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Old 10-14-2007, 10:23 PM   #1
sense of nature
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Default 2.0 2.5. knock sensors

Does anyone know why the 2.0 has a knock sensor designed & used for a n/a ?
comparing p/n the only real turbo knock sensor is used on the forester & sti others vary but it specificaly says for non turbo when the p/n is used for the forester here's the link check it out

http://www.subarupartsforyou.com/cp_...el=Impreza+STI

http://www.subarupartsforyou.com/cp_...C+Knock+Sensor

http://www.subarupartsforyou.com/cp_...C+Knock+Sensor
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Old 10-14-2007, 10:25 PM   #2
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Has anyone switched to the sti sensor on their build ?
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Old 10-15-2007, 08:34 PM   #3
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A knock sensor isn't designed for a turbo or na. It is just a simple transducer (basically a microphone). There might be wiring harness, ECU related expectations, impedence, etc. differences between the catalog listings, but it isn't really due to na vs. turbo. I'd use whatever sensor the ECU you are using wants.
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Old 10-15-2007, 09:36 PM   #4
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Surely there must be a difference in sensors between the 2.0 & the 2.5 But there is no Forester w/ a 2.0 so why have 1 specifically to a 2.5 n/a & 2.5 turbo ? Since the displacement is the same for both & the induction being the only difference. Must be more ,This being a "built " motor discussion Who has switched is more my wondering I've convinced myself to replace the one that came w/ my 2.0 already
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Old 10-15-2007, 09:58 PM   #5
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"root" may be on to something, but every different transduser has to have its effective range, in my own, and sense's case we are running 2.0l sensors on a 2.5 block, so can the 2.0l sensor have the same effective range as the 2.5 or would it me nessiasary to change, for tuning purposes??? Woundn't the two different motors have two different sounds, and running a 2.0l sensor on and 2.5 screw things up!!
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Old 10-15-2007, 10:31 PM   #6
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I could see a 2.0 knock producing a slightly different pitch than a 2.5 knock. However I wouldn't think it would be different enough to specifically require a different sensor. I'm certainly not an expert here though. Just seems reasonable from what I know in general.

And if you really want to know, see if you can track down the technical data sheets for each sensor in question.
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Old 10-15-2007, 10:36 PM   #7
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Quote:
Originally Posted by root View Post
And if you really want to know, see if you can track down the technical data sheets for each sensor in question.
Good Idea
I may just have to do that
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Old 10-15-2007, 11:58 PM   #8
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Quote:
Originally Posted by root View Post
I could see a 2.0 knock producing a slightly different pitch than a 2.5 knock. However I wouldn't think it would be different enough to specifically require a different sensor.
Actually, you are right.

Knocking generally occurs at frequencies that are a function of bore diameter. Different bore sizes can use different sensors.

There are 2 kinds of KS used in automobiles. There are ones which are wideband, and others which are narrowband. Wideband sensors have a relatively flat sensitivity to a wide range of frequencies, while the NB version is tuned to a small range. NB senors are cheaper to make, and are good for detecting knock early. It also requires less processing on the ECU to read them. WB sensors are better IMO, because knock doesn't always occur at specific frequencies. Knock can appear at lower-order frequencies, which NB sensors will usually miss. It does take some complex DSP to make the best use of WB knock sensors, which isn't cheap and can be hard to get right.
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Old 10-16-2007, 01:32 AM   #9
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Quote:
Originally Posted by Silverpike View Post
...It does take some complex DSP to make the best use of WB knock sensors, which isn't cheap and can be hard to get right.
Or analog filters (op-amps, capacitors, resistors and a "little" knowhow combining them).
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