JB4 Thread for Lotus Emira AMG i4 (M139 Engine) – Tuning, Setup, Results & Support

Milk242 · 2025-07-27T12:32:16-0500

I never got the chance to hear @675430VME car with the jb4 but I can attest that the Mach 5 downpipe paired with his (I think is a custom) SS exhaust sounds extremely good for an i4. So much so that I also bought the downpipe.

Aforst · 2025-07-27T17:52:16-0500

ManuelB said:
That's great! 400 hp US version?
At crank, right? Thank's for sharing!

JB4 just arrived. Gonna mount it this week. Already installed the MACH5 GPF off, sports cat. It was a PITA to remove the original one..

400HP US version. Power figures are at the wheels. Hub dyno. Supposedly a stingy dyno that.

675430VME · 2025-07-28T01:38:17-0500

ManuelB said:
Yeah! Even with just the Mach5 downpipe, the sound at full throttle is already amazing — aggressive and sharp! And the pops during gear shifts and deceleration are absolutely out of this world. I can only imagine how insane it would sound with an upgraded rear muffler too.. hehe :-D

If noise is not a concern for you, I would go for a well design SS straight pipe. Cheapest, lightest, and sounds really badass through out the whole rpm. Some of the new straight pipes come with modified valve control so NO CEL as well.