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Steve@Rennsport Steve@Rennsport is offline
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Join Date: Jul 2001
Location: Portland Oregon
Posts: 6,992
Quote:
Originally Posted by trond View Post
my 4000 miles old 3.2SS conversion has 10.5:1CR CP 98 mm pistons, twin spark EDIS ignition run by MS2 and stock SC cams. On 95RON (=91 US octane R+M/2) fuel I have pinging under load, that only goes away if I run as little as 10 degrees@3500 WOT ignition advance or back off on the throttle. Also pinging goes away with 98RON fuel but unfortunately this is getting increasingly difficult to find.

I would have thought this configuration should have been able to run 95RON/91 US ? What do you think
With those cams, you have far too much cylinder pressure below 5200 RPM for 95 RON fuel. Reducing mid-range & total timing will simply kill throttle response and make the engine run too hot.

I would either:

1) Install lower CR pistons (best choice)

2) Install longer duration cams (narrows the effective RPM range, requiring close-ratio gears)

3) Use 98 RON fuel even though its not convenient
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Steve Weiner
Rennsport Systems
Portland Oregon
(503) 244-0990
porsche@rennsportsystems.com
www.rennsportsystems.com
Old 08-21-2018, 11:42 AM
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