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+--- Thread: Wyvern 4-in-1 Titanium (/showthread.php?tid=4388)
RE: Wyvern 4-in-1 Titanium - PowerDubs_imp - 06-09-2022
Yea- blue is a stock run.
...and although I haven't heard a 4-4 in real life yet, my guess is that it sounds good enough you may find yourself opening her up a little more than you would on a 4-1 4-2...
RE: Wyvern 4-in-1 Titanium - j3gq_imp - 06-09-2022
One word about the charts shown. When you look up from a given rpm, and figure that this exhaust gives you just another 5hp at that rpm, you might likely say “irrelevant”. But that’s not the most interesting way to look at the chart. When you look at the same chart along a line of constant power, from left to right, checking for example where 80 hp is produced, you find that the single exhaust system makes the same power at 1000 rpm/s less. That IS relevant, for noise, vibrations, comfort and your neighborhood. It also reduces internal friction, and such your gas consumption.
RE: Wyvern 4-in-1 Titanium - tommymck - 06-09-2022
(06-09-2022, 06:19 PM)j3gq_imp Wrote: One word about the charts shown. When you look up from a given rpm, and figure that this exhaust gives you just another 5hp at that rpm, you might likely say “irrelevant”. But that’s not the most interesting way to look at the chart. When you look at the same chart along a line of constant power, from left to right, checking for example where 80 hp is produced, you find that the single exhaust system makes the same power at 1000 rpm/s less. That IS relevant, for noise, vibrations, comfort and your neighborhood. It also reduces internal friction, and such your gas consumption.
It's not clear to me that generating higher power at a given rpm necessarily equates to better fuel efficiency. Also not clear to me that I'd change my shift pattern based on the availability of the extra power for normal riding. You may be right...but it's not obvious to me. I agree that it's an interesting way to interpret the curves in any case.
RE: Wyvern 4-in-1 Titanium - j3gq_imp - 06-09-2022
Can be explained. Example, you go up the hill behind your house, at a constant 60 mph, in third. This requires a very specific amount of power from the engine with stock exhaust. After you switched to another exhaust, this amount of power PN is still the same for that hill. But with the new exhaust, for the same result (remember target speed and shape of the hill haven’t changed), your right hand would have turned the gas grip less. No need to change your habit. The better exhaust aus (according to the charts !) has done it all for you.
First question: internal friction (call it losses, or useless heat produced) go up with rpms, and indeed it goes up significantly. So less rpms for the same power output requires less fuel (= less fuel is needed to produce excess heat).
Helps?
RE: Wyvern 4-in-1 Titanium - PowerDubs_imp - 06-09-2022
While it is true that these dyno charts are wide open throttle power- generally if the bike makes more power at any given place than before, it means the bike is more efficient at moving air at that RPM.
So minus any velocity differences inherit just due to sheer volume of airflow delta between part throttle and WOT- it is probably a safe bet to make the choice of the exhaust that makes the most power for the RPM you ride in the most, even if you aren't concerned about power and never crack the throttle past 1/4.
We could argue that an even smaller diameter pipe- one small enough to hurt / make less power than even stock at higher RPM could have more velocity at very low part throttle therefore giving it more economy- but that you would still want that smaller theoretical exhaust to be free of pumping losses such as the cat and choked off quiet muffler.