I just purchased a Competition Werkes exhaust. Unfortunately, I will have to wait to install it until after I purchase a PCV...

 

Peter, I'm glad you had a chance to read the long thread by Formula390 documenting his prolonged but ultimately unsuccessful efforts to create an alternative to the OEM underbody exhaust. Knowledgeable people who have studied the stock exhaust are genuinely impressed by its engineering and effectiveness. This is a very cleverly designed piece that extracts excellent power from the engine, emits a civil exhaust note and meets developed country pollution standards, all in a compact, mass-centralized unit that is nearly invulnerable to crash damage and does not interfere with luggage.

Sadly, this highly-developed product of KTM's engineering team is underappreciated by a sector of 390 owners: it is most often maligned for being too quiet and vilified for not producing a more raucous exhaust note. (NB. I just learned from watching a YouTube evaluation of the new 2017 Duke by an Indian tester that the new exhaust reportedly was necessary because the 2013-16 exhaust could not meet Euro 4 NOISE standards - the outgoing stock exhaust was sufficient to meet the emissions standards but was TOO LOUD!!) Those who criticised the Gen 1 exhaust's moderate tone will find even more fodder for frustration with the new 2017 unit! Still, many 390 owners have been eager to spend large amounts of cash on aftermarket cannister exhausts that are only marginally lighter, produce little if any gains in power/torque, require an expensive fuel controller to protect the engine, and are very vulnerable to crash damage. The chief "benefit" of these exhausts seems to be that they are less successful than the stocker at dampening exhaust noise.

To my mind, really the only sin of the Gen 1 stock exhaust is that it is rather heavy - about 14 lbs (6.4 kilos). Likely for reasons of production costs, the whole unit is fabricated from mild steel, rather than alloy, resulting in a somewhat hefty lump - but still much lighter than the 2017 stock exhaust.

To date, the only worthwhile potential candidate to replace the Gen 1 stock exhaust - IMO - has been the Werkes Competition unit, a small underbody canister that fits in the OEM location. The Werkes is very simple and lightweight, reportedly saving about 10 pounds over the stocker. Reports about its effect on power are unclear, but certainly it will require a fuel controller. Until recently the Werkes was considered unacceptable because, as delivered, the unit has no sound packing and is extremely loud. However, some recent experiments with disassembling and packing the Werkes reportedly have been quite successful. Our colleague CDN Duke is presently testing a packed Werkes on his bike and appears to be pleased with early results. We will have to see how durable the packing may be. So if you are interested in saving weight over the stock Gen 1 exhaust, the Werkes, IMO, is your best candidate. Stay tuned. But you will have to be prepared to fit a controller.

 

To date, the only worthwhile potential candidate to replace the Gen 1 stock exhaust - IMO - has been the Werkes Competition unit, a small underbody canister that fits in the OEM location. The Werkes is very simple and lightweight, reportedly saving about 10 pounds over the stocker. Reports about its effect on power are unclear, but certainly it will require a fuel controller. Until recently the Werkes was considered unacceptable because, as delivered, the unit has no sound packing and is extremely loud. However, some recent experiments with disassembling and packing the Werkes reportedly have been quite successful. Our colleague CDN Duke is presently testing a packed Werkes on his bike and appears to be pleased with early results. We will have to see how durable the packing may be. So if you are interested in saving weight over the stock Gen 1 exhaust, the Werkes, IMO, is your best candidate. Stay tuned. But you will have to be prepared to fit a controller.

Packing options are being discussed here: Packing Werkes Exhaust + Dyno!

Note that the Werkes pipe does come with packing from the factory, but the original packing doesn't tend to last long. Mine has been repacked by Competition Werkes with a ceramic material rated at 2300 degrees. Not sure if this is upgraded from when they first released the pipe or not. However, it is quite common for these to blow out the original packing in relatively short order. Competition Werkes will repack at no charge, you just need to pay for shipping. When packed, I think the pipe sounds great but it is admittedly on the louder side.

 

@Diploman; I followed your recommendation and spent the last 1-2 hrs studying the RC 390 "Exhaust development work" thread. (We can now we're retired). That is some amazing R&D and absolutely nails what you have been telling everyone. "The stock (2013-16) exhaust is a masterful work of very complex engineering". My interest isn't sound or power it is weight. I would like to get rid of the cat which is heavy and not required by legislation down here. Having read Formula 390's comments on his decatting experience I accept that's in the too hard basket for me. Going for a lighter product using the existing geometry just increases noise with zero performance gain and more likely performance decrease. What is really interesting is that the 2017 has this additional exhaust, clearly to meet Euro legislation, that can only be detrimental to performance and detracts from the original design genius..

 

That ground-breaking experiment & video was made by ex-forum member Rick D. He sold his 390 shortly after for a Yamaha MT-07 & we haven't heard much from him since.

 

Hmm
https://youtu.be/Qy-7OrV5e1k

 

In creating the 390's underbody exhaust, KTM evidently did a thorough job of research and testing, ending up with a system that contributes in a major way to the engine's class-leading power output. The principal feature of this exhaust is a carefully-tuned header and exhaust length such that the resonant frequency of the exhaust pulse waves helps scavenge the exhaust gasses, leading to better cylinder filling/more power. KTM engineers did their homework and produced a very successful component in terms of power extraction from the motor. Unfortunately, very likely for reasons of cost, it was decided to build the exhaust cannister out of mild steel, resulting in a rather heavy lump which could have been significantly lighter if built with other materials.

The video posted by Sinha shows a Duke owner, in a quest for "better sound/more noise" amateurishly cutting a hole in the the exhaust cannister. The probable result of this uninformed intervention is to disrupt the resonant frequency of the tuned exhaust system. Undoubtedly, if this bike were tested on a dyno, first measuring power with the intact OEM exhaust, then comparing this with the altered exhaust's performance, the latter would show a power loss.

Exhaust design is a complex engineering project that draws on several sub-disciplines of physics. It is not for amateurs, or even for aftermarket companies without the necessary design and testing resources. Just to illustrate the difficulties of exhaust design, read the thread below from the RC forum, describing Formula390's efforts to build a lighter, better sounding, more powerful underbody exhaust for the 390 engine:

Exhaust development work

 

Understood Diploman, it's why I was asking if a hole was placed in the spot as shown in the video, what do we think would be the impact, after comparing to the dissection views previously shown. I need to take a closer look at the opened exhaust, it's possible a hole here actually bypasses the full reroute through the catalytic, but I can't be sure yet due to limited time to carefully review the pics.

 

has anyone tried this on the duke 390 ?

https://www.youtube.com/watch?v=TAk1ABgcO04&app=desktop

How does the hole cut in this video match up with the structure in the 390 mufflers that have been dissected?

It actually sounds decent to me and with Akra map, maybe there won't be too many negatives?

 

Nope, but I would do the same thing !

 

Ever see the Honda commercial where the new owner dives across the hood when a flock of birds flies over ?

 

Funilly enough... yes ! Waxed once, washed, vacuumed & interior detail twice. Am I a clean-freak or what ! And then there's the 3D Printer.....

 

Howdy,

No update from my experiments. Life is getting in the way of fun stuff at the moment....

 

Too busy waxing your new ride ? >

 

Any update on modifying the stock exhaust?

I have a PowerTronic, K&N filter, and need to open the exhaust up. I too like the location of the stock exhaust. I'm about to just weld something up myself and use a muffler from something else.

 

Aesthetics be damned for you guys pulled out on the dyno in my opinion. Now if it was only 1-2hp gain that's another story.

 

One drawback of any aftermarket company making a compact underbody similar to OEM is the short header length and its detrimental effects on power. I fully understand not wanting a can hanging off the side, but we're making over 40% more power in the midrange with the MIVV, so that's a trade off I'll gladly accept. It's just too fun.....

 

Maybe IXIL will design a muffler similar to the one they build for the FZ09 that has a carbon cover with a side exit which resides in the original location. If and when I pipe my Triple this is the way I'm going.

 

I ended up buying a stock exhaust for peanuts from a guy who'd ditched it for an aftermarket one. The plan is to use it for experiments to see if anything can be done to improve the tone while making the least changes to the existing design, but life is getting in the way of being able to spend much time on it.

I have done some exploratory keyhole surgery already to see what the innards really look like & have some ideas to try... just need the time to do them.

 

Unless there's a after market that tucks up like the stock I'll wait...

That said, very interested in the install...

 

GPR Ghost...

 

Inquiring minds want to know, Johann! The pressure is building....
We know you have other priorities, such as the O2 sensor. But if the SuperTrapp works (without being obnoxiously loud), and the fuelling can be correctly mapped with a piggy, I think many would be interested in that mod.

Despite its rather stifled tone and ample mass, the stock exhaust is so well engineered that - as Binoy the PowerTronic guy affirmed - it is extremely difficult to find any aftermarket exhaust that can beat the stocker for power.

 

Inquiring minds want to know, Johann! The pressure is building...

[DISCLAIMER] Super busy on all fronts of life at the moment, so projects and participation on the forum is less of a priority and not so desirable time allocation wise. I'll let you know how it turns out when I get to it, but there's no reason it shouldn't be the perfect tunable and tucked away solution. [/DISCLAIMER]

 

I'm curious to see how the Supertrapp muffler works, too.

 

Hi Johann,

Any updates on fitting your SuperTrapp ?

 

If you want to be heard for safety, a better alternative to a loud exhaust is to fit a good set of aftermarket horns, such as FIAMM, Hella, Denali, etc.

 

I love where the stock exhaust is situated, would happily keep it. But.....it's not loud enough. And my main reason is safety. Nobody can hear you.

 

This thread seems to perpetuate the myth that an open pipe or one with less internal obstructions merely needs fueling changes to outperform the stock design. It is not nearly as simple as that and even reputable companies only sell replacement systems that are dyno proven to produce the same power as stock. They may claim slightly more torque in parts of the rev range but can almost never produce significantly more top end power.


The standard exhaust is designed to have an effective length which is matched to cam timing and other engine parameters and it operates in a resonant way which is completely broken if you remove its internals or replace it with an open pipe.


The exhaust design of this bike is one of its best features for exactly the reasons described above and in my opinion even the factory approved alternative is no improvement except for a better sound.

 

I like the GPR underbody exhaust.
looks even more compact and simpler than the OEM.

https://www.youtube.com/watch?v=UzMyanqmy0I

 

Buddy of mine had Dual Supertrapp's on his 1985 V-Max and a Dynojet Stage 3 carb kit done at local Dynojet facility here and when they had it on the dyno his neighbors started coming over to see what the H**L he was tuning ! I rode it and next to my K1300s it was the fastest bike I've ever ridden. Was definitely the loudest by far !