Knock Sensors on a 3.5 block

FarnhamStag · Post by **FarnhamStag** » Tue Aug 05, 2014 8:07 am

Has anyone successfully fitted knock sensors to a Rover 3.5 block without drilling or tapping & if so where were they mounted?
I'll only fit them if it can be done relatively easily with the engine in, going to feed into the MS3 as safety measure whilst I get more adventurous with the timing whilst on boost.

ChrisJC · Post by **ChrisJC** » Tue Aug 05, 2014 9:00 pm

Never heard of anybody managing that......

Chris.

FarnhamStag · Post by **FarnhamStag** » Wed Aug 06, 2014 7:00 am

Thought that might be the case

stevieturbo · Post by **stevieturbo** » Wed Aug 06, 2014 5:51 pm

Find a bolt, bolt a knock sensor on.

Job done.

It may be preferable to bolt them to the sides of the block, further away from the valvetrain, but in most cases it shouldnt be essential.

Noise travels well through solid metal regardless.

if you're stick, bolt it to the intake manifold or somewhere similar.

FarnhamStag · Post by **FarnhamStag** » Wed Aug 06, 2014 10:07 pm

Thanks, I'll give that a go..not the answer I was expecting!

Dorian

DaveEFI · Post by **DaveEFI** » Wed Aug 06, 2014 10:41 pm

They are basically a contact mic with a filtered input - filtered to emphasis the sort of frequencies pinking produces. You can hear an engine pink above the other noises it makes, so although there may well be an ideal place for it on the block, other places may still be better than nothing. With decent filtering and software.

stevieturbo · Post by **stevieturbo** » Wed Aug 06, 2014 11:16 pm

All the filtering will be in the software, so you'll need to take the time to ensure all settings are correct and usable for your engine.

And manually listen for detonation to ensure the sensor/software is calibrated properly to your engine

The problem with most knock sensor setups....is if not set up correctly either they wont do what you want at all, or they'll continually hear things and treat them as detonation and you'll forever be pulling timing.

FarnhamStag · Post by **FarnhamStag** » Thu Aug 07, 2014 7:57 am

I guess that's the problem, you still need to calibrate them to work correctly but to do this you need the engine to knock and recognize that correctly. By that time will the damage have been done!

Not sure if its worth the effort/risk

FarnhamStag · Post by **FarnhamStag** » Thu Aug 07, 2014 8:23 am

Changing the subject slightly but still thinking about detecting detonation
would EGT be an easier way of detecting a problem?
Is there a known max EGT before detonation or again is it a question of waiting until it happens and then setting the maximum just below?

stevieturbo · Post by **stevieturbo** » Thu Aug 07, 2014 8:27 am

FarnhamStag wrote:I guess that's the problem, you still need to calibrate them to work correctly but to do this you need the engine to knock and recognize that correctly. By that time will the damage have been done!

Not sure if its worth the effort/risk

Whether it is worth it depends on the engine, the ecu's ability, and the tuners ability.

And no you would not do any damage or harm setting it up. And yes you could induce some harmless knock if you wanted, but setting base noise thresholds without knock should be enough.

stevieturbo · Post by **stevieturbo** » Thu Aug 07, 2014 8:56 am

EGT is not in any way a means of doing anything about detonation. It would be far too slow to start with

And its measuring long after the exhaust valve has opened, long after any detonation event would have occurred

FarnhamStag · Post by **FarnhamStag** » Thu Aug 07, 2014 12:17 pm

Thanks for that, all very helpful stuff.

So going back to the Knock sensors I guess what your saying is might be possible to trim the MS3 so it says you have knock when you don't and then back off the sensitivity slightly so it's just below the threshold in normal conditions? I don't have enough confidence in my ability to induce knock, recognize it in time before something melts!

DaveEFI · Post by **DaveEFI** » Thu Aug 07, 2014 12:33 pm

I'm pretty certain the threshold can be adjusted. The problem is getting the sensor electronics to differentiate between pinking and other noises.

With my MS2, the knock sensor needs its own ECU - rather like a wideband sensor. I dunno if MS3 has this built in.

FarnhamStag · Post by **FarnhamStag** » Thu Aug 07, 2014 12:52 pm

Phil at Extra EFI does a dual input Knock module for the MS3..Not sure if you adjust this or its in the MS software or both!

stevieturbo · Post by **stevieturbo** » Thu Aug 07, 2014 2:35 pm

DaveEFI wrote:I'm pretty certain the threshold can be adjusted. The problem is getting the sensor electronics to differentiate between pinking and other noises.

That's why your setting the thresholds. Once set up properly, the knock detection should work quite well in most cases.

But as with all aspects of tuning, it depends on both the person using it and the hardware/software.

Some are crap, some are great.

It sounds like it should be easy, but in reality it is far from easy, which is why it isnt simple.