RE: Compression ratio testing

[Terry Rudd]

I wonder how big the bore is on this engine - it's huge or the math is a bit dubious to me. A L20B capacity is 1972cc or 493cc per cylinder.   Take a L20B +40' which is all but 500cc per cylinder (it's around +7cc per 1mm per cylinder on L20B)   CR is chamber volume + cylinder volume then divided by chamber volume   (500 + 45)/45 = 12.1:1   OK, that's still up there, 98 octane is good for around 11:1 +-.5:1 depending on a lot of things i.e. chamber design (squish properties), cam specs (wild). This engine is in Avgas territory by the looks of things anyway.   regards Terry -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Rob P Sent: Friday, 29 November 2002 7:46 PM To: [EMAIL PROTECTED] Subject: Compression ratio testing While we're on the subject, here's an update on my L20B rally motor (as yet still not tested since purchased complete). I put number one piston to TDC and tilted the engine on a stand so that the sparkplug hole was facing directly up. Filling a 60cc syringe with oil, I then squirted it into the chamber and filled it to the top of the spark plug hole, fully covering the threads (accidently). It came to 45cc exactly, less if you remove the sparkplug volume. My mechanic buddy calculated a compression ratio "of 12.84 to one, let's call it 13:1" We all stood around grasping our beers, shaking our heads and looking suitably impressed. ;-P Does this sound right? (Flat top alloy pistons, head still within 3 mm of maximum shave) If so, do I need to run 101 racing fuel or will BP Ultimate 98 do to avoid pinging? Will a Bluebird series II/III fuel pump adequately feed the twin 45 Webers? I have a Holley Blue fuel regulator but am told a Malpassi rising rate regulator may be the go?   Any advice always greatly appreciated --membersozdat------------------------------------------------------- OZDAT Mailing List Please Note:- Send (un)subscribe requests to [EMAIL PROTECTED] Send submissions to [EMAIL PROTECTED] No unauthorised redistribution of this email http://www.ozdat.com/ozdatonline/index.htm http://www.ozdat.com/ozdatonline/listindex.html http://www.mail-archive.com/membersozdat@datascribe.com.au/ --------------------------------------------------------------------- --membersozdat------------------------------------------------------- OZDAT Mailing List Please Note:- Send (un)subscribe requests to [EMAIL PROTECTED] Send submissions to [EMAIL PROTECTED] No unauthorised redistribution of this email http://www.ozdat.com/ozdatonline/index.htm http://www.ozdat.com/ozdatonline/listindex.html http://www.mail-archive.com/membersozdat@datascribe.com.au/ ---------------------------------------------------------------------