M42 compression ratio?

[CraigG]

i dont actually know what i want to do to get more power(i need it.) go NA with throttlebodies, go turbo, or transplant(id rather not, but its easy.)

so whats the compression ratio of a standard M42? and what would be the easiest way of dropping the compression, are there pistons from another engine that would be suitable, or am i looking at custom forged items, (i know these would ultimatly be the best option, but i dont have a platinum credit card...)

so yea, compression ratio, and easiest way to drop it? what are the internals like? what kinda power would they withstand?

[e30_Turbo]

Ways to drop compression:

custom pistons
shorter rods
decomp plate
or a combination of stock rods/pistons from other lumps

I would think the M42 was quite high but I have no exact figures, TIM_S where are you?

[CraigG]

need to know the compression ratio, i was thinking about just running standard internals with either a large hotside so that it dont boost until high in the range(4k+) or setting up a boost controler to stop it boosting until 4k, as that would limit the dangers to the internals.

custom pistons, would allow me to get a fast spooling turbo(GTseries) and have good boost low down, meaning that it would loose the 'vtec' style power delivery of the engine atm. but they are a fair chunk of the proposed budget.

different pistons from another engine seems like the best way forward, i can get standard pistons for tuppence. but which ones to use? i dont want stupid low compression, somewhere around 9.5 would be ideal from changing the pistons, but as i said, i could get around changing the pistons by biulding the boost later in the range, depending on the comp ratio...?


so, anyone know the compression ratio?

[Omi]

10:1, unless I'm very much mistaken.

I'm about to restart the turbo project again, so if your engine is good and you decide to do a transplant, I'm interested in it!

Need to keep my car running while I build a new motor.

[tim_s]

yeah, 10:1! There's many ways of dropping the CR, depends what you want.
Still not got an engine Omi