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Old 04-21-2007, 07:40 AM   #26
Zak Shaker
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quick question,
why don't we use standard knock sensor to read knock ?
I'm new on sub forum, don't tell me there is no knock sensor on sub engines?!
now, what is the ej20 knock sensor type (resonnant/non-resonnant) and frequency?
Emanage ultimate can monitor knock, but you need to tel him your sensor type and frequency.
cheers
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Old 04-21-2007, 09:17 AM   #27
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There is a knock sensor on our engines. Some people do use it by intercepting the signal but for those that don't want to (me) pick up a separate one. Some systems will come with their own knock sensor like the TurboXS Tuner Pro so there is no need to use the stock one.

The EJ20 sensor is not frequency tuned. The ECU does the grunt work.
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Old 04-21-2007, 10:11 AM   #28
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thanks for your answer

the thing is, I will use RON95 on an ECU that was probably mapped for RON102 (V5 JDM STI type R) for the simple reason we don't get any better fuel over here (exept avgas for race)
So I would love to read from the standard knoc sensor to see when knock occures and do a proper RON 95 ignition map.
as I have an EMU ready to fit in, I just need to know standard sensor type and frequency

Last edited by Zak Shaker; 04-21-2007 at 05:18 PM.
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Old 04-25-2007, 07:58 AM   #29
nhluhr
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Since this is such an old thread, readers should be aware that TurboXS now offers a nice setup:
Knocklite

http://www.turboxs.com/more_info.php?ID=212
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Old 07-24-2007, 08:02 AM   #30
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Quote:
Originally Posted by cdvma View Post
The EJ20 sensor is not frequency tuned. The ECU does the grunt work.

really?? this counters something I heard (EFI school) taht knock sensors HAVE to be tuned to the SPECIFIC engine... now if I/that's wrong, I'll admit it, but I presumed that my txs knock AMP would work w/stock sensor.
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Old 07-24-2007, 09:20 AM   #31
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All they do is essentially amplify the engine noise. Granted, its not every frequency in the book but it isn't tuned to the specific frequency of knock on the specific engine that it rests on. The ECU does the digital signal processing (DSP) to listen in on specific regions which makes the whole setup tuned for the specific engine but not just the knock sensor. I've found this based on actually taking a stock knock sensor and recorded the sounds it produces. Its all over the place and NOTHING like what a frequency tuned setup sounds like. The Link knocklink ect is just a simple noise based comparison. You turn a knob to adjust its sensitivity based on the noise floor alone...this is a horrible way of doing it. TXS has good DSP stuff in other products so I'm assuming the knocklight has some of that intelligence.
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Old 07-24-2007, 12:32 PM   #32
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You can always use the analog signal processor called the human ear. I'd love know what frequency the stock sensor is listening to.
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Old 07-24-2007, 12:43 PM   #33
cdvma
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Its not that simple and obviously you haven't heard the raw block noise or you would know. If you listen to what the sensor produces, knock gets tossed amongst other noise and is very hard to detect without either lots of experience or signal processing.

The general rule for finding the frequency of knock is freq = 1,800,000 / (Pi * bore_mm) and you apply a window around it to listen in.
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Old 07-24-2007, 07:30 PM   #34
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Quote:
Originally Posted by cellobro View Post

really?? this counters something I heard (EFI school) taht knock sensors HAVE to be tuned to the SPECIFIC engine... now if I/that's wrong, I'll admit it, but I presumed that my txs knock AMP would work w/stock sensor.
From the OEM world, I've worked with both. We've used "narrow-band" knock sensors that are tuned for a specific frequency range. The downside of these is that you're stuck with that particular frequency range and while it may work great at some RPM/load regions, it may have a piss-poor signal to noise ratio at others. (note -- cdvma's frequency is a good one for knock, but sometimes the signal to noise ratio is better at the resonance frequencies of the actual knock signal).

For some other packages, we use "wide-band" knock sensors which will read a broader frequency spectrum. Then use the ECU (actually, a specific chip on the ECU) to pull out a specific frequency spectrum, sometimes varying with RPM or load. These work more better but are a PITA to tune for.

Also note that a "good" knock system will always be adapting to the "background" non-knocking engine noise and look for a delta between the non-knocking signature and the current sensor output. I haven't seen much on the over the counter setups, but I don't trust them on this point.... They will, however, warn you of moderate-severe knock before the big parts of your engine vacate the block.
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Old 07-24-2007, 09:24 PM   #35
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Very well said. Yea the equation is a "rule of thumb" for finding the frequency but that didn't mean its the best place to listen. Obviously finding where the harmonics are depends on the frequency and the ability of the engine to carry them.

Its all basically boils down to, its not easy as just listening in or using a volume gauge like the KnockLink
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