Exhaust pipes: 2-1-2 vs 2-2

[Raux]

What are the pros/cons of the 2-1-2 of the current Ducati exhaust systems?
What are the pros/cons of using 2-2 exhaust system?

[rule62]

Something about the 2-1-2 crossover evening out the exhaust pulses and helping scavenge.  If you're going for a 2-2 system the lengths of each have to be similar or the bike may not run right.  No FHE, just recalling a little what I've read.

[RB]

everything i have read/been told says that your headers need to be equal lengths to the crossover, then from there it won't matter.
i am in the disegn phase still. My exhaust will be 1-5/8" and 23" long until it hits the crossover, this will be for a 2-2 system..i like the way the S2R stacked pipes look.

[Speeddog]

For some reason, the Duc motors seem to prefer a crossover.

2-1 systems don't seem to work well either.
Although, given the layout of the OEM Monster header, I can't see how the motor could tell the difference if the 2-1 was sized correctly. 

There's folks that have played at that on dynos.

[Raux]

ok so a 2-2 with a crossover guess that's basically a 2-1-2 without the single pipe section.
Moving the crossover should allow you to 'tune' the range of the power.

Found this

NOW - A couple of people ask about the Cross Over on a Motorcycle - They usually only have 2 Cylinders.

It is actually a little more technical but I'll try to keep it simple.

In the case of 4 stroke motorcycle engines, the reason for a cross over is this...

After a cylindar fires and the piston cycles “up” - exhausts gas vents through the Exhaust valves, along with the remainder of the “explosion”, exiting the cylinder into the exhaust system.

This explosion creates 2 pulse waves… a Sonic Pulse - and a Thermal Pulse.

When the faster Sonic Pulse leaves the exhaust it has created a vacuum in the pipe behind it, which air pressure will enter the pipe to fill the vacuum. This air will collide with the Thermal Pulse and cause it to reverse. The timing of this event causes exhausted gases to be returned to the cylinder while the exhaust valve is still open therein not allowing all the spent gas to escape and also polluting the environment for your next stroke cycle with fresh air/fuel mix.

This “Event” is call Reversion and seriously degrades performance and lifetime of valves and cylinder heads.

The Cylinders fire opposite of each other â€" or nearly so on a Harley. So when One side is firing, the other side is idle. Having the cross over pipe allows the pulses to dissipate back and forth between the tubes instead of - or before exiting the exhaust and therein greatly diminishing the effects of reversion and so improve performance and engine life.

Yes - you see a lot of bikes with duels and no cross over. These are usually "Tuned Pipes".. meaning their length and size are tuned to work with the S/T Pulse in such a way that reversion can not return to the engine before the exhaust cycle has ended.

[RB]

ok so a 2-2 with a crossover guess that's basically a 2-1-2 without the single pipe section.
Moving the crossover should allow you to 'tune' the range of the power.

Found this

NOW - A couple of people ask about the Cross Over on a Motorcycle - They usually only have 2 Cylinders.

It is actually a little more technical but I’ll try to keep it simple.

In the case of 4 stroke motorcycle engines, the reason for a cross over is this...

After a cylindar fires and the piston cycles “up” - exhausts gas vents through the Exhaust valves, along with the remainder of the “explosion”, exiting the cylinder into the exhaust system.

This explosion creates 2 pulse waves… a Sonic Pulse - and a Thermal Pulse.

When the faster Sonic Pulse leaves the exhaust it has created a vacuum in the pipe behind it, which air pressure will enter the pipe to fill the vacuum. This air will collide with the Thermal Pulse and cause it to reverse. The timing of this event causes exhausted gases to be returned to the cylinder while the exhaust valve is still open therein not allowing all the spent gas to escape and also polluting the environment for your next stroke cycle with fresh air/fuel mix.

This “Event” is call Reversion and seriously degrades performance and lifetime of valves and cylinder heads.

The Cylinders fire opposite of each other – or nearly so on a Harley. So when One side is firing, the other side is idle. Having the cross over pipe allows the pulses to dissipate back and forth between the tubes instead of - or before exiting the exhaust and therein greatly diminishing the effects of reversion and so improve performance and engine life.

Yes - you see a lot of bikes with duels and no cross over. These are usually "Tuned Pipes".. meaning their length and size are tuned to work with the S/T Pulse in such a way that reversion can not return to the engine before the exhaust cycle has ended.

Just to clarify...
Harleys DO NOT fire nearly opposite. Our L-Twins do.

Take a look at the 696 & 1100 exhaust...if you have an air-cooled.
The pulses may be translated as....if proper length to the crossover, one pulse will actually help the second pulse pull from the exhaust stroke by creating low pressure behind the exhaust pulse in front of the second...and perhaps i am not making it easier to understand.


sorry, just saw that you actually have a 696....measure your pipes from the exhaust valve to the crossover. Your pipe diameter should be 1-5/8"...or close to that. You can have Burns Stainless take you engine specs and tell you how big your pipe needs to be and where the crossover should be....and then buy some stainless from them for their work. You will need to know cam lift and duration, they have a form to fill out.....i am not affiliated with Burns Stainless....eventhough my last name IS Burns....ha!

[brad black]

some ramblings of mine.

if you search the af1 aprilia forum there's a thread somewhere about 'modifying oem header" in the old tuono or rsv section.  it appears the 2-1 fitted to the early rsv and tuono limits midrange, but the top end is about the same.  that thread is about modifying the oem 2-1 headers will joining tubes to help fill the midrange.  the only 2-1-2 early aprilia was the falco, which was the SS equivalent of the range sort of thing.  they have a heap of midrange.  never dynod one tho.

999 full systems and 1098 with the long single tube seems to cause the midrange hole they have - the zard 1098 system looks like a 916 system.  i'm tuning one this week i believe, which will be interesting.

i don't know if the 2v models rev high enough to really have top end issues, altho my 900m with the arrow 2-2 certainly suffered compared to std headers and slip ons over 7,000 rpm.  maybe a touch better under that, but it was then a very narrow power band and a lower peak.  in general without a cross over i don't think you'll make the top end.

696 will have relatively short cams and large valves for its size so probably needs to be able to flow more air quicker in terms of diameter maybe.

and i always say it's more a packaging concern first, then a tuning concern later.  especially with the ports so far apart.  a parallel engine is much easier to tune exhaust wise.

tuning lengths gets back to a specific rpm range too.  and it's repeating at multiple frequencies too, so it can be good and 4 and 8, crap at 6 sort of thing in the extreme.  or lower peak torque, wide power band versus high peak torque, narrow power band.  so it's a compromise.

[supertjeduc]

Why does NCR always uses a 2 in 1 on there race bikes if a Ducati doesn't like a 2 in 1

[Raux]

http://kaemna.de/cms_en/katalog.htm?&view=artikel&artikel=2092

2-2 exhaust, 118hp

[RB]

http://kaemna.de/cms_en/katalog.htm?&view=artikel&artikel=2092

2-2 exhaust, 118hp

but isn't that 118hp coming from a totally built motor....not just the exhaust?
I am not crazy about the way it looks, but i do like the idea of not needing a crossover to scavenge more ponies(hp).

[brad black]

both interesting.  maybe ncr just like the look of 2-1, or want to package them that way.  maybe the shorter length of the kaemna system is what works ok there, but you'd also need to know what other systems they've tried on the 118hp bike and what the differences were in terms of output and curve shape.  std length systems may differ.  the honda that won sbk in 2002 had a 2-1 for the second half of the season and it didn't seem to have any issues.

the problem is that unless you build a lot of header sets that are the same except for all being different then you'll never know.  and no one has done it as people will only buy what they think looks good or what someone who races and wins uses because it must be better or what they can afford.  or what they or a mate can make up.  there's no money in it and really other than curiosity not a lot of point.  and it's one of those things that if you try 10 different things someone will say "what about 11, you didn't try it" which is really annoying when you like playing and get cut short for some reason.  lots of my tests i'd do differently or more thoroughly if i could do them again.

the fact the std style stamped x header on all the older non sbk models seems to work so well for what it is, even on st4s models, probably makes it harder to improve too.  and it comes back to packaging more than anything - in terms of an oem system with good sound reduction, etc, two muflers and a cross over may be more effective.  the kaemna system is probably lighter as it doesn't have excessive pipe to allow for a crossover that you may not need.  altho put that short style on a 999 with two oem style mufflers with cats, etc, and you'll have more weight and cost.

[Raux]

saw this on http://www.europeancycleservices.com/index.asp

2-1-2? 2-2? what is that?

EDIT: found it. Zard full 2-2 sport classic system but the photo looks like they added an H pipe between the two? wierd

[RB]

a friend of mine has that system...sounds righteous! I have no idea about performance though.
and yes that is the way the Zard system comes out of the box.

[brad black]

the vertical pipe comes around and joins into the horizontal pipe as you can see on the rh side.  so it's not a full cross over style exhaust.  in my testing sample of one it makes a bit less than a monster or ss, but more than the dual pipe sport classic header.  is very loud.

[Adam in TX]

fyi -the DP high mount carbon kit on my FI 900 is 2-2.