Harley Davidson is developing a dynamic exhaust system design that redirects exhaust gases depending on engine RPM and throttle opening. The exhaust system has 2 paths for the exhaust with a cable operated valve directed by a control unit sensing engine speed and throttle opening.
The valve operates to control the torque curve of the engine by moving the valve in the “crossover region of (the) first and second torque characteristics.”
Basically, the valve operates automatically to maintain a higher torque than would be available if using either exhaust path by itself, switching between a more or less restrictive path. Drawings indicate applications for both a regular Harley Davidson twin exhaust and the same system within the Buell under belly exhaust. The twin exhaust system has a valve either within the muffler or in the pipe before the muffler.
Besides the performance advantages the system can also be set to control noise emissions at cruising speed.
UPDATE:The differences in the exhaust paths seem to be primarily length, meaning they are tuned for different RPM ranges, whatever the differences in restriction may be.
More drawings below:
Clive M-Sanders says
My sentra had the same thing.
sanglant says
So it’s basically a Suzuki SET valve or a Yamaha EXUP valve, just less efficient. Good job, Harley!
Ry says
This is not a new Idea , it is just new for H-D.
I have been seeing these for prototype on H-D Cruisers for about a year and a half now. They are scheduled on the 09 models. I have not seen any buell model systems but that doesn’t mean they don’t have them.
Rashomon says
This is not the same thing as an EXUP valve at all. The EXUP increases back pressure by blocking the main flow path when it is engaged. The Buell/H-D offers different tuned paths for exhaust flow depending upon conditions, and can yield larger increases in mid-range torque because of that.
taxman says
i believe the buell xb12’s have been using this since they came out. i had a xb9r and it did not. but i know the 12’s had some sort of variable exhaust system.
willie schmitz says
Hopefully, this will work well enough Harley owners will keep their exhaust systems stock and quiet.
Does Harley’s really need anything like this in the first place? It’s a low RPM torque oriented motor. The higher RPM motors that are a little skinny on low and mid range torque benefit from the set up. Whatever benefit the Harley would gain might be lost in added wieght, cost and repairs.
ROHORN says
The Buell S1 Lightning had a huge lower midrange hole in the power with the stock muffler. Swapping it out with a Supertrapp made a huge difference.
So I’m guessing – with the help of some experience – that it will help a lot.
I’m also betting it has something to do with the catalytic converter’s effectiveness……
Richard says
“Besides the performance advantages the system can also be set to control noise emissions at cruising speed.”
I think you have that backwards.
The “performance advantages” on a Harley will be negligible, but they desperately need to control the noise if they want to continue selling those barcoloungers on wheels as more restrictive noise ordinances become common. So, the noise control is the primary concern, and the performance improvements are secondary.
Harley is in for a rough time, after so many years pushing the myth that “loud pipes save lives”. It’s an integral part of that “Harley-Davidson culture and spirit” that they’ve been selling along with their “stylish MotorClothes apparel”. If they tinker too much with the mythology, the brand name becomes meaningless and sales will plummet.
GAMBLER says
YAMAHA EXUP
greer says
i doubt making bikes quieter will affect sales that much, how many harley owners keep their stock pipes?
bob says
The H-D/Buell system is nothing like an EXUP or SET valve. If you actually look at the EXUP or SET valves, all they do is shut off the exhaust, they do not redirect it or change the flow path in any way. I have a SET valve sitting in my shop & I assure you that all it does is turn a butterfly valve to shut off the exhaust pipe. It “helps” torque in the same way pounding a potato into the tail pipe would “help” torque.
The H-D/Buell system redirects the exhuast & forces it to take one of two different paths through the exhaust system – one path being longer then the other. This changes the exhaust tuning & does exactly what the chart at the end of the article shows – it fills in the natural torque dip in the midrange that is almost always seen in a single length systems.
Whether the system is tuned to lower noise is an entirely different subject – not saying it couldn’t, but it’s not necessarily the main objective.
BW, all H-D & Buell products meet all noise regulations in all markets they are sold in when they come from the factory. If you hear a loud Harley, it has (obviously) been modified by its owner & the factory had no involvement.
Ricky says
bob you may have a shop but let’s see some credential in physics before you drop-kick the exup.
Sam-I-Am says
“If you hear a loud Harley, it has (obviously) been modified by its owner & the factory had no involvement.” Also, haven’t HD dealers modified exhaust and emissions on the bikes they sell for years? Even more so now that all their bikes have EFI? As far as the factory not having any involvement, I read that HD has stopped selling their Screaming Eagle “For Off-road Use Only” pipes and is attempting to curb the noise of the “loud pipes save lives” crowd. Yet aren’t HD dealers still selling other aftermarket pipes; Bub, Vance and Hines, etc., and remapping the EFI systems for these new pipes? If this is true, wouldn’t you think the MoCo would be aware of this?
willie schmitz says
The muffler that was on the S-2 Buells “tuned” at higher RPM at the expense of midrange. Conversion to a Super Trapp (and some rejetting) showed HP gains through the entire RPM range at the expense of noise levels (6 disks). Rideability was the big payoff.
Another problem is the heat generated off the engine (rear jug). The open exhaust systems and fatter fuel curve really cool things off. Early Buells would fry your right leg.
Be nice if all works well with the setup Harley has spent untold millions on.
rapidray says
can you say…snuff-or-not..??
ROHORN says
Willie,
My ’99 M2 didn’t respond like the S1 to a pipe change – for the reasons you stated. It already had a fat midrange.
Ricky,
It takes very little knowledge of physics to know the functional differences between this and the EXUP system.
I never cease to be amazed at how technically illiterate the average motorcycle enthusiast is – one would think that “technically superior” machines would attract more knowledgeable enthusiasts.
Sad, really.
ZoeR says
I agree that this has little to do with an EXUP valve (which serves only to increase back-pressure at certain RPMs, but does not change the exhaust path itself). However, while this may be a new idea for Harley, it’s hardly a new idea in exhaust system design, and I fail to see what is new here that would allow HD to apply for a patent (of course, applying for a patent doesn’t necessarily mean that one will be granted).
bob says
“bob you may have a shop but let’s see some credential in physics…”
I don’t have a “credential in physics” but I am a degreed mechanical engineer & I worked for seven years in the engine group for one of the big three automakers & then several years for an international powertrain consulting company. In both places I did design & development work on intake & exhaust systems, primarily in the area of tuning & noise performance (no, I did not work on the Suzuki, Yamaha or Buell exhaust systems).
The main point I want to make here is that the H-D/Buell system is nothing like the SET or EXUP valve. One system just closes off the exhaust system & the other actually changes the tuned length of the system. They are completely different in how the work & the effect they have. I frequently hear people say the Buell system is exactly the same as an EXUP & the reality is that they are not at all alike.
Richard says
bob says, “If you hear a loud Harley, it has (obviously) been modified by its owner & the factory had no involvement.”
Not so! The current Harleys meet the government noise criteria only because those criteria do not measure the bikes the way they are used in the real world. So what if the muffler is “quiet” when idling? HD owners don’t sit at stoplights with their bikes idling; they repeatedly rev up their engines to make as much noise as possible, to make sure everyone at the intersection sees “how cool/hot/rad/bad” they are! The government tests don’t measure that noise level.
You’re correct that HD owners typically modify their exhausts to make EVEN MORE noise, but they typically get that done for them at the shop at the time they buy the bike. Why? Because the HD company has been pushing the idea that “loud pipes save lives” (despite the obvious fact that they don’t) for many years, and because you can’t be an “outlaw” if you don’t make lots of noise (and wear the right clothes!). It’s all a part of the “bad-a$$ biker” mythology that they sell to the masses.
It’s true that the head of HD made a feeble anti-noise statement recently, but his statement was feeble precisely because he knows they are skating on thin ice by messing with the Harley outlaw image. If they mess with it too much, sales will plummet.
They almost killed the H-D brand, just by over-licensing the name and logo. They licensed everything from Harley-Davidson footwear to H-D cigarettes, H-D prophylactics and even H-D cake-decorating kits! This over-extension of the brand diluted it to the point of hurting sales, so they have now begun to realign their global brand and licensing strategy. After wising up, former Harley CEO Richard F. Teerlink told MBA students at the UW-Madison School of Business, “Don’t prostitute your brand. Licensing is not free money.”
Heck, their sales is destined to plummet regardless, because the boomers are starting to get too old and too infirm to hold up their heavy hogs and younger people are just not that interested in the Harley myth. That’s why HD has been trying to expand into new markets, like China.
ROHORN says
Richard,
This isn’t American Angst – I’m hoping (obviously in vain) that most people around here are much smarter than that.
You are wrong – H-Ds are no louder than any other bike – out of the box. I worked for a while at a dealer that would not let a bike out the door with stock baffles. He did not want the locals to know just how quiet the bikes could be. Revving a stock H-D is like cranking up a 1 watt stereo – louder than off, but not loud at all.
The 2 magazines I buy (I don’t buy H-D oriented magazines) have loads of supersport systems. I don’t find them any more enjoyable to listen to on the street. On the other hand, I did like the 6 into 6 open megaphones on my last CBX – it would drown out ANY H-D or zoomsplat. I never saw outlaw CBX riders…..so much for outlaws chasing after the loudest bikes.
I also never ever experienced ANY “Loud pipes save lives” crap promoted by H-D at any corporate level. Your comments are as misleading and intellectually corrupt the first time you’ve said them as the last time.
As far as the overlicensing bit, yeah, it sure did get awful lame. But nobody ever wanted CBR condoms or cake decorating sets, either. Or ever will. Maybe CBR licensed hand lotion and paper towels would sell? Otherwise, it’s just loud CBR pipes.
In the mean time, why is it that the same predictable people regurgitate the same stale cliche’s every time anything H-D comes up? While I have no desire to ever own a Harley again, the complete ignorance of the American Angsters makes the comments section here look like mental flypaper for morons.
Richard says
Rohorn asks, “why is it that the same predictable people regurgitate the same stale cliche’s every time anything H-D comes up?”
I can’t speak for anyone else, but the reason I have said what I think about Harleys is that the vast majority of bikers where I live ride Harleys and they all wear the same clothes, including that oh-so-protective bandana covering the core of their CNS, they all wear the same leather fringe, and they ALL sit at stoplights and rev their engines to make as much noise as possible. And if what you say is correct, they have ALL modified their pipes to assist them in making as much noise as possible. My description of and reaction to what I have actually seen around me is not “regurgitating” a “stale cliche”.
Nothing in the world can change the FACT that the main thing H-D sells is a mythology, rather than a machine. (Talk to their marketing people if you don’t believe me!) People who buy into the mythology aspire to buy the machine. People who don’t buy into the mythology are free to purchase whatever machine happens to suit their riding requirements. For many years, a crucial part of that mythology has been NOISE. (In fact, it’s a very particular type of noise, with a single crank pin V-twin going lub-dub, lub-dub, lub-dub, sort of like a heartbeat.) Mess with the myth too much, and the target audience will not accept the change, and they will not shell out the big bucks for the hardware and accessories and clothing and logos. That is an undisputable fact of marketing. Don’t blame the messenger.
BTW, if you think I am “predictable”, you have not been paying attention. But I am not likely to change my opinion about H-D motorcycles unless the bikes themselves change significantly and the company somehow does break free of it’s self-created, and highly limiting, mythos. I know they are trying to do just that, but it’s a risky move and I don’t expect them to be successful long term.
ROHORN says
Thank you for clarifying the stereotypes. So, if I understand correctly, stereotypes are always based on FACT and make further thought about the harware pointless! Who needs technical articles? What we really need around here is celebrity rider gossip and What’s Hot and What’s Not lists! Like don’t become a totally major Motorcycling Fashion Don’t!! Bandanas are just sooo Eeeew!!!
Don’t ever make me write that way again.
But seriously now:
As far as H-D falling on its face, hey, my opinion about that is unsuitable for public viewing. While it is obvious a lot there are just riding the wave ’til it requires some real work in the area of creativity and original thought, I know they have (or at least had) a crew that is looking very far ahead. What the management does with what it is handed is another matter. Will it be golden parachutes for the alphabet people as they watch the company spiral into the ground? Who knows.
BMW was once stuck with a customer base older and more “conservative” than the current H-D demographic. They got out of that rather well. It did take them a while.
If big dumb American air cooled V twins, among other things, are made and sold 10 years from now, it will be thanks in part to the above hardware developments. And I don’t think mythology will have anything to do with that.
Ry says
WOW! Sure is alot of love in here.
Rashomon says
Richard says: >>
Absolutely not true! The EPA references a SAE standard for noise measurement, which requires a full throttle ride-by in 2nd or 3rd gear (which is used depends on a formula based on gearing and peak power rpm) at a specified speed. While the standard is gamed by manufacturers (for example, by shutting the EXUP snuff-or-not during this time of acceleration, or by having the ECU reduce the opening of secondary throttle butterflys as used on many Japanese four-cylinders at a very specific speed), it represents a fairly realistic test of motorcycle exhaust noise.
Wild Bill says
About 40 years ago I bought my first motorcycle a 57 FLH HD Panhead and my life took a direction no one myself included could of ever imagined.I have 5 Harleys now and many miles,memories,scars and stories…I always did all my own mechanical work and had great success overhauling the outdated designed engines and trannys.The obsolete engineering was user friendly and led to creative repairs on the side of the road when something went wrong..No cell phones then by golly.I’ve met some great human beings and have learned much in my journey.WHAT IS the point in the debate here anyway?Is anyone really going to have their mind changed…Come on…crank up your bike and lets go riding and flush our heads out..Everybody is right ha ha ha..I’m outa here…yeeeehawwwww
F. John Davie says
Sirs,
The IC engine is in effect a ‘air-pump’.
The greater mass of air that you can promote to pass through the engine, the greater its effectiveness. From the greater mass airflow – the greater mass of fuel that can be burnt and energy produced.
For any given size of engine a measure of its efficacy is expressed in its ability to pump air.
In a nutshell, get lots of the stuff into the cylinders – get the resultant combustion gasses out just as efficiently.
So called ‘back-pressure’ has no place in an efficient exhaust system. The performance of any exhaust system (and by analogy the engine) is degraded by the degree of energy required to expel the combustion gases.
Where performance gains are to be made is in the area of pulse-tuning. This being the art of using pulses in the hot exhaust gas to promote cylinder scavenging and prevent ‘charge’ loss.
This could be where this (HD) system appears to score, in that two ‘tuned lengths’ of header-pipe appear to be provided. However the header pipe(s) is just a component part along with the collector and tail pipe.
One just wonders, looking at the various diagrams how efficient the HD solution is with regard to header-pipes/collector and tailpipe.
My own experience with tuned exhausts (Road-race Sidecar outfits) demonstrated that significant gains could be made, BUT attention to the basic equations governing size and lengths was essential.
The other thing to remember that with regard to ‘pulse-tuning’ the exhaust system ‘stops’ at the first major section change, which can be viewed as the entry of the tail pipe into the expansion box (silencer).
The iron rule however is test the ‘packages’ and believe that the Dyno never lies!!
My own analysis of the Exup valve was that it provided differing ‘tuned’ header-pipe lengths. However I never attempted a close look at the system.
Regards John Davie
James says
Ever hear about the silent grey fellow? good old one cylinder Harley’s, they had a muffler that had an built in bypass just like these with a few differences, like the ecu controlling the valve, ect. ect. you know one is modern the other was modern 100 years ago. And don’t listing to F. John Davie I’m afraid to say that he clearly only knows the base knowledge about engine operation, back pressure helps to cool the exhaust valve as well as clear the cylinder creating a vacuum to aid in drawing in fresh air as to this nonsense arguing over Harley, they are modern there goals may not be in line with yours the reader but they are modern and well made in both company and machine if you need proof read on, if not and your will to drop it at that just skip it you probably already know what is said.
myth does not run Harley Davidson, costumer loyalty does, myth does not drive costumer loyalty, experience does long term experience, not just one or two years on the hottest rocket. And historical engines don’t augment any of that if it did Royal Enfield India would be the company to beat. So why are Harley customers so loyal? Because years of dedicated engineering to a very few engines has led to a very stable fuel efficient (per engine size mind you) power plant as well as a long list of racing performance parts. (read that last little bit carefully I wrote RACING parts, and I mean it) and most of all they rely on the consumer only know what they want to know, most don’t care for an 200 Hp machine but those that do it’s there and possible (no matter how difficult). Mix that with an easy to repair engine, that has as few failure points as possible (read as; moving components that are vital to said engine running) and top it off with real good low end torque, and decorative tins that look like something out of the 50’s (not really but most people don’t know the difference) and you got a winner.
And if that is not enough to convince those whom criticize without true experience (no listing to the graybeard complain about the AMF years does not count those are long over) think about this, how many of the naysayers of H-D would tattoo Honda, Suzuki or whatever; on your arm, back, or whatever? not many….