Exhaust Tuning

[piranha-bro2]

Short answer - Yes.

Some years ago David Vizard came out here and gave a talk at a tuning forum. I've still got the very useful handout literature (free ! )
He was keen on a resonator in the tailpipe of joined systems but cautioned specifically not to extend the pipe into the resonator as you then effectively put a stop to wave activity at that point.

Vee twins - My personal rule of thumb is only use a 2:1 on engines under 700cc. Above that I'll always use separate pipes.
I have tried what you could call "H" layouts with a joiner at the length I need to achieve peak torque at the RPM I want.
The spread is probably better - but peak HP down.
For a biggish twisted twin I'd start with separate pipes.

I'd love to read that handout! What exactly is the 'resonator' you describe, Greg?

As for the single pipe idea, it won't be hard for me to create two separate pipes in place of the X-pipe in the pic. I've also got the start of a Jotas type collector I can play with (basically two parallel tubes sliced and siamesed along their length).

On top of thinking about performance design, I've had to squeeze my system onto the bike, around the big Honda swingarm and with a muffling system that hopefully won't cull my HP. I don't want a bike that goes fast but makes a massive racket on the road and attracts too much attention!

 

[piranha-bro2]

as written before in this thread, both my Jota (180?) and my SFC 1000 (120? obviously) have modified or completely re-designed exhausts. I can confirm what Piet says: the Jota basically has a similar design now to the big-bore collector (wich is basically 2 pipes in parallel, joined together to share the volume). My collector was modified by removing the center piece and welding in 2 pipes that run in parallel back to the mufflers...

Really interesting, Lothar. I can see that a lot of thought and work went into your designs. And you got some great results out of it!

Where you removed the centre piece 'welding in 2 pipes that run in parallel back to the mufflers' - are those parallel pipes joined in any way or completely separate?

 

[sfcpiet]

Firing intervals at play again, Piet. All seems to demonstrate how important it is in ex design - always surprised at how many V-twins have 2/1s. Mine always ran fine on it's 2/1, but I'm interested in what diff a twin or semi-twin (2-1-2) system works.

See my reply #8 earlier in this thread... lots of thought went into our 2-1 for the Sportsters.

Recieved some pics of our bikes from way back when, Daytona '97.  #60; Mr.St?ggi

piet

 

[tom3c75]

Bit of a thread hijack, but the reference to Harley racing reminded me of this pic in one of my old bike mags. 

 

[Laverdalothar]

Really interesting, Lothar. I can see that a lot of thought and work went into your designs. And you got some great results out of it!

Where you removed the centre piece 'welding in 2 pipes that run in parallel back to the mufflers' - are those parallel pipes joined in any way or completely separate?

pics tell more than words...:

 

[GregT]

I'd love to read that handout! What exactly is the 'resonator' you describe, Greg?

The handout was I think simply reprints of articles and papers he'd written and published. Collected together in a useful form. Pretty sure most if not all are somewhere on line.

The inline resonator chamber is simply a volume added into a tailpipe to compensate for length lost due to installation compromises.  Rear engined formula cars run into this problem. Correct sizing can work well for HP plus it's an extra silencer. Some of the late bikes with pipes in the fairing lower and no tailpipe length to speak of have large chambers squeezed in to meet Euro silencing standards.

Piet - Great pics. I must hunt out the Evo tuning handbook by Jerry Branch I have somewhere. He goes into great detail over pipes - with dyno charts for 5 or 6 of them. Both separate and joined systems. I've always looked at HD pipes as unique to them. The relatively low revs - compared to a Ducati - mean different solutions work for the HD's vs the Ducs.

 

[piranha-bro2]

Piet - Great pics. I must hunt out the Evo tuning handbook by Jerry Branch I have somewhere. He goes into great detail over pipes - with dyno charts for 5 or 6 of them. Both separate and joined systems. I've always looked at HD pipes as unique to them. The relatively low revs - compared to a Ducati - mean different solutions work for the HD's vs the Ducs.

And a 60 deg(?) vs 90 deg config probably alters the game a bit as well.

Some great pics indeed.

Nicely configured collector, Lothar! What sort of muffler is used with it?

 

[sfcpiet]

And a 60 deg(?) vs 90 deg config probably alters the game a bit as well.

Some great pics indeed.

45?!

piet

 

[GregT]

And a 60 deg(?) vs 90 deg config probably alters the game a bit as well.

As Piet says - 45 deg.  The Britten was 60 deg. First version of the "own motor" had a 2:1 with a reverse cone mega at the junction. I was working there at the time and convinced John to let me make a slip-on longer tailpipe. They tested it on the usual country road and came back saying it was cutting out at high revs.
When we looked at the data logging it was spiking rich at the top end. The pipe actually had working reverse wave action which the mega didn't have. I wanted them to lean it out at the top and try again - but usual John, if it didn't immediately work, it was ditched.

The final bag of snakes pipes are individual headers - one from each of the 4 exhaust ports - joined in cylinder pairs at the right length for the torque peak. Then the total pipe length incl mufflers is correct for peak power rpm. So each cylinder is a 2:1 pipe. Worked out I believe by Wayne Wright - Wobbly - the well known 2 stroke tuner.

 

[rowdypat]

Seen at Broadford a few years back  8)

 

[The Sock]

Athodyds and expansion chambers:
Anyone seriously interested in the subject could do worse than reading the work of the late Professor Gordon Blair, of Queen's University Belfast.
Here's a taster:
https://daro.qub.ac.uk/pages/2016-rebrand/news/obits---all/obits-professor-gordon-blair

http://www.ulsterclassicmotorcycleclub.com/urm.html

 

[piranha-bro2]

Cluey man indeed! Now that's what you call research!

 

[Tippie]

What a place to study engineering!

 

[BOETJE]

    "  Worked out I believe by Wayne Wright - Wobbly - the well known 2 stroke tuner "

Nah.......not really....
Actually....not at all... 

 

[Laverdalothar]

Nicely configured collector, Lothar! What sort of muffler is used with it?

Campbell Jota Pipes in very thin steel, chromed, with a 32mm diameter and roughly 6cm long "Helmholz" Pipe at the end. Headers are 37mm (outside, inside they are roughly 34-35) stainless from Keihan I think to remember. The front part of the collector is what is left from the Keihan collector. 

Must make a pic of the SR-Racing configuration... 

 

[Adam K]

Just a couple of pictures of the pipe I had made for my bike.

 

[Paul Marx]

Reminds me of Marving tubework.

Paul

 

[piranha-bro2]

Looks good. Is the bike a 'replica'? If not, angling the left leg of the centrestand would haver given you a clear run all the way through - a la 74 and later SFC. Just needs the lug on the frame welded closer in on the left side. Totally eliminates clearance issues and straightens out your pipe. No downsides. Just sayin' ...

 

[Adam K]

This bike was mentioned a few years ago on the forum. I bought it out of a museum in Tasmania as a genuine SFC and got ripped off.
The motor is one of the last three 880 twisted twins Red built.
The pipe was made by CES Racing the same guy that builds Red's race bike pipes.
Just have to do the wiring and fit a set of Mikunis and she's good to go.
It's been a long project but I am nearly there.
Can't wait to take it for a ride and see how it goes.

 

[piranha-bro2]

I do remember the tale (of woe!). You've done a great job on it - pity it's not the genuine article, but you can enjoy owning any SF as much as an SFC if you set them up right.