Help with dissasembly of the inside of the exhaust * End *

[fj_pastor]

Hello All,

Firstly, I would like to thak everyone in the forum for their support.

Let me explain my problem:
I run my R1150R for 4 years now with the Djdownunder mod: No exhaust, only cat. I am really happy with the settings, particulary
because the motor revs up much more free than with the exhaust.

However due to a new and strict law to avoid modifications on cars and bikes, I am obligued to install again the original exhaust to pass
the MOT.

I would like to know if there is a way to modify the original exhaust to allow a better flow of the exhaust fumes that allows the motor
to rev up better. I am almost sure I have seen some pics that show the way to dissasembly it at remove some of the inner tubes,
but I have not been able to find it.

Does anyone have an idea of how to dissasembly it and modify it so it does not restrict the flow so much ?


Thanks in advance,

Javier

[kryter]

is a no cat exhaust system an option?

[CycleRob]

A good way to have the nicest sounding stock exhaust is to use the stock muffler with a Y-Pipe header. I have actually heard it running and immediately decided it was the best. Unfortunately, some places require a working catalyst in the exhaust, so that's not an option. I kept the catbox because of the Y-Pipe cost and the funny big gap look under the motor to the centerstand.

I performed muffler mods by cutting open 2 mufflers, some years apart. The first attempt was to relieve the internal back pressure without making it too loud or degrading the sound quality to something flat and nasty. After removing the huge wad of stainless steel (BrilloPad) mesh and drilling about a dozen relief holes in the solid tubes and internal partitions plus welding the cut out panels back on . . . it proved to NOT have been worth the effort or cost. The change in sound level was barely noticeable, although it seemed to have less power "taper off" near redline.

Mod #2 was a much better plan. I was motivated and ready to go radical. Cut it open and remove all the internal partitions and transfer tubes, except for short extensions at each end to partially enter the sound chamber, then weld it back together.

I had several pics on the cloud and I just added 6 more. You can use these pics to locate your cutting locations or make them larger. The ones I made, the smaller one first, were nearly ideal, although a longer rectangle on the larger one would have helped the extraction. The smaller rectangle was located by looking thru the exhaust outlet, allowing the inner cut to determine the length of the necessary for sound quality internal pipe. Longer and slightly smaller diameter internal pipes lengthen the exhaust pulse duration so it doesn't sound shallow or nasty. BTDT on a 1978 Yamaha XS-750 triple where the muffler's welded on end cap was made removable for easier future mods. Just compare the sound of a trumpet to a trombone.

Here are the dial-up friendly thumbnails to access the pics. Click the Thumbnail, Click big pic for full size. Moving mouse cursor off the big pic auto-hides the top menu icons if they are in the way.

[gregor]

However due to a new and strict law to avoid modifications on cars and bikes, I am obligued to install again the original exhaust to pass
the MOT.

I think that you had better check exactly what you can do before chopping the original, expensive, exhaust about.
BTW Which country is inflicting such draconian measures?

[Cohiba54]

CycleRob - Excellent work on the gutting out of the exhaust can, your quite the resourcefully one!

Heres ya a challenge and if i had an extra cat and exhaust can I'd do it my self adding your muffler mod. I've always liked a symmetrical exhaust and have been wanting to have that look on the R bike. So cut open a cat box add a port on the right side add a second exhaust can (mod both cans) and there I am back to 1968 riding my Honda SL 350 or the CB750 or my '72 Bonnie or the Comando 900, the Connie. Do i need to go on?

I just like the look what can i say. Come on you can do it.......

[riceburner]

CycleRob - Excellent work on the gutting out of the exhaust can, your quite the resourcefully one!

Heres ya a challenge and if i had an extra cat and exhaust can I'd do it my self adding your muffler mod. I've always liked a symmetrical exhaust and have been wanting to have that look on the R bike. So cut open a cat box add a port on the right side add a second exhaust can (mod both cans) and there I am back to 1968 riding my Honda SL 350 or the CB750 or my '72 Bonnie or the Comando 900, the Connie. Do i need to go on?

I just like the look what can i say. Come on you can do it.......

you'd need quite a long pipe to clear the Paralever arm and swinging arm assemblies......

[riceburner]

A good way to have the nicest sounding stock exhaust is to use the stock muffler with a Y-Pipe header. I have actually heard it running and immediately decided it was the best.

don't normally like to disagree with you Rob, but I really do have to say my piece here.
I've ridden the bike like this - and the gases coming out of the end of the can get REALLY hot - hot enough to melt the plastic of the BMW panniers - not where the panniers contact the exhaust - but on the rear face of the panniers - ie AFTER the gases have left the can and curled around to brush against the pannier. (this is in UK/Europe too - where the ambient isn't ever above 26-28 degrees C (and that would be HOT!) - I'd hate to see what would have happened in a much hotter environment).

I believe that the exhaust gas heat gets trapped in the can (because it's restrictive) and so the heat can build up. Normally the heat build up happens in the Catalyst, and the cat (and the can) disperse the heat by radiation (and some of it is used to "excite" the catalytic reaction), but the can can't disperse it so well by itself and so the gases existing the can are hotter than they would otherwise be.

Unfortunately, some places require a working catalyst in the exhaust, so that's not an option. I kept the catbox because of the Y-Pipe cost and the funny big gap look under the motor to the centerstand.

I performed muffler mods by cutting open 2 mufflers, some years apart. The first attempt was to relieve the internal back pressure without making it too loud or degrading the sound quality to something flat and nasty. After removing the huge wad of stainless steel (BrilloPad) mesh and drilling about a dozen relief holes in the solid tubes and internal partitions plus welding the cut out panels back on . . . it proved to NOT have been worth the effort or cost. The change in sound level was barely noticeable, although it seemed to have less power "taper off" near redline.

Mod #2 was a much better plan. I was motivated and ready to go radical. Cut it open and remove all the internal partitions and transfer tubes, except for short extensions at each end to partially enter the sound chamber, then weld it back together.

I had several pics on the cloud and I just added 6 more. You can use these pics to locate your cutting locations or make them larger. The ones I made, the smaller one first, were nearly ideal, although a longer rectangle on the larger one would have helped the extraction. The smaller rectangle was located by looking thru the exhaust outlet, allowing the inner cut to determine the length of the necessary for sound quality internal pipe. Longer and slightly smaller diameter internal pipes lengthen the exhaust pulse duration so it doesn't sound shallow or nasty. BTDT on a 1978 Yamaha XS-750 triple where the muffler's welded on end cap was made removable for easier future mods. Just compare the sound of a trumpet to a trombone.

Here are the dial-up friendly thumbnails to access the pics. Click the Thumbnail, Click big pic for full size. Moving mouse cursor off the big pic auto-hides the top menu icons if they are in the way.

[Buckster]

I gutted my stock pipe. The only thing that is in there is the main tube that comes off the cat and upto the exhaust. I also cut the lenghth down too. It was a royal pain to do. I did not cut into the side like cyclerob did. Everything came out of the end where I cut the lenghth off. Riceburner is right about the heat. Although my case hasn't melted, it does get really really warm. I love the sound. It was not a fun job....a hackjob! One other thing....No one has noticed what I did to it.

[Xdot]

I believe that the exhaust gas heat gets trapped in the can (because it's restrictive) and so the heat can build up. Normally the heat build up happens in the Catalyst, and the cat (and the can) disperse the heat by radiation (and some of it is used to "excite" the catalytic reaction), but the can can't disperse it so well by itself and so the gases existing the can are hotter than they would otherwise be.

First, more metal means more heat dissipation so yes, the cat has more internal volume and exterior surface area than a Y-pipe so is going to dissipate a lot more heat. That heat will flow further down the pipe and heat up the muffler. The inside of the cat has thousands of metal passages that conduct heat out of the exhaust gas and to the exterior of the converter can very efficiently.

Second, the 'cat' catalyzes the O+CO --> CO2 reaction to prevent highly reactive and poisonous carbon monoxide from leaving the tailpipe. To a lesser extent it also catalyzes to form N2 and H2O. With the cat in place these reactions take place almost entirely in the catalytic converter. Basically you are burning the carbon monoxide so you are releasing additional heat. Without the cat in place this reaction still takes place (though far less efficiently) all along the length of the exhaust pipe. So instead of having warm CO2 exiting, you now have burning CO.

[fj_pastor]

Hello All,

Thanks to all (specially to CycleRob and Riceburner) for the kind replies ... The post I had seen and was not able to find was CycleRob's

Regarding the other questions, the Cat must stay (the exhaust fumes will be tested to check that it does work).

Regarding the hint that I may trash the exhaust with this modification, the next option will be to buy an homologated Akrapovich or similar exhaust
that runs freely, so if this mod is not working, I will have anyway to purchase another exhaust

Regarding the country, it is Spain. The legislation is so unclear that ANY modification can turn the once-every-two years inspection down.

The legislation was risen to get rid of non-homologated car-tuning, but the apply it as the check station responsible wishes.

As an example of modifications not allowed (depending on the person that approves the bike) you have:
- Mirrors
- Aditional fairings i.e. tank wings, PIIAA lights , white turn signals ....
- Darkened windows (on cars)
- Non homologated fairing screens
- Metallic brake tubes

Regarding the exhaust the test that is performed is:
1) If it is installed (original or homologated ) or not
2) if the noise at 4000 rpm is conform to the homologation of the machine type (but they may allow some deviationm because the original noise level of our bikes is very low).

So it seems I will try to rework the exhaust and reinstall it .... ... I liked the naked view of the rear wheel

Thanks to all of you !!! I'll keep you posted of the final situation

Javier

[Buckster]

No windscreen or braided brake lines? WOW that is pretty strict. You would think that metal braided lines would be safer than rubber ....I'm guessing that's what a metal brake tube is.

[riceburner]

No windscreen or braided brake lines? WOW that is pretty strict. You would think that metal braided lines would be safer than rubber ....I'm guessing that's what a metal brake tube is.

It's all about preventing "unsafe" modifications to any machinery. The legislation is put in place to allow the cops to impound unsafe bikes, or to prevent unscrupulous sellers selling shoddy stuff that makes the bike unsafe.

Unfortunately the way they go about the legislation means that anyone who wants to sell a modification item has to jump through lots of hoops (manufacturer approval, government approval etc etc) and so most just don't bother unless they can make a large (before type-approval costs) profit. So for a relatively rare bike like BMWs, you don't get much.

The EU Commission (an unelected body of busy-body statesmen) are trying constantly to get the same sort of laws passed Europe-Wide. "It's for our own safety" apparantly....

[NoRRmad]

I run stock exhaust, with the cat in place, and my RR has plenty of power for my uses. My last big trip, I pulled in to a rest area next to a car, and the driver got out to say that it sure was nice to hear a quiet smooth-sounding bike, and how much he hated those damn Harley riders with their obnoxious loud pipes. I agree.

[Xdot]

I run stock exhaust, with the cat in place, and my RR has plenty of power for my uses. My last big trip, I pulled in to a rest area next to a car, and the driver got out to say that it sure was nice to hear a quiet smooth-sounding bike, and how much he hated those damn Harley riders with their obnoxious loud pipes. I agree.

[gregor]

Sounds a complete nightmare for anything apart from a bog standard new bike. How will hidden safety items like brake pads be checked?

And will mean the death of windshield/windscreen threads.

[Dr. Strangelove]

Is this the EPA at work?


Idea: Put it on for the inspection, then take it off when the exhaust Nazis aren't looking.

Stella! has the DJDO mod for well over 50k miles.

what state is dictating this?

[CycleRob]

I believe fj_pastor said it was in Spain.

About the heat . . . that rewelded muffler goes back inside the chromed outer heatshield shell, looking exactly stock. The sound also would sound stock, especially compared to most bikes. At a steady 4,000 RPM it would sound legal. I got no complaints about exhaust noise volume from my wife. It was noticeably louder on the road under load than the stock muffler was, to an OilHead owner's trained ear, but not so loud that shadetree modification would be suspect by the emissions testing official. The mod was worth the trouble and $35(?) welding expense.

BTW, I sold that muffler and shipped it to the buyer in the UK.

[fj_pastor]

Hello all of you for the kind answers ...

This is what happenend in the end:
- A colleage suggested to check the bike at an Inspection Station about 30 kmts away from my town where they are more open to bike modifications and
exhaust noise ...
- So I arrive with the DJDO mod to the Inspection Station, everything goes fine until the noise test : 3500 rpm 86 Db at 50 cm of distance .... No way.
Even at idle the bike was over 90 DB .... at 3500 rpm was over 97 Db
Tried to convince the Inspector to look to the side and pass the bike ... no way
- Finally had to assembly the original exhaust and return ... everything goes ok now (87 Db at 3500 rpm ...)

My surprise was that the lose of performance at 4000 rpm that ocurred with the stock can (and the reason why I removed it) did not appear this time ... the bike runs now very smooth.
My opinion is that the motor was not broken-in when I got the bike, but now with 40.000 kmts it is running much more smoothly.

---> My final surprise came when the inspection was passed and finished: a picture of the bike was taken and included in the inspection papers returned to me, as reference of the
state of the bike at the Inspection Station .... or the police pulling you aside to check your papers

It is clear that I will have to maintain the original can and not modify it, I doubt it would pass the noise test in the future ...

Thanks to all anyway.

Javier from Sunny Spain

[riceburner]

My surprise was that the lose of performance at 4000 rpm that ocurred with the stock can (and the reason why I removed it) did not appear this time ... the bike runs now very smooth.
My opinion is that the motor was not broken-in when I got the bike, but now with 40.000 kmts it is running much more smoothly.


Javier from Sunny Spain

I'd totally agree. I've run a couple of these bikes now from new to "very" run in and with most exhaust configs and the bikes only feel restricted when new.
I only run mine without the can these days to save the weight!