Do You Want A Lean OR Rich AFR? | Fuel VS Power!

What does rich or lean mean? Which one is best? Theory AND practical demonstration on our Mainline dyno.

How does your AFR influence engine performance, specifically the amount of power it makes in your 4 stroke gasoline piston engine?

Ask this question or similar on an internet forum or similar and you're likely to get as many different answers are there are replies. AFR is a widely misunderstood topic, even sometimes with professional tuners themselves, and today we're going to dispell a few myths for you on this topic.

Andre is going to show you what happens to the torque output over a wide range of Lambda settings as well as explaining why at full load you want a slightly richer AFR, but not for the reason you might think.

#highperformanceacademy #learntotune #morepower #afr #rich #lean #lambda

[KjV]

0.75 = 11.0 AFR
0.86 = 12.6 AFR
0.92 = 13.5 AFR
1.0 = 14.7 AFR
1.15 = 16.9 AFR
I pause the video and do the maths so you don't have to :D

[hambo]

This is, by far, the most impressive explanation (and demonstration!) of AFR tuning that I've ever seen. This channel is the cream of the crop.

[haydent]

You can be rich your whole life but you can only be lean once

[maxtorque]

The reason AFR has a greater effect on an engine than demonstrated here is due to the interaction with ignition timing (fixed for your test) especially for engines that are spark limited (ie run into detonation or pre-ignition before they reach maximum BMEP) Had you run your test at an engine speed closer to peak cylinder filling (ie peak torque) chances are, if you had an ignition timing also optimised for max BMEP, the engine would have started to detonate at the lean AFR settings. So, by running richer, the extra evaporative cooling and additional heat absorption of the greater fuel mass, would reduce the temperature of the charge during the compression event, and allow you to run with an earlier ignition point, which results in a higher mass fraction burn at a smaller average chamber volume, and as a result greater energy transfer to the piston, as opposed to it just going out the exhaust (which is why EGTs fall with advanced ignition angle despite peak combustion gas temperature being higher (effectively you get a higher dynamic expansion ratio)

[SouthernCrossMotors]

This video is an awesome find.

I ran my ISF on a Dyno today and asked to show the AFR. The Lambda dipped to as low as 0.79 or so and I could see the dip in the horsepower curve in relation to the Lambda curve.

My engine did make less power when below about 0.88.

Will have to do some investigation as to why but thank you again for this video.

[mattparker]

You explain things so in detail very well done video

[XHikotheproX]

That's amazing I had no idea a NA engine would care that little. I like how you displayed torque only because it's what is really being measured for one, and is easier to see a difference all across the entire Rev range with torque rather than Power. The tune that I have for my car which is a NA V6 not dissimilar to the 350z engine has a target of .84 lambda at wot.

[mateuszb.]

Explanation was 10/10 but I sometimes I had to rewind the video because I couldn't understand what you were talking about 😂. Apart from your accent the video deserves milion views 👌

[realvanman]

I'm impressed with how little difference such a wide variance in AF ratio made. As in virtually no difference! I would not have expected that. It would have been interesting to see a plot of EGT during each of those runs as well...

[fredjones]

Best afr demonstration ever! A comsummate professional. Hats off.

[caribbeangtr]

Such an important topic with massive impact on power and longevity of your expensive engine.

[getahanddown]

Damn Andre you're making 300+Nm at 2k!
Am going to wire in an aftermarket ECU soon and will 100% sub to the courses

[jdsimons]

Great demonstration. thing i take away from this basically is the AFR needs to be "correct" for the application. more lean or more rich within that spectrum makes little difference but outside of that either direction results in power loss etc.

[ronbown]

Maybe on the next demonstration you can demonstrate for the best lambda reading on methanol and see how wide of a tuning window there is with very little change in torque.

[thhonyytone]

Awesome to share your tune on this part of a ECU...mostly on Dyno!!!!Thanks bro!!

[rogerking]

In my experience A/F ratio is actually more important on light throttle where small variations can make a big difference to driveability. You have successfully busted the myth about A/F ratio being crucial for max power though, neatly demonstrating the BS you hear where the operator says he went up one jet size or increased the fuelling by 2% and suddenly found another ten horsepower.

Have you ever tried this with a 2-valve engine? When I was involved in the business I generally found that it was necessary to run these very slightly richer, which I always put down to the less efficient combustion chamber; another effect of 2-valve combustion chambers being that exhaust valves were far harder to decoke due to the resultant much higher exhaust gas temperatures flowing over them (not because of the richer A/F ration which would have the opposite effect, but because of the less efficient combustion causing less of the heat to be turned into kinetic energy).

Biggest danger to engines in my experience is not A/F ratio, but when the mapping guy has pointlessly pushed the ignition advance to the very limit and then the car gets a tank full of fuel that is very slightly lower octane than the test fuel. That didn't happen in the days of distributors simply because the timing was wobbling all over the place anyway and to think you could increase advance by half a degree meant you were laughably deluded.

Am I giving away my age?

[shhhdontshout]

Why this channel still not 100k subs yet? Should be more than a mil already.

[opexo]

if you could make the same 3 runs with temp. probes in the exhaust and show their data on the screen would be very helpful

[peterkroeker]

Well I just got a $5000 education for 5 minutes of attention

[mugenriosk]

Lamda+ignition timing( with lots of resolution) + knock sensor with lots of resulution+ EGTs again with lots of resolution and good response time on a load based dyno... MAN I MISS TUNING CARS