laughingman868

I am hoping someone may be able to chime in with some other areas that I can inspect myself before dropping the car back off to the shop. I have read through all of the pre-detonation posts I could find and it would seem that this combination of parts should be ok together and not require something like a twin plug setup, I hope I am not over simplifying it. Recently the engine was rebuilt by a reputable shop near me and has been running real strong besides the pinging at semi high rpm(4-5k and more so when hot). The car has an 83SC engine that has the JE 9.5:1 3.2 pistons installed with a web cam 964 cam set. From what the JE rep said their advertised compression ratio is based on a deck height of ~1mm(which is what I was told was used). If the heads had a valve job and nothing else I assumed that the current compression ratio of the car is less than 10:1, and around what is advertised for those pistons which would mean it should be ok on 91 gas. Also checked recently were items such as the WUR, distributor, timing and fuel pressure which all seem to be functioning properly or within spec.

Is there anything else that could be contributing to this pinging?

Cloggie

You might look at the J&S Safeguard as a solution, it effectively is a spark retard system with knock sensor you can retrofit to you '83 engine.

I had a 3.2 short stroke with 9.8 compression, and while it did not detonate at all particularly as I was at 1000 m elevation, I was nervous about detonation and fitted the Safeguard...which worked great! I even put the led display (basically a line of small LEDs going from green to red as it sensed knock and retarded the offending cylinders into the clock so it all looked stock and like it belonged there

Completely eliminated the problem.....or risk for that matter.

laughingman868

I have looked into that before and it seemed like a great option. The current shop said they played with the timing a little and it didn’t have any impact on the pinging but I think I may call them back and ask a few more questions. If this can be used that would be ideal as it’s been on my mind for awhile.

How was the install? Did you have to buy anything additional that was not included in the box? Thanks for the reply by the way!!

Cloggie

The install was not trivial, but not all that bad, and yes, the kit was complete - there is a Porsche 911 specific kit.

There is a box that I put under the passenger seat, wiring to power and such, the actual knock sensor on the throttle linkage plate. A day would do it if you are handy.

The issue may be that you just have one cylinder that is misbehaving and retarding all cylinders via the distributor is a pretty coarse tool, you give away power and fuel economy if you dial way back and it still may not solve the problem.

The Safeguard has a number of capabilities including a sensitivity adjustment as well as some selectability as to how fast and how much it retards a cylinder if it hears knock so you have some range. Once I put it in, the display I put into my clock would flicker and show it was retarding cylinders, particularly on low rpm/large throttle opening situations so it was doing something for sure. I know that after the install I never worried about it again.....the thing just plain worked.

Support was good, he helped me diagnose a few issues and tune the Safeguard properly, so I am a fan.

laughingman868

That install doesn’t sound too bad, and for ~600-700 dollars seems like a great idea. I will call J&S today for some more into. I see that the site says not for cdi, I think I read this incorrectly at one point and believed it may not be an option with the current ignition system.

Cloggie

There is a specific unit for the CDI - look on their website under Products, it is the one I used and it worked perfectly.

laughingman868

Good to go, I see it. It’s under universal and mentions the Bosch CDI. I think I originally went to the Vampire unit seeing Porsche listed but then saw not for CDI. Thank you!!