There's an interesting article on Ars Technica today about engine improvements for increased efficiency:

The road ahead: How we’ll get to 54.5 mpg by 2025 | Ars Technica

In particular, I was interested in homogeneous charge compression ignition and how it could be implemented (if at all) in a rotary engine like the 16X prototype.

 

Good post!

 

Mazda's been working on HCCI for some time as part of their Skyactiv research!

 

A completely HCCI engine has a long way to go before making it into production. It would require gasoline engines to be built to the same strength standards as diesels which would add a lot of weight. HCCI causes a VERY fast combustion event to the point that it looks and sounds similiar to knocking. GM has worked on it a lot and is mainly wanting it for low load/cruising to avoid having to make the engines heavier and by mixing in a lot of EGR so they can slow down the combustion event to make it easier on the engine. Also the exhaust is much colder (hence the almost 0 nox even before exhaust treatment) which makes it more difficult to turbo charge. They have had trouble getting to rich mixtures as well, basically having to stay above 2 lambda which means they'll have just as hard of a time making peak power as diesels do. Gasoline does a very good job of allowing you to burn a lot of fuel for the associated amount of air in spark ignited engines.

Small displacement with turbo, idle stop, and cylinder deactivation are the main trends beyond just normal increases in efficiency. Gasoline engines do a great job of making power but the throttle and pumping loses are what kill them from having the same cruising and low load efficiency as diesels. Though as diesels keep dropping in compression ratio and gasoline engines rising, they're pretty much ready to meet in the middle and start using the same ratios.

 

meanwhile, in the 70's...

 

nice!

 

Meanwhile, in my 13 year old honda:

 

I LOVED our old CRX HF! 55mpg all day long.

 

I'm calling you out on this one, only because you beat me to this thread. All you did was reset the FCD and then drive a short and ideal distance of 4 miles, probably slightly downhill.

If you are going to post Insight mileage pictures, then at least post them over some reasonable distance.





I'm also not impressed by 54.5 MPG. That's about the minimum mileage you get by lead footing a 2000 Insight around without a single care for efficiency. Whomever wrote the article didn't do much research.

Auto start stop? Insight has always had it and I have never found it easy in practice to stall the engine, quite the opposite actually. You can just dump the clutch and the motor powers through.

Lean burn stratified charge engine with NOX absorbing catalyst? Yep, Insight has it. BOSCH even had to build a special wideband O2 sensor to cope.

Homogeneous charge compression ignition? That is a backwards step compared to spark ignited stratified charge. Gasoline is a far more temperamental fuel in compression ignition than diesel, and manufacturers would need to build blocks to handle the high compression and possibility of frequent detonation.



You know what I think would improve fuel efficiency about 20% - 30% across the board? All new cars should have a realtime mileage and average mileage display, calibrated not in MPG or L/100KM but in "dollars per mile" or "dollars per 100 KM". The fuel pump would transmit the current cost of fuel to the ECU/ECM/PCM/thingie during fillup, and the gauge would automatically update. Not even remotely technically difficult. Maybe a little animation that shows dollar signs leaving the tailpipe when drivers are driving inefficiently.

 

haha, there would be little fort Knox's or oil rigs coming out of my FD.


This is beginning to make me wonder what Honda has up their sleeve.
1986 CRX HF +13 years = Insight.
Insight + 13 years = ??

 

oh, my picture is misleading, but still shows what is possible in ideal conditions. I have one with worse MPG (I think 126) and at even higher speed over a longer distance (8 or 9 miles) but it was blurry.

I was driving in the mountains and going downhill for what felt like forever, and following in an SUV's wake.

I've never managed MPG in the 100's for more than 30 miles before killing the battery or having something else less than ideal happen. I did get 82mpg on my last roundtrip to london, though.

My car is far from optimal, it still runs rough in lean burn sometimes and my aero currently leaves a lot to be desired, between my bent hood and my completely missing undertrays.

I agree completely that real time fuel economy information is the #1 tool to get better MPG. Sometimes it's like a game for me. But usually I just drive it like I stole it and get tanks in the 60's or 70's. I've put almost 30,000km on the car since april. 20,000 more or so and it paid for itself.

 

2013 Honda CR-Z is a greener shade of purple

At a glance, it's just a worse insight.

In reality, it gets quite good milage (not as good as the insight but not bad) and has twice as much power. Too bad nobody is buying them. And I still think they put the engine in the wrong end.

 

As a former CRX owner, i was completely let down by that car.

 

Our 99 Saturn SL2 could get 55mpg round trip to Vancouver - and speeds on the Coquihalla are often sustained 130-140kmh cruising. A reasonably efficient motor in a chassis weighing about the same as an NB Miata made for a reasonably spritely and agile car, also - although it didn't do 55mpg stock, that was after I swapped a SL1 transmission, with taller 4th and 5th (made it quieter at 130 than it had been at 115 before - the SL2 box was a short ratio box had the car buzzing at 3200 rpm at 120).