FI Forged pistons from other cars for various bores: M42/M44/overbore

[nuvolarossa]

Hi, I'm searching to make a list for what pistons can be used from other cars, for use with turbo or supercharger on our M4x, instead of buying expensive custom pistons.

the list will be something like this.

 
 
1) OEM M42 block, 84mm
 
a) from car xxx model yyy
PISTONS: bore xx
compression height:
pin diameter:
RODS:
 
2) OEM M44 block, 85mm
 
a) from car xxx model yyy
PISTONS: bore xx
compression height:
pin diameter:
RODS:
 
3) block overbored to 86mm
 
a) from car xxx model yyy
PISTONS: bore xx
compression height:
pin diameter:
RODS:

So clear from you mind the template of the list upper. I'll upgrade it when more info will come.

Let's start with options for 86mm bored blocks:

OPTION #1 FOR 86mm BORED BLOCK: AFTERMARKET FORGED PISTONS FOR OPEL C20LET ENGINE
Ludiagsm (from m42club.com) use 86mm Wossner forged pistons for C20LET, with a 86mm bore block. They have 30,43mm of compression height, and they use a 21x13x55.5mm pin . So this is his setup:

PISTONS: 86mm bore from C20LET
compression height: 30,43mm
pin: 21x13x55,5mm
RODS: 138,8mm from honda K20A, 51,1mm big diameter

But he grinds the engine block 2mm, then he has 1mm clearence between up site of pistons to the top level of engine block. He says that the engine with this setup has a cr of 7,9:1.

So, for not grinding the block, we need
-a piston with 2mm more compression height for fit with that honda short rod.
- or a rod 2mm more lenght with same other specs as honda one.
It's right this theory?

OPTION #2 FOR 86mm BORED BLOCK: OEM FORGED PISTONS FOR OPEL C20XE ENGINE

PISTONS: 86mm bore from C20XE
compression height: 30,43mm
[COLOR=#ff0000]pin: oem opel 21mm

OPTION #3 FOR 86mm BORED BLOCK: AFTERMARKET FORGED PISTONS FOR TOYOTA MR2 TURBO 3s-gte ENGINE
PISTONS: 86mm bore from 3S-GTE
[COLOR=#000000]compression height: 35mm
pin: 22mmX14mmx63mm
[COLOR=#ff0000]RODS: NISSAN SR20DET, 136.25mm, 22mm pin diameter
still lot to check about option #3...

this is what I've found this night... here now is night

if you find some compatible parts that are oem forged it's better because they can be found used, and they will cost nothing compared to aftermarket brand parts.


I want to find three rod-piston combos
1)that fitted on m42 (stock bored) give a compression ratio near 8:1
2)that fitted on m42 (bored to 86mm) give a compression ratio near 8:1
3)that fitted on m44 (85mm bore) give a CR of 8:1.

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EDIT: the E30 and e36 m42 pistons are differents! same bore, same compression height, but different combustion chamber volume...

all sizes are in mm.
KH=compression height
VT=valve recess depth
MT=combustion chamber depth
Mdiam=combustion chamber diameter
GL= total lenght
here are 318is E30 piston specs:

here are 318is E36 last M42 piston specs:

here are 318is M44 piston specs:

I need to know the head combustion chamber volume on m42 and m44, please
I know that 20% of combustion chamber volume is on the piston, the other 80% in in the head, but other than that I know nothing.