There was also the Honda Civic VX that got some pretty insane fuel economy just off petro, about 45mpg.
Question: have you have any luck with carb-mods?
Discussion
There is some complexity when engine efficiency is being considered. Gasoline engines suffer from volumetric inefficiency, that is to say that for spark ignition to happen the air and fuel has to be in the correct stoichiometric ratio for the full volume of the cylinder. If a carburetor modification moves the ratio outside of the flammability range the engine won’t run. Diesel engines are the most thermodynamically efficient internal combustion engines in widespread use because they draw in air alone and inject only the fuel required to produce the requested power, no volumetric inefficiency. The Prius uses an Atkinson cycle gasoline engine that increases efficiency by elongating the piston stroke to fully utilize combustion pressure at the cost of power to weight ratio, still an equivalent displacement turbo diesel would be much more efficient.
That's a good rundown, thank you.
The Honda Civic VX from 92-95 introduced a type of valve lifting that created a vortex with the air and fuel as it entered the combustion chamber. They explained that it was a clever way to achieve more efficient fuel atomization. I remember a mention of the droplet particle size; the smaller, the more complete fuel burnoff.
Quick question: what kind of diesel van would you say is the most efficient and reliable?
Regarding the diesel van, what country are you considering?
USA.
This is complex because of US emissions law. The big three use truck engines in their vans. This is not ideal because of the large displacement, unnecessary unless towing heavy trailers. The import options are technically ideal, but parts and service can be an issue. I would choose the Mercedes sprinter, parts are expensive but available, rarely needed. A 2006 or older Duramax from GMC can achieve 20 mpg and offer incredible durability. I’d avoid Cummins or the Ford Navistar engines unless you’re considering a 7.3 or a 12V Cummins.
That's a good run-down, thanks for the info!