Mercedes-Benz

I wanted my V8 to sound like a real engine and not a sewing machine. After doing a lot of research, I decided to go with a straight pipe solution. Below is a summary of what I learned during each step of the process.

Step 1: Remove stock secondary cats, resonator, and muffler. (Pics attached)
I had this work performed by Fabspeed in Fort Washington, PA. They did a great job using T304 high quality stainless and custom CNC Mandrel bends. The challenge was that I wanted a true duel out. But, because I have a cabrio, both pipes need to exit one side.

Lesson learned: After going to straight pipes, it appears the car loses power. But, what is happening is that the power band shifts. The car loses torque on the lower end but gains are greater at higher RPMs. The transmission is used to the higher lower end torque and the adaptive transmission is used to that. A quick solution is to use the key/pedal ECU reset solution. This worked wonders and returned the responsiveness by allowing the transmission to shift better between speeds of 20-40 mph.

Ideally, the car should now be driven as a manual for best results. This will allow you to keep the RPMs up. The engine is a beast now starting at about 1800 RPMs. During normal highway driving, you can keep it in auto. But for full power when driving around town, stick to the manual mode. I also like manual for very quick passing on the highway.

Step 2: Get an ECU tune to match the new exhaust.
I had this work done by OE Tuning. I ordered the MyGenuis device. It arrived very quickly. After pulling the ID off the car, I sent that to OE Tuning. They returned back tunes for 93, 91, and 100 octane along with a valet tune (20 km/h). At first, I had an issue writing the tune. But it was resolved quickly and was just a simple issue with the file. When it works, it takes only about 90 seconds to write the new tune. Overall, they provided great service.

Lesson learned: You really need the ECU tune to further help issues as mentioned above in Step 1. This made driving in automatic mode a lot better. But, I still prefer manual shifting. The car feels a lot more powerful.

Sound: The car is a loud during cold start and heavy acceleration. It sounds like a V8 should sound! During normal driving it is fine and the cabin noise is a not an issue. The car get really loud starting at about 3000 RPM when under load. Normal driving at about 2000 RPM is fine. (sound clips coming soon)

MPG: After the straight pipes, I gained highway mpg lost city mpg.

Before exhaust and tune cluster readings:
City ~18-20; Highway ~22-27; lowest cluster read 18 mpg city
After exhaust and tune:
City ~15-18; Highway ~23-26; lowest cluster read 12 mpg city

Overall average based on 99% highway driving commute of 45 miles @ 80 mph: 25 mpg using gallons filled/miles driven (not the cluster mpg reading)

Fatz

That's really neat! Just finished my exhaust a couple months ago. Really would like to hear the exhaust note. Looks like excellent work.

Mercedes-Benz

Once I get a mount for my video camera, I will post a few videos

Jamesbbh

In the end, in your honest opinion, was all of the hassle/$$$ worth it? The work looks awesome btw.

Mercedes-Benz

100% Yes. The sound is amazing and manual shifting is even better because I can hear the engine. I have more power and the engine just feels better IMHO. When the top is down, it is like a motorcycle with 4 wheels!

omega48er

^ what i hate a about the stock exhaust is that i do not hear the power, lol. i like how the g37 sounds, you can hear that engine. i wish the w209 came stock like that because we have the AMG exhaust.

Im planing on doing my flowmaster with high flow cats soon.

Mercedes-Benz

Yes that was my major issue as well. Especially for a car with a paddle shifter. It was tough to feel what gear I was in unless looking at the tach. But now there is no question when I hit 2500-3000 RPMs!

IamBrianHartman

Did you ever replace your exhaust? If so, where did you shop the parts?