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Registered
Join Date: Jan 2006
Location: Santa Barbara, CA
Posts: 2,307
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MSD or other detonation detector on early 911?
Interested in hearing from anyone who has installed an MSD or other detonation detector on an early 911. Car in question is a 74 2.7 with PMO's, no electronics except for an MSD CD unit and optical "points" . Does the unit work effectively? Where is the sensor best mounted?
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jhtaylor santa barbara 74 911 coupe. 2.7 motor by Schneider Auto Santa Barbara. Case blueprinted, shuffle-pinned, boat-tailed by Competition Engineering. Elgin mod-S cams. J&E 9.5's. PMO's. 73 Targa (gone but not forgotten) Last edited by moneymanager; 10-13-2007 at 11:02 AM.. Reason: data left out |
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10-13-2007, 10:22 AM
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Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
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Jim:
MSD's are ignition systems, not knock-detection ones. J&S makes knock detection components. I've installed a LOT of MSD's on 911's and they work very well. There is no good position to install knock-sensors on the 2.0 through 3.2 (3.3) motors. Porsche knew this and thats why they designed the sensors to sit on a cast-in boss near the bases of the cylinders found on the 3.6 motors. Remember, these engines have sophisticated engine management that not only detects knock, but pulls the timing back to get rid of it. IMHO, the best way to deal with potential detonation on a pre-3.6 is to either install twin-ignition or run very conservative timing when using low-octane premium fuels.
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Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
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10-13-2007, 10:35 AM
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Registered
Join Date: Jan 2006
Location: Santa Barbara, CA
Posts: 2,307
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Hi Steve,
I'm familiar with, and have, MSD ignition on my car, but they also show a knock detector (Knock Alert) as a separate product. I'm the guy with the four broken gaskets, just grasping at straws for the future. I'm disappointed to know there isn't a way to use one of these effectively on an early motor.
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jhtaylor santa barbara 74 911 coupe. 2.7 motor by Schneider Auto Santa Barbara. Case blueprinted, shuffle-pinned, boat-tailed by Competition Engineering. Elgin mod-S cams. J&E 9.5's. PMO's. 73 Targa (gone but not forgotten) |
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10-13-2007, 11:00 AM
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Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
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Those MSD knock alerts are OK for water-cooled engines that make little mechanical noise but of little value for a 911.
I think you need to have someone who is VERY experienced to look carefully at your pistons, rings, plugs, pin bores, and rod bearings for any signs of detonation. A qualified person will know what to look for and have the experience to recognize the signs. If nothing is found, chalk this up to a machining mistake and move forward. 
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Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
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10-13-2007, 11:06 AM
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Wer bremst verliert
Join Date: Jan 2005
Location: Toronto, Ontario
Posts: 4,767
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I am aware of two setups to that are working on cars here in Sydney. Both are supercharged air-cooled 3.0 engines. They are both running twin-plug ignitions.
One has a bosch knock sensor tapped into the engine case under the breather cap. This has 4 mating surfaces between where detonation happens and the sensor so there ahs been a lot of debate about whether it is a good location, however the sensor appears to work. The other setup is a set of 100MM Perfectbore cylinders that have been tapped and fitted with a pair of 993-style "bridges" and sensors attached. I am not familiar with the MSD knock sensors though I am with their ignition bits which I have been happy with on several cars.
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2007 911 Turbo - Not a toy 1985 911 Cab - Wife's toy 1982 911 3.2 Indiash Rot Track Supercharged track toy 1978 911 3.0 Lichtbau toy "Gretchen" 1971 911 Targa S backroad toy |
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10-13-2007, 02:52 PM
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