herbg26
Expert Class
Posts: 141
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posted October 26, 2009 06:29 PM
Knock Sensor
Has anybody mounted/or figured out how to mount a knock sensor on there bike.
Next year, the wife is going to let me buy a ZX14, LOL.........so I can turbo it. I'm going to be doing all the tuning myself, and I was wondering one critical symptom when a turbo is added is detonation., which requires remove timing, to keep from burning pistons etc.
Have any of guys thought about this.....
Herb
I'm about to be turbofied.....ZX12 and ZX14 rule
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KZScott
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posted October 26, 2009 06:40 PM
i have heard of them being used on slowmobiles.. er snowmobiles, but not on a bike. sounds interesting.
this may or may not be true, but i heard that the AFR will jump all over the place when detonation happens?
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herbg26
Expert Class
Posts: 141
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posted October 26, 2009 07:19 PM
Yeah....also heard them being used on snowmobiles......found this site while doing a search..http://www.parkermotorsports.com/products.php..I guess the biggest issue will be the noise factor(distinguishing an actual knock and not another noise)....But that is interesting, about AFR, that if it flutuates then detonation/pinging is occuring, which may make sense, due to the heat, simulating a lean condition.
Interesting
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dougmeyer
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posted October 26, 2009 07:33 PM
There is nothing to mysterious about knock sensors. They simply detect a shock vibration in the structure of the engine. Detonation (knock) is a fairly violent event in the engine structure and easily detected. You may need to find the right spot with a little experimentation and calibration. Ideally you'd want it on (in) the head near the combustion chamber, maybe in a tapped hole in the wall of the head. Do some research and you'll find they come in a lot of configurations. I've used them screwed into an unused bolt boss on the side of a block or head on a V-8. The one on an LS- x deries GM engien is in the valley under the inlet manifold. In the early days we would calibrate them by tapping the engine with a wrench......
Doug
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rgeorge
Expert Class
Posts: 220
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posted October 26, 2009 08:19 PM
I am planing to install a knock sensor on my ZX12. I don't have any experience with knock detection so I cant give any advice, it will be a learning experience for me. This is what I intend to use.
http://www.turboxs.com/more_info.php?ID=212
I like the visual indicator, and hopefully I'll be able to log its output too.
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dougmeyer
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posted October 27, 2009 12:55 PM
I just read the advert and instructions on that piece. It's very deceiving and lacks credibility. They talk about "listening" and "noise" and that would or could lead somebody not as smart as you guys to think that the engine "noise" they are "compensating for" is audible sound (see their reference to the "tinkling" sound-Their way of describing "ping")
Knock sensors don't work that way- they pick up spikes in ambient vibration. They actually detect the shock wave through the engine structure caused by the detonation event. They are transposing the definition of background vibration generated electronic signal "noise" with sound wave noise, but you already figured that out I'm sure.
It seems to me that what you get with that unit is a light that can be hooked to any "real" knock sensor and that will trigger along with the reaction the actual sensor has when sending a knock signal to the ECU.
That's not a bad thing, I like the idea of a warning light, but it's not a real knock sensor and I am suspect of the verbal games they seem to think are necessary in their advertising.
Anyone please correct me if I'm wrong here.
Doug
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Y2KZX12R
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posted October 27, 2009 02:37 PM
I agree Doug.
I don't think who ever wrote that write up for the product did a good job of describing what detonation is and how its detected etc.. Or they just don't know.
Detonation and pre ignition are two totally different events and can happen in the same cycle or independently in different cycles.
With out getting into detonation (because there have been many threads over the years on it) I will say that an OEM knock sensor is tuned to "listen" at a specific frequency. The engineers know the exact resonant frequency of a supersonic shock wave bouncing around in the cylinder of THERE engine is. The resonant frequency of detonation in an LS-1 engine is different from an iron headed BBC engine.
So really a knock sensor needs to be "tuned" to send a signal if the amplitude of a specific frequency goes above a predetermined level. The frequency and level are very important.
On GM ECU's there is amplitude monitoring so the ecu can determine how bad the detonation is. There is whats called a "burst knock signal" and its when the ecu has seen strong detonation for multiple firings of each cylinder. It yanks the timing back very fast and a lot.
Not all detonation is harmful or damaging to the engine and light detonation is manageable by adding a tad of fuel and or taking just a little timing out.
Pre-ignition on the other hand is almost always immediately devastating to an engine under heavy load.
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