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SuzukiSavage.com Rocks!
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Valrico, FL
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Boberticus wrote on 04/01/19 at 12:39:38:wait, so everything ive read about performance mods say that the header size is too small, but Lancer your saying for what the bike is tuned for from factory its all correct, and it only needs to be enlarged after getting past the ~35hp mark? and by needs, i mean that that is when the size of the header actually starts to become a bottleneck for power?
the motor literally doesn't breath well enough stock to need it?... is this also why people say to not bother with grinding out the exhaust port until after you've done the camshaft swap and wiseco piston mod, because it wont do much if it doesnt need that air to move that fast/quickly/laminar/smoothly...
all this is at sea level, right? does the lower pressure of altitude change the required volume, kinda like how we dont use a single stage rocket to get to orbit? the nozzles dont work right because of the shape of the exhaust bell once you get too high. surely there is a perfect "pressure" for exhaust, does that have to do with ambient pressure, or is it not a factor? The stock port and exhaust will provide acceptable performance if you are a new rider, or if you don't accelerate hard or ride at higher speeds. Judging by the number of posts from people who are modifying theirs, a good portion of us like more oomph from our bikes. A good porting job and better flowing exhaust will make a noticeable improvement even on a stock engine. Even with only a rejet and a Dyna muffler you will feel a difference in performance.
Lancer's chart sizes exhaust by the HP. I figure pipe diameter by gas velocity, and we end up with similar sizing. His chart says 1.3" is near the limit for a stock engine, and that 1.5" ID is just a hair big for it. My numbers say 1.3" is too small and that 1.5" would be a better choice. I don't know if his chart uses HP at the crank or at the wheel though. If it is at the crank, then his chart matches up spot on with my method of calculating size by gas velocity. Either method will give acceptable pipe diameter recommendations for normal street riding.
Going to a larger bore and/or hotter cam is when the porting and pipe size will show the biggest benefits. The LS engine suffers from chronic asthma so anything that improves breathing will reap rewards.
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