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This is the first part of my upcoming video on air:fuel ratios. I felt the need to cover this topic before I release the Lindbergh Pacific video as it's helpful to understand this concept when talking about fuel efficiency. Just to clarify, THIS IS NOT the whole video on mixture, it's just the first part. The whole video should be done in a couple days and will be followed by a video on Lindbergh.
Also, I think I'm going to make a response to Matt Walsh's comments on Star Wars.
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Comments (5)
Greg, great video and right up my alley as a Powertrain calibration engineer at Harley-Davidson. Couple comments: leaner lambda at peak torque vs peak hp. I think there is both reasons based on science and carburetor legacy there. Legacy in that carburetors tended to run leaner at peak torque vs peak power, as main jet circuits were not as tunable at Wot so you tend to jet for peak torque (max fuel requirement per cycle) which results in a rich mixture at peak power. There is science there as well however (and you hit on it with your ‘better mixture’ comment), but peak engine efficiency is always at peak torque, and specific fuel consumption is minimized there. Assuming peak power rpm is not equal to peak torque rpm , Peak power is almost always at a higher specific fuel consumption as the engine isn’t as efficient there, so it takes more fuel per cycle to produce a given amount of torque. Switching up to your comment about OEM’s running very rich lambda at WOT, can’t speak for automotive but one of the big reasons that happens in my world on air cooled motorcycle engines is to protect the exhaust valve from overtemp, with upper EGT limits between 1300-1500 degrees (depending on exhaust valve material). I suspect exhaust valve overtemp was a concern on WW2 aero engines as well, especially the air cooled poppet valve ones. Awesome channel keep up the great work!
This is fascinating - thanks!
Appreciate the refresher, the details in this video, particularly the last few minutes discussing power versus air/fuel mixture and what has impact on produced power.
Greg, referring to the graphic at the 7:00 minute mark, I think you mean 26 oxygen ATOMS, not molecules.
I haven't watched it yet, but he is likely correct in saying molecules: O2 is the most common atmospheric form of oxygen and it is indeed a molecule formed of two oxygen atoms in a double covalent bond.