What Is The Typical Knock Reading For Rb With The Vipec Ecu?

[Swiper the Fox]

  Taso84 said:

Abit off topic but was wondering if the PFC takes timing out automatically when it knocks like the Vipec does?

no it doesn't.

[robots]

the Vipec plug-in board doesn't support knock monitor/ignition retard on knock, right ?

[TiTAN]

It does support it, as long as you have an external signal filter/amp.

[Zurlox]

Sorry if im commandeering the thread

i have been reading around and getting some mixed views on this topic, what id like to know is, what is the raw output of a stock knock sensor, and what is the ecu looking for after the knock sensor is amplified?

so just in regard to the Knock amp/filter, they are bloody expensive, has anyone rigged up one from say...a jaycar kit?

any advice is much appreciated

Zurlox

[TiTAN]

mine is running off a jaycar kit but they are hardly compact.

The ecu is looking for a 0-5v input 0v being no knock and 5v being your engine about to explode with a signal somewhere in the region of 5-9khz.

[BoostedBarge]

  Zurlox said:

Sorry if im commandeering the thread

i have been reading around and getting some mixed views on this topic, what id like to know is, what is the raw output of a stock knock sensor, and what is the ecu looking for after the knock sensor is amplified?

so just in regard to the Knock amp/filter, they are bloody expensive, has anyone rigged up one from say...a jaycar kit?

any advice is much appreciated

Zurlox

I looked into this a few months back. The knock sensor is basically a microphone. The amplifier just amplifies this so that it can be detected by the ECU. The problem is that the engine makes noise at all frequencies. We only need to detect the knock which occurs at specific frequencies. The frequency of knock depends on a few things. Bore size was one of them I believe. I found a formula somewhere that calculated the frequency for you.

So the external amplifier needs to amplify to right level and filter out any unwanted noise outside of the knock frequency. There is an IC out there that is designed specifically for this (I can look it up if you want). It is surface mount and not commonly available from shops like Jaycar.

Also, knock only occurs at a certain point in the engine cycle. Therefore, a smart amplifier/ECU will only switch on the knock sensor input at those points in the cycle where knock is expected. I'm not sure if the Vipec does this or not.

After reading all this I was thinking I'd go for the amplifier sold by Vipec/Bob, but then you need to induce pinging in your engine to set the gain correctly, etc. That kinda scares me, so I've stuck with no knock amplifier and trusted by tuner's tuning

[STATUS]

  BoostedBarge said:

After reading all this I was thinking I'd go for the amplifier sold by Vipec/Bob, but then you need to induce pinging in your engine to set the gain correctly, etc. That kinda scares me, so I've stuck with no knock amplifier and trusted by tuner's tuning

if your smart you can do it in a non detrimental way, obviuosly you dont want to induce knock at full load, full boost and so forth but it is simple enough to do it safely at the right time.

Edited April 27, 2009 by URAS

[BoostedBarge]

Zurloc PM'd me for further details on the knock amp, but I thought I'd reply here for the benefit of everyone else.

The knock amp IC is the TPIC8101 http://focus.ti.com/lit/ds/symlink/tpic8101.pdf

Autospeed article on DIY knock detection

http://autospeed.com/cms/title_DIY-Detonat...48/article.html

According to that article the frequency of knock can be approximated as 900/(3.14*Cyl Radius). I read somewhere else the frequency also depends on cylinder temperature and the location of the knock sensor, so I dunno how accurate that formula would be.

I was trying to find a Subaru site that I read a few months back. It had lots of info including sound recordings etc. Anyway, if you do a Google search you will find a mountain of information.

I wonder how different the knock amp settings will be from one engine to the next. Perhaps it would be good to collate everyone's settings in a database or maybe the Vipec forum. It would be awesome if we could say RB26 = frequency...., gain....

The stock ECU and the power FC must do the amplifying and filtering on board, so I guess engines must be fairly similar.

Zurloc: Keep us posted on how you go

Edited April 27, 2009 by BoostedBarge

[Zurlox]

Update:

i got the knock kit from jaycar, but the frequency band is wrong, it detects noise within 4.8Khz to 6.4Khz, which is too low, i am looking for a band of about 6.5Khz to 9Khz, so in order to achieve this i need to change a couple resistors. the one you change are the 2.7K resistor (inbetween the two 5.6K resistors top right of board) and i changed it to a 1.6K resistor to beef up the low pass filter, the other one you change is the 10K resistor (inbetween two 6.8nF caps top middle of board) and i changed it to a 12K resistor.

Now i havnt confirmed these changes but they should be pretty close

[Zurlox]

Right from the horses mouth:

"Changing to the higher frequency range is easily done by changing the capacitor values in the filter.

The 6.8nF capacitors in the high pass filter become 5.6nF and the 3.3nF to 2.2nF and the 12nF to 10nF for the low pass filter."

This has come from the designers of the Jaycar Kit KC5444 to achieve a frequency band of 6-6.5Khz high pass to 8-8.5Khz low pass.

consult this diagram to get a better picture or things - Knock Schematic

Zurlox