Player0

A neighbor mentioned to me the other day that I need a digital torque wrench to install the knock sensor on a 944T. I have a standard analog version. He says that if I do not get the torque exactly right, the sensor might not detect knock or might be too sensitive, retarding timing too much.

I've been looking around but I can't find a torque measurement for the knock sensor. What is the torque specification for this, and is there any sort of lube I can use to get more precise action out of my analog wrench?

max_boost951

15 ft lbs is the spec. I wouldn't worry about the "exactly right" comment. You could tighten to a 1000 ft lbs and it would still be making the same contact to the engine.

zerMATT951

All you're doing when you bolt the knock sensor to the head is squeezing a steel collar. I can't imagine that it can be "over tightened" short of stripping the aluminum threads out of your head. It's an 8mm bolt, so Porsche specs say 20Nm (15 ft lbs). No lube is necessary.

Player0

Thanks, glad I don't have to run out and spend loads of cash on a new tool. I mean, it'd be nice to have, but I'd rather fix the 944 first.

Would it be a bad idea to use anti-seize then? I would worry about the knock sensor bolt 'backing out' and not notice detonation. But I've been dealing with so many frozen bolts on this thing that I've been trying to use anti-seize where I can get away with it.

zerMATT951

I wouldn't be afraid to put anti-seize on that if you have lots of seized bolts on your car. I've been using high-temp copper anti-seize on all of my exhaust components, and a few bolts that go into the block that are near water (water pump bolts/studs, bolts holding the coolant elbow to the head, etc), but I didn't use anti-sized on the knock sensor because I don't have a corrosion problem there. If you do, then go for it - it won't hurt anything.

It's worth noting that adding anti-seize to the threads of something that you are torquing to a specific value will throw off your torque reading. Anti-seize will act like a lubricant, so you will the affect of 20Nm value by actually putting a little more stress on the threads because friction has been reduced, thus throwing off the reading that your torque wrench is giving you. Torque value are always stated for dry fasteners.

I wouldn't worry about it in this case, but it's something to think about when you are torquing critical components like head studs or nuts, which is why those components have their own special method of torquing to remove lubrication from the equation.

Sorry if I'm over-complicating a relatively simple procedure...

Jfrahm

BTW I would argue that a digital torque wrench is no more accurate than a good-old beam wrench and probably less accurate if not maintained and calibrated properly. Easier to read maybe but that does not mean you are reading an accurate number off it.

Player0

Thanks for the info guys. Yeah, I was reading that you should reduce torque by something like 20-30% to counter the anti-seize friction reduction.