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Old 11-12-2012, 06:42 PM   #31 (permalink)
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Quote:
Originally Posted by Billyram View Post
Try tuning a single cylinder engine. The exhaust plays a more critical part in tuning than a multi cylinder engine. With out a pulse from another cylinder you have to have a baffle to reduce reversion in the low to mid RPMs or you'll only have power in a very narrow band usually in the upper RPMs. Some times it's much better to have a broader power band than to have a bit more hp in the upper RPMs that you would rarely be in. In mini dragsters using lawn mower motors running at a constant RPM have no use for baffles and are tuned to make peak power in a very narrow RPM range. The torque converter they use is tuned to keep the motor in the peak torque. Dirt bikes can use a bit broader torque curve in the midrange. Super Trapp has been doing tunable pipes for singles for years.
Billy


this is my single cylinder quad, tq is pretty flat and i have true dual exhaust...i will also say this is on bad rings is smoked the dyno room out hahahaha ill be going back when i install new rings in the spring

but anyways, i have no real baffel system on these pipes, not like what comes in a harley....pipes do play an important role but it is the combination of all the parts that will give the best results....or worst

i will also add that my bike only made 88 hp when i first dyno'd it after a quick cam timing advance, ignition timing retard, and leaner jetting from where i first was, power went up to 97 and the curve improved, so maybe the pipes are not his problem, maybe it just needs to be retuned and perhaps a cam change, i was never fond of the ev-27 anyways
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Old 11-19-2012, 05:42 PM   #32 (permalink)
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For what it's worth, the exhaust design has to take into consideration the RPM band where you want the power. Open pipes will produce maximum power at high RPM's and a little restriction will produce more power in the lower and mid-range. For street use, a little restriction is welcomed.
For all out racing the littlest amount of restriction is what it's all about.
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Old 11-19-2012, 06:22 PM   #33 (permalink)
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We loosely call it back pressure that helps with low to mid rpm torque but a proper baffle doesn't cause that much back pressure. It allows exhaust to flow out quite easily but cuts back on reversion.
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Old 11-19-2012, 08:59 PM   #34 (permalink)
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I want it all. I want lowend torque and topend HP. So..what do I do??? Punt???
Buy a bike with a big ass V-8 in it and hold on for dear life when you dump the clutch.
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Old 11-19-2012, 09:15 PM   #35 (permalink)
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Buy a bike with a big ass V-8 in it and hold on for dear life when you dump the clutch.
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Old 11-20-2012, 07:12 AM   #36 (permalink)
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Exhaust flow

Exhaust flow is not constant. As a cylinder fires, the pulse or wave passes thru the exhaust as a pressure wave. Like a big fart. When the pulse leaves the exhaust pipe, a reverse wave passes back up the pipe towards the cylinder and back into the cylinder if the exhaust valve is still open. Backpressure. The wave can reverse again - scavenging the cylinder. The timing of the alternating pulses is very important and depends on the length of the exhaust pipe and the cam timing. The length of the pipe is more important than the diameter. Pipes too big tend to slow the waves and may make less power. The torque peak of an engine is where the cam timing and pipe length are ideally matched. My experience is that straight pipes really suck for power - they result in good power only at very high RPM. My low rider with super trapp exhaust flat runs away from a friends low rider with straight pipes and I out weigh him by 100 lbs.
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Old 11-20-2012, 08:03 AM   #37 (permalink)
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Quote:
Originally Posted by mrmetal View Post
Here is a quote from RB racing.
Our testing has shown that the Harley V-Twin is extremely sensitive to back pressure which is why 2-1's that use small or restrictive collectors don't breathe well, and why restrictive baffles shut the motor down. Disc type baffles are good for spark arrestors on dirt bikes but they have no place on a big inch V-Twin. You don't make power by adding restrictions to your exhaust system whether it's a bunch of stainless discs or some damn piece of aluminum billet machined into a Harley butt plug! Ever wonder why they had to put a hole up the center of the discs? Well, one reason was the discs are so damn restrictive you have to have several pounds of them to get enough flow through their waffle shaped passages. Good mufflers, but they have nothing to do with performance and they sure as hell do not create vacuum as has been claimed.

When you get confused by all the bullshit simply ask the following question.." Do they run them in NASCAR or in Formula One?". Nope, they run straight pipe collector systems without any stupid discs or aluminum butt plugs. It's always funny how, when the money is on the line, all the little things like discs, billet caps, anti-reversion flaps, reverse megaphones and other such nonsense somehow don't make the field. Black Hole technology does not involve stupid eye candy or outdated, or just pain dumb, ginger bread.
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Old 11-20-2012, 08:03 AM   #38 (permalink)
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Originally Posted by 98DARKHORSE View Post


this is my single cylinder quad, tq is pretty flat and i have true dual exhaust...i will also say this is on bad rings is smoked the dyno room out hahahaha ill be going back when i install new rings in the spring

but anyways, i have no real baffel system on these pipes, not like what comes in a harley....pipes do play an important role but it is the combination of all the parts that will give the best results....or worst

i will also add that my bike only made 88 hp when i first dyno'd it after a quick cam timing advance, ignition timing retard, and leaner jetting from where i first was, power went up to 97 and the curve improved, so maybe the pipes are not his problem, maybe it just needs to be retuned and perhaps a cam change, i was never fond of the ev-27 anyways
Out of curiosity how do you have a true dual exhaust with a single cyl. engine?
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Old 11-20-2012, 08:04 AM   #39 (permalink)
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Back Pressure

You guys are missing a serious element of motorcycle tuning and I see it a lot. Especially when people have common "super big" exhaust problems.

There is also another reason to have back pressure.. (Or more restrictive exhaust). Keeping positive pressure in the exhaust keeps the pressure high enough to allow the exhaust gas to make it through the pipe without atmospheric pressure being allowed to mix with the exhaust gasses that are exiting the pipe. Air from outside the pipe cannot mix with the exhaust gasses, this causes backfires. Less pressure... more air and when it gets enough air to detonate it backfires. Remember you "fire" triangle... it applies here as well.

What happens to the idiot that decides to put big exhaust on his bike to make it "loud"? He gets pops and backfires when letting off the throttle. Then some "genius" decides that he is "lean" and rejets or remaps his bike to "adjust out" the backfire problem. The issue here being that the bike was already at optimum Stoichiometric air/fuel ratio... Yes, there is only ONE optimum air fuel mixture... 14.7:1

so you have a bike running down the road with gas almost pouring out of the tailpipe to stop the bike from popping and backfiring when the PROBLEM is the pipe that was installed, NOT the A/F ratio at all.

Too many times I hear people say "The bike runs lean from factory for emissions" - If you think that, you need a lesson on internal combustion theory severely. A bike runs best at 14.7:1... PERIOD.
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Old 11-20-2012, 08:12 AM   #40 (permalink)
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