Pistons for m20 Stroker

[zaq123]

so I just found out who bought the 85mm Mahle pistons I was trying to buy :hitler:

doesn't IE has more or they are out?

[ForcedFirebird]

The s54 has notches in the bottom of the cylinder bores in the block, and notches on the piston skirts to accommodate bob weights. The biggest trick in a short rod:stroke engine is to keep as close cylinder/piston boundary as possible, maximize the piston skirt. Side loads are high and rotational clearances get tighter. TDC dwell has become near non-existent. Now we are talking about stuffing that in the shorter m20 block with more primitive valve train.

[apostate]

...

[2mAn]

doesn't IE has more or they are out?

Im sure they have more, but the price is different when bought new from IE VS in the r3v classifieds. I just waited too long because I really am nowhere near close to actually building a 2.8L M20

[digger]

by my calc

pin is 22 mm
throat is 5.5 mm
rod 133 mm
CW R70.5 mm
throw 44.8 mm

then the clearance is 1.2 mm to the pin boss.

[bmwmaster81]

Thank you for calculation digger. Seems to be tighter than I expected but schould be enough.
The squish on oem m20 is also 1.2mm without Problems. I will check if the tolerances are right an when everything appears equal between the different cylinders I think it schould rotate free also unter high rpm.


Because of the long stroke I also wouldn't rev more than 6500 rpm.

[digger]

the calculation is relatively straight forward

CL = rod length - throw - CW - Pin/2 - throat

[digger]

im using 135mm rod and 46.9mm throw but 20mm pin to fit

[apostate]

...

[digger]

With the rhd intake, good head and appropriate cam you will peak closer to 7000

[bmwmaster81]

I got the pistons today ;D
Unfortunetly in the manuel they don't write how much bore clearance the pistons need
Do anyone have some information?

[digger]

What Pistons ? If you mean IE best call them

[zaq123]

I got the pistons today ;D
Unfortunetly in the manuel they don't write how much bore clearance the pistons need
Do anyone have some information?

IE/Mahle pistons? all clearances are in the booklet that should've came with the kit:
Piston-to-bore Clearance: .002 inches over the coating, measured at 7mm from bottom of skirts; Drag/Endurance racing applications : additional 0.001-0.003"
valve to piston minimums: IN- 0.080";EX-0.100"; radially-0.050"
piston to head: 0.040"- steel rods; 0.060"-aluminum rods

[bradnic]

Pics?

[SkiFree]

IE/Mahle pistons? all clearances are in the booklet that should've came with the kit:
Piston-to-bore Clearance: .002 inches over the coating, measured at 7mm from bottom of skirts; Drag/Endurance racing applications : additional 0.001-0.003"
valve to piston minimums: IN- 0.080";EX-0.100"; radially-0.050"
piston to head: 0.040"- steel rods; 0.060"-aluminum rods

This.

Also, for posterity, I scanned the pamphlet and included other useful information in this google docs file. You should be able to download what you need from here.

https://drive.google.com/open?id=1aRSPzAuGtGjvpHVJJZI20A1fwGlRhHVS