austin25uk wrote:righty ho.
im going to build myself a 2 litre M10 turbo
i will be aquiring myself a e30 M10 318i some 2002 pistons and 2 litre crank.
is it possible to build the engine with out removing the head, i will be taking the head of eventually and fitting a de comp plate ready for the turbo but would rather not have to do it twice and i need to run the car NA for a while. turbo kit will come when i can afford the bugger!
im thinking it could be a pain in the ass getting piston ring compressors to sit on the inside though to get the pistons into place??
would also need to borrow some ring compressors of somebody when that time comes but thats a problem to worry about later on
any hints and tips would be great and suggestions.
oh and the long term plan is to build a 250 hp turbo engine with 50 nitrous so suggestions on best parts to achieve this power safley please. i like cheap options
How much compression does the stock euro 1.8 m10 run?
You cannot rebuild the motor with the head on. It just doesn't make sense, for one, but you hit the nail on the head, a ring compressor won't work well from the bottom. If you're serious about making good power and having a good rebuilt motor, you need to go through the head, do a valve job, and at a minimum you'll need to hone the bores for new rings. This of course assumes the cylinders don't need rebored. If they are ridged significantly, they WILL need rebored in which case you will need new pistons anyway. At that point, you might as well spring for 90mm or 91mm forged pistons to build a stout 2.1L m10, and I'd aim for something in the 8.5:1 compression ratio.
A thicker head gasket is not a great way to lower compression because you loose squish. Squish is the area of the combustion chamber where the piston comes very close to the flat portion of the cylinder head. The closer you come to the head (without touching), the better, because this squish are creates turbulence within the chamber. This turbulence greatly increases combustion efficiency, maximized power and fuel economy. A thicker head gasket can wreak havoc on combustion efficiency, cause tuning issues, heat issues, etc and can actually induce knock due to the loss in efficiency. Go to bimmerforums and look up an MLS head gasket thread by boomerdj. After swapping in a thicker MLS gasket his engine ran hot and it would spark knock every time it would boost. He was running EDIS and no amount of ignition tuning could tune it out. We chalked it up to the thick head gasket.
For a good cheap build (like mine), your cheapest option is a simple hone job (again, this depends on the condition of your block), a stock rebuild with rings, bearings, and at a minimum a valve job on the head, and use flat top pistons from a 2.0L m10. The flat tops are common and cheap here in the states, I believe the 320/4 might have also used them over your side of the pond. This combo (along with the 1.8 head) will yeild a 7.9:1 or 8:1 compression ratio. Assuming a good tune (no detonation), the stock head gasket will hold about 14-15 lbs of boost, stock pistons will hold about 15 lbs before you break a ring land.
On a well designed and well matched system with a properly sized turbo, some head work (port/polish) and a mild cam (I'm running a 280), you CAN make around 250 bhp with stock internals. If you rebuild with forged pistons, o-ring the block using a stock head gasket (or use an MLS gasket), and run ARP head studs, the sky is the limit on how much boost you can run.
Just remember, sizing the turbo properly is going to depend on how much power you want to make as much as how big your motor is. For more info on sizing a turbo, check out my website and also the turbo section of the FAQ thread on bimmerforums. I've written up a ton of stuff that will be helpful, and I also have an excel spreadsheet that you can download to help you calculate how much airflow your motor will pump at a certain boost level which is critical for sizing a turbo.
If you don't care about the math, the best turbo you can run for your power goal is the GT28RS. If that's too expensive for you (it is for me), the T25 from an S13 nissan silvia has been awesome on my car.
