Its such a good idea it makes my head hurt... when i first read sludgys post before any of the other I just thought to myself, just buy a diesel then read his closer and he wants a gasoline one.:rolleyes:

Diesels could effectively use "Atkinson" VVT too. Diesels are frequently designed with high compression ratios (20-22:1) in order to help cold starting. High compression ratios increase bearing loads and frictional losses more than any energy derived from more expansion. Optimum diesel efficiency occurs at about 15-16:1.

Diesel VVT would allow high compression ratios at startup, after which the intake valves would be retarded to lower the compression ratio. The expansion ratio would stay the same, so this would lower both the frictional loads, and still keep the high expansion ratio, for a double benefit.

I already have a diesel F350, and I hate it. It gets worse mileage than either of my GM half tons, and it rides, well, like a truck. I can't wait to trade it for a new GMC or Chevy. Two more years of payments..... argghhh

Ford ought to rename it the "Powerjoke".

As long as we're daydreaming in this thread, how about this for a wacky idea? First add lean burn to the car, then change the A/F ratio as a function of engine air consumption. In other words, as air consumption decreases (light throttle) set the A/F ratio really lean, like 20:1, so power is reduced not only by the ammount of air going into the engine, but also by the weak A/F ratio. Then as airflow increases bump up the A/F ratio for more power. Power would be reduced at light throttle without closing the throttle too much, reducing pumping losses. It's similar to coasting in gear with the fuel off and throttle wide open, but not quite. As more power is needed, it's supplied by a larger percentage of fuel, so airflow through the engine stays more even. It's not quite like a diesel, but closer than the way gas engines are currently run.


Then meter some EGR gasses to act as a type of WAI to help promote atomization of the fuel, as well as the usuall EGR benefits.
I think it could work. :)

The problem with any lean burn system is NOx, just like diesels.

Yeah , I agree.
While it is possible to reduce to mixture to gain FE in extremely light load conditions I belive that the engine is dirty.

An excessively lean mix doesnt burn well causing rises in bad gasses.

https://www.ae-plus.com/Technology%20...une%202006.htm

Fiat apparently though of the idea too, but BMW beat them to production.

Fiat tends to focus on the cheap compact car market whereas BMW doesn't.
They probably could justify the complexity and cost for most of their range.
Perhaps they will use it on the sports cars , and the extra costs involved would be charged for accordingly on those models.

Lean-burn? Another way to spell "burned exhaust valves"! The temp. rise will be high(er?)! Just a thought....
Then, there are emissions to consider ...with higher combustion temps, all this lean burn stuff screams higher NOx formation! If it won't pass emission specs...it ain't legal!

Ah, you're being realistic. I thought this thread was about 'Crackpot Ideas'?

DRW and Ted -

Is the 1992-1995 Honda Hatchback VX highway speed "lean burn" mode running dirty? Granted, if emissions standards were less stringent, it might just be "conforming to it's time", but I keep thinking that there are lots of "lean burn lurkers" out there that are emissions compliant and running fine.

:confused:

CarloSW2