Will dual exhaust increase my HP?

[chrisstroh]

I don't care about emissions! Is this a common change done on 2002 RT's?

[Paul Mihalka]

I don't care about emissions! Is this a common change done on 2002 RT's?

Chris, you better put on your asbestos suit No, dual exhaust is not a common mod, all I know are two into one. And no, just modifying the exhaust will not noticeably increase HP.

[ShovelStrokeEd]

In a word, no.

 

The standard exhaust is more than adequate for the stock motor and even a mildly modified one. The 1100S does benefit from larger head pipes and dual exhaust but that motor has different cams and compression.

 

If you want more HP just get a K12S or K12R. For that matter the new hex heads make more power than your bike, get one of those.

[ashleybiker]

I have not seen a 2 into 2 (dual) exhaust on a 2002 RT. I have seen several 2 into 1 exhaust upgrades mostly from REMUS and TWO BROTHERS RACING (many doing this to save weight as much as increase HP). I am curious what information you will generate on this subject.

[DouglasR]

I have not seen a 2 into 2 (dual) exhaust on a 2002 RT. I have seen several 2 into 1 exhaust upgrades mostly from REMUS and TWO BROTHERS RACING (many doing this to save weight as much as increase HP). I am curious what information you will generate on this subject.

 

I put a Two Brothers Racing Y-pipe and can on my 1150GS, taking the stock catalytic converter and can off. I was SHOCKED that the stock set-up weighs 29 pounds to the TBR's 8 pounds. Losing 21 pounds (4% of the total weight of the bike!!!!!) had a marked impact on performance. I can't tell you whether it allows more horsepower, but it does rev faster and of cousre feels more powerful because of the loss of a significant amount of weight.

 

Downside: the TBR pipe is LOUD. I like the tone and sound, but damn it gets kinda tiresome after just a few miles even with earplugs in. I've oredered a re-pack kit and will see if that quiets it down enough to make me want to keep the pipe on. If I can't quiet it down significantly I'm going to put the fat pig stock setup back on.

[No_Twilight]

I bet you make quilts out of baby seal pelts too!!!

 

I've always been intrigued by all the expensive exhausts that people want to put on motorcycles. it seems more like a fashion statement than anything else. Oh, almost forgot. There are those who LIKE loud noise who do it also. --Jerry

[David]

I've always been intrigued by all the expensive exhausts that people want to put on motorcycles. it seems more like a fashion statement than anything else.

 

You'd be wrong to put them all in that category. In addition to saving weight and increasing HP/Torque, their main feature is to smooth out the HP/Torque curve. That's not true of all of them, but it's particularly true for engines in a high state of tune already, particularly if we're talking about front to back systems.

 

The R bikes don't fit in that category, of course.

[No_Twilight]

I've always been intrigued by all the expensive exhausts that people want to put on motorcycles. it seems more like a fashion statement than anything else.

 

You'd be wrong to put them all in that category. In addition to saving weight and increasing HP/Torque, their main feature is to smooth out the HP/Torque curve. That's not true of all of them, but it's particularly true for engines in a high state of tune already, particularly if we're talking about front to back systems.

 

The R bikes don't fit in that category, of course.

 

Maybe I'll figure this out when I get a sport bike. However, it looks like my next bike will be a dirt bike. Just bought my son a Yamaha PW-50 today. I wonder if an exhaust would help it? It's 2 cycle, 1 cylinder, 49cc engine makes 2.5 hp. And based on the blue smoke, I'd say it makes more pollution than the my 2300cc of bmw's combined. Oops, that's a different thread. Thanks, Jerry

[Eschelon1]

Like most have mentioned here, there isn't a aftermarket dual exhaust for an oilhead RT. However, the weight savings from a Remus or Two Brothers Racing exhaust will do more than any HP increase

 

[SDMike]

I have not seen a 2 into 2 (dual) exhaust on a 2002 RT. I have seen several 2 into 1 exhaust upgrades mostly from REMUS and TWO BROTHERS RACING (many doing this to save weight as much as increase HP). I am curious what information you will generate on this subject.

One of the things I've seen GS riders do is eliminate the muffler entirely. Run a short section of exhaust pipe right off the cat and then you can run a full-size left bag!

 

FWI hear, it isn't any louder than with the pipe on. (I haven't done it myself, I have an 04 RT!)

 

M

 

I put a Two Brothers Racing Y-pipe and can on my 1150GS, taking the stock catalytic converter and can off. I was SHOCKED that the stock set-up weighs 29 pounds to the TBR's 8 pounds. Losing 21 pounds (4% of the total weight of the bike!!!!!) had a marked impact on performance. I can't tell you whether it allows more horsepower, but it does rev faster and of cousre feels more powerful because of the loss of a significant amount of weight.

 

Downside: the TBR pipe is LOUD. I like the tone and sound, but damn it gets kinda tiresome after just a few miles even with earplugs in. I've oredered a re-pack kit and will see if that quiets it down enough to make me want to keep the pipe on. If I can't quiet it down significantly I'm going to put the fat pig stock setup back on.

[WeirdHarold]

I've oredered a re-pack kit and will see if that quiets it down enough to make me want to keep the pipe on. If I can't quiet it down significantly I'm going to put the fat pig stock setup back on.

 

 

Thank you.

Thank you.

Thank you.

 

 

Don

[ShovelStrokeEd]

Douglas,

Assuming you weigh 170 lbs your weight savings will be 2.7% not 4%. The bike won't ride itself despite all the electronic wizardry BMW put on it.

 

You might be able to just notice that gain at a drag strip. Doubtful in normal riding. Since the weight removed is very low and near the center of the bike, it won't effect handling very much either.

[SWB]

I was SHOCKED that the stock set-up weighs 29 pounds to the TBR's 8 pounds. Losing 21 pounds (4% of the total weight of the bike!!!!!) had a marked impact on performance. I can't tell you whether it allows more horsepower, but it does rev faster and of cousre feels more powerful because of the loss of a significant amount of weight.

 

If losing 21 lbs does that much, I wonder how my RT would ride with 40-50 lbs less weight on it?? I regret that peanut butter and jelly sandwich I just ate already.

 

Back to the diet....

[David]

Maybe I'll figure this out when I get a sport bike. However, it looks like my next bike will be a dirt bike. Just bought my son a Yamaha PW-50 today. I wonder if an exhaust would help it? It's 2 cycle, 1 cylinder, 49cc engine makes 2.5 hp. And based on the blue smoke, I'd say it makes more pollution than the my 2300cc of bmw's combined. Oops, that's a different thread. Thanks, Jerry

 

I don't think an exhaust will help your son's bike! But you've put your finger on the irony of this--worrying too much about it (potentially) while we contribute huge amounts of air and noise pollution with our mowers, trimmers, leaf blowers, power washers, chainsaws, and tillers.

 

Or if you want to have a little fun, look into the efforts that just one volcanic erruption will reverse and how impervious the earth seems to our input anyway.

[Paul Mihalka]

But you've put your finger on the irony of this--worrying too much about it (potentially) while we contribute huge amounts of air and noise pollution with our mowers, trimmers, leaf blowers, power washers, chainsaws, and tillers.

 

Or if you want to have a little fun, look into the efforts that just one volcanic erruption will reverse and how impervious the earth seems to our input anyway.

Yes, it's good to put things sometimes in perspective

[Wooster]

"Will dual exhaust increase my hp ?"; conceivably, yes.

 

W/o flying in the face of board's evident consensus (perhaps plainly stated as "if you want hp, get a Kawasaki"), whenever you increase air & gas going into combustion (with implicit increased exhaust flow, so that the afore-stated intake increase can occur), you've got more hp; plain and simple, no smoke & mirrors.

So, should your after market exhaust increase flow (this can be equated to increased noise) and you increase air intake (open up air box so not limited by 2 inch diameter "snorkle"; can you say K & N ?) and fuel, well, w/o waking any rocket scientists, hp increases.

Now, some believe in magic aftermarket exhaust that increases flow but not noise; these folk also believe in tooth fairy, santa claus and other myths. The sad fact (sad if you want solically responsible hp) is that increase in exhaust flow increases noise.

Lastly, most recognize benefit of internal modifications, e.g., polishing and porting intake and exhaust passages, increase in valve size. Well, for sure these mods are effective; just the same, hp can increase with only external mods, e.g., open up intake & exhaust.

I have three intake & exhaust options on my '00 honda xr4; stock, offing intake snorkle, and replacing airfilter; stock exhaust, stock muffler w/aftermarket tip , and aftermarket muffler. Each mod increases hp w/accompanying increase in noise. FWIW, I've choosen offing snorkle, aftermarket airfilter and aftermarket exhaust tip as an acceptable middle ground (about 93 db vs stock 82). In my garage is aftermarket exhaust (104 db) which doesn't get out much.

 

Wooster

[Paul Mihalka]

If the exhaust is not the limiting factor ( not more back pressure than needed for the engine tune) opening up the exhaust will not increase HP, it might even reduce it under some conditions.

[Davis]

Exactly!! On your XR4 the intake and exhaust tracts are more limiting than the flow through the head so increasing the flow to and from the head improves performance. As has been demonstrated with numerous dyno runs, on an oilhead the intake and exhaust tract already flow more than the head so changing to a less restrictive air filter or exhaust does not provide a performance increase. If you port and polish the head, then other modifications to increase the flow will help, but until then your just making more noise.

[Wooster]

Paul,

 

While I have little interest in this topic (stealth is more in keeping with my idiom), I reiterate the assertion that increases in intake and exhaust flow, with resultant increased noise, will increase hp. As an example, consider the "Boxer Cup". Here, beemers boom around race tracks, emitting more decibles than any street legal boxer; increased exhaust noise isn't just dramatic effect, it's part of hp improvement.

Perhaps my interest here is in supporting some universal principle, applicable to all internal combustion engines, namely, increased intake and exhaust flow increases hp. Our engines of choice (mostly berlin boxers) aren't exempt from this principle.

 

Jonathan w/stock RT exhaust

[Wooster]

As has been demonstrated with numerous dyno runs, on an oilhead the intake and exhaust tract already flow more than the head so changing to a less restrictive air filter or exhaust does not provide a performance increase.

 

Davis,

 

I'm not sure what you mean by "intake and exhaust track already flow more than the head" but I can respond to your "changing to a less restrictive airfilter or exhaust" statement. Ahem, change the conjunction "or" to "and"; now you've got something, hp increase !.

 

Jon w/"let every or in this land become an and" as campaign slogan

[Ken H.]

I don't care about emissions!

Don't like to breath clean air huh? Some of the rest of us do though.

[DouglasR]

Douglas,

Assuming you weigh 170 lbs your weight savings will be 2.7% not 4%. The bike won't ride itself despite all the electronic wizardry BMW put on it.

 

You might be able to just notice that gain at a drag strip. Doubtful in normal riding. Since the weight removed is very low and near the center of the bike, it won't effect handling very much either.

 

Semantics. The bottom line is the stock setup is heavier than the TBR setup by 21 pounds, which is a significant amount of weight regardless of how you do the math (are you a statistician, Ed?? ). I think I can tell a difference in performance with the TBR pipe on, especially in how fast the engine revs.

 

The jury is still out on whether it's worth the added noise, we'll see what the re-pack kit does for it. I'm not a big fan of noise, there's plenty of it in our lives already. One reason I got out of motocross racing years ago because of the noise, it just got so tiresome. I got serious about trials riding for that reason, it's very quiet and calm compared to motocross.

 

One reason people put aftermarket pipes on their GS (or just take the stock can off and put a stinger on the cat) is to make room for larger left-side luggage. The left bag on the GS is 1/2 the size of the left bag on my RT because of the whopping big stock can sticking up at a big angle (for ground clearance, I guess). With the smaller TBR pipe/can I can run a full-sized left bag.

[Ken H.]

we contribute huge amounts of air and noise pollution with our mowers, trimmers, leaf blowers, power washers, chainsaws, and tillers.

Yes, and fortunately small engines is one of the new areas the EPA is focusing on. They've already started with better emission standards for lawn mowers.

[russell_bynum]

As has been demonstrated with numerous dyno runs, on an oilhead the intake and exhaust tract already flow more than the head so changing to a less restrictive air filter or exhaust does not provide a performance increase.

 

Davis,

 

I'm not sure what you mean by "intake and exhaust track already flow more than the head" but I can respond to your "changing to a less restrictive airfilter or exhaust" statement. Ahem, change the conjunction "or" to "and"; now you've got something, hp increase !.

 

He's saying that the exhaust and the intake are not the bottleneck. Yes, and engine is just an air pump and if you get more air in and let more air out, you get more power. But...you're assuming that the limiting factor to "Getting more air in" is the intake (air filter, etc) and the limiting factor to "Getting more air out" is the exhaust. On the oilhead, that is not the case.

 

With everything else stock (head, cams, etc), you could REMOVE the air filter AND the exhaust and you would not see an increase in power.

[Wooster]

Well, Russell I wonder

 

Reverting back to my wish for universal principles, i.e., opening intake and exhaust systems has positive effect on hp for virtually all vehicles (how about noisey little 2 stroke scooters ?), I remain resistent to making oilheads an exception.

I suspect that virtually all internal combustion engines benefit from internal intake and exhaust work yet even w/o those mechanically intensive mods, simple external attempts to increase flow do improve hp on their own.

So, how could my assertion be proven (my pov) or disproven (your pov) ? Well, I'd want increased access to airbox, i.e., let's discard stock box top (don't want air horn's small opening to negate any increased air flow possible with aftermarket (say "K & N") airfilter); now on to the aft end, I want some exhaust system (not an absolute absence of piping here), but one with less restriction. This, from my point of view, will result in increased hp (I'm assuming motronic mind will increase gas on it's own vs. traditional change in carb jets). Now, if after these relatively accessible mods are made, someone comes along and does internal flow improving mods, e.g., porting, well, better still.

If all this is discounted, well, let's revisit boxer cup. Haven't those bikes been given more open exhausts (certainly louder) in an effort to increase hp ?

 

Jonathan who asserts one million loud harleys can't be wrong

 

"The short fortune teller who escaped from jail was a small medium at large."

[Boffin]

Well, Russell I wonder

 

Reverting back to my wish for universal principles, i.e., opening intake and exhaust systems has positive effect on hp for virtually all vehicles (how about noisey little 2 stroke scooters ?), I remain resistent to making oilheads an exception.

I suspect that virtually all internal combustion engines benefit from internal intake and exhaust work yet even w/o those mechanically intensive mods, simple external attempts to increase flow do improve hp on their own.

So, how could my assertion be proven (my pov) or disproven (your pov) ? Well, I'd want increased access to airbox, i.e., let's discard stock box top (don't want air horn's small opening to negate any increased air flow possible with aftermarket (say "K & N") airfilter); now on to the aft end, I want some exhaust system (not an absolute absence of piping here), but one with less restriction. This, from my point of view, will result in increased hp (I'm assuming motronic mind will increase gas on it's own vs. traditional change in carb jets). Now, if after these relatively accessible mods are made, someone comes along and does internal flow improving mods, e.g., porting, well, better still.

If all this is discounted, well, let's revisit boxer cup. Haven't those bikes been given more open exhausts (certainly louder) in an effort to increase hp ?

 

Jonathan who asserts one million loud harleys can't be wrong

 

"The short fortune teller who escaped from jail was a small medium at large."

 

Jonathan, perhaps a picture is worth a thousand words:

 

The top picture represents the inlet engine and exhaust of a standard oilhead - not preped for the boxer cup.

 

The second an oilhead with high-flow inlet and exhaust - still got the restricted in-head inlet and exhaust so no difference.

 

Picture 3 is a standard Harley, restricted by inlet and exhaust.

Picture 4, Harley with high-flow inlet and pipe, more flow = more power.

 

The boxer cup bikes have flowed inlet and exhaust ports and so are closer to picture 4.

 

Cya, Andy

[ghaverkamp]

The bottom line is the stock setup is heavier than the TBR setup by 21 pounds, which is a significant amount of weight regardless of how you do the math (are you a statistician, Ed?? ).

 

I'm sure you've made all of your comparisons with fuel at the same level, then. Have you weighed all of your gear? Shouldn't drink much water. And, to get back to the beginning, I assume you only keep a little over 2 gallons in the tank at any one time, saving yourself another 20+ pounds compared to filling up.

 

All of which is to say, I have serious doubts that most anyone could blindly tell whether an RT has gained or lost 21 lbs.

[chrisstroh]

I don't care about emissions!

 

 

--------------------------------------------------------------------------------

 

Don't like to breath clean air huh? Some of the rest of us do though.

 

--------------------

Ken & Donna H.

Quiet Pipes Rock!

 

It's unnecessary to be a smartass Ken. If you'd read my last posts I asked a simple question and the thread went way off in a different direction and not answering my original post. Back off!

[Wooster]

Andy,

 

I appreciate your diagrams and, yes, they do depict the majority (of this board) opinion that internal flow of dated, twin valve Harley Davidsons is superior to modern four valve BMWs. However, with no disrespect intended to the honorable brand of HD, I can't wrap my mind around the proposition that Harley's dated cylinder head flows better than BMW's modern head.

Lastly, I suspect that, regardless of where bottle neck exists, some improvement (albeit not maximum) in hp is gained by increasing flow at any place in system.

Here in USA, a popular comedy show is "The Colbert Report", a spoof on political talk tv: one term coined by Colbert is "truthiness", defined as, "I don't have the facts but this should be true". OK, this is a silly leg to support my argument but there it is.

Has anyone the facts ? Do dyno studies exist showing the impact or lack of same when external mods (intake & exhaust) are made to oilheads ? If available, my "truthiness" would have to take a back seat.

 

Jonathan

"Time flies like an arrow: fruit flies like a banana."

[Boffin]

Jonathan, the BMW head does flow better thanthe Harley head, but then so does the stock inlet and exhaust, so much so that the restriction is in the head. In particular the inlet port angle is such that the port turns through about 120 degrees in a small distance - this is to permit the throttle bodies/inlet tubes to be inside the riders legs. This is a compromise brought about by the opposed twin design. The "Rennsport" racers of the 1950's and 1960's had inlet ports angled outwards, with carburettors outside the riders legs as this gave a significant increase in power. The (motorcycle) Boxer design is intrinsically inefficient in inlet - and to a lesser degree exhaust - due to the need to place the fuel system inboard of the riders legs, and the road surface in the event of a crash. The Harley engine is less ineficient in this and UJMs even less so. A good inlet tract runs straight from atmosphere to piston top without any bends or _sudden_ changes in cross-section. A good exhaust does the same. This is why modern crotch rockets are laying the engine down, with steep forward slopes. The inlet can be straight and the exhaust only minimally bent on the way to the outside world. BTW in an earlier post you said you can't increase flow without increasing noise, actually you can _at one engine speed_ by the use of acoustic tuned cavities, these absorb energy over a narrow frequency range and so can lower sound without impacting flow for a small part of the engine rev range. Many European EC marked cans use this effect to lower noise at the engine speed prescribed for the noise test.

 

Cya, Andy

[ShovelStrokeEd]

Jonathan,

This debate hits the various BMW boards time after time.

 

The guys over on the Pelican Parts R1100S forum have run dyno run after dyno run. Extensive modifications to the intake and exhaust tracts on these bikes, which are already superior to the systems found on the RT, GS, and RS series, has come up with about 10 RWHP increase. Allowing for variations in dyno readings on a per day basis and the like.

 

Yes, a chip, an exhaust system and modification to the air box will yield some results. On the order of 3-7 RWHP. The head pipes are a big culprit here and are really built to fit the fairing not get maximum flow. The cost, on the 1100S series, comes to about 2500 with chip, airbox mods and exhaust system. If $400/HP is what you consider a reasonable investment, by all means, go ahead.

 

5 HP on an 800 lb rider and bike combination is of dubious merit, IMHO. That is all you can expect to see without internal modifications to the motor. Once you get into cylinder head porting, more displacement, higher compression, and cams you can probably expect some decent gains. You can also expect a shorter life from the motor.

 

Now, you can realize some well documented improvements in driveability through after market chips, devices like the Techlusion and the PC III. If I were riding an RT today, that is the direction I would be tossing my money. Unless you regularly participate in contests of acceleration or top speed, chasing HP gains on these bikes is an exercise in frustration.

 

The HD bunch do see significant gains from their modifications as the bikes come pretty corked up from the factory to meet noise emission regulations which they so dearly love to flaunt.

[Wooster]

Andy, Davis, Ed, Paul, Russell (alphabetically speaking) and others,

 

Even truthiness has its limits. While I enjoy taking a minority opinion, sometimes I know when to quit. Sooo OK, I can better direct my limited disposable income on microbrewed beers than on the few hp attainable via aftermarket external mods.

Funny, the belief that worthwhile hp are there for the taking is almost gospel on 4stroke.com forums where honda, yamaha, et al, dirt riders agonize over which pipe will make for easier 3rd gear wheelies. However, even in that select company, the idea of losing ten pounds of fat as less expensive path to performance boost has its adherents.

 

Now, Chris (OP), what about that Kawasaki ? Just joking, best wishes in your search for extra oomph.

 

Jonathan

 

If you don't pay the exorcist, you get repossessed.

[Matts_12GS]

Don't like to breath clean air huh? Some of the rest of us do though.

 

Sounds like a fine KC whine Ken.

 

Give it a rest man, the guy asked a legit question and got hijacked....

[Ken H.]

Don't like to breath clean air huh? Some of the rest of us do though.

 

Sounds like a fine KC whine Ken.

 

Give it a rest man, the guy asked a legit question and got hijacked....

In his very first post in the thread the OP made a statement about his disregard for emission control systems and I replied to that exact wording in his post. I think that is fair game.

 

Now if he had ONLY asked about the advantages of dual exhaust on his bike, I would plead guilty to a hijack. But he didn't.

[chrisstroh]

Except my FIRST posts heading was under a different title. "Will removing the CAT increase HP?" You're just an onry S.O.B looking for a fight. Look elsewhere.

[chrisstroh]

And now I'm going to burn some old tires in my fireplace to keep warm and use oil to start them.

[David]

Except my FIRST posts heading was under a different title. "Will removing the CAT increase HP?" You're just an onry S.O.B looking for a fight. Look elsewhere.

 

Ken's post was not out of line.

 

Yours is a personal attack.

 

One more of those (or arguing about moderator actions) will result in your account being deactivated for 30 days.

 

Thank you for playing by the forum guidelines (which you agreed to just days ago).

[chrisstroh]

All I asked was would removing my cat increase HP and the thread took a life of it's own. I disagree with you, but I have found this forum to be a valuable one. I'll be more careful in the future.

[Matts_12GS]

Ken,

I didn't mean to insinuate that you had hijacked, it sort of happened. Peace out!

[FlyingFinn]

No comments about increased/decresed HP and/or emissions, but talking of dual exhaust on R-bikes here's a picture I wanted to share.

Looks good if you ask me.

 

 

 

--

Mikko

[ashleybiker]

Looks like 2 into 1 back into 2.

[Ken H.]

Well I'll give whomever did it points for looks. And the catalytic converter is still there, so no emissions issues. Wonder what it's like sound wise? And idea whose units those are? Also looks like they would preclude the use of the OEM (and others?) side cases?

[FlyingFinn]

Here's a link to where those dual pipes are available: zachauspuff

 

Click on "R 1200 GS" from the list on the left and scroll down.

 

--

Mikko