Why no more lean burn??

[aerostealth]

I owned a Honda VX for a while (traded it in because it did not have an AC) and the damn thing worked as advertised. We got 55 mpg routinely and sometimes more. Car drove and ran like a sports car if you got on it.

[Panther140]

The reasons are as follows:
- Combustion stability is too low when running lean (engine knock and/or pre-ignition is caused)
- NOx generation is too high
- Power is decreased

[ar5boosted]

Originally Posted by pgfpro

To me, their lean burn engine looks like a direct-injection Engine judging by the diagram.

Originally Posted by ever_green

What you have to do is induce a fulltime open loop behavior and then have the Maf sensor underestimate airflow by reduce Maf scaling.

Any blog write-ups on that ?

Originally Posted by pgfpro

This is a lot of work as it requires you to reduce the engine load scale across the board in ecu or else it will think there is less cylinder pressure than actually is and run too much timing (this is just one example).

I was watching this video. They show it being done on a spreadsheet.

https://youtu.be/kBk0KudOVAg after about 4:20

Using pattern-matching algorithms, I'm really confident that this could be done in software with some type of blanket-algorithm. (True, I don't value car engines like I used to :-) )

Translated into young peoples language, "like a facebook bot? or iPhone app?" but I mean some type of spreadsheet macro or script code.

It's a good conversation, so keep going.

[rmay635703]

NOx can react in a fuel cell to make electricity, I wonder why they don't just do that

[Xist]

RMay, do you have a source for that? I just get stuff about Bloom Box, which does not mention NOx.

Google does not even bother asking "Do you mean box?"

[Randy]

Originally Posted by ar5boosted

To me, their lean burn engine looks like a direct-injection Engine judging by the diagram.

The Honda one (HLSI on that diagram) is port-injected. I think part of what drove Honda to develop this was that they could keep using lean-burn after emissions standards kept them out of cars. They have a bunch of 4-stroke lean-burn outboards, for example.

[cRiPpLe_rOoStEr]

Even running lean-burn, port-injection is expected to decrease the NOx emissions compared to direct-injection. Particulate matter emissions, which plagues Diesels and has become an issue for spark-ignited direct-injection too, is another reason for some engines to retain port-injection.

[ellenor2000]

Originally Posted by cujet

Those who have aftermarket, stand-alone engine management computers have done some interesting things with lean operation on very modern engines.

Lean operation requires more throttle opening, and the throttle by wire can compensate without driver input. Driveability issues are minimized with such setups.

My current "fun" car is a 2004 Turbo S2000 with stand-alone ECU, 8.8/1 compression, 19.5Lbs boost. It does not run lean under light loads, and does not return very good MPG's. (about 20) . My plan is to re-map the ECU for 17/1 operation under light loads. Those that have done this see overall increases to 25 to 27MPG.

It's my understanding that modern direct injection engines have been configured to operate smoothly at much leaner A/F ratio's. And coupled with high compression, can achieve BSFC numbers almost 25% better than the very same engine operated at stoic.





Take a look at the lower picture. That's my 1971 Cessna 177RG. I'm operating it in very lean mode! (GAMI injectors and other tweaks) I'm achieving a solid 25MPG at 125MPH. I promise, there is no tailwind and I'm actually climbing in this pic. What I do is lower the RPM to 1900-2000, pull throttle to 17 inches manifold pressure and lean it to it loses significant power and misfires a touch, then richen it just a touch. I then fiddle with the controls to achieve a bit less than 5 gallons per hour fuel flow. (the gauge is just to the right of my iPad)

Note: in non lean operation, the same speeds consume about 8GPH.



Look at the airspeed indicator, 113MPH at 4500 feet. That's 125 true airspeed. (remember, the higher you go, the lower the airspeed indicator is for a given speed, due to thin air)

Twentyfive miles per gallon at what, 180km/h? I hope you're able to run UL fuel... If so, that's impressive. If not, LL is leaded and not what we want. Get a conversion to 92UL done and show us your fuel economy running on UL.

That's f'ing impressive

[towndrunk]

We are running lean burn in first gen Chevy Volts with good results, but does require a custom tune and open loop.

We run leanest (~20:1) at 1400 rpm (idle speed) and normal AFR above 2200 rpm. Running lean requires a lot more cam advance and a lot more spark due to the loss of power and slower burning mixture when lean. You also don't want to run lean with a cold engine, which created a lot of hurdles, but I think we handled it quite well. With the addition of a alcohol sensor ($45 in parts), the mixture is accurate with either premium fuel or ethanol blends of E30 (due to higher octane) to E85. Since the first gen Volt is high compression, we decided to stick with premium fuel to take advantage of it. Our tune is highly optimized even with E85.

It may not sound so impressive running max lean at 1400, but we're able to maintain 1400 rpm at highway speeds of up to 59 mph for an extended period of time.

More info on HPTuner's forum. forum.hptuners.com/showthread.php?63020-First-Gen-Volt-Tune-(Volterado)

[RustyLugNut]

Originally Posted by Old Tele man

What "Warranty" does that tuning offer against burned vales and piston tops?

. . . that comes from the full power crowd. Once past the 18:1 AFR point combustion temperatures actually start to drop.