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01/24/2007: "and from left field comes the DIY diesel hybrid"

After so much pondering about commuting to Toronto, one of the lines of thought I had been pursuing was - surprise, surprise - what kind of vehicle would be best for commuting such a distance. Should I get a tiny car with an equally tiny gas engine? What about a used hybrid, either a Honda Insight or a Toyota Prius? Then again, diesels seem to be very good for long-distance driving - maybe a used VW with a TDI engine, or even a low-end smart fortwo, depending on the price. (For the record, I would have gone diesel.)

As my mind is wont to do, it came up with an idea that is as equally fascinating and promising as it is out of my ability to actually implement it: a do-it-yourself diesel hybrid.

Some of you may wonder why a diesel hybrid would be such a big deal. Well, right now there are two (economically feasible) competing strategies (that have infrastructure in place) for saving fuel. One is the hybrid, which mates an electric motor with a gasoline engine. This works wonderfully for in-city driving, as evidenced by mileage ratings that are actually higher for city driving than they are for highway. Of course, the highway mileage is still really good (really, really good) compared to "regular" cars. On the other side we have diesel engines. They are able to extract more energy out of their fuel than a gasoline engine can, and thus they use less fuel to travel the same distance (all else being equal).

You'd think, then, that mating the two together would provide a superior fuel-savings, right? Well, it would... but price gets in the way. Hybrids add an electric motor, a battery pack, and lots and lots of electronics to a vehicle. Pricey. A diesel engine commands a price premium over gas engines (for various reasons I won't get into here, partly because I'm not well-versed in the design differences). So if you put the two together, you'd have a car that can go a LONG way on little fuel, but it likely won't sell because it would simply be too expensive as compared to other vehicles of similar size and capacity. And that's where the industry sits today. It'll happen eventually (when hybrids are being produced in the millions, instead of the 10's of thousands, and diesels become even cleaner-burning), but not today.

Unless, of course, you're a mechanically-inclined tinkerer with some electronics ability.

Here's my idea: start with a Honda Insight hybrid. It was the first hybrid to market, beating the Toyota Prius by a year. The Insight is pretty much unknown, however, because it is a two-seater (whereas the Prius can seat four) and have very little cargo capacity (500 lbs total, including the driver and passenger). It uses a 1.0L 3-cylinder engine to power itself, complemented wth what Honda calls an Integrated Motor Assist system, the electric motor. All said, it's supposed to give you 3.3L/100km (86 mpg) on the highway. Nice.

A much newer-to-Canada vehicle is the smart fortwo (smart doesn't capitalize their names, for some reason). It's also a two-seater (although Europe gets four-seaters as well), and has appeared on our shores with only a diesel engine. It's an 0.8L 3-cylinder turbodiesel, and delivers 3.8L/100km (75 mpg) on the highway. Nice.

You see where I'm going yet? Yup, you got it. Take the smart fortwo engine, and replace Honda's gasoline engine with it. You will likely need to make some electronic adjustments (if not some full-out Frankensteinesque cobbling) to get everything to play nicely together, but you should then have your very own diesel hybrid with mileage figures superior to just about anything on the road. What's even better, with a diesel you'd be able to run biodiesel, further reducing your need for imported oil-based fuels, and if you really wanted to tinker you could even set it up to run on waste vegetable oil (aka WVO), which you source FREE from your local restaurant's deep fryer.

Drawbacks? You need to buy a smart fortwo engine (but you get to sell a Honda Insight engine). The IMA system also works as an engine vibration cancellation device - putting a different engine on there may not jive well with what's been programmed, and you might be in for a DIY ultrasonic butt massage. Warranty? Hah! Funny. And when it comes right down to it, even if you get a 20% increase in fuel economy, saving 20% of a figure that is already really good isn't going to save you all that much. The stock Insight gets 3.3L/100km on the highway. If you get down to 80% of that with your home-grown diesel hybrid, you'd be getting 2.6L/100km. So for every trip to Toronto and back you'd save yourself 1.2L of fuel. Even at $1.00/L, you're not going to get a very good return on investment. This would be done for the thrill of doing it, and/or the bragging rights, not for any economic benefit.

Having said that, I should point out that diesel hybrids are still very much a good idea. While it doesn't necessarily make sense to marry a diesel with a hybrid drivetrain on the thrifty end of the fuel efficiency spectrum, doing so for a standard vehicle, or even much larger trucks, would provide enormous benefit. Simply put, the more fuel you use, the more benefit a diesel hybrid provides. Big rigs are lucky if they can get 55L/100km (5 mpg). If you improve that by 20% up to 44L/100km (6.5 mpg) suddenly they're saving 11L of fuel for pretty much every hour they're on the road - likely over 100L of fuel a day! Those savings add up quickly.

In any case, there is my interesting, plausible, highly impractical idea that is outside of my ability to implement it; the Honda-smart Insight diesel hybrid. Please go right ahead and do it with my blessing, just send me a picture if you do.

Replies: 6 Comments

on Wednesday, January 24th, Violet said

Another consideration is that a diesel vehicle can be easily (read: with your own two hands and some tools) converted to use biofuel when/if it becomes readily available or if you feel the urge to manufacture it yourself.

on Thursday, January 25th, Mike said

I thot of this a while ago (nyah! nyah!).

Those hybrid engines are really integrated tho - not like an electric motor just bolted on the side of a piston engine.

I would think an all-electric vehicle with a diesel-pusher for extended range would be better for you. (A diesel-pusher is the front-end of a VW pushing an electric vehicle through a trailer hitch, via remote control). Then you could unhitch the pusher for in-town trips. (

on Thursday, January 25th, mr.ska said

Yes, I've seen the EV pusher trailers before. Neat stuff for sure. But if you're looking at lots of highway driving, wouldn't it just make sense to start with a robust chassis and put an electric drivetrain on whichever end isn't being used by the ICE? A parallel non-integrated hybrid, if you will.

on Thursday, January 25th, mike said

The nice thing about the pusher is that when you don't need the ICE, it can be left behind and not weigh down the EV.

I spose if you have the pusher linked up 90% of the time anyway, you might as well...ok, yeah, I'd say adding electric drive train (with regen braking?) to the other axle is a good idea. And you get 4WD too.

on Thursday, January 25th, roberthahn said

I have no idea what you have in mind when you say that a hybrid vehicle is 'economically feasible', but I've seen several accounts that say that compared to a similarly priced gas car, the hybrid is significantly more expensive to run over the lifetime of the vehicle. I assume you already know this, which leaves me wondering what the heck you actually meant.

on Friday, January 26th, mr.ska said

Actually, the lifetime cost of a hybrid was restudied, and shown to pay for itself (in terms of premium over a non-hybrid). They are not more expensive to run (less fuel), just more expensive to purchase initially. The studies looked at whether that premium was recouped through fuel savings, and apparently it is (within a reasonable time).

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