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Knocksense knock sensor with WBX
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DanHoug
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PostPosted: Sun Feb 28, 2021 7:16 am    Post subject: Knocksense knock sensor with WBX Reply with quote

well... this is a $100 experiment. i've ordered the Knocksense kit that will give an LED indication of engine knock. does no tuning, adjusting, etc. just flashes a blinky when it 'hears' something like knock. the kit price is very reasonable.
https://www.viatrack.ca/

why? because i'm a nerd. i run an over advanced engine and while the wbx is pretty knock resistant, it'd be cool if this could actually detect knock because i have a really hard time hearing it with the engine way back under an insulated cover. if reliable, i might advance the timing a skooch more.

why not? there's all sorts of engine noise that will fire a knock sensor into trigger. OEM manufacturers spend big research dollars to develop filters for these non-knock noises.. water pump, bearings, accessory belts, piston slap. for $100, all it has is a sensitivity threshold adjustment and apparently peak resonance can be somewhat tuned to piston diameter. knock sensors are just piezo elements encased in a robust bolt-on housing. they're dumb as rocks, it's all about the filtering of the signal to separate the wheat from chaff.

anyway, the kit has a nice breakout of the LED so i can run it up to the dash. maybe someday i'll come up with a mechanical advance/retard on the dist like the old Indian motorcycles had... one throttle grip controlled carb butterfly, the other grip controlled advance. maybe mount an old John Deere B advance lever on the steering column!

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MarkWard
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PostPosted: Sun Feb 28, 2021 7:52 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

2 questions. Where will you mount it? How will you know it works and is measuring detonation and not some other frequency? I appreciate you going down this path. Best of luck.
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DanHoug
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PostPosted: Sun Feb 28, 2021 8:16 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

i've removed my AC compressor mounts and there's some nice bolt holes there to mount solidly to the block. bolt diameter may be bigger than the sensor hole. have to see when the kit comes.

as to whether it is working... you first set the sensitivity to flash the LED when the engine is running but not under load then back off a 1/2 turn or something. i think to test it, i may really over-advance the timing and see if it triggers under load. lowest RON fuel around here is 87-- it'd be nice to try some crap gas. one thing i'll play with is setting sensitivity to near the no-load trigger threshold with 87 octane and see if triggering is less with a load of 91 octane.

as i say, this is a $100 experiment. not sure it will be useful or even provide meaningful feedback. but if it DOES, i'm going to grab another few degrees of advance! had an old Buick with a 401ci V8, man that thing would knock so loud on poor gas, so audible. i've never heard the wbx knock to be honest. it probably IS knocking buried under the mattress foam and 2" foam engine cover.
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4Gears4Tires
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PostPosted: Sun Feb 28, 2021 8:16 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

Mount it to the AC holes if the AC is gone. I think inducing some knock and then backing it down is the way to tell it's working. Shocked

This is neat. I am looking forward to updates.
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PostPosted: Sun Feb 28, 2021 8:35 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

Up into the mid 50s Mercedes had an octane adjust system. Twist the knob. A sleeve thing sat between the distributor and the engine block.

But, thinking about it, you can do it electronically, just like the little digital idle stabilizer does....duh!

Sounds like a job for an Arduino mounted inside an old idle stabilizer box.

Have fun, it been years since I worried about this knock topic.....
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PostPosted: Sun Feb 28, 2021 8:40 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

AC mounting holes are 10mm. The knock sensor usually takes an 8mm bolt. You could make a thread insert out of a 10 mm bolt with some patience to reduce it down to 8 mm.
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DanHoug
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PostPosted: Sun Feb 28, 2021 8:41 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

r39o wrote:
Up into the mid 50s Mercedes had an octane adjust system. Twist the knob. A sleeve thing sat between the distributor and the engine block.

But, thinking about it, you can do it electronically, just like the little digital idle stabilizer does....duh!

Sounds like a job for an Arduino mounted inside an old idle stabilizer box.

Have fun, it been years since I worried about this knock topic.....


anyone have a link on HOW the idle stabilizer works? does it trigger something in the ECU or does it somehow affect the dist signal before it gets to the ECU?
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PostPosted: Sun Feb 28, 2021 8:45 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

MarkWard wrote:
AC mounting holes are 10mm. The knock sensor usually takes an 8mm bolt. You could make a thread insert out of a 10 mm bolt with some patience to reduce it down to 8 mm.


That certainly already exists as a timesert or other reducer.

https://www.amazon.com/Thread-ADAPTERS-Female-Thre...mp;sr=8-16
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MarkWard
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PostPosted: Sun Feb 28, 2021 8:53 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

Iím used to making things I can. Good to see a need was realized and put together a solution.
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DanHoug
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PostPosted: Sun Feb 28, 2021 8:57 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

4Gears4Tires wrote:
MarkWard wrote:
AC mounting holes are 10mm. The knock sensor usually takes an 8mm bolt. You could make a thread insert out of a 10 mm bolt with some patience to reduce it down to 8 mm.


That certainly already exists as a timesert or other reducer.

https://www.amazon.com/Thread-ADAPTERS-Female-Thre...mp;sr=8-16


these look perfect for that AC hole. thanks! when i deleted my AC, i installed a short M10 bolt to keep dirt out knowing it would be useful for SOMETHING!

i'd love a dash knob to adjust timing like on the Mercedes. a vac advance distributor mechanism would be easily tapped into for this with a long control cable. anyone have a Digijet dist they'd like to sacrifice for science?
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PostPosted: Sun Feb 28, 2021 9:02 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

these are too spendy for this science project but the form factor i like:
https://www.millsupply.com/vernier-heavy-duty-adjustable-locking-control-cable-17125.php?p=337000
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MarkWard
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PostPosted: Sun Feb 28, 2021 9:08 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

DanHoug wrote:
r39o wrote:
Up into the mid 50s Mercedes had an octane adjust system. Twist the knob. A sleeve thing sat between the distributor and the engine block.

But, thinking about it, you can do it electronically, just like the little digital idle stabilizer does....duh!

Sounds like a job for an Arduino mounted inside an old idle stabilizer box.

Have fun, it been years since I worried about this knock topic.....


anyone have a link on HOW the idle stabilizer works? does it trigger something in the ECU or does it somehow affect the dist signal before it gets to the ECU?


The digijet uses a digital idle stabilizer to control idle speed by advancing and retarding timing. Itís standalone to the fuel injection ECU. Itís wired between the distributor and the ignition module. The ECU does get an rpm signal from the coil. So Iíd say the logic is built into the idle module, not the FI ECU.

The Digifant has the coil drives and timing map built into the ECU
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PostPosted: Sun Feb 28, 2021 9:15 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

Watching with interest.

A steep open road may be another way to test and tune... 4th gear, <30 mph, try to accelerate. That induces knock in every car I own that has the engine in front of me.

r39o wrote:
Up into the mid 50s Mercedes had an octane adjust system. Twist the knob...


All British cars back when had a Vernier knob on the distributor for easy, calibrated timing adjustment. Very handy for dialing advance back a bit at your first fill-up when driving into California.
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PostPosted: Sun Feb 28, 2021 9:19 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

The GoWesty EFI kit has the knock sensor mounted with an 8mm bolt to the top of the #3 cylinder head near the thermostat. Pretty convenient place with nothing else using this threaded hole.

Cylinder head seems the best place to sense knock, since the sound comes from there.

Pic from the GW manual:

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PostPosted: Sun Feb 28, 2021 9:35 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

When engines knock, in general, do they favor one cylinder over another or will it be spread across the board evenly? Would a single sensor over #3 hear a ping clearly in #2?

Hans
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PostPosted: Sun Feb 28, 2021 9:55 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

How does subaru address knock sensors on their EFI systems? Do they use them? Where are they located?

Hans
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PostPosted: Sun Feb 28, 2021 10:01 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

hdenter wrote:
When engines knock, in general, do they favor one cylinder over another or will it be spread across the board evenly? Would a single sensor over #3 hear a ping clearly in #2?

Hans


engines will use multiple knock sensors but mainly to null out engine noises to prevent false positives, sorta like having multiple AoA sensors on aircraft. i MAY try two sensors, paralleled, one on each side to see what that does. if the signals are in phase, it should increase the overall amplitude of what the filter circuit is dealing with so i envision the sensitivity would have to be turned down. BUT it might pick up a knock event from either side better. worth a $25 experiment for a used Bosch knock sensor.
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PostPosted: Sun Feb 28, 2021 10:16 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

location is important and sensor torque is very critical, usually in the 10-17ftlbs range.

they work at a frequency range of typical pre ignition so they don't pick up ambient noise.

a lifetime ago i had a guy with a ferd ranger that had a slight knock in the engine. it pulled so much timing you couldn't get about 40 mph out of it. i pulled the Ks off the block and went for a ride. it restored power 100% but did zero for his rod knock Laughing

anyway, here is a good article on how they work

https://www.azosensors.com/article.aspx?ArticleID=50
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PostPosted: Sun Feb 28, 2021 10:27 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

Looks like a neat device.

The J&S safeguard I run has an LED out port to mount a light on the dash. I didn't install that option.

FWIW, if you are running a stock MV at 40ļ or so you will never experience pre ignition.

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PostPosted: Sun Feb 28, 2021 10:38 am    Post subject: Re: Knocksense knock sensor with WBX Reply with quote

If I recall correctly, the Ford Model T had a lever on the steering column.

Like a choke, part of the pre-start ritual was to advance the spark.

Dave
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