Knock Sensor location for J&S Safeguard

polizei · 01-30-2012, 08:56 AM

Hey Guys,

For those of you that have used the J&S Safeguard for knock sensing and timing retard, where did you mount the knock sensor(s)? How many knock sensors did you install? And how many can the Safeguard reliably handle?

It seems that a good approach would be to mimic the location where Porsche installed knock sensors on the 993, which requires the heads to be tapped. Has anyone tried this with the J&S Safeguard?

Thanks,

sjf911 · sjf911's Garage

I placed one on the crank breather cover and it seemed to work very well there. The J&S will take 2 sensors but I am unclear on how they operate together. I am now adding a second sensor but I am having the heads machined to take the 993 cylinder knock bridges.

polizei · 01-30-2012, 10:16 AM

Hi Steve - If the breather location worked well, why are you considering moving to the 993 knock bridges? Do you feel that it's retarding too much or not enough?

sjf911 · sjf911's Garage

It's sort of one of the "while you are there" things, since I have my engine apart anyway, I would prefer a more stock location. However, they have developed a dual channel knock control add-on board for the MS3/MS3X so I am looking at running simultaneous knock modules for a while and seeing which works the best.

polizei · 01-30-2012, 10:56 AM

That's an interesting experiment. I'll let you know what I found out regarding the ability of the Safeguard to process input from 2 knock sensors if I go that route. Good luck!

sjf911 · sjf911's Garage

I drilled and tapped the top of the breather cover. The sensor is from J&S. Here it is compared to the 993 cylinder bridges.

jpnovak · 01-30-2012, 01:26 PM

I have my knock sensor mounted at the base of the "CIS linkage plate mounting stud". This is the long stud that sticks up from the case at the base of cylinder number 3. I turned down the aluminum spacer the height of the knock sensor. (19mm IIRC).

I am not running a J&S but this seemed to be the best logical location considering it is directly mounted above a case web and there is no isolation from a gasket.

sjf911 · sjf911's Garage

I worried a bit about the gasket but finally decided the all metal contact through the studs/nuts into the housing should be sufficient and it appeared to be the simplest location to access. The J&S appeared to have no trouble picking up knock in that location. What does matter is getting the proper torque on the knock sensor itself.

proffighter · proffighter's Garage

Mine is here, under the throttle bracket:

Cloggie · 01-30-2012, 05:27 PM

I just mounted mine on the throttle plate...forgot to take a picture of it, but it is the plate mounted on top of the engine where the throttle rod comes up from near the transmission and drives a bellcrank to the butterfly. There is an empty threaded socket there, just used a bolt (6 ot 8 mm I think).

It works perfectly. Fantastic product.

D.

nocarrier · 01-30-2012, 05:35 PM

Quote:

Originally Posted by sjf911

It's sort of one of the "while you are there" things, since I have my engine apart anyway, I would prefer a more stock location. However, they have developed a dual channel knock control add-on board for the MS3/MS3X so I am looking at running simultaneous knock modules for a while and seeing which works the best.

Do you have any more info on the knock module? This sounds exactly what I have been looking for!

sjf911 · sjf911's Garage

Quote:

Originally Posted by nocarrier

Do you have any more info on the knock module? This sounds exactly what I have been looking for!

Only a few have been released for beta testing.

Megasquirt MSEXTRA / MS3EFI • Knock module for MS3 (beta test) (View topic)

polizei · 01-31-2012, 08:54 AM

Quote:

Originally Posted by sjf911

I placed one on the crank breather cover and it seemed to work very well there. The J&S will take 2 sensors but I am unclear on how they operate together. I am now adding a second sensor but I am having the heads machined to take the 993 cylinder knock bridges.

Steve - I took another look at your post and saw that your signature includes the J&S Interceptor. I've been emailing back and forth with John from J&S, and that's the one he suggests using if you're going to use dual knock sensors. I'm not sure if that will work for me since I'm running a distributor-based ignition with the Bosch Motronic DME. John's looking into this for me. I'll try to get some more details regarding how processing is performed with two knock sensors. John's pretty good about getting into the forums, so perhaps he'll pop in.