Knock Sensor Torque Setting

Hi,
I'm about to replace the cylinder block knock sensors but I can't find what the torque setting is for tightening the new items up in the workshop manual. Anyone know what the torque setting is ? These are expensive and sensitive items, so don't really want to guess.

Cheers

I just went through it and you're right - it doesn't look like the torque value is in the service manual.

I replaced both of mine when doing an engine rebuild, but don't remember what I torqued them to. Do the new ones say how much torque you shouldn't exceed on their instructions? I used aftermarket ones - not OEM. Maybe they came with instructions?

From what I recall, they are large diameter course-cut threads, so you could probably put a good 15-20 ft-lbs on them without worrying about the aluminum block threads or damaging the crystals inside the knock sensors. Just a guess... Whatever I torqued mine to, they seem to be working fine the past few years.

Wasn't much help. Sorry.

I don't know about the sensors on the NSX; but, for the Bosch stud / bolt mount style sensor, Bosch recommends a mounting torque of 20 +/- 5 Nm. 20 Nm - 25 Nm is just a hair below Mac Attack's suggestion of 15-20 ft-lb so his numbers are probably as good as you are going to get. Factory service manuals for Euro cars usually specify 20 Nm; but, that is probably because they use Bosch sensors. The Toyota's that I have seen also use 20 Nm along with some GM vehicles.

wixer said:

Hi,
I'm about to replace the cylinder block knock sensors but I can't find what the torque setting is for tightening the new items up in the workshop manual. Anyone know what the torque setting is ? These are expensive and sensitive items, so don't really want to guess.

Cheers

Click to expand...

Just to close the loop on this for future people searching, Kaz stated 30 Nm of torque on the similar thread over at the nsxcb forum. This aligns pretty well with Old Guys high-tolerance value of 25 Nm for Bosch sensors, and my guess of 15-20 ft-lbs.

There have been instances of these going bad on old cars, either dying for no reason or the brittle wires breaking, and the front sensor is impossible to get to without removing the OEM intake manifold. Also, piezo knock sensors get noisier with age, and could send false signals to your ECU causing the timing to be retarded, and therefore, a loss of power.

OEM's are expensive, but the one's I used on my engine rebuild work just great. I can see their output on my AEM system, set my knock thresholds, and was able to tune the engine myself correlating their output to the TFX engine analyzer on one of my cylinders. I've since gone back to the OEM ECU and the engine runs REALLY strong. No issue with compatibility to the OEM ECU.

I used these as a replacement... They're about $100 less per sensor than OEM. You can get really cheap ones for about $15, but Airtek products seemed legit when i did a search:
https://www.stockwiseauto.com/airtex-5s2139-ignition-knock-detonation-sensor?fit_id=12844749&Year=1993&Make=Acura&Model=NSX&source=googleps&

There's nothing really special about these resonant-type, piezo sensors. Non-OEM will work fine as replacements. Here's a little more info if interested:
http://www.nsxprime.com/forum/showthread.php/139892-Supercharger-amp-Knock-sensor?p=1342921&viewfull=1#post1342921

As our cars age, it doesn't make financial sense to remove the intake manifold just to replace knock sensors. However, I highly recommend doing it at the same time as a preventative VVIS butterfly valve rework (and fuel injector rubber washer replacement). Some new owners may not remember the VVIS valve screw ingestion issue on motors a few years ago (there's more than a few motors that were ruined). Seems like that's died down recently....