Not that this is a metro. .. but it is putting a 1.6 vw engine in a car that was never intended to run it. Lots of good information
VWvortex Forums: 1985 vw diesel swap into honda crx
I'm actually planning a similar project with a 91 civic hatchback. Already have the cars just sorting out a injector pump problem and I'll be up and running. What I've discovered is that vw engine/transmission is rather long... like 40" or close. I'll actually have to notch out part of the civic body to fit the transmission. I don't know how the engine bay of the metro compares but If it's a close fit in a civic it might be extensive mods in a metro. Also when your deciding what engine to put in your car you have to forget some of the preconceptions developed from driving gas cars. First off is just because it has a smaller displacement doesn't mean it's more efficient. Take for instance the 1.6 TD compared to the 1.9 TDI. Even though the 1.6 is a smaller engine it's nearly 20% less efficient than the 1.9, all because of a better engine design. A really good comparison to make when choosing an engine is look for the g/kwh (grams of fuel / kilowatt hour of work) measurement. the lower the number the more efficient the engine. Anyways hope this information helps.