Amazing things exhausts, Ron Grant back in the late 70s managed to pull some more boogey out of my old XS650 playing with the exhaust system, mind you the Kenny Roberts bits he sourced also helped. lol
I was surprised how much longer and quicker the revs were on the FB after the simple Hi flow air filter and re tune were done.
The heat and subsequent heat loss of the pipe effects the heat of exhaust gasses, ergo it effects the length at which it resonates.
modern two strokes use both heavily retarded timming and fine control of electric powerjets after peak power to put additional heat into the exhaust, there by making it respond as if the tunned length was actually shorter.
They also use carbon sheilds to prevent exposed areas of chamber being cooled at high speed.
https://www.kiwibiker.co.nz/forums/a...5&d=1413875766
Opinions are like arseholes: Everybody has got one, but that doesn't mean you got to air it in public all the time....
And I to my motorcycle parked like the soul of the junkyard. Restored, a bicycle fleshed with power, and tore off. Up Highway 106 continually drunk on the wind in my mouth. Wringing the handlebar for speed, wild to be wreckage forever.
- James Dickey, Cherrylog Road.
Thanks Guys for all the responses and sharing of knowledge and experience.
The 2 into 1 Hi output exhaust is on its way with some new seals. Big thanks to Pete, (motorcycle Alley) another good bugger who went out of his way to give me good advice and service.
Been a big month for the old girl with front and rear suspension upgrades happening and a new exhaust system. I had no intention of doing any upgrades when I got it just over a year ago, Bikes are funny bloody things, no wonder they get given girls names.
The gains and variation on a Harley are of course less than a two stroke, but it is a real phenomenon.
All you are doing is increasing of decreasing the temp and speed of the exhaust gasses. Hence the effective tuned length of the pipe.
Thats why all decent exhaust pipe calculators use the exhaust gas speed.
It's the same theory behind the HPC coating of exhausts.
Not really, the ceramic coating is to keep the heat within the exhaust rather than a variable manipulation of an exhaust tuned length. The response of the coating only effects the tunned length which is irrelevant as they are application specific.
2 stroke expansion chambers require different lengths depending on the gauge or the material ie mild steel or SS or TI. But this is factored in at design stage
HPC like coatings do have advatages when used on internal components such as combustion chambers. as they prevent heat disipation and mitigation which (additionally) also helps burn off deposits
But it’s mostly to look pretty and be durable on exhausts.
It does have an advantage of not transferring the heat to the engine ancillaries though which i actually the real reason Nascars actually used heat wrap, mainly to stop the alternator cooking and other heat soak to engine and carb etc.
Nice to see the ANZA Harley boys working out of City Honda in Palmerston North.
Nothing better than talking to guys who know their Brand and when leaving your bike knowing it is in good hands.
Big thanks as well to Crasherfromwayback for giving me the heads up on a couple of things that I needed to research.
great site this Kiwi biker.
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