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A Closer Look: Turner Motorsport F10 M5/F13 M6 Race Inspired Axle-Back Exhaust

Product Review: Turner F10 M5 / F13 M6 Race Inspired Axle-Back Exhaust

** Updated 03/21/2013 **

“The F10 is clearly one of the fastest, best performing BMWs ever made. It's deceivingly fast - the first thing this car needs is some exhaust noise to go with all this power” – Will Turner

With the twin turbos and extensive sound deadening materials the engine sounds are too distant and unexciting. It's so quiet in fact that BMW had to develop a soundtrack of the engine to play through the stereo just so you knew it was there. With the windows down or from outside the car there is a slight hint at what the M5's V8 is capable of. How about exploiting that sound and letting more of it be heard? The new Turner Motorsport race-inspired exhaust will release more of that glorious M5 thunder!

That the M5 is so quiet is suprising given the lack of resonators and mufflers in the exhaust system. A look at the stock exhaust reveals a very open system. From the back of the turbos to the tailpipes there is only: small catalytic converters, a pair of moderately-sized resonators, and a pair of small mufflers. Any increase in volume would have to come from removing the factory mufflers. Muffler delete modifications are a recent trend in the BMW market. They offer a way of getting more volume from an exhaust, a modest power gain, and a nice weight savings. It's been very common with V8 E39 M5 owners. So with our Frozen Grey M5's mufflers barely a few months old we took a saw to them and set about developing a highly crafted axle-back exhaust kit.

From the start of development our #1 goal was to have a finished product worthy of a $100k+ car. While cutting out the stock mufflers is 'easy', applying the finishing touches and providing high quality pieces is what takes the extra effort. Any muffler shop can weld on some pipes or even a set of universal tips. But our final product is as nicely finished and well manufactured as the OE exhaust it replaces. We use a 304 stainless steel, mandrel bent 1-piece tubing in the same pipe diameter as the factory system that also re-uses the factory hangers. To meet market demands we specified two tip styles - brightly polished stainless or polished piano black tips. Once the mufflers are removed, our kit simply clamps to the stock exhaust pipes. The tips fill out the rear bumper perfectly and greatly improve the rear appearance.

The mufflers create backpressure which makes the turbos work harder. Testing with a DynoJet came back with a 14hp and 19ft-lb improvement over the stock exhaust.

Installation

Removing the mufflers involves cutting them off the exhaust but this can be done with the whole exhaust remaining on the car. Of the M5s that we have inspected, all had dimple marks to use for a cutting referance. Once we measured and marked where to cut we used a standard sawz-all electric saw. After de-burring the pipes with a file we applied some Acousti-Seal sealant to the edge and slid the new straight pipe on with the clamp. Remove your original hangers and reinstall on the new pipes. Repeat for the other side. We left everything loose so we could get the tips positioned perfectly. Slide the tip section onto the pipe and align within the bumper opening. Once you're satisfied, tighten the exhaust clamps all the way. The kit comes with plugs to cap off the vacuum lines for the start-up valves. Total time for our first install was under 1.5 hours and we were taking our time.

First Impressions

Immediately upon initial start-up we were smiling. The exhaust barked back at us with small pops and burbles thereafter. This is mainly due to the absence of the butterfly valves installed at the factory to quiet start-up noise. Revving it in the shop produced a fierce ripping sound that perked the ears of anyone within hearing range and drew them in for a closer look. Revving the exhaust released more of that snarl and we knew this mod would be a winner.

In Depth Impressions

Out on the road the exhaust is still quiet. There's just not much exhaust noise that overwhelms the Active Sound system. We've seen full exhaust systems for this car that don't make much of an impact on sound within the cabin. The turbos keep exhaust volume lower than anything else. And with the Active Sound managing engine noise equally throughout the cabin there won't be much difference with performance muffler upgrade. With the radio on and the windows up the muffler delete pipes are not a massive change from stock. But roll the windows down and there's no longer any doubt that you're behind the wheel of an M car. The sound is very much like the stock exhaust note but it's louder and with every downshift the exhaust pops with more vigor. Change into a higher gear for cruise and it's as quiet as any luxury car. But drop down a gear or two and exercise your right foot and you're met with a bark and roar. There's a Jekyll and Hyde persona at play here. We tried very hard to get this system to drone and we only witnessed it under 2,000 RPM in too high of a high gear (i.e. 'lugging' the engine). On the highway at 70-80 MPH there is no drone at all.

At under $1,500 this kit accomplishes much of what more extensive and more expensive systems do and it looks the part. A complete and quality product was our first requirement. If it looked homemade or like it came from a chop shop garage there would little chance a product like this would survive first impressions. But by engineering the system correctly and designing it expressely for the M5 we're proud to install it on our own car and offer it to like-minded customers. It's an excellent choice for someone who loves the stock sound and just wants to hear more of it. If you want to alter the sound and create a different aural experience, there are other systems that will do that. But this kit is designed to enhance the stock sound, improve the looks of the exhaust, and be right at home on a car of this caliber.

Product Links

	Turner Motorsport F10 M5 Race Inspired Axle-Back Exhaust

	Turner Motorsport F13 M6 Race Inspired Axle-Back Exhaust

Specs

section:	rear section (rear muffler delete)
connects to:	stock section 3 pipes (ahead of mufflers and just aft of rear subframe brace)
tip style:	102mm (4.0") quad angle-cut round in polished stainless or satin black with Turner logo
material:	T304 stainless steel
power gains:	+14hp / +19ft-lbs
weight savings:	15lbs total