Two Brothers Racing Comp S Gen-II Exhaust Review
You only need to attend a large group ride once to see the huge variety in exhaust systems.
The defining characteristics of motorcycle exhaust systems fall into four major categories:
For most riders performance is the last consideration.
With a $1,500 exhaust you might be able to get around 80 rear-wheel horsepower out of a 1200cc Sportster with an intake and a tuner, but with a system half that cost you might get 70-75 horsepower with the same add-ons.
As far as looks are concerned, most of the time you can’t see your exhaust because you’re out riding.
The number one and two aspects of an exhaust are usually cost and sound, particularly on cruisers such as a Harley-Davidson Sportster.
Choosing the proper system for your build should be well thought out rather than jumping the gun and buying something cheap, but doesn’t have an acceptable balance of the other aspects.
I have 2000 miles on my 2016 Sportster XL1200CX Roadster’s new exhaust, a Two Brothers Racing Comp S Gen-II system.
I picked this system because it’s the closest to how I want my bike to sound and because it’s a 2-into-1 system.
No Stains on This Style
I elected to go with the stainless steel version over the black. My Sportster Roadster is gloss black with a black trans, and I didn’t want the exhaust to disappear. The brushed stainless is also more subdued than a chrome exhaust.
With so much black on the bike a black exhaust would be like staring into a dark tunnel. You stop seeing details, and aesthetically it’s less pleasing to the eye. The stainless is a perfect contrast to Harley’s gloss black without the flash of chrome. Note: the Comp S Gen-II is only available in black or stainless steel.
One of the draws to stainless is its tendency to accrue a bronze or gold color after a few heat cycles. Mine had a brief bronzing phase before turning blue with a pretty dark blue tiger striping. This bluing goes all the way through the collector and stops at the muffler. Note: this is very aggressive bluing.
That’s not to say yours will even turn blue; the color change is highly dependent on your tune and riding style. If you want a more uniform look or the fresh-out-of-the-box look, be sure to install the heat shields. I personally like the bluing, but it’s not for everyone.
The Comp S Gen-II is different than the original Comp S, and I would be surprised if TBR designed the Gen-II without the Roadster in mind. The original has the carbon fiber cap whereas the Gen-II doesn’t.
The Gen-II is also de-badged and appears to have a more aggressive up-sweep in the muffler. The gen-II up-sweep and the full stainless look with the updated, slightly louder, slight deeper sound, screams the exact look Harley was going for with this retro styled, cafe racer inspired bike.
The brushed stainless also gives the whole bike more of a home-built feel. If you’re going for the cafe racer style, having the hand-made, built in your garage, home brewed attitude is essential. It doesn’t have the polish of a factory built, trailer queen, and it’s not supposed to with this style in mind. A cafe racer has the scuffs and dirt from being ridden everywhere as well as the sleek lines found on a bike intended for the track.
The whole system tucks in closer to the engine and frame in comparison to the stock system. You will scrape the pegs before you get close to this thing. Another benefit of it sitting snug against the bike, is it’s even harder to hit with your foot or your leg. My wife often melted her boot a little on the stock rear pipe because of the passenger peg placement. She hasn’t done so with the Comp S. She also hasn’t complained about her foot being on fire in these past two thousand miles either.
But Does It Sound Like John Wayne Looks?
So enough about appearances; how does it sound? The great thing about the TBR Comp S Gen-II exhaust is TBR has an official preview sound clip of the original Comp S and the Gen-II on their YouTube channel.
They do sound notably different. I haven’t heard the gen-I in person, but in the video it sounds like it has baffles and is stock-ish levels of quiet. The gen-II sounds as if it has no baffles, more akin to a hollow, empty megaphone.
I was quite pleased by the difference between the video of the Gen-II and the system running on my bike. It sounds slightly deeper and slightly quieter than portrayed by TBR. It also doesn’t have the distinct hollow echo of the muffler being empty. It instead sounds like the well packed, straight through design it is.
This system has a rumble to it, but you’re still dealing with a Sportster. 1200 or not, there’s only so deep you’re going to get. The Comp S Gen-II is definitely on the lower end of the deep tones available on the market for fuel injected Sporties.
As far as sound level goes it’s not quiet by any means, but if you’re trying to be stealthy you can get home at 1 a.m. without waking your neighbors. It doesn’t hurt most people’s ears when standing next to it at idle.
That being said, it does vibrate my 100-year-old farmhouse’s windows 12-feet out. Not badly, but you can hear them rattle a bit and feel it in the floors. It’s not uncivilized; not something you can only start up at the track.
Clearly TBR had street and track use in mind when redesigning the Comp S, and they probably updated the design to get as close to the edge of reasonable loudness for everyday use. It’s a bit loud, but perfectly livable. For those of you looking for something where you can hear your exhaust over wind buffeting on the highway, the TBR will do okay.
One of the advantages of the up-swept design is you don’t get an echo effect from the ground like you would with a slash down pipe. A slash down can create an echo where the sound wave hits the ground and bounces back up. This can make the bike sound louder to those close to it, and alter the overall tone. With the up-sweep you’ll only get an echo during a hard right lean turn or, of course, those hallowed halls we call tunnels.
Air Cooled but Adrenaline Fueled
If you’re thinking about an exhaust like this, there’s a question that needs to be answered first. Does your bike have a tuner? If the answer is no, then you have to get one. No exceptions. Fuel injected bikes can compensate for small changes in air flow, but large changes can give your computer a digital aneurysm.
A digital aneurysm can flat line your engine with a dangerously lean air/fuel mixture. Adding something like a set of slip-on mufflers might not be enough to cost you an engine. An exhaust like this however, or worse, an exhaust like this and a performance intake will do it in no time.
Sportster oxygen sensors are what’s called narrow band sensors. They only see approximately 14 to 15:1 air/fuel ratios (lower numbers mean more fuel). These narrow minded sensors can’t comprehend the changes from the Comp S.
This is where the tuner comes into play. While the tuner can’t broaden the sensors’ horizons, it does come with a pre-installed air flow and fuel map that is much closer to what you need. Just about every reputable tuner company provides their own auto-tuning function to really dial in the air flow maps. The added benefits aside from not blowing up an engine, is greater performance than just adding the exhaust, along with better drivability.
While we’re referencing oxygen sensors, the Comp S comes with 18mm oxygen sensor bungs, so you can upgrade to more enlightened sensors with a broader view of your engine’s world. Pre-2014 fuel injected Sporties use 18mm narrow band sensors. 2014+ bikes use 12mm sensors.
Provided in the Comp S kit is a set of adapters to downsize the 18mm bungs to accommodate the 12mm sensors. You’ll also get a set of plugs for the 18mm bungs in case you don’t want to run any oxygen sensors such as with a carbureted conversion.
The gen-I version claims a 7.95 horsepower and 6.68 ft/lbs of torque gain (no official numbers on the gen-II). I haven’t had my Roadster on a dynamometer, but the butt dyno says these numbers are very doable.
To be more specific, I felt a definite increase from about 2500 rpm to 5000-5500 rpm. This is all in comparison to the set of carbureted Sportster Screamin’ Eagle race slip-ons I had retro-fitted before this. With the race slip-ons my bike used to run hard up to 7k. Now it runs hard to 6k.
This doesn’t mean it makes less horsepower than the Screamin’ Eagle pipes. It’s possible the power increase below 6k in the Comp S is enough that if the systems are the same above 6k, the plateau can feel like a drop off in power.
Most people upgrade their intake along with the exhaust, but my Roadster has the factory air cleaner. The reason for this is the factory intake paired with the Comp S evens out the volumetric efficiencies (VE) of the cylinders. I tried a couple of air cleaner systems, but the factory one proved to be the most even.
Don’t mistake this for the most powerful option; this is the most balanced in terms cylinder air fill across the board.
While the highest VE of the rear cylinder dropped, the highest VE of the front cylinder got a boost in the same RPM as the rear cylinder’s loss.
The boost in the front was larger than the loss in the rear, and they’re now within 5 percent VE instead of about 15-20 percent. I wanted the cylinders to perform as close to the same as I could without dumping everything into horsepower gains.
Without any other mods besides the exhaust and tuner, my fuel map is on the richer side to maintain 400 degree or lower cylinder head temps under extreme abuse/high speeds. Even with getting my oil temps to 200 and head temps to 380, I can run full throttle for a solid five miles without going over 400 on a 100-degree day.
Built for the Track; Tested on the Street
Maybe something a little further from everyone’s priorities is how tough is the system? If you plan on riding as often as you can for as long as you can, how your exhaust is built will be a high priority.
The TBR Comp S Gen-II looks to be hand TIG welded, and that’s not an insult. These welds are clean, pretty, and as light as reasonably possible, accented by the rare rainbow effect.
TIG welds have a lower chance of causing protrusions that interrupt exhaust flow, and they can be lighter with the same strength as a bigger MIG weld.
I talked at length regarding the stainless steel appearance, but stainless has performance benefits as well, namely being lighter than factory. TBR claims a 10-pound drop with the original Comp S, and I imagine the gen-II weighs the same give or take a few ounces.
Stainless is also weather/rust resistant, giving it a longer use life than non-chrome counterparts. In some cases, stainless can outlast chromed systems because chromed pipes generally aren’t chromed on the inside. This makes them susceptible to rusting from the inside out. If you’re looking for a system you can polish up nicely, but isn’t as high maintenance as chrome, stainless is a good middle ground.
Despite TBR’s 10-pound claim, I’m a bit disappointed they didn’t go for the easy one or two pounds in the mounting bracket. They have the bracket bolt up to the factory bracket rather than replacing the factory one altogether.
However, I feel like I understand why they made their bracket. It would vastly complicate installation if they replaced the factory bracket by requiring you to pull off the front sprocket cover.
Not that this is unbelievably complicated to do, but you need a wider array of tools to pull it off. Allen keys, for example, as opposed to needing some wrenches and sockets. I have a wide variety of tools, and my Allen keys don’t get a lot of glory. The bolts are also rather tight.
The Allen keys in my case are 5/16ths and 3/16ths, although my 8mm fit the 5/16ths more snugly. You’d also have to disassemble the rear brake master cylinder linkage. To do that you’d need to take off the rear brake master cylinder which requires a T-40 Torx bit in my case. Needless to say, not tools everyone has lying around.
There’s also the small E-clip you have to avoid losing on the master cylinder rod. Imagine having to do all this to replace the exhaust. If you’re in racing conditions, replacing the exhaust will keep you on the sidelines for a significantly longer amount of time. With the bracket they implemented it’s much simpler.
I’m also a bit disappointed in the collector because of how it’s made and how it looks. It has a Y collector instead of a V. With how well made and designed this system is, seeing a Y collector is disappointing.
A nice V collector might not net you any real top end power gains, although it does help, the V helps in mid-range power and exhaust scavenging. Based on my VE readings, the scavenging has a strong high-low wave pattern. This can be caused by just about anything and everything you can imagine in the engine.
It’s turbulence, pressure waves, heat, distance, and a medley of other engineer level intricacies above my pay grade. In general, a nice V helps to even those waves out. Where 3000 rpm is the lowest of the low dips, if it had a V, it probably wouldn’t be as huge of an up-down swing on the VE table.
The Y also has the infamous mid-range dip in the power band, but with a good tune you can compensate for it. For example, you could dial back the power in the two high points of the curve. If it had the V to start with, the dip probably wouldn’t be as severe, and there’s a slight chance the dip wouldn’t be present.
Disappointed or not, it’s understandable TBR would elect for a Y collector. It’s a lot faster, cheaper, and easier to manufacture than a V collector. If you can find an off-the-shelf exhaust with a V collector, expect to pay 50% to double the cost of the Comp S.
Speaking of the collector, some of you might be wondering what the benefit is to a 2-into-1 exhaust. 2-into-1s are supposed to allow for more even breathing between the two cylinders.
A 2-into-2, stock style with a pressure cross-over, allows the pressure to equalize between the two cylinders to try and negate some of the differences in things like length of the exhaust and turns in the system between the front and back header pipes. A
2-into-1 has them both come out the same muffler, and preferably have the exact same length header tubes. One of the big advantages is the exhaust pulses have a chance to do something similar to slip streaming one another.
There’s also pressure shock waves which can be used for scavenging. If tuned properly for your engine, cam, and intake system, the scavenging can allow the engine to slightly self supercharge.
As a side note and example, my bike with the factory intake and this exhaust, runs a manifold pressure of 104 kPa instead of atmospheric 98-100 kPa at most RPMs. With a 2-1 you can have a racing exhaust that’ll perform well on the street instead of something that only performs at top RPM.
Putting it All Together
In short, it takes longer to get the old exhaust off than to install the Comp S. How difficult is it to get the old exhaust off? In an acronym PITA, although in reality it depends on how old your stock exhaust is.
How many miles you’ve put on it, how much salt you’ve ridden through, the number of monsoons you’ve weathered, etc. The rustier it is, the more of a PITA it’s going to be. If you only have five miles on a bike built two months ago, removal isn’t going to be nearly as difficult.
My first bit of advice is get a pair of cylinder hear exhaust gaskets. They’re going to run you about $5 for both at the most. Generally speaking, when the factory or the dealer installs the stock exhaust, they bang up the stock gaskets. On my Roadster the gaskets are a tapered fit type, which should be the same as other Sportsters the Comp S fits onto.
My gaskets in particular were far from ideal. Using bad gaskets causes leaks and in more extreme cases, loss of performance. Damaged gaskets can prevent the exhaust stream from flowing smoothly. When you replace the gaskets, they more or less pull out, but a hooked pick will help you out. I also suggest taking a light duty scotch bright pad to the seating surface of the gasket after you get the old parts out before trying to install the new ones.
Anything left over on the surface can increase PITA levels more than necessary when installing the new gaskets. Another suggestion is to use the right size seal driver for the gasket to prevent waffling upon install. Be gentle and slow, like your girlfriend’s first time. Don’t force it, or you won’t be happy with the results.
The instruction sheet from Two Brothers Racing was fairly cohesive with black and white photos to help as much as black and white photos can. The system uses a muffler with a Y-pipe and two separated header pipes that slip into the muffler, held into the muffler by springs.
TBR provides both the springs and a nice stainless steel tool to hook the springs and pull them into place. After all, they’re strong springs. Use the tool. The purpose of the springs is so you can get the header pipes off quickly without removing the muffler.
For example, during race conditions when you need quick access to the engine. You can just undo the header pipes: two bolts at each head, one spring at the muffler for each header pipe, unplug the O2 sensors (if you have them), and they’re out. This makes things like changing cams a lot faster and easier.
The Comp S is:
- Well built
- Provides more turning clearance than your pegs can handle
- Gives you more straight up ground clearance (like speed bumps) than your frame
- Sounds nice and loud (but not unreasonable)
- Adds HP and TQ across the entire RPM band over stock
- Goes on rather seamlessly
- Looks right at home in a 1970s AMA race
The TBR Comp S seems best suited for riders looking for a cafe look; riders intending to put their bike on a track (including other than drag); and riders looking for a reasonable rumble out of their Sporties.
For more, visit Two Brothers Racing.