Honda Civic 240DEX concept
 

I am new to hypermiling, this is my first post, and I haven't done any mods so far.

A few days ago, an idea came upon me to couple the engine of a Mercedes 240D onto the gearbox of my 2000 Civic EX. It seems ideal, they're both inline 4's, the Mercedes engine is powerful and runs with computer control, and might fit inside if turned 90 degrees to be mounted laterally.

It seemed like an even better idea when I compared the similar MPG's, despite the weight and final gear ratio differences (240D weighs in at 1.5 imperials tonnes with 4th gear at a ratio of one, and the EX is 1.25 tonnes with 5th gear at 0.7), so the Mercedes engine will require less effort to turn the wheels, and the wheels turn more per engine rotation.

The problem is that I'm not sure about this idea. Is the length difference between them too great to fit the OM616? Is it too wide to put in without ruining the cooling? What kind of extensive modifications would need to be made to the gearbox and engine mounts to allow it to be attached if the bay is large enough?

I know that this isn't the most sane idea, and might be impossible. If it works, it could push the miles per gallon into the 50's (sorry for thinking so small), but before we consider the resulting efficiency gains, I need to ask: Is this physically possible to do without completely changing the drive train of the Civic?

None of these questions are rhetorical, I'm genuinely asking if it's a feasible idea that could be done.

I'd also like to know if I put this in the right part of the forum.

From what little I could glean from the Internet, I got this: A little Mercedes diesel engine info I found.

I can't find much information on the engine dimensions. IMO you will have height clearance issues as most inline diesels are tall engines. Is it turbocharged? You will have have better efficiency and power with a turbo. Win-win right there :D

You will need custom motor mounts and a custom adapter plate in order to install the engine and hook up the transmission. The transmission should be fine with the diesel, as long as it is not abused.

It is possible to do this swap. However! Are you expecting a quick Return On Investment, or are you wanting a custom high-mpg car and don't care about ROI? 60 mpg would not be out of the question with your overdrive, less weight and better aerodynamics.

I'm going to move your thread to Ecomodding Central so it will get more views. We have many knowledgeable diesel folks around here who can chime in. When and if you start, you can start a build thread and later explain in DIY/How-to how to swap this motor in a Civic.

Best of luck!

Honda engines spin "backwards" compared to others. Using the Honda transmission won't work. A bigger and older engine might not be the right direction for economy either. A VW diesel engine and transmission might be a better fit in a Civic. But a Civic is capable of a lot more than 50 MPG without the hassle of swapping engines.

In addition to what others have said, the transmission from an EX isn't ideal, either, as it's relatively short compared with a DX or HX transmission. I'd love to see a diesel Civic though.

In the UK at least, the Civic was available with a diesel engine.Here's some information:
MG Rover forum

Another part of the project, or a separate project, that I had planned was to put in an HX transmission because of the higher gearing, but that's something for another time. What do you mean by relatively short?


Backwards? You mean counterclockwise instead of clockwise, I'm guessing. Why is that?

Also, I chose the OM616 due to its extreme and rugged reliability, something that isn't there as much for the VW engines.

Can one of those engines be shipped to the USA?

I meant the gearing.