Amochosto

I'm one of the weird ones, who don't mind a new exhaust for power, but don't need more noise to let the police know I'm around. How much louder are these units than stock in db, under load at say 5000 and 8000 rpm?

brandon@heel.toe.hero

It's hard to measure dB volume outside of the car under load at high RPM consistently, but inside the cabin we saw 75-77 dB at 70mph stock and 78-80 dB once the OAP were installed. I can measure that again today to confirm, I am going off of memory.

The difference in sound level at highway speeds is pretty minimal, though. It's higher RPM and under load that we see a bigger increase in sound level.

I can also try to get a 2nd or 3rd gear pull to redline and measure the dB level inside the car to see what it's at now. Stay tuned, I should be able to get that today.

brandon@heel.toe.hero

Ok, did a pull in 2nd and 3rd up to redline. Phone was mounted to the roll bar about 4" from my head to get the closest measurement to what you'll hear inside the car.

77.2 dB measured at 70mph in 6th gear on flat ground holding speed, windows up of course.
104.2 dB max measured sound level between both pulls.
48.5 dB at idle.

brandon@heel.toe.hero

Just got our GT4 RS OAPs in and internal measurement of the pipes are approximately 67mm ID and 71mm OD for both resonated and non-resonated versions.

brandon@heel.toe.hero

Our first set of 4RS resonated OAPs has been installed, dyno numbers coming this week...

Visceral

Install of the 4RS OAPs was straight forward. Fitment was great. Weight savings is approximately 5kg/11 lbs. Time is slipping to get a dyno this week at we have an AutoX out of town this weekend... but its definitely a high proiority.

The sound is good. No additional exhaust drone going up a long highway incline with the valves shut. The trick with the 4RS is that because 7th is so short, the 2000-2500rpm zone requires going pretty slowly in the slow lane. Driving at the typical 70+, the exhaust and the intake are both in the less drone-prone ~3000-3200rpm. It's definitely 90% tire noise at that point.

With the valves open, the car clearly has a modified exhaust. I'm still unsure how it sounds at full song as I can't hear much over the intake.

I'm really pleased with the sound. Power TBD.

Visceral

There's no resonated option like the ones I received from 9m. Just with or without a cat. The ones I received are not of that same "mid" quality.