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Knock sensor question
Posted: Tue Jan 24, 2006 9:10 pm
by darkstarmedia
I have read a bit about the knock sense circut and the upcoming update. I was wondering how a wet sleeve style block would effect the knock frequency? I was wondering because there would be no real connection between the sleeve and the block. I was thinking the head but the head gasket is there... those whom are in the know, please share....
Posted: Thu Jan 26, 2006 12:33 pm
by rufusbooth
Hi Richard,
I am no expert by any means and I am sure somebody will jump in and correct me if I am wrong. I do not believe the wet block will affect the frequency of the knock. I believe that is a function of cylinder diameter and shape of the combustion chamber and piston face.
I know that Ford actually places the knock sensor (5.0L V8) on the intake manifold towards the back of the engine. That being the case you should be able to mount the sensor on the intake or the block as it does not appear to be affected by separating gaskets.
I (personal unfounded opinion, Danger!, Danger!) would avoid placing the sensor on the cylinder head as there will be a lot of valve train noise up there. From what I understand that is the hardest thing to filter out of a knock sensors signal.
Hope that helps,
Cheers,
Rufus
Posted: Thu Jan 26, 2006 12:37 pm
by darkstarmedia
any formula to figure the frequency??
Posted: Thu Jan 26, 2006 12:50 pm
by wes kiser
Rougly equal to C/(2*b). Where C is equal to the speed of sound at the temperature you are concerned with, and b is the bore. Practically what you should do is to pick a sensor circuit from an engine with a similar bore size. Using the equation I mentioned, you will still only get close (because we don't know the exact temperature, and this is the real world not a textbook). Also the wet part doesn't effect the actual frequency, but will affect the amplitude of the noise. Valve train noise is difficult to deal with because it is frequently close to the knock frequency.
Posted: Thu Jan 26, 2006 12:55 pm
by darkstarmedia
how close would the bore have to be?? I have a 93mm bore (3.6614 in).
Posted: Fri Jan 27, 2006 5:23 am
by wes kiser
A chevy 305 has a 3.74 inch bore. I would think that would be close enough. Lots of them (complete with knock sensors and esc modules) are conveniently sitting in junk yards.
Posted: Mon Mar 27, 2006 11:50 am
by IcantDo55
rufusbooth wrote:Hi Richard,
I am no expert by any means and I am sure somebody will jump in and correct me if I am wrong. I do not believe the wet block will affect the frequency of the knock. I believe that is a function of cylinder diameter and shape of the combustion chamber and piston face.
I know that Ford actually places the knock sensor (5.0L V8) on the intake manifold towards the back of the engine. That being the case you should be able to mount the sensor on the intake or the block as it does not appear to be affected by separating gaskets.
I (personal unfounded opinion, Danger!, Danger!) would avoid placing the sensor on the cylinder head as there will be a lot of valve train noise up there. From what I understand that is the hardest thing to filter out of a knock sensors signal.
Hope that helps,
Cheers,
Rufus
The 5.0 blocks with knock sensors have them mounted into the BLOCK not the intake. Its behind the intake on the block just about where a Cheby distributor goes. The intake is in front of it.