[Malek@MRF]

Hello everyone,

I have read this thread over in good detail and I am going to do my best to clarify and answer everyone's questions in this post. I am not going to quote every person and respond individually because I am hoping this response will help address any of those curiosities and/or questions. Let me clarify a few things about the MRF Engineering Velaforza mid-section. It is not like all the other systems that have been made for the S65B40 power plant. The system is 100% and fully engineered for the S65B40 engine and does not employ standardized procedures in its design.

1) The system utilizes a true Motorsport X merge in the pipe which is TIG welded, not MIG. The system is also constructed of SS321, not SS304. All other systems to date use the balance tube design and not a true flow optimized X. The other systems out there, are using 2 curved tubes that are tangentially cut and mated together, some are even using off the shelf Borla or Magnaflow units. The factory system is designed this way as well. When it comes to power, volumetric efficiency and exhaust system scavenging, the balance tube design is inferior to the flow optimized Motorsport X-design, but it is also tremendously easier to manufacture in mass quantities. Now for obvious reasons, we will not divulge the proprietary specifications as to what goes on inside of that X with respect to its sizing, radius or merge angle.

2) The position of the “X” is moved as close to the transmission as possible, where it should be. The majority of other systems available do not do this because of system packaging and fitment into the E9x under body. It also makes it very difficult to add catalysts or resonators to the system. The factory configuration is most ideal if one wants to have flexibility in their system by being able to add resonators or catalysts.

3 )I have seen quite a few people post in here regarding piping diameter. Unfortunately most of these posts are improper or misrepresentative. What is not being mentioned is that unless the primaries from the exhaust manifold (header) and into the factory 4-1 collector are changed in sizing, switching up to a 3" or 3.5" pipe will offer almost no gain and will hurt low RPM range torque output. How do we know this? We built a 3" version of the MRF Velaforza system and it only hurt torque and did not improve HP output. This was also done on a fully built, supercharged M3. After tuning, the low RPM range torque loss was not recoverable and no appreciable gains were found. 2.5" diameter piping is well more than enough, even on ESS VT3 equipped cars , given the mid-section system is flow optimized. To clarify on the Akrapovic system, it is 2.39” I.D. piping, not 2.25” based on my digital vernier caliper.

4) The MRF system as mentioned earlier is an engineered system for this car. During the prototyping phase, the system was fully tested on a flow bench to optimize scavenging and system efficiency.

5) 100 Cell catalysts VS. Catless. Power wise, there is almost no difference at all, especially when high quality catalysts are used. If cheap units are used, they will eventually clog and restrict flow. In many cases, cheaper systems choke up the flow when excessively heated. This would not be the case with Akrapovic catalysts or HJS units. 100 CPI cats were tested during the prototyping phase of the MRF pipe and saw no difference in power and volume. The only aspect of the system that was affected was overall weight and it reduced a small amount of rasp, however overall volume was not changed. The MRF Velaforza mid-section was never produced with catalysts and never will be.

6) The effect on the naturally aspirated S65 M3 is substantial. Peak RWHP gains up to 28 RWHP along with 22 RWTQ and amazingly up to 35 RWHP and 40 RWTQ gains in the mid-range (if not greater) along with a smoother power curve. The dyno below illustrates the gains. The runs were done on the same day, same dyno, same tank of gas (Chevron 91 octane) in the same climate conditions. The only thing missing here were the use of fans in front of the car during the dyno session. 1 week later, the same car on the same dyno, this time with a tune, and fans in front of the vehicle, put out 404 RWHP. No other bolt on mods are installed on this car.



7) Sound. The Velaforza system was initially designed to be used as a complete set. The mid-section was tested on many axle back systems and not to our surprise, a lot of the typical rear section systems could not tame the MRF mid-section. The only other rear section that does a great job of controlling the inherently motorsport type sound of the mid-section is the MRF rear section and the well-known and popular Akrapovic. The MRF mid-section is very exciting when it comes to sound compared to other cat-less mid-sections available on the market. It really feels like a true motorsport, drivers car with it with some F1 undertones. Only if it could rev up to 12,000+ RPM... I personally love it as do some of the other guys that have it. Subjectively, it is daily drivable with the Akrapovic rear section. The initial batch of the MRF rear sections utilized finer perforated tubing and larger portions of the tubing to control the sound of the MRF mid-section. Over some time we realized that some may just want to use the rear section just on its own, so therefore the production versions we reduced the amount of perforated tubing so it wouldn’t be as docile if paired with a factory mid-section. The finalized version of the MRF rear section is louder than the prototype and it ended up introducing some minor drone into the cabin, whereas before it was as drone-free as the Akrapovic Evolution, however still daily drivable. The MRF paired with the Akrapovic rear is a great combination of excitement and civility with virtually no in cabin drone.

Below is a YouTube clip of the MRF full system in its final iteration. One clip is on the dyno, one clip is a GoPro bumper mounted camera.

8) Weight… The MRF mid-section weighs 19.6 lbs with all clamps and hardware (not including the 2 factory mid-section to rear section clamps, and not including the 4 factory nuts and bolts that mate the system to the header)

9) Last but not least... System availability. The MRF mid-section was a limited production system that was released at Bimmerfest 2011. The system sold out rather quickly. Since the posting of this thread by esquire, we have received many inquiries about this mid-section. Given the interest we are seeing for the MRF mid-pipe, we are strongly considering placing the system back into production on a pre-order basis.

-Malek@MRF

Originally Posted by aus

Good info. Looks like the first run was also 10 degrees hotter?

I could see the 100cpi cats/resonator causing some restriction on a blown car. It's way more gas flow than it was designed for. Evolve did pressure test on their X-pipe and didn't see much loss with the 200cpi cats in the secondary position, but I'm guessing that was on a FBO motor.
Maybe they could do another test on a blown motor??

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Originally Posted by Rapture

The Akra x-pipe is 2.25" piping. I believe the MRF x-pipe is 2.5" or greater. That is where A LOT of the power gains are made. I'm sure moving the X up helps a ton as well; Gintani has been doing that since the beginning and they have been making a ton of power from just their x-pipe as well.

Originally Posted by GOLFFRR

what about the weight difference between the two?

Originally Posted by img

Im redoing my exhaust system.the 2.5'' xpipe aren't doing it for me. I'll post some pics soon
Love your car btw

Originally Posted by esquire

Thanks man. Feeling is mutual. That's insane that 2.5" isn't working for you. Does your car need more flow (i.e. wider piping?)