Increasing Speed from a muffler?

[freaky_beef]

Okay...this isnt exactly a motercycle were talking about. Its a Yamaha Moterized Scooter (gas). So I apologize that this is about a scooter...and not a motercycle.

Anyway...my friend strongly believes that if he were to put on a new muffler...that his scooter would go from 40 MPH to 55 MPH. I said that there is no way possible. I said that mufflers increase gas mileage and HP.

So can you increase speed on a cycle/scooter from a muffler? If not...then how can you?

[sharpmagna]

The muffler may increase how fast you get to your top speed but won't increase your top speed. Your top speed is going to be governed by your gearing.

[freaky_beef]

Is that the ONLY way to increase speed?

So what your saying is...that there is no way possible to increase speed from a muffler?

[dieziege]

Speed on level ground is often/usually limited by how fast the motor can spin without breaking. Changing the muffler won't change that. Only two things can: rebuilding the engine to spin faster, or changing the sprockets/drive so that a given engine RPM results in a faster ground speed. However, changing the drive ratio may not actually result in that much of a boost depending on drag.

Besides, mufflers usually give a 5% power boost if you are lucky and the old muffler was horrible. That's not even true on many engines...changing the exhaust system often reduces the power. If the scooter has 10hp now, that change will give it 10.5HP... if he thinks .5HP will give him a 15HP top speed boost... he's a born mark, sell him something quick!

[Dichotomous]

sure there is, if the engine is not getting enough airflow through it you can sometimes increase this with a muffler and/or air intake improvements. However, you wont increase top speed unless your scooter is not redlining at that speed (has more revs left but cant push the wind) and isnt electronically speed limited. It IS a possibility that the gearing on the bike is designed to top out at that speed, and then no matter how much power you add to the engine, the rear wheel wont spin faster because the engine redlines at the same speed. This may or may not be the case. Then there is the possibily that the scooter is a 2 stroke. If thats true then a new muffler might be very usefull, if its designed specifically for the engine and bike, the expansion chamber has to be just right. The bike is most likely going to be a CVT type transmission, like a snowmobile, which should allow you to add some speed with power. but it might also be topping out. If thats the case then changing the rear gear (the one on the rear wheel) to one that is smaller, but designed for the bike and the chain used, will gain you some top speed, but might take longer to get there. Getting a taller tire may help do this same thing, but may mess up your speedometer making you think you are going slower than you are, it may also effect the handling in a bad way.

[freaky_beef]

His Scooter is a Yamaha Zuma...if that helps.

What exactly does a muffler do anyway? I know it might help with gas mileage and HP...and possibly make the emissions cleaner? I dont know.

[Aggroton]

From what i understand...when you take you muffler off...header and all...there will be a washer welded in place inside the tube...this acts as a restricter...take it out.

[Dichotomous]

the only thing a muffler should do is muffler the sound of the rapidly expanding air and gas coming through the pipes. It gives the sound a lot of surfaces to bounce off and sometimes material through which the sound waves will lose amplitude (sound volume). Also mufflers are much larger in volume than the pipe itself, which allows the sound wave energy to disapate in the air inside the muffler instead of outside where it cane be heard more. Often mufflers reflect the sound waves back upon themselves in many directions to cancel out some of the sound, and often they will have fiberglass or other materials that will absorb some of the energy of the sound. Unfortunetly in order to effectively quiet down these sounds there has to be a lot of these measures, and that often creates a bit of a restriction on how easily the air can flow through the muffler. Remember an engine is an airpump, and if you block off part of the pump's intake or output then you wont get all the power you can out of it. (this is refering to open throttle top speed, there are much more complicated things going on at lower engine speeds and such).
I would think a performance muffler would help the yuma zuma, but I would check with you local yami dealer to see if they think so as well, they deal with these all the time and often know how to trick them out.

[CORSCO]

From what i understand...when you take you muffler off...header and all...there will be a washer welded in place inside the tube...this acts as a restricter...take it out.

I don't believe Zumas have restrictors but the exhaust will get carboned up and kill power. If ever notice hard starting/no start or major power loss, clean out muffler. You use compressed air to do so.

The welded washer is on the Vino line. It also has a spacer on the drive sheeve to restrict it.

[freaky_beef]

So what your saying then is:

It is impossible for a muffler to increase the speed of a Yami Zuma. And for that matter...impossible to increase the speed of any scooter.

A muffler might increase performance a little....HP by a bit...and thats it.