Eisennmann x RKP Ultimate Buyer's Guide for E9X M3

There are few exhaust manufacturers that carry the same prestige as Eisenmann. For over thirty years, Eisenmann has hand-crafted some of the very best OE and aftermarket exhaust systems for BMW, Porsche, and Mercedes Benz vehicles.

IND has been the proud North American distributor for the iconic brand for more than a decade, introducing our far-reaching enthusiast following to the German staple and, in some cases, helping put our own stamp on steering exhaust development for specific model offerings. The F8X M3 / M4 exhaust was a shining example of this—IND’s input was paramount in shaping the canister design, sound characteristics, and subsequent rollout. But even before that, IND was heavily involved in one of Eisenmann’s standout releases—the E9X M3 exhaust.

The Eisenmann E9X M3 Exhaust

The Eisenmann exhaust for the BMW E90, E92, and E93 M3

It must be said that the S65 is, in its own right, a crown jewel of BMW M’s history. Eisenmann’s accrued library of knowledge helped extract the very best parts of the S65’s glorious soundtrack while also improving upon the OE canister’s ghastly appearance. Indeed, the low hanging OE exhaust was an eyesore and the punitive tips out back were a dismally sharp disparity to the mighty V8 that lurked up front.

By contrast, Eisenmann’s effort mates a beautifully crafted canister with their iconic Le Mans tip—a striking 4x83mm quad configuration that fills the E9X M3’s rear bumper void. Connecting pipes are now standard fare and make installation plug and play where earlier versions required cutting of the OEM pipes. But the real transformation happens when you start the car—with the Eisenmann Sport fitted, the car bellows with eagerness for the open road. With the Eisenmann Race, the E9X M3 roars to life with a dominating presence. There are unique Eisenmann exhausts for E90 (sedan) and E92/3 (coupe/convertible) models which correspond to tip lengths and do not impact sound level.


Choosing Between Eisenmann Sport and Race

While it’s an indisputable upgrade regardless of sound level choice, both the Sport and Race have their virtues and both systems represent an admirable weight reduction from stainless steel construction. While the decibel delta between Sport and Race is obvious (20dB), it’s the backpressure reduction that represents a valuable distinction between each variant.

Explained: The main purpose of the exhaust is to, as the name suggests, exhaust spent combustion gasses as quickly as possible. By reducing backpressure, those high pressure spent gasses are able to exit more freely rather than meet resistance within the exhaust pathway. Since the overall pipe diameter between OE and Eisenmann remains consistent (i.e. not more or less restrictive), the exhaust gas velocity and scavenging also stays constant, which means backpressure is the only variable that will control viable power gains.

TL;DR: The Race exhaust will represent a slightly higher power output versus the Sport.


Finish Options & Special Editions


In an age where customization is a paramount concern, Eisenmann offers two unique finishes for their E9X M3 exhaust: standard (polished) and a Black Series variant (an IND exclusive). The latter adds a matte high temp ceramic coating to the exhaust canisters and connecting pipes. The LeMans tips are treated to a high gloss coating for that extra bit of flair and contrast.

For those of you who are envious of the interchangeable tips on the F-Chassis Eisenmann offerings, IND has spawned a trick version of the E9X M3 exhaust that can accommodate these new, larger slip-on 4x90 units. Just like the F-Chassis cars, the new, larger tips easily install onto the canister with the supplied clamps and can be swapped out for a different style in minutes.




Turn Up the Volume: The RKP X-Pipe

The Eisenmann E9X M3 exhaust is no slouch on its own, but its intensity and personality are amplified with the addition of an RKP X-Pipe. RKP has crafted three 304 stainless steel variants to suit the wide variety of emission compliance demands: street, sport, and race—all made in USA.

RKP’s street x-pipe is the tamest offering—it reuses the OEM primary catalytic converters while deleting the secondary units. Two twin resonators help control sound while ensuring no available power is robbed in the process. Because it reuses the OE primaries, the street x-pipe features a slip-fit front section for easy installation. No check engine lights or emission concerns here—just a bit more noise to amp up the Eisenmann—and a 10whp/15tq gain for good measure.

The RKP sport x-pipe is the happy medium of the three. As you can see from the graphic above, the full bolt-on sport variant deletes both of the OE primary and secondary units, but replaces the latter with high flow Magnaflow catalysts (400 cel). Like the street variant, two twin resonators at the tail end of the x-pipe help control sound and drone without depleting power. Speaking of gains, this is a setup that nets more oomph by virtue of deleting the primaries without the full catless odor, but still requires an ECU reflash or CEL delete to turn off the check engine light. Paired with the Eisenmann, the E9X M3 features a ferocious bark above the that coveted 4500rpm and absolutely sings to redline.

The RKP E9X M3 X-Pipe race variant installed

At the more extreme end is RKP’s bolt-on race x-pipe which deletes both primary and secondary catalysts for maximum power gains and, by virtue of its simplicity, is the lightest of the three. The familiar twin resonators carry over from the other two variants, but make no mistake—it is still very loud. An ECU reflash or CEL delete is required to eliminate the check engine light. Couple this with the Eisenmann (especially the Race variant), and your E9X M3 will carry unmistakable presence everywhere you go and is an aural treat to experience through the gears and on every downshift.



So What do I Choose?

As with any exhaust, individual tolerances play a big role in dictating the right choice for you. Our Eisenmann + RKP configuration guide represents our collective opinion on how we would rank sound and performance with each setup respectively. The Eisenmann Sport + RKP Race setup is a favorite within these walls—this combo is neighbor-friendly at start up and low RPM levels, but comes alive with authority as the car climbs to redline. We believe the Eisenmann Sport offers the most flexibility to add the x-pipe of your choosing, whereas the Eisenmann Race is often run alone or in conjunction with a "tame" x-pipe. The Race + Sport / Race x-pipe configurations have a menacing cold start and authoritative exhaust note throughout the rev range, but it's not for the faint of heart.

Whichever configuration is best for you, you're guaranteed to experience some of the very best that is readily available for the E9X M3 market and is bound to induce even more ear to ear smiles with every push of the throttle.

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