Cat Shield 2 Makes Noises after professionally installed

Yeah... On some installs this has been a problem.

I once had my day ruined and had to give money back after pulling a cat shield off because of this. Basically, similar to the skin on a drum, the cat shield has a certain frequency of engine noise that is louder than all the other frequencies and it rattles/amplifies. In my annoying customer's instance it was turning hard while accelerating on city streets slightly uphill.

When I checked it out I found that if you kept accelerating the noise lasted for less than 1/4 a second, but my annoying customer who insisted on me riding with her during the peak of covid would take her foot off the accelerator soon as she heard the noise, which prolonged the noise and no matter how many times I told her to not take her foot off the gas every time she heard the noise she freaked out and took her foot off the gas.

Then, the next person I installed the shield on I took the advice of a mechanic to prevent that noise and screwed a block of wood between the back edge of the cat shield and the pipe between the cat and the resonator. This got rid of the previous noise, but created a lower frequency rumbling on cold engine start up. So I asked 'em to choose which of the two noises they prefer and they chose the noise they hadn't heard yet and never complained nor heard that second noise after I removed the block of wood.

Meanwhile on my own Prius and others since I've skipped including the plastic cover that used to be where the three nuts at the front of cat shield bolts into and haven't heard any noises from past 4 or so Prius.

So the current theory for me is that the unnecessary plastic cover where the front of the cat shield has three bolt holes creates a dampening effect on the edge of the front of the shield that amplifies it's ability to act like a skin on a drum and make a rattling. So I now have four of these plastic covers in my art supply section of my parts rack...

 

Can't wait to hear what noises come from the a piece of 'expanded metal', assuming it gets installed, either way it'll sound better than stolen.

 

Not a Gen 2 but basically like the same offending rattle on my Prius v.

When I first installed rge plate in 2017, fortunately, I used the rivet nut method with security screws. For at least a month I had the annoying rattle which I finally addressed.

The plate contacts the catalytic converter at the rear. THe converter 'hammered" a cavity in the aluminum plate at the point of contact. I found that out when I removed the plate and that I needed at least a half inch of clearance below that point of contact.

To achieve that, I bent the plate over a 2x4 so that the place of contact was at least a half inch down. I used opposing up and down longitudinal bends on each side like the photos show.

I then reinstalled the shield and got the half inch of clearance that I needed.



Six years later and still no rattles.

 

Maybe replace the rubber hangers if there worn out. The instructions for my Millercat shield reccomended to replace the hangers at the same time as the install to avoid rattle sounds. I didn't actually replace my rubber hangers and it doesn't make any odd souncs.