Detonation occurs in the combustion chamber, opposite the spark plug. As the flame front burns across the chamber, heat & pressure builds up until the remaining gas explodes. With higher compression, you already have more stored heat in the charge, making detonation more likely. Higher octane gas burns slower than lower octane gas, reducing the pressure & heat. This allows you to run higher compression. Timing can also help because reducing spark advance delays when the spark starts & puts the piston further down (lower pressure) when the flame front is moving across the head.
Compression ratio is important but head design is just as important. Chrylser's Hemi engine runs higher compression because of its domed combustion chamber & centered spark plug. The design has a very short flame front because it travels from the center out. A wedge design can't come close because the flame has to travel from one side to the other (twice the distance), giving more time for detonation. Thanks, Tom Hargrave www.kegkits.com 256-656-1924 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mike Canfield Sent: Friday, January 05, 2007 7:07 AM To: Mercedes Discussion List Subject: Re: [MBZ] compression ratio 300SL Compression ratio is the biggest factor in octane requirement......Higher compression = more chance of preignition and dictates use of higher octane fuel........ Ask any performance engine builder if an engine with higher than 10:1 compression will require high octane to keep preignition to a minimum. Timing is the next most relevant factor. Mike ----- Original Message ----- From: "TimothyPilgrim" <[EMAIL PROTECTED]> To: <mercedes@okiebenz.com> Sent: Thursday, January 04, 2007 11:34 PM Subject: Re: [MBZ] compression ratio 300SL > Funny, my motorcycle (1999 Honda CBR1100XX) has a ratio of 11:1 and it > runs on RUG-87. It also Compression ratio can't be the only factor in > determining octane rating required. > > http://www.motorcycle.com/mo/mccompare/97opensb/honda.html > > :) > > Tim > 1982 300TD > 1991 300TE 4Matic > > ---------------------------------------------------------------------------- ----------- > Date: Thu, 4 Jan 2007 17:55:39 -0500 > From: "Mike Canfield" <[EMAIL PROTECTED]> > Subject: Re: [MBZ] compression ratio 300SL > > That's what I was looking for.......Compression ratio that high most > certainly requires high test. > > ----- Original Message ----- > From: <[EMAIL PROTECTED]> > >> If thats the 300 SL I'm thinking about its 10.5:1 > > _______________________________________ > http://www.okiebenz.com > For new parts see official list sponsor: http://www.buymbparts.com/ > For used parts email [EMAIL PROTECTED] > > To Unsubscribe or change delivery options go to: > http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
