Same engine, different capacities

daveharnett

As a theoretical exercise, what would it take to turn a 523i into a 530i? Same block, same bore. Not actually thinking about doing it, just wondering what the differences are, and whether the cheaper variant is actually cheaper to make.

Obviously the crank would need to provide a longer stroke, and the ecu would be mapped differently.

Would the length of the conrods need to change?
I imagine the bore being the same size means the valves are the same size?
Different timings (cams)?
Different manifolds?
Uprated injectors, waterpump, transmission?

Cheers

shamwari

I'm not a massive expert on this, but I am pretty certain that if the block and bore are the same, the only way to alter the capacity is with the stroke. That would imply differnent conrods, crankshaft, and probably pistons. The ancillaries around the engine, the fuel maps and the running parameters would need adjustment to take account of the increased capacity.

Owen

There's a kit to do this for the R53 Cooper S, it increases the displacement from 1.6 to 2 litres by putting in a different sump/crank/conrods/pistons/injectors/fuelling map, but essentially it's all done with lengthening the stroke.

daveharnett

Cheers lads, just realised a while ago that the conrods would have to be shorter. Hadn't thought about the sump either.
Still can't figure out why the valves would have to change though. Different rocker arm to let the valves open a little longer?

Oblomov

If you want to check engine dimensions, bore/stroke etc... try: http://www.ultimatespecs.com/