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copbait73 copbait73 is offline
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Join Date: Nov 2003
Location: Chesterfield IN
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Originally Posted by Ken911 View Post
i just switched to a 3.4 with 7.5/1 JE pistons and a 1 bar spring. this mean i have a ticking time bomb? I still am breaking it in and havent re adjusted the WUR for the new compression and displacement.
Id forgotten about this thread until your posting brought up a prompt.

Are you living on the edge? Possibly. Don, Les and Voitureltd are at 12.3:1 and I suspect these points are in fact very good guidance. If you expand the chart adding every turbocharged air-cooled Porsche street motor you will find that even the last of them stayed below 12:1 and that is with every electronic technology in existence - knock listening - pressure, temperature and flow measuring - then adjusting fuel, spark and boost.

Your increased compression against 1Bar boost places you with these three however they are twin plugged and you are not. Also, I dont know of your charge cooler, as your banner reflects none, but the best of the best would also be needed. Lastly, southern FL is not a mean ambient condition.

I read the chart and suggest lowering your boost to .8 bar. After all, that small amount of extra boost is not giving your motor configuration a large power boost for the potential risk it presents. Effective 11.5:1 on pump gas running at elevated temperatures still presents risk if that is how you roll.

Last edited by copbait73; 11-28-2009 at 07:31 AM..
Old 11-27-2009, 05:40 PM
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