Can you convert a gas engine into a diesel?

Answer 1

It would definitely not be possible to convert a gas engine into a diesel engine because the cylinder block and head would not be strong enough. A diesel engine needs a much higher compression ratio than a gas engine, which means the gas engine's cylinder block and cylinder head would probably explode under the higher pressure.

You would have to change so many things:

* the crankshaft, to get a longer piston stroke, because the compression ratio for gas is much lower than for diesel;

* the connecting rods and pistons * the cylinder head and camshaft to get the right valves and holes for diesel fuel injectors instead of spark plugs

* the fuel injectors and fuel pump - and maybe the tank too, to get the right vents and filler cap for diesel instead of gas * the exhaust system to get the right catalytic converter for diesel * the gears in the gearbox to get the right gear ratios to suit a diesel engine * diesel does not use any spark plugs so you would have be sure to use a safe method to disable the high voltage ignition system (which supplies sparks for gas ignition) and replace it by the right kind of electronic engine management unit to control the diesel fuel injectors * etc. In short, it would not make sense to try to do it from a cost point of view. You could perhaps buy a reconditioned diesel engine made to go in the same model of car, but, unless you could fit it yourself along with all the other bits and pieces, it would be far cheaper just to buy a secondhand diesel model of your vehicle and sell your present gas model.

Answer 2

It would be better to start with a small diesel engine. Although they have some similarities and both work on the four stroke (Otto) cycle, there are too many technical differences. A diesel engine works at higher pressure (compression ratio). You will need to throw away the carburettor and add injectors and some sort of timing system, to inject the fuel at high pressure, at the right time.
Starting with a diesel engine, it will already run on bio fuel. You only need tweeks to the timing and fuel filtering.