to understand it. Personally, I made the decision some time ago to "think" in terms of lambda and am now perfectly comfortable with it. A side interest of mine is postprocessing of ECU logs for tuning purposes using various algorithms. Most of these algorithms are laid out in various patent and engineering technical papers and they all use lambda as a term. Therefore my use of lambda is for clarity in these equations. Likewise, dudeman offers his thoughts on why he uses AFR - which is excellent rationale! Different strokes, different folks, it's all the same relatively speaking.

 

Bingo.

 

Correct.

B