[johnta1]

Can your gauge read out lambda? (not Gasoline afr)

[Brentco]

Originally Posted by johnta1

Can your gauge read out lambda? (not Gasoline afr)

Yeah it can display lambda. I usually use AFR.

[johnta1]

But if your fuel isn't 'gasoline' how do you know the afr for that mixture?


Lambda of '1' is good for whatever the fuel is?
(or .8 for power or whatever)

[Brentco]

Originally Posted by johnta1

But if your fuel isn't 'gasoline' how do you know the afr for that mixture?


Lambda of '1' is good for whatever the fuel is?
(or .8 for power or whatever)

All California gas is a 10% ethanol blend. So I use the stoich AFR for a 10% ethanol/gas mixture (14.1).

[johnta1]

What afr # do you use for idle, cruise and full throttle?

[Formula jg]

johnta1, see post 169 for his idle/cruise AFR and I believe he mentioned mid 12's for WOT

[johnta1]

Thanks!

[johnta1]

Here is a quick comparison:


(I didn't use the idle in park, looks rich)





BTW, do you know if the gauge reading is 'correct' for e10? (10% ethanol gasoline)
Does it actually show 14.1 when using the gas mixture you have at stoich or lambda of '1'?
Or even better what is the lambda when idling in gear?

[Brentco]

Ah, I think I get what you’re asking now. I should have provided more details on how my AFR gauge works. The wideband I use (Innovate MTX-L Plus) reads the mixture from the sensor in lambda and then converts the reading into AFR, which is the number that displays on the gauge. The internal calculation from lambda to AFR is based on the stoich of the fuel you’re using. It comes defaulted to pure gasoline (14.7) but you can program it for methanol, ethanol, etc. You can also enter in a custom fuel stoich, which is what I did with a 14.1 value for e10 gas. This made a small change to the displayed AFR that corresponded to the slightly different stoich.

The gauge can only display one number at a time — either an AFR value or lambda — so I can’t necessarily compare an AFR number to lambda in real time. But it’s just a straightforward calculation performed automatically by the gauge, so I have no reason to question the numbers.

And thanks for the lambda comparison chart, that’s helpful.

[johnta1]

Thanks for the explanation!



Clears up my confusion.



One other thing that I would say but not sure on your gauge is that the response may be too slow to show an accurate reading for the 'stabbing'?

But in any case, trial testing should fix the problem.

[Brentco]

That’s a good point — I’ve heard some AFR gauges have some lag, maybe even to the point of missing changes in the mixture. Thinking about this more, the gauge probably dampens the readings it transmits to the display, because if it showed every AFR reading it sampled the numbers on the gauge would just be a blur.

But once I felt the bog and started testing it with one eye on the gauge, it clearly picks up the lean spike. You can also see it clearly on the logs. Throttle to the floor, vacuum drops near zero, rpms shoot up, AFR shoots up even higher, all at the same time. So I’m not relying on just the gauge read out (and if anyone’s curious, I’ve actually found that the Innovate gauge’s response time is lightning quick).

I think you’re right I just need some more seat time and testing to nail down a solution.