knock detection systems

[cooperquattro]

what are peeps thoughts on these for tuned motors?what is available to us??recently went in an evo that had a gauge with a warning if knock occured

[QuattroFever]

Stethoscope with 3-4m of 8mm hardwalled hose put on the end instead of the chest plate. Then a push a peice of metal alu/copper/stanless 8mm pipe in the end and flatten the end left sticking out and drill a hole in it so you can bolt it to the block.

Voila...Det cans

Get a good stethoscope £10-15 with decent gel/soft sealing eartips. Cheapo silverline mechanics steth's are rubbish BTDT.

Not electronic but you can check for knock on lesser quality fuel. You'll be hard pushed to better the motronics knock detection.

[KRIENG]

Stethoscope with 3-4m of 8mm hardwalled hose put on the end instead of the chest plate. Then a push a peice of metal alu/copper/stanless 8mm pipe in the end and flatten the end left sticking out and drill a hole in it so you can bolt it to the block.

Voila...Det cans

Get a good stethoscope £10-15 with decent gel/soft sealing eartips. Cheapo silverline mechanics steth's are rubbish BTDT.

Not electronic but you can check for knock on lesser quality fuel. You'll be hard pushed to better the motronics knock detection.

Thank you I have some PIC (that guy isn't me)
http://forums.neons.org/viewtopic.ph...4e46c7e2139edf

[prj]

Those gauges are utterly useless.

You can use a stethoscope or an eletronical stethoscope, which is basically a mic embedded in glue attached to the engine block, and then an amp.
This is what I use.

[EspenW]

For tuning, definitely use stethoscope/det cans, but for a permanent/warning type solution, I have luck with the following:

I'm running a KnockSense http://www.viatrack.ca/ unit in my 11:1+ compression 8v Golf. That one lights up like a x-mas tree on 99 octane or less, but keeps silent on E85 so it definitely gets the job done. The downside to the Knocksense is that it isn't rpm compensated, so it lights up at very high rpm from engine noise.

In the RS2, I run a Knocklite: http://www.knocklite.com/
Hooks up to the signal wire from the knock sensor and indicates knock with a flashing LED. Mild knock is indicated with an amber light, while severe knock is indicated with a red light. Also doubles as a shift light (very handy).
The Knocklite takes an RPM input, and generates a noise vs. rpm curve when free revving the engine. This to distinguish knock from engine noise at various rpms.
I have programmed the shift light (green light) to flash at 7000rpm.
The Knocklite is cylindrical, approx 20mm x 60mm. I placed it inside the nearside vent, velcroed to the airduct. Totally stealth, but the flashing light is visible thru the vent-cover-thingy

[prj]

For tuning, definitely use stethoscope/det cans, but for a permanent/warning type solution, I have luck with the following:

I'm running a KnockSense http://www.viatrack.ca/ unit in my 11:1+ compression 8v Golf. That one lights up like a x-mas tree on 99 octane or less, but keeps silent on E85 so it definitely gets the job done. The downside to the Knocksense is that it isn't rpm compensated, so it lights up at very high rpm from engine noise.

In the RS2, I run a Knocklite: http://www.knocklite.com/
Hooks up to the signal wire from the knock sensor and indicates knock with a flashing LED. Mild knock is indicated with an amber light, while severe knock is indicated with a red light. Also doubles as a shift light (very handy).
The Knocklite takes an RPM input, and generates a noise vs. rpm curve when free revving the engine. This to distinguish knock from engine noise at various rpms.
I have programmed the shift light (green light) to flash at 7000rpm.
The Knocklite is cylindrical, approx 20mm x 60mm. I placed it inside the nearside vent, velcroed to the airduct. Totally stealth, but the flashing light is visible thru the vent-cover-thingy

Both of those things are fairly useless.
Electronics are rubbish at determining knock, without lots of advanced features.

One of the most important features is to have an accurate knock window, otherwise it is just not possible to distinguish between high rpm engine noise and knock.

Those knock lites, phormulas and other cr*p don't have the ability to take a phase signal, so they can't determine knock window.

Just use headphones for tuning, and an engine control unit with correctly working knock monitoring for when you drive.
If the ECU is set up properly, none of those playtoys will ever show any knock, because by the time they do, it can be too late. Especially on cars running stock rods, and 600nm with random petrol being put in.

[EspenW]

Agree with most of that, but they actually tell you when there is knock going on, so you know if you have crap fuel, etc. As I mentioned, the Knocksense in the Golf does not light up when I run on E85, due to the massive octane, but once I run it on petrol, it starts to flash at high load and medium rpm, telling me that the engine is knocking and it is time to either let off the throttle some or get some of its preferred alcoholic fuel in the tank
Both these units take the signal from the stock knock sensors, so they get the same signals as the electronics in the engine control.
They just let you see what the ECU sees and that can be helpful. The Knocklite differentiates engine noise from knock, while the Knocksense does not do that and thus it lights up at very high rpm. It still tells me if the engine knocks below approx 6500rpm and for me that is better than not having that information in case the gas station by accident should serve an ethanol blend with way less than the minimum of E70, etc.
The Golf is K-Jetronic w/o electronical ignition, BTW, so for that car, the Knocksense is very helpful.

[prj]

Agree with most of that, but they actually tell you when there is knock going on, so you know if you have crap fuel, etc. As I mentioned, the Knocksense in the Golf does not light up when I run on E85, due to the massive octane, but once I run it on petrol, it starts to flash at high load and medium rpm, telling me that the engine is knocking and it is time to either let off the throttle some or get some of its preferred alcoholic fuel in the tank

And by then it can be too late for a highly tuned engine where the internals are pushed to the max.

Both these units take the signal from the stock knock sensors, so they get the same signals as the electronics in the engine control.
They just let you see what the ECU sees and that can be helpful.

This is completely wrong!
They don't have phase signal, crankshaft position and they don't know the timing advance, the boost level ETC.
The ECU actually changes frequency, gain, knock window, adaptation and has threshold levels defined for every state of the engine, for every cylinder, for every boost and rpm level.
It has accurate calibrations done for every cylinder using in-cylinder pressure transducers, and knows the exact moment knock can occur, which cylinder is firing, etc.

Sorry, but no. They don't see the same that the ECU sees. Not in the least bit. Not even close.

[prj]

P.S.
Read this document as a start:

http://www.ti.com/lit/an/spra039/spra039.pdf

Bosch knock detection is way more complicated than this, that's why all these knocklites and other cr*p are just playtoys.

[EspenW]

And by then it can be too late for a highly tuned engine where the internals are pushed to the max.

Or it can provide the warning needed to step off the gas and save things like rod bearings from getting beaten up in a more standard engine, which is rather helpful in an older engine without knock sensing ignition.

They receive the same raw signal from the knock sensors as the ECU does, but of course the ECU is vastly more advanced in how it interprets and uses that information.

[EspenW]

P.S.
Read this document as a start:

http://www.ti.com/lit/an/spra039/spra039.pdf

Thanks, looks like an interesting read for the weekend.

[prj]

They receive the same raw signal

Again no.

The signal is not only the data from the knock sensors. The data from the knock sensors is useless alone.
The ECU's knock detection primary inputs are:
* RPM
* Phase
* Ignition timing
* Boost level
* Crankshaft position
* Knock sensors
Secondary inputs include IAT, calculated EGT...

So yeah, those devices have 1/6th of the inputs the ECU has.
Again, one sixth of the data.

[EspenW]

Alright, but in the case of the K-Jet car, having even one sixth of that data is better than not having it.
It does not flash on proper high octane fuel, but it flashes when it detects knock on low octane (ie. petrol), so it does what I need it to do.
Would listening for knock reveal the same thing. Probably, but that is not always easy to hear over noisy exhaust, stereo, etc.

[prj]

Would listening for knock reveal the same thing. Probably, but that is not always easy to hear over noisy exhaust, stereo, etc.

Again, completely wrong, sorry.
There is no instrument better than a human ear at listening to knock.

And when you listen to it, you use sealed headphones, plus either a stethoscope connected to the block, or a mic embedded in glue, connected to the block.
You hear exactly what you need to hear.

Those playtoys usually go off when it's way too late. On a 2.2 with properly configured Motronic or on any good engine management, even if you go from 98 RON to 95 RON, they will almost never go off or show lots of false positives on the higher octane level, because the ECU will instantly bring the engine to a knock free state.

Systems that were developed 20 years ago are lightyears ahead of these little gadgets.

Please, just read about how knock detection algorithms and DSP's work, and you will realize that a constant threshold detector with a fixed noise filter is absolutely useless at detecting knock.
You can use a level filter for your ears to filter out low frequencies, but even that is not needed, as your brain can do that very well on it's own.

[EspenW]

I prefer not to drive around daily with earphones, when this thing does what is supposed to do on the Golf, which has a crude K-Jet injection system and not Motronic.
It tells me when the engine knocks when I have to run the Golf on petrol. It does not flash when the octane of the fuel is high, but it does flash when the octane of the fuel is low. This tells me it works. If I roll the windows down, I can also hear the pinging noise when the LED goes off. Not easy with the windows up and stereo on full blast. Thus, the system serves a purpose on that particular car.
It has helped me keep the rod bearings in one piece since 2006. I had to replace them back in 06 after a few weeks driving on 11:1 comp, 99 octane and no knock warning. With the knock warning it tells me something is wrong and I step off the gas a little or pull off the vacuum advance for the distributor. For me, not having to replace the rod bearings at regular intervals this is well worth the 30 something quid I paid back in 2006.
I agree that it has very limited value on a Motronic car, but on a K-Jet car like my Golf, it certainly does a good job.

Some rather favorable experiences from the Volvo forum, with comments from Boris, the guy who makes the KnockSense:
The knocksense registered non audible knock that showed up in the knock log:

http://forums.turbobricks.com/showthread.php?t=100085