E30 318i M42B18 Exhaust Question
Posted: Sat Aug 02, 2025 4:47 pm
Afternoon Zoners
Long time lurker here.
I bought a pretty nice E30 318i 3 years ago and have spent some time making it my own. I am a OEM+ kind of guy. Don’t know how to add pictures here, anyhow.
I recently swapped a m42b18 from a z3 into the car and it’s going well, it’s got a lightened fly wheel from JB racing. I have the original 318i exhaust fabricated on for now but intend to replace it.
My question is, how much different, if at all, was the IS exhaust compared to the I?
Secondly, will I see any performance gain by going aftermarket and am I restricted flow with my current set up?
Lastly, do you guys have recommendations for a back box type set up? I’ve seen the super sprint options and it’s expensive.
Best
Scott
Long time lurker here.
I bought a pretty nice E30 318i 3 years ago and have spent some time making it my own. I am a OEM+ kind of guy. Don’t know how to add pictures here, anyhow.
I recently swapped a m42b18 from a z3 into the car and it’s going well, it’s got a lightened fly wheel from JB racing. I have the original 318i exhaust fabricated on for now but intend to replace it.
My question is, how much different, if at all, was the IS exhaust compared to the I?
Secondly, will I see any performance gain by going aftermarket and am I restricted flow with my current set up?
Lastly, do you guys have recommendations for a back box type set up? I’ve seen the super sprint options and it’s expensive.
Best
Scott