Coming Soon Stainless Downpipes and Exhausts

[lawvar]

I have been in touch with black widow exhausts.
They currently make downpipe for the g's but not the twin cam models like mine.
De cat stainless downpipes will be available within two months three at the most along with a selection of exhausts.
Prices are VERY good compared to the competition.
http://www.blackwidowexhausts.co.uk/bmw-r-1200-gs--adventure-downpipes-collector-100-p.asp#
Price for downpipe around £205.00
A full system from £329.00
If anyone else is interested maybe we can get a group discount?
I'm having one and then a hilltop job !

 

[DING-DONG]

Prices are VERY good compared to the competition.

How much is good !

 

[lawvar]

I can tell you how much is expensive
£442 Remus downpipe
£346 keihan

 

[Sgt Bilco]

No balance pipe?

 

[lawvar]

Just checked and Remus don't have a balance pipe either ?

Does anyone know if it makes a difference or what its supposed to do ?

 

[sethmopp]

Doesn't a full system from a single cam fit a twin cam, thought it was mix and match you couldn't do?

 

[lawvar]

Apparently single cam DOES NOT fit twin cam ?
However they are making twin cam specific in next couple of months with similar prices and design to single cam.
That's why I posted the link so you guys can see the design/quality hopefully there will be some interest ?

 

[Sgt Bilco]

Just checked and Remus don't have a balance pipe either ?

Does anyone know if it makes a difference or what its supposed to do ?

Exhausts are a dark art and I'm not sure of the reason. However, BMW didn't just put it there for no reason as the manufacturings costs are a lot higher. The Keihans and Akra's use the pipe but Remus don't. The Remus have a much bigger bore though so I guess they get round the balance pipe issue with this solution.

 

[Bendy toy]

A single cam exhaust system DOES fit the twin cam but you need the full system. Exhaust outlet stubs and tube hangers are the same on all models.

The difference between SC and TC is a gap in the link pipe to take the flappy valve. So you can't easily fit a late model header to early model silencer and vickie verkie.

Using a link pipe on a 2 to 1 system with unequal length header pipes really doesn't add up. The exhaust pulse timing has to get mixed up at the Y joint. But, the Akraprovic header also has a conical section just after the link pipe probably to create a suction effect and balance the gas flows. But it can't be cheap to make and the effect wont work at all revs.

 

[lawvar]

I asked keihan why they incorporated the link pipe they said a client requested it to look oiginal!
So much for experts

Sent from my SM-G920F using Tapatalk

 

[BigDan]

They were previously known as Sandy Bike Spares, and their products were pretty sketchy at times. Complete luck of the draw as to whether you got a set of pipes that were quality or even fit correctly.

There is certainly a reason they are cheaper. But hey, who knows, they might have improved.

 

[Sgt Bilco]

I asked keihan why they incorporated the link pipe they said a client requested it to look oiginal!
So much for experts

Sent from my SM-G920F using Tapatalk

Not true. My bike was the donor bike for the Keihans and we all agreed at the time that although it would be more pricey to retain the balance pipe, BMW had spent mega bucks designing the exhaust system to make it the most efficient it could be so who were we to argue?

If it wasn't needed for a bloody good reason, it wouldn't be there.

 

[BigDan]

Not true. My bike was the donor bike for the Keihans and we all agreed at the time that although it would be more pricey to retain the balance pipe, BMW had spent mega bucks designing the exhaust system to make it the most efficient it could be so who were we to argue?

If it wasn't needed for a bloody good reason, it wouldn't be there.

I see your line of thinking, but maybe that bloody good reason was to get it through some stupid regulation or emissions test that practically none of us care about. All i know is that after changing the exhaust system and getting it tuned properly, these bikes get more power and some seem to get better MPG too!

 

[Bendy toy]

To expand on what I said before.

With equal length header pipes and an even firing pulse a link pipe can give added suction. Gasses from cylinder 1 cause a suction in the link pipe drawing out gas still lying in the other side. When cylinder 2 exhaust the link pipe flow reverses and the opposite side is sucked out. But when pipe lengths are not equal it can't work properly. The same effect happens with a Y joint so there should be no point having both.

The standard headers have odd length pipes between cylinder head and cross pipe and cross pipe to Y joint. There is no way that cross pipe can have much useful effect as its got to be cancelled out by shock waves coming back from the Y piece. Its probably there because the airheads used them though they don't have the Y joint. (most of them anyway).

My Akaraprovic headers have a cross pipe but they also have conical sections after the cross pipe. Presumably the cones even out the suction effects so the cross pipe can help to draw gasses from the opposite cylinder. The effective rev range will be limited. I got mine used but new it was silly money. A big price to pay for perhaps one or two bhp at full revs.

Remus just use a larger bore header pipe and no link pipe.

I had headers from Sandy Bike Spares whiich fitted fine on a Diversion 900 though I did use Beowulf cans and custom link pipes. The headers were actually Delkevic brand (owned by DK of Stoke on Trent).

A much better header, and cheaper to make, was offered by Jama Originals. That used two Y joints under the engine and a link pipe after the Y. There was no clunky collector box as used by DK and Yamaha and no sleeve gaskets to slip and leak.

 

[lawvar]

Not true. My bike was the donor bike for the Keihans and we all agreed at the time that although it would be more pricey to retain the balance pipe, BMW had spent mega bucks designing the exhaust system to make it the most efficient it could be so who were we to argue?

If it wasn't needed for a bloody good reason, it wouldn't be there.

Its what they stated !
when i enquired what was the reason for the balance pipe?

Sent from my SM-G920F using Tapatalk

 

[Bendy toy]

This calculator http://www.wallaceracing.com/header_length.php gives the correct pipe stats. If anyone knows the necessary values give it a try.

I used it to check the pipes on my Divvie 900. It came out pretty much as Mr Yamaha intended and surprisingly the same as the Delkevic headers. It hits peak power at 8250rpm giving (IIRC) something around 22 inches from exhaust valve to Y joint. Presumably valve centre to Y joint centre though its not clear. The BMW hits peak power at 7000rpm so the header would be longer. The revs ratio between the bikes is 1: 1.178 so on fag packet scribble says the GS pipe should have the Y joint at about 26 inches. But my Akra is at least 36" from exhaust port to Y joint plus the extra bit in the cylinder head and its unlikely both are the same length.

So the standard system is far from correctly tuned and who knows if the cross link pipe is in the right place. But I suspect its done to look nice and **** to the power figures.

I have the Akraprovic shotgun system with twin stacked exhaust cans. I do wonder why they didn't run separate pipes right through. Space restrictions I guess.