What type of exhaust for power. (2019)

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acotrel said:
In fact with the Dunstall pipe, you could fit an Exup system into the bit where the pipes converge
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Did anyone actually use ExUp with twin's? I've been out of the new motorcycle technology loop for 21 years, and counting.

I had ExUp on a Yamaha Deltabox FZR1000 and a Deltabox FZR400. I pulled those ExUp things apart and wasted a hour or two on each smoothing out the rough casting on the valves. I can't remember how much difference it made, but my guess is none. I think I ended up putting FCRs and a full Yoshimura pipe on that FZR400. That 400 ended up being annoyingly ear piercing loud, but it ran pretty good. I didn't race it, because I was too busy working and searching for the best frilly knickers available. :)
 
I was able to get a 2:1 exhaust to work well up top on my Norton, but I have nothing to really compare it to. It just never runs out of legs. I had to lengthen it and open it up. Unfortunately, I think I'm repeating myself. Might be time to go back into the rubber room, or go for a ride.
 
There are no corners on the Bonneville Salt,Flats, but would you use a megaphone exhaust for drag racing ? You would get best power.
 
@acotrel

For what I would know and therefore say one would use short straight pipes (zoomies), and not megaphones, in order to have the hardest negative return on the scavenging wave as one simply doesn't need the spreading of wave action due to the reflection of a mega.
And after all the most important thing in drag racing is/would be highly efficient volumetric efficiency over a well defined rev range.

Kind regards

Christian
 
Best power comes from separate pipes with megaphones, but you get less power lower down in the rev range and there is usually a bump where the power comes on strong. On the Bonneville Salt flats, that does not matter because you have a longer run up. In drag racing, you need immediate power to get you off the start line. If the revs drop off, the megaphones do not work. Straight pipes would be faster. Normally close ratio gears give better acceleration, because you are always using the part of the rev range where the motor pulls strongest. If the revs drop too low, your acceleration depends on throttle response. With the heavy Commando crank, throttle response is poor, unless you keep the revs high.
 
Tell me this. If you are riding around an 80 KPH corner on as bike which has 60 BHP and there is a guy who is beside you going into the corner who has an 80 BHP bike. and needs to have it upright before he accelerates - if you turn under him and accelerate from well back in the corner so you are 10 KPH faster coming out. If there is a 500 metre straight in front of you, who would reach the next corner first ?
 
acotrel said:
Tell me this. If you are riding around an 80 KPH corner on as bike which has 60 BHP and there is a guy who is beside you going into the corner who has an 80 BHP bike. and needs to have it upright before he accelerates - if you turn under him and accelerate from well back in the corner so you are 10 KPH faster coming out. If there is a 500 metre straight in front of you, who would reach the next corner first ?
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The one with the best braking ...
 
@acotrel:

Please read up on academic texts ( eg. classics are by: smith, annand and roe, blair) on gas dynamics and finite amplitude wave propagation.
You will see or better read (from people that might be more trustworthy than me) the strongest and shortest scavenging impulse you get is from an open pipe end and not from a propagation weakening/broadening megaphone.
One of the reasons why n.a. flatheads and dragsters prefer straight short pipes that are tuned to the heaviest return wave harmonic, because they need all the scavenging action possible in order to achieve the necessary volumetric efficiency.

Kind regards

Christian

Ps: i always found my way around such situations on my H1 with using the clutch and stay in the needed rev range and I guess the H1 is more pipes than a race 4T, or as mentioned by fast eddie braking hard into the corner and then accelerating hard out of it.
 
Perhaps an appropriate time for a reminder of the title of this thread?

”What type of exhaust for power?”

It was interesting till it got derailed ........ as most threads do !
 
I don't like coming down from very high speed on a race bike. Sometimes it is possible to just lightly touch the front brake and find yourself rolling down the bitumen with the bike sliding after you. Nigel is right. The fastest bike to the next corner is often the one with the best brakes. On speedway brakes are banned. If you want to stop, you just turn into the infield. With road racers, it is dangerous to pop in front of another bike while braking.
 
A lot of hot air and noxious fumes.... Blow it out your.....

BUT.. To quote a tobacco ad back in the day when they were allowed: 'A pipe does something for a man'
:)
 
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