Knock ears Piezo/microphone location

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Knock ears Piezo/microphone location

Postby grip-addict » Wed Dec 01, 2021 5:23 pm

Has anyone done dyno tuning with a set of knock ears? Where did you place the sensor? There doesn't seem to be any obvious GOOD spots on the front of the block to me, so I'm wondering if there's an easy-to-access (haha) spot on the back of the motor or if someone was able to use one of the lower bolt holes near the downpipe with any reasonable success.

using the factory knock sensor location is probably the BEST spot, but that's definitely not easy to use with the motor in the car... :\
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Re: Knock ears Piezo/microphone location

Postby Gert » Mon Dec 06, 2021 2:46 pm

I use Chassis Ears and connect the clip on the intake stay bar. Not easy, but do-able.


Image
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Re: Knock ears Piezo/microphone location

Postby grip-addict » Mon Dec 06, 2021 3:23 pm

Did/do you get good results ? Happy with how it's allowed you to tune?
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Re: Knock ears Piezo/microphone location

Postby Gert » Mon Dec 06, 2021 3:30 pm

Yes, I mapped several cars with it. My own car is having an KnockLink too and results are almost the same. My expierience.

On high revs (7.000 +) it is almost impossible to hear knock. The KnockLink is going nuts at those rpm's, but I have had never issues with it.
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Re: Knock ears Piezo/microphone location

Postby grip-addict » Mon Dec 06, 2021 3:57 pm

That's really useful information! Thank you so much Gert!! I'll definitely look into those. They seem useful for tracking down creaks/rattles/etc in the chassis, too.

Do you have any [positive] experience with the factory knock sensor? I still have that installed - and as far as I can tell, it IS doing something, but it probably needs calibrated a bit better inside the Haltech software. Switching to a Bosch donut style some day down the road would be nice, but I think the engine would need to come out to make the switch and I don't have any current plans to do so. So as you can imagine, I'm trying to get as much out of the existing setup while the engine is still in the car. Any insight is appreciated!
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Re: Knock ears Piezo/microphone location

Postby Gert » Mon Dec 06, 2021 6:28 pm

grip-addict wrote:Do you have any [positive] experience with the factory knock sensor?

Can't say anything about it. When I installed the Autronic, the OEM knocksensor was out off use, so we removed it.

Later on, I installed an KnockLink. I really don't know if these are sold these days.
The KnockLink does use an Bosch sensor.
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Re: Knock ears Piezo/microphone location

Postby grip-addict » Tue Dec 07, 2021 5:05 am

That sounds about right. I know that knock sensor support in EMS has only come along in the last decade or so. I did notice knocklink on link's website, so I think it's still a thing.

My Haltech elite is getting a signal from the knock sensor on the gen3 motor but I just need to tune it. I did some mild adjustment while forcing the engine to lightly knock while free-revving and setting the hz level for the ECU to listen. The nice thing about the elite is that it'll automatically retard timing by x degrees you set and then make long-term recommendations, but for it to really work, you have to basically already have a good solid ignition table tune then set up thresholds based on what you expect the knock sensor to observe in the real world. I don't have either of those. So instead my real world experience is the ECU tries/is retarding timing even at idle from -5 (probably already too low) to 0 and some other places in the map up to maybe 3k rpm. I guess the good news is that it's not making any suggestions when on boost; the only recommendations are being made below 0 bar.

I really need to get to the dyno and use something like these chassis ears to nail down the table. I figure that at a bare minimum, I can tune to MBT for everything off-boost and use the ears for on-boost tuning. But if I have chassis ear pickups already on the car, might as well just do the whole map that way :)

Thank you so much for the info! very helpful.
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Re: Knock ears Piezo/microphone location

Postby Gert » Tue Dec 07, 2021 11:56 am

I never had knock at no boost, so I cannot tell anything about that.

The times I heard knock was with boost and between 3.000 to 6.500 rpm. If that happened I checked A/F and if that was rich, then I retarded timing.
In high rpm levels, the valve train is making so much noise that nothing is audible. Even the KnockLink is going crazy at 7.000 + rpm.
So I keep on the safe side there. Some tuners are telling me that I should use more advance in timing in high revs, but I did destroy my engine once at high revs on the highway at about 250 km/h, and the results were not nice.
I have 13° at 1,0 bar and 11° at 1,25 bar.
In the past I had about 20° advance in that regions. But, if you know my history with the T-vis, you know a lot happened.

When my T-vis was dying, first the axle/spindle with two butterflies (from one side) came loose. This was resulting in no good fuel burning in all four cilinders at the same time.
The result of this was that the KnockLink was detecting knock. That was strange because nothing changed and still there was knock. So I suspected bad fuel nowadays or what ever.
To eliminate the knock I retarded ignition. The knock was not so often there anymore, but unfortunately this retarding did not rescued the engine. At the moment the butterfly came loose and 'walked' through the engine and turbo, disaster was happened.

Anyway, after breaking in the rebuilded engine I should map the engine again for the high rpm regions. But to be honest, it has no priority. The engine is doing really good, feels strong and she flies to 7.500 rpm, very nice and aggressive.
Second is that I have an E34 M5 (S38B38)to maintain and recently I got myself an Challenger 392 for project. So busy doing other stuff too.
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