Knock Sensor

[mrjezza]

Reading through some of the articles posted by john318isau (nice work btw , I've seen quite a few of the reviews mention knock sensor(s) in the E30 M42.

Common opinion seems to be that the E30 M42 doesn't have any.  Is it possible only he US E30 M42 didn't ship with the knock sensors, or maybe only the UK E30 M42 did?

[318-is]

No m42 has a knock sensor im afraid afaik, the motronic 1.7 is not capable of dealing with it i dont think. Also, there is no space in the block for the sensor itself to be fitted. spose you could get one machined at a risk but its not really worth it mate

[silverblades181]

As far as I know only the M44 has knock sensors.

[318-is]

As far as I know only the M44 has knock sensors.

i agree. The m44 also had lambda, making it closed loop. also, i dont think the motronic 1.7 found in e30 318is m42s has the ability to deal with knock? i know the eprom doesnt have look up tables for lambda as tim_s tried it!

[doigal]

late M42s (e36) have the knock sensor.

[mrjezza]

The reviewer must have been wrong then because I found what I had read in Road and Track December 1989:

"DME 1.7 provides knock protection, self-diagnosis and even cuts off the fuel when the car is coasting".

No doubt about what it says, but obviously not correct then.

Did the they use a different version of the Motronic in the E36 M42?

[bmwman91]

The E36 uses the Motronic 1.7.2.  It has support for the knock sensors as well as the DISA intake manifold.

All US cars had lambda input on their Motronic units, and definitely run in closed loop when not at WOT.  Definitely do cut off fuel while coasting as well.  Just look at the instantaneous MPG gauge when you got off the gas 100%.  If you open the throttle even 1% the needle will make an abrupt change as the injectors begin firing again.

E30 M42: Bosch PN 0 261 200 175, Motronic M1.7 (PIC)
E30 M42: Bosch PN 0 261 203 282, Motronic M1.7.2 (PIC)

[Frankie]

So, you are saying that there is no way to install knock sensor to a E30 M42?

[jajou318]

Ok, then question, how would I find out if mine has a knock sensor? It may be possible that it does because I had my engine replaced with a manufactured one from BMW in '98.  It's wierd cause it has an m44 oil filter.

[RED IS 91]

on the left side (driver side US) there is the coolant temp sensor and behind it is the sensor for the temp guage. Right below that and a little further back is where the knock sensor would be if you had one .you have to remove the upper intake manifold to access it .

[jajou318]

hmm i'll check for that tomorrow

[Alibi]

Ok. The M42 in E30 doesn't have knock sensor. But the engine block is the same. So if we take a knock sensor from E36, then we can install it on the E30 M42 block. Right? I am runing MegaSquirt, so in my case it is good to have knock sensor.
My idea is to take one from E36 (or perhaps from some other car) and to mount it where normally the knock sensor in E36 stays. Than wire the sensor with the MS and from the MS I can wire a LED and see if there is a knock.