Exhausting theory

[SOTVEN]

Hello all, general question. "If someone installs an exhaust without any restrains or muffler devises on an internal combustion engine, will the engine have any significant wear and tear?" More specifically, I own a Yamaha motorcycle, air cooled v twin 750cc, and its exhausts were falling appart. I "customized" them i.e. threw away all the rotten parts and left the two outer pipes only. The sound has gone up quite many dBs, throttle response has improved dramatically, but I do not want to do any damage to my engine. Any ideas? (Sorry Robi for putting this topic here, but I did not know if it should be here or in the soap box, since it was not m-related but it was technical issue.)

[Paul in Kempner, TX]

Most ignition (spark) fired internal engines have to deal with exhaust back pressure.

In two-stroke engines, a certain amount is necessary and uninformed youngsters who remove the baffles from their mufflers actually experience some power loss - even though it "sounds really kuwell, man."

In four-stroke engines, the least back pressure the better - except when the sound pulse is engineered to enhance the total flow from the intake through the engine and on to the tail pipe. That is why some intake manifolds have long runners and why headers are built so that all tubes have effectively the same length.

Having ridden various motorcycles for over 55 years, I am comfortable telling you that removing the baffles from the mufflers on your Yamaha, air cooled, v-twin 750cc, motorcycle, will have no significant effect other than to make it noisier. The added noise with greater discernible cylinder pulses usually makes you think there has been an increase in actual power or acceleration, but if you measure it accurately with good instrumentation you will find this is not true.

Mostly the added noise will attract the attention of police. It will also let other knowledgeable bikers know that you are not keeping up with all the needed maintenance. Riding a "rat bike" may not increase your social standing.

Good luck.

[SOTVEN]

Paul thank you very much for your input. I thought that there would not be a problem, but I could not justify why. Regarding the social status that you very correctly brought up, indeed people tend to look at me in a certain way, but right now my "pocket status" can not raise my "social status." Thanks again.

[Paul in Kempner, TX]

I really enjoyed your "pocket status" / "social status" response. We've all been there.

[tstephenson]

enjoyed the pocket book/social coment. 6 months ago bought a m37 for the ranch/grandkids riding them around looking at cows deal, thinking I could fix it up, no worries. Now one kid in hospital, one I Iraq, and one devorcing and losing part of the ranch to the ex daughter in law. They say "it" happens, well I am here to tell you it does and there is no end. I say if you can't aford a muffler then let er rip for the rest of us
Tim

[SOTVEN]

Tim, I am sorry to hear about your kids' misfortunes. My theory is that only good things can reach a maximum point and come to an end. Bad things on the other hand have a tendancy never to stop showing up, and usually their duration seems to last for ever. In any case I wish your kid comes out of the hospital very soon and healthy, the other kid be afar from harm's way in Iraq, and as for the divorced child, I wish the best of luck in the new life ahead.