2023-02-11 Swap to Janspeed Exhaust
My current exhaust is a custom 2.25" stainless system with a large Powerflow straight-through silencer, which was developed to reduce back-pressure for when she was turbocharged.
Nowadays she's running NA and I've been curious to fit my old Janspeed 1.75" mild steel cat-back system stored in the garage to see if the smaller pipework helps improve gas velocity/scavenging/low-end torque and see how different it sounds
Comparing the janspeed system to the powerflow system.
Notice the janspeed silencer is smaller but very long, which may foul the suspension, and the resonator is slimmer.
Janspeed system weighs 11.8kg
Powerflow system weighs 13.2kg
Fitting the janspeed system in place, it's originally had fitment issues.
The mid-pipe here rubs closely against the sway bar especially whilst cornering
The bend over the axle going to the very long silencer would foul the rear upper trailing arm bracket when going over big bumps
The long silencer also sits pretty close to the rear bumper.
So overall the pipework needs a slight adjustment
Finish making the gasket between the silencer & mid-pipe
Marked & welded the 2.25" stainless decat pipe to the exhaust adapter flange I machined
To correct the clearance/angles of this janspeed system, I had to narrow/shorten the mid-pipe by 40mm.
I used a piece of cereal box to mark the section to cut
Used the chopped section as a sleeve to hold & seal the join
Welded up. now you can see the pipe clears the sway bar much better
To mount the silencer to my modded chassis without altering the janspeed hangers (incase I sell em), I made this simple hanger
Welded onto the silencer (it can be chopped off in future)
Mounted onto the rubber bobbins
With the new angle, the pipe now clears the upper trailing arm bracket
But due to the long silencer, I've noticed it sits really close to the panhard rod by 28mm.
The rear suspension has 45mm of bump travel so it will definately hit when going over speed bumps
Everything all reassembled & ready to go.
Needs painting soon afterwards
That big shiny rounded tip is looking much better than the old 2.25" stainless straight tube
Hearing from my seat, they both sound similar at idle, cruise & high rpm.
The main difference is a deeper louder boom/drone at low rpm / high load (probably due to the smaller silencer/resonator)
and more pronounced/raspy gassy sound at the tail-pipe when rapidly blipping near idle (maybe due to the funnel shape of the tailpipe acting like a trombone).
Torque-band kinda feels slightly broader but I think that's probably due to the de-cat and a colder night air.