The E46 M3 "Rasp-X" mid-pipe - GENERATION 2

This component is the most effective way to get rid of the M3's typical exhaust "rasp" sound.  

Due to the origination of this sound and the specific wave characteristics, the only way to sculpt and tune this sound is with a dramatic modification to the midpipe section.  No standard rear mufflers, regardless of manufacturer, will eliminate the sound.  It is only through the precise sound wave tuning of the UUC Rasp-X components that the undesirable sound is eliminated.

The result is a pleasing tone, slightly deeper than original, and without the raspy tone.  When used with any aftermarket rear muffler, the results are the same.

"Often imitated, never duplicated" - the success of the original Rasp-X has produced a swarm of look-alikes.  We know, from our testing of these other products, that none of them has done the waveform analysis and tuning that we have.  None of them are "the same thing".  Nothing works as well as the Rasp-X.

NEW!  GENERATION 2 RASP-X NOW SHIPPING.

What's new with Generation 2?  We took everything that was great about the original Rasp-X, and redesigned everything to make it easier to assemble, modular for future expansion, and compatible with the BMW European-spec catalytic converter section:

1) Fully flanged connectors at front of section 1, rear of section 2, front of section 2, and rear of section 2 designed for a precise fit and installation exactly like the original mid-pipe.

2) Modular for custom-built replacement of section 1 with catalytic converter section when replacing the original in-manifold cats with headers.

3) Section 1 directly interchangeable with BMW European-spec catalytic converter section, enables use of European-spec headers.

COMPARISON VIDEO!  See the difference between a completely original BMW exhaust and the Rasp-X.  

Download the VIDEO [4.8mb] (Windows users should right-click and select "Save Target As..." to download to you computer.)

side by side comparison: click for a larger view.

We designed the E46 M3 "Rasp-X" mid-pipe section with several performance goals in mind: elimination of the M3's raspy tone. exact factory fit. compatibility with the original BMW muffler or any aftermarket muffler. no change in ground clearance. no impact on emissions or warranty. compatible with Euro catalytic converter and headers.

Images (click each page for larger view)

side view under-car view factory-style flanges factory heat shield for universal joint is retained. all mandrel-bent H-pipe design retained for optimal flow and balance characteristics uses all original mounting points. front section connected to engine rear section connected to muffler

Superior Materials and design

All UUC performance exhaust components are built from T-304 stainless steel.  All bends are smooth mandrel bends to retain full-diameter flow, and all joints are TIG-welded.  Factory-style mounting flanges are used, and all factory mounting points are retained.  100% made in USA.

UPDATE: Beware of so-called "stainless steel" exhaust systems using a 400-grade steel.  403, 404, etc., are grades of steel that are "stain resistant" but will eventually rust.  This cheaper material is often responsible for the significant price differences.  UUC uses T-304, a true "stainless" steel that will never rust.

Fundamentally, the exhaust fitted to the US cars contains compromises, and is different than the Euro models.

Because of US emissions laws, all E46 models have the catalytic converter in the exhaust manifold itself. The thick unit you see under your car (underneath the front seats) is simply a single asymmetrical resonator in the same location as Euro cars have their catalytic converters. Further downstream is a very small resonator that is not specifically tuned to any certain tone.

With these differences in mind, the Euro cars make a different sound and do not suffer from the same rasp that the US cars do.

The UUC Rasp-X mid-pipe uses UUC's hybrid resonator/muffler design in two locations - one in the area of the Euro cars' cats, and another in place of the downstream very small resonator. The dimensions of these hybrid sound-tuning devices are tuned very specifically for the rasp frequencies. These are free-flow units that re-structure sound waves without impeding exhaust flow.

Another characteristic of the original mid-pipe is that several parts of it are crimped and flattened for clearance. Keep in mind that factory specs for space clearances are more than generous, but when the "design the new BMW" rulebook says that nothing can be within X number of centimeters of the exhaust pipe, the result is that a small underbody clip or bolt causes the exhaust design team to dimple the pipe to retain "rulebook" clearance. The net result is a pipe with compromised volume with absolutely no chance of contact with any part, even if it moved over 100% of its width.

UUC uses a pipe diameter within 2mm of factory spec (our pipe is larger) to retain the flow characteristics of what is fundamentally a good mid-pipe design. We eliminate all of the crimps and flattened areas, substituting mandrel-bent pipe with sufficient clearance on all sides.

When only the Rasp-X section is installed with the original muffler, the net result is a slightly deeper yet rasp-free tone. Although prototype testers claim they are feeling a small increase in power, we are not making any significant power gain claims for this section, rather just a tuned sculpting of the sound.

The Rasp-X section is a direct bolt-in replacement for the original mid-pipe and uses the original support brace. No permanent modifications are required.

Pricing and Ordering

PRICE $1050.   - click here to order