Exhaust pipe diameters

acotrel · Jun 23, 2016

I notice in this photo of the Ducati Exup, there are two cables coming out of the unit which look like throttle cables. The write up on the Yamaha Exup mentions a servo motor run off the ECU.
http://www.superbikeplanet.com/image/ar ... 16/013.htm

edgefinder · Jun 23, 2016

From what I hear the exup valve servo from an R1 is the same as on the old RZ 350 and 500. An Ignitech ignition has features to drive that servo and would be an easy way to try it on a Norton. The only hotrod motor I've got is a Ferracci built F1 750 Ducati. Its my last roadrace bike but it has tag and registration so I can ride twisty mtn roads. It only stumbles under 2500 rpm and I've wondered if an exhaust valve would help.

Rohan · Jun 23, 2016

Good find on the Ducati MotoGP 'exup' pic.
Interesting comment about Yams exup not working, if that is what is inferred. (!).

With a note that you sometimes have to be wary about such racing publicity stuff,
its often as much about throwing the opposition off on a false scent ... ?
(Iannones bike needs a collision avoidance system ?)

Ducs (roadbikes) have had exhaust valves for quite some time.
This old spiel says it was all about emissions and noise requirements.
http://www.ducati-superbikes.com/index. ... th-no-cel/
Needles to say, aftermarket pipes make more power/noise, take your pick....

Danno · Jun 23, 2016

Ducati's are big-bore, short stroke, 4-valve per cylinder 90 degree twins requiring no balancer mechanism to make them run smooth and not blow up. Talking about EXUP valves for Norton exhausts is so much hooey, putting the cart before the horse. When you can figure out a way to make a 360-degree vertical twin of antiquated origins spin up reliably past 10K rpm at 1000cc-1200cc capacity, you can start worrying about filling holes in the powerband with trick valves in the mufflers. :lol:

Rohan · Jun 23, 2016

I said that about Yam exup short stroke 5 valve 4's somewhere earlier in this spiel....

Nethertheless, race bikes are subject to noise controls.
Although controlling the noise low down in the rpm register may not be very helpful in this respect,
its on full noise where the concern is....

brxpb · Jun 24, 2016

The interesting comment about Yamaha's exup valve not working, is referring to the well known problems of them sticking mechanically, you needed to keep on top of maintaining them, purely from where the servo was mounted, down in all the salt and road crap!
Obviously ducati would bolt 1lb of extra crap on their GP bike just to mislead Honda and Yamaha!

Rohan · Jun 24, 2016

And arrange for a photographer for it to be recorded......

Red herrings abound in that game, never underestimate that.
Could also be that the road bikes have/had them, so its good marketing to show them.

Just could be that having an exhaust that progressively opens up to free flow may do wonderful things
to the powerband too. Be interesting to see suitable dyno charts, wouldn't it.
Or even hear what MotoGP engines actually produce, rather than all the hype ?

We diverge from Commando exhausts, muchly.

brxpb · Jun 24, 2016

http://www.1000rr.net/forums/1000rr-exh ... stion.html

acotrel · Jun 24, 2016

'We diverge from Commando exhausts, muchly.' ? ?

I don't think so, this might be an avenue worth pursuing. Why are you attempting to censor this discussion ? Naysaying won't promote development of Commando engine systems. What MotoGP does with bikes is highly relevant even if there is a quantum leap in the speeds involved. When it rains and the track is smooth, a Commando at speed is probably relatively as fast as a MotoGP bike is in the dry

Rohan · Jun 24, 2016

Censoring it ?
I'm just commenting.
If you can't tell the difference, what hope is there.
Besides, its LAB with the big red pen.

acotrel said:
development of Commando engine systems.

Commandos already have good low down rpms torque.
We'd be dubious there is anything to be gained along this avenue for a Commando. ?

They need +10,000 rpms performance !!
And its 40+ years too late for this to happen, although Mr Garner may disagree.

Bernhard · Jun 25, 2016

acotrel said:
'We diverge from Commando exhausts, muchly.' ? ?

I don't think so, this might be an avenue worth pursuing. Why are you attempting to censor this discussion ? Naysaying won't promote development of Commando engine systems. What MotoGP does with bikes is highly relevant even if there is a quantum leap in the speeds involved. When it rains and the track is smooth, a Commando at speed is probably relatively as fast as a MotoGP bike is in the dry

re;"When it rains and the track is smooth, a Commando at speed is probably relatively as fast as a MotoGP bike is in the dry[/quote]"

NO CHANCE :!: :?

Dano · Jun 25, 2016

My commando must be worn out

acotrel · Jun 25, 2016

Note the word 'RELATIVELY'. A commando with skinny tyres on a wet slippery circuit is probably as difficult to keep upright as a MotoGP bike in the dry. I can se a use for Exup on a Commando on rainy days when you need really smooth/gentle power delivery. If the butterfly valve was operated from the throttle - almost closed at low throttle, wide open at full throttle - it's main effect would be to help the bottom end of the power band behave itself.

acotrel · Jun 25, 2016

Haven't you guys noticed that Commandos have rocket propelled acceleration as soon as you run off onto the wet grass ?

acotrel · Jun 26, 2016

Noticed this on the sportsbike forum :

'have been dyno tests that showed that taking the EXUP valve off does nothing, you do not lose any horsepower, you also don't gain much, simlpy because the slip ons on the bike are straight pipe.

most people (there are some still out there who believe it functions like the other yamaha EXUPS) agree that the valve is really there for noise suppression.

so don't worry about losing low end grunt or horsepower, the bike will still be the same, maybe just a tad louder. '

Exhaust pipe diameters

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