HELP WITH COMP RATIO

RodPenrose Insano Dub Head

792 posts · joined Apr 2005 · 4 Jul 2012, 6:59 pm

#911129

I am going to build another engine for my circuit car to use at Valla this year and would like to know how much compression you have used with the 98 octane fuel . I have some exotic fuel , but I want to stay with the V power as the fuel . I will be using a new set of Comp Eliminator heads that were the last set of heads ever ported by the late Dean Lowrey . These have 43.5cc in the chambers and I would like to run around .040/.050 deck height . I have used 11.90:1 before in a drag racing engine and it was pinging as I drove it up the return road . Please let me hear your options , ROD.

More boost + More fuel = More power
1968 Beetle fastest run 8.96 sec @ 161 mph 4th Nov. 2001
2010 New Beetle 8.12 sec on 8th march 2014
http://www.rodpenroseracing.com.au

colin Fahrvergnugen

984 posts · joined Mar 2007 · 4 Jul 2012, 7:24 pm

#911132

My little 1916cc hillclimber was set at 11.3-1 and never pinged.
I was using 98octane BP Ultimate.
If your using a long duration cam it will bleed a little comp out. Also backing the timing down will help.
Thanks for the pistons you supplied Larry.👍

Cheers Col

Craig Torrens 6 times Australian, 7 times State Hillclimb Class Champion

8,040 posts · joined Jan 2003 · 4 Jul 2012, 8:51 pm

#911144

yep, depends on the cam you're using 👍

like Colin, I've run low 11's on 98 without pinging.

BiX Veteran Volks Folk

2,499 posts · joined Sep 2002 · 5 Jul 2012, 10:37 am

#911208

Mine runs low 11 on 98 octane. Flush the tank normally every few monhts if it hasn't been driven to keep it fresh.

I have no sympathy for my car, only the wallet that pays for it!
Go hard or go home!!!!

Sides Veteran Volks Folk

2,220 posts · joined May 2007 · 5 Jul 2012, 11:00 am

#911212

My 1915 with 044's am running 11:1 with an FK87 - no worries at all on Caltex 98.

👍

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Craig Torrens 6 times Australian, 7 times State Hillclimb Class Champion

8,040 posts · joined Jan 2003 · 5 Jul 2012, 11:54 am

#911214

BiX wrote:Mine runs low 11 on 98 octane. Flush the tank normally every few monhts if it hasn't been driven to keep it fresh.

Good point, fuel octane drops off after about 3-4 weeks in the tank.

RodPenrose Insano Dub Head

792 posts · joined Apr 2005 · 6 Jul 2012, 8:48 am

#911305

Thanks guy's for your imput . I have taken this all on board and with the restricted cooling of the comp elimimators I have made a decision based on your engines . I have had the barrels machined and will end up with a .048 deck and a comp of 11.26 . I will now start a post in the circuit racing section about the new engine for Valla , ROD.

More boost + More fuel = More power
1968 Beetle fastest run 8.96 sec @ 161 mph 4th Nov. 2001
2010 New Beetle 8.12 sec on 8th march 2014
http://www.rodpenroseracing.com.au

BiX Veteran Volks Folk

2,499 posts · joined Sep 2002 · 6 Jul 2012, 12:43 pm

#911320

Rod the other thing to think about is treatments for the engine. Everybody has their opinion, but I have used (at engine builders advice) various ceramic coatings on the engine, Inlcuding heat dissapaiting coatings on the fins (barrels and heads), low friction on skirts, heat retaining on the inside of barrels, chambers, piston top, valves and exhaust ports. Never done a back to back run with and without these, but in theory they should help stop heap build up and potentail detonation.

I have no sympathy for my car, only the wallet that pays for it!
Go hard or go home!!!!

JVLRacing Custom Title Time!

1,100 posts · joined Mar 2007 · 6 Jul 2012, 3:36 pm

#911334

BiX wrote:Rod the other thing to think about is treatments for the engine. Everybody has their opinion, but I have used (at engine builders advice) various ceramic coatings on the engine, Inlcuding heat dissapaiting coatings on the fins (barrels and heads), low friction on skirts, heat retaining on the inside of barrels, chambers, piston top, valves and exhaust ports. Never done a back to back run with and without these, but in theory they should help stop heap build up and potentail detonation.

BINGO😎 very much agree

bigrudi Wolfsburg Wizard

401 posts · joined Apr 2005 · 6 Jul 2012, 6:59 pm

#911381

Have done back to back on coatings, but have good cooling set up to start of with, tried it on valves piston tops inside of chambers no noticeable variation in hp or temps . 11.1comp sounds good to me but make sure the fuel is fresh easy to hurt it with stale fuel .

matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 · 6 Jul 2012, 8:15 pm

#911392

x2 on coatings, my engines are generally street driven so I prefer lower CR's

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