retrofiting knock sensors

[bmwmaster]

I have some questions about knock sensing.

I have got an bmw m20 engine which is stroked from 2.5l to 2.8l capacity. It hast an cast iron block. It has no knock sensor from factory but i really would like to add this funktion as im using emu and it would be great to use emus knock sensing possibility.
My plan is to drill holes in the block in same posittion where knock sensors normally are mounted (near the head). Then i would mount knock sensors. But im not sure which kind of knock sensor would work. My first idea was to use m52b28 bmw oem sensors because its also an 84mm bore cast iron block but I have heard that oem knock sensors are setup for just their partikular engines and just can record an specific frequency range.

Now im not sure if this plan would work.
What would be the right way to install knock sensing ?

[RHD]

I would be more concerned about drilling holes in your block than the type of sensor!!

I know m20's extremely well, theres a bolt hole on the side of the block just in front of the starter i would try putting one there first.

As far as i know sensors that most bmw's use like m50 m44 etc are just a generic Bosch same as many other vehicles use so the sensor is not critical but that style is often considered the best type to use, they don't target a specific frequency you will be setting that in the EMU software. I found around 7.5Khz and 0.5 gain works well on the m50. (also 84mm bore)

[bmwmaster]

Thanks for advice.....i know about your knowledge
I just thought the sensers should be as near as possible to the burning chambers. I know the hole you mentioned as my engine is disassembled and i painted the block yesterday.

Do you think it will make problems when i drill the block, cut threads into the holes and install the sensors whit some sealing lube ?
Im also not really sure about that idea.........
Maybe your sollution would be really better and less dangerous.

But im also courious why you don't use knock sensors on your race engine builds ? Wouldn't this be an sensfull and altough cheap addon?

[RHD]

yes down a little bit lower is not ideal but its worth trying i think sound will travel through the block quite well. if thats no good you might find somewhere on the head to try??

The block generally is not very thick maybe only 5-6mm so drilling into it will go straight into the water jacket and its only cast iron so the strength of the thread is not going to be good

If my race engine was turbo i would consider using one just for logging and to keep an eye out for any detonation but its much less of an issue on an atmo engine thats tuned well and always uses the same fuel etc.

[bmwmaster]

I will give it a try with this possition. I think the 5th zylinder on m20 engines is most prone to knock and this hole is near to it.

I also found interesting information about positioning the knock sensor on Engine. Its nothing special but for those woh want to do the same maybe helpfull.

http://www.plex-tuning.com/news/item/9- ... ould-apply.