E30 Zone

Hiya

Ive decided to go down the m20b28 route for my e30 turbo project. Aim is around 450bhp

At the moment, i have a m20b25 engine, m52b28 crank from a z3, and m20b20 engine in the car at the moment.

What compression ratio should i expect from the m52b28 crank, with b20 rods, and b25 pistons? (which mls headgasket do i need) - i dont intend to deck the block.

I intend to get the m20b25 head welded up, use an ebay manifold and hx35 - which BOV is recomended, and also can anyone recommend a company to do the head welding?

Im near heathrow if that helps.

Thanks

Q

http://e28-535i.com/upload/M20_CR_Calcs.xls may help some.

dont forget to take into account that the piston will sit 0.5mm aprox lower down the cylinder bore.

gromgsxr wrote:http://e28-535i.com/upload/M20_CR_Calcs.xls may help some.

dont forget to take into account that the piston will sit 0.5mm aprox lower down the cylinder bore.

thanks for the link

just making sure im using it right, i take it that i need to be looking at the 2nd row (8.8:1 standard)

then changing the head gasket thickness to 0.07, and adding 0.02(inches) to make up for the 0.5mm block difference, i get a Cr ratio of 8.37

Is that an ideal CR for boosting, or should i go lower to 7.55 without and machining of the block!

Mind you, these values will raise a bit as there is no compensation for the head skim. Will i need a vernier pulley?

gromgsxr wrote:http://e28-535i.com/upload/M20_CR_Calcs.xls may help some.

dont forget to take into account that the piston will sit 0.5mm aprox lower down the cylinder bore.

Useful excel

dont forget to change the engine cc size as well up to 2793cc as will change the compression as well

gromgsxr wrote:dont forget to change the engine cc size as well up to 2793cc as will change the compression as well

where do i do that?

edit - i didnt realise you can change that value - makes more sense now.

thanks

9.3:1 without being decked 0.5 mm this is nominal and fine for a turbo engine

I worked it out to be 8:1 with 0.14 gasket