Kit P&C Mahle RSR2.8 for stroke 66mm...C.R.=?

[dan67]

Hallo!
for my engine projet I was offered MAHLE kit "RSR2.8" bore 92 mm with CR and CR 1.10.5. question: this kit Is not specific ONLY for "long stroke" 70,4? its adaptable with 66mm stroke?
thanks all!
danilo
italy

(DATA: 66 stroke-2.7heads-7R case-MFI-E cams)

[YTNUKLR]

I like! They make a GREAT engine with a 66mm crankshaft. 2.63L short-stroke.

"10.3:1" was advertised with the RSR heads, which had bigger head volume than 2.7 engines

On a 2.4/2.7 70.4mm crankshaft with 2.7 heads (usually about 76cc chamber volume), compression is probably around 12:1

With a 2.0/2.2 crankshaft it drops to about 11:1, maybe even a little higher..no other modifications needed with a 2.7 case.

VERY snappy! Twin spark plugs are a MUST

[gestalt1]

am i missing something here? i've heard this before and am wondering how the crankshaft changes the CR. isn't the deck height the same? are you using the 70.4 rods on the 66mm crank? i would think if the 2.0-2.2 rods on the 66mm crank would mean the piston does not extend into the cylinder any more/less, the stroke into the case would be less. is the difference that pistons meant for the 70.4 crank have different pin position than pistons for 66mm cranks?

[ajwans]

Longer stroke means a larger volume to compress, hence higher compression given the same
clearance at TDC.

andy

[Henry Schmidt]

[gestalt1]

i get it, compression RATIO - thats the key. i should have looked at the formula. thanks!

[Steve@Rennsport]

Originally Posted by YTNUKLR

I like! They make a GREAT engine with a 66mm crankshaft. 2.63L short-stroke.

"10.3:1" was advertised with the RSR heads, which had bigger head volume than 2.7 engines

On a 2.4/2.7 70.4mm crankshaft with 2.7 heads (usually about 76cc chamber volume), compression is probably around 12:1

With a 2.0/2.2 crankshaft it drops to about 11:1, maybe even a little higher..no other modifications needed with a 2.7 case.

VERY snappy! Twin spark plugs are a MUST

Hi Scott,

The 92mm RSR P/C's make around 11.5-11.7:1 with the 70.4mm crank using the normal 2.2-2.4-2.7 heads.

With a 66mm crank and the same heads, they make around 10.5-10.6:1.

As you wisely said, twin-plugs are a must.

[blue72s]

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