This is on our SpecE30 race car. I noticed a weird noise this weekend. It almost sounds like someone tapping their knuckles on the body of car. Here's a recording of it, pay no attention to video portion as I'm not trying to show anything, just using it for the audio recording of a knock sound that is only audible in the cabin.
Video was taken at 2000rpm where it seems the easiest to hear. Note the frequency of the knock does change with engine speed but not in sequence with RPM (2000rpm=33.3rev/sec) or with a single cylinder's firing. No change if the clutch is in or out. Cannot be heard from outside the cabin as the normal valvetrain noise is louder. You can feel the knock if your hand is on the cowl steel just below the windshield. You cannot feel the knock with a hand on the intake manifold or on the transmission from the bottom side but this may just be due to it being washed out with other normal engine vibrations. Rigid poly engine mounts, no crank driven fan.
I have no idea how long this has been there. Afterwards noticing this, I ran qualifying with one of my best times ever and the race including standing start with no ill effects or change in the noise which is the same as it was when I first noticed it. Noise is the same with the engine cold or hot.
Any ideas? I'm stumped.
Video was taken at 2000rpm where it seems the easiest to hear. Note the frequency of the knock does change with engine speed but not in sequence with RPM (2000rpm=33.3rev/sec) or with a single cylinder's firing. No change if the clutch is in or out. Cannot be heard from outside the cabin as the normal valvetrain noise is louder. You can feel the knock if your hand is on the cowl steel just below the windshield. You cannot feel the knock with a hand on the intake manifold or on the transmission from the bottom side but this may just be due to it being washed out with other normal engine vibrations. Rigid poly engine mounts, no crank driven fan.
I have no idea how long this has been there. Afterwards noticing this, I ran qualifying with one of my best times ever and the race including standing start with no ill effects or change in the noise which is the same as it was when I first noticed it. Noise is the same with the engine cold or hot.
Any ideas? I'm stumped.
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