World's Only Diesel-Electric Honda Insight

Jake Staub writes "Just replaced the gasoline engine in a Honda Insight with a Diesel engine. On a 3,000 mile cross-country shakedown journey the car averaged 92mpg over 1,800 miles. Around a very hilly town in Northwest Washington, the car is averaging 78mpg. These mileage averages are without the electric side of the vehicle fully functional. With a bit more tinkering on the electric side and through a slight gearing change through tire size, it is anticipated that the car will likely average 100mpg. The build for the car has been documented on the web site and is as close to open source as my time allows. The car was built by two guys in a garage in Southern Maryland. If we can do it I don't see any reason why major auto manufacturers can't do it since we used their parts."

Comments

Can't capture the same benefit twice

[redelm]

The main reason gasoline hybrids get better mileage than direct-coupled engines is that the gasoline engine is not forced to operate at inefficient points on its' BSFC map (near closed throttle). The engine only runs when needed, and then it runs near its' BEP (Best efficiency point), or occasionally at maximum power which also has decent efficiency. It is not forced to idle and off-idle conditions where the pumping losses are horrible and efficiency s#x (5x fuel for same marginal power).

Diesel engines have entirely different BSFC maps, and do not suffer the same pumping losses (vacuum across throttle plate). Their drop off at idle is _much_ lower than for gasoline engines, so they're great in city-wide European traffic jams. Diesel fuel also is ~15% denser (more heat per gallon) and the higher compression ratio is about 5% more theoretically efficient.

But a diesel hybrid does not have much to gain by hybridization. The BSFC map is much flatter, and the engine restarting power & wear is considerably higher.

Re:Because ..

[kick6]

For various reasons the industry in the US has shunned diesel for private vehicles. That has to change before any headway can be made.

I disagree. Diesel is a BYPRODUCT of gasoline refining. A barrel of oil (42 US gallons), when refined, yields about 19.5 gallons of gasoline and about 9 gallons of diesel. Part of the reason diesel prices got so expensive last summer is because there was no supply. Nobody was buying the expensive gasoline that accounts for more than half of all refined goods, but the big trucks and ships needed the diesel that nobody wanted to make because they couldn't sell the gasoline. Starting to see the vicious cycle? Therefore, if a bunch of people started driving diesel cars, you'd see last summer's diesel prices becoming a bit more permanent. Leave diesel to work vehicles. Cars should run on gasoline. The headway needs to be made in technologies like gasoline direct injection.

Re:Diesel is so obviously better for hybrids

[d3vi1]

The irony is that hybrid diesels would be perfect, but nobody takes the concept to it's true potential.
Diesel electric all the way, like in train engines. A Diesel likes to have a constant RPM at it's peak performance value. Imagine connecting an alternator directly to the engine and giving up the inefficient gear system. Imagine a Diesel engine that is always at it's peak performance RPM, even when there's barely any electrical load on it. That car would be a rocket that goes for free (or almost free). It's also pretty easy to build if you have 2 things:
1) 1x 150kW alternator (it's the right amount) that also fits under the hood along with the engine.
2) 4x 40kW electric engines that you connect directly to the drive shaft (and should also fit in there somewhere).
As far as I know a 150kW alternator is very big (about as big as the engine itself) and the 40kW engines are also huge, but at least in theory this would be by far the best way to bring the top possible performance of an engine to the tarmac. Electricity is the best way to transfer energy between two points and a constant RPM diesel is the most efficient and performant diesel out there.