Prothane motor mounts = Knock

[Fattie92]

Well i finished installing my prothane motor mounts a few weeks ago when i was putting in my clutch. Ever since i have put them mounts in, i get counts of knock as i start to accelerate. I will get anywhere from 2-45 counts in 1st gear, and it usualy continues into 2nd and 3rd, but it tappers down after first. If i bring the revs up and accelerate from a stop i will get no knock in any of the gears. The car is tuned well, and there are no boost leaks. Id hate to put in stock mounts just to cure this problem, but so far its the only thing i can come up with. Anyone else have this problem that has prothanes? It would sure be nice to get this resolved.

 

[SlowSpyder]

Prothane motor mounts will cause more vibration to be felt in the cabin not knock. You have a tuning issue or something else but its definitely not your motor mounts

 

[Fattie92]

Prothane motor mounts will cause more vibration to be felt in the cabin not knock. You have a tuning issue or something else but its definitely not your motor mounts

So your saying that all the extra vibration cannot be picked up by my knock sensor? I do not agree with that... if that is indeed what you are saying. I never said my engine was knocking. I siad that im getting knock counts.. There is a BIG differance there. You even said yourself, "Prothane motor mounts will cause more vibration," and what exactly is a knock sensor sensing for? VIBRATION!

 

[R3dR]

The knock sensor picks up noise not vibration but the vibration may be causing a noise that the sensor is able to pick up so what have you came up with ? Did you try and grease the mounts to see if it stops the knock?

 

[talon1979]

Many people run prothane motor mounts and do not have knock issues. I think you are looking at phantom knock issues. Also, I wouldn't knock on people who are trying to give you advice, especially when they are giving you good advice.

 

[Fattie92]

i wasnt trying to kock on him. I just think he missread the post. I greased the mounts as i put them in. I dont know where to start with this issue.

I said vibration cause vibrations usualy cause a noise. If you hooked up a piezoeletric crytal knock sensor to a scope, then put the sensor against anything that vibrates, it will pick something up depending on the intensity of the vibration. As long as its strong enought to distort the crystal, itll produse a voltage.

 

[realhp=turbo]

A knock sensor is ALWAYS mounted directly into the block. The only thing it hears is the knock that the motor is producing. Where else would you have a knock issue in the rolling chassis? Unless you have an extremely bad wheel bearing you will not get any knock from the rolling of the car. Not even when driving over those little bumps the put down for lines on the freeway or big potholes. If your getting knock then you should probably start with running premium fuel and adjusting your timing.
mike