Quiet Muffler

Switched the muffler out on the car to make it quieter.

The previously installed muffler was a motorcycle muffler which featured two types of glass packing surrounding a straight thru steel mesh tube. I opened the muffler up and found that some of the glass packing was blown/burned out in a few areas.  The canister of this muffler is about 18” long with a diameter of 4.5”. This muffler was very loud and had a lot of drone at idle. It did sound awesome when the throttle was full on.

Installed a newer muffler. This one is off a motor cycle. It is longer than the old one. When you look down the pipe there is a mesh tube and what looks like a baffle, so it is not a straight thru design. The muffler is labeled Yutaka 2334 and seems to be off of a Honda CBR600.   The muffler has a 2-2.25” inlet and a much smaller outlet. The muffler is a lot quieter and should be quiet enough for the inspector.

Yutaka 2334 muffler
New Muffler
Old muffler, opened and glass packing unravelled. Glass was burned out in a few locations, but mesh tube is in reasonable shape.

Brake Repair

Had to find and issue with the brakes that the mechanical inspector noted. Symptom observed was brake pedal slowly lowering when pressure is applied.

Looked around for a while, and found that brake fluid was leaking slightly around the proportioning valve I have installed. I purchased the adjustable prop valve from Flyin’ Miata, and it came with metric M10x1.0 to SAE adaptors, as the Miata brake lines are metric and the prop valve is SAE.   The fluid leak appeared to be between the adaptor and prop valve body. I tightened the rear and began to loosen the front brake line when the adapter sheared off.   Will need to get more adapters and am looking at getting a different adjustable proportioning valve that has a built in sensor to indicate when there is hydraulic fluid pressure loss/differential from front to rear.

I think this one will work,


But I need to confirm that the sensor is not just a brake light switch. Summit confirmed that the sensor is a low pressure sensor for detecting brake failure.


Brake proportioning valve from Summit Racing linked above actually just has a brake light switch, not a failure warning switch.

Found a standalone brake failure warning switch from an older Chevrolet (photo below).

Differential pressure warning switch.

Generic diagram below:

Rock auto seams to have something like these here:


***UPDATED June 30 2018***

Hooked up the brake system and found a leak at the willwood proportioning valve again. Took a look at the CPP prop valve I ordered from summit tools and the front and rear plumbing are seperate so we used the CPP prop valve to just run the rear brake lines thru.  Hooked it up and bled the brakes to get all the air bubbles out. Went thru about .5 litre of brake fluid. Brakes are firm now with no leaks at the prop valve or elsewhere.

Front and Rear Bumpers.


Built bumpers from extra 1” steel angle, 3/4” square hss and 3/4” round tube. Materials cut and welded together.

Rear bumper made of 1” steel angle.
Mock up of front bumper. Still needs mounting to the frame.

Mechanical Inspection Action Items

Had the mechanical inspection performed last Monday. Was given a list of items to change or modify on the car including the following:

  1. install bumpers front and back
  2. install fender washers where seats bolt to the steel pan of the car.
  3. Install quieter muffler
  4. fix soft brake pedal issue
  5. install warning light indicating hydraulic brake pressure failure.
  6. Install missing washer on rear lower left control arm.
  7. Install more muffler shielding
  8. Fix powersteering pump leak

Started fabricating the rear rear and front bumper this weekend. Also found a new muffler with baffles that fits on the current exhaust. New muffler is a Yutaka 2334, from an older Honda CBR600.

Yutaka 2334 muffler
Rear bumper made of 1” steel angle.
Mock up of front bumper. Still needs mounting to the frame.
Sheared SAE to M10x1.0 brake adapter.