2004 to 2020 Mazda 3 Forum and Mazdaspeed 3 Forums banner

1 - 6 of 6 Posts

·
Registered
Joined
·
143 Posts
Discussion Starter #1
I have a project air-cooled V-twin (7k -8k rpm) carburetted motorcycle on which I've modified many times over for the past 15 years..... and I've learned a lot of things with that vehicle. I bought it brand new, and one of the first mods was a $250 after-market exhaust (not a full exhaust, but the mufflers). It was a performance exhaust, which had less baffle (and therefore less resistance) than the stock setup. It was louder, and it claimed to make a power increase.

...after three different intakes, four different exhausts, and many (too many) re-jets (cams too), all moving toward more air flow = more power, I moved the max torque point from 2500 rpm to about 3500 rpm (and a flatter torque curve) and increased max HP from about 55 to 75. Now, a lot of guys were claiming these kind of increases on their first exhaust mod (and only mod). LOL! yeah right! Anyhow, it made highway driving much more responsive, at the expense of losing low-rpm grunt, which is nice during city cruising. Do I want the grunt back? Do I spend all my driving at full speed? In the end, maybe I should have just gotten another motorcycle that was designed to make high-rev power in the first place. Why? Because the initial exhaust replacement made things worse, and because it became an addiction to get the thing actually making more power like I originally wanted when I got the first after-market exhaust, and because a stock 650 lb. vehicle with 55HP (0.09 HP/lb) is never gonna do sport driving like a stock 450 lb. vehicle with 175 HP (0.39 HP/lb).

These principals are no different for cars than they are for motorcycles.

The point: Buying a performance muffler is something usually done out of a desire for performance but also out of ignorance, and the result is only the illusion of performance (LOUD), and the cost is actually giving up some performance.

In other words: "Hey, do you hear how fast it sounds? It's actually slower now, but I drive it fast so I still look cool! You think I look like a moron? That's okay, because all the other morons still think I'm cool!"

Sorry, but I've become old.... like my grandpa.... who is wise.... now I believe him.

(fire back, if you must)

Peace, Ya'll!
 

·
Super Moderator
Joined
·
5,985 Posts
The point: Buying a performance muffler is something usually done out of a desire for performance but also out of ignorance, and the result is only the illusion of performance (LOUD), and the cost is actually giving up some performance.

In other words: "Hey, do you hear how fast it sounds? It's actually slower now, but I drive it fast so I still look cool! You think I look like a moron? That's okay, because all the other morons still think I'm cool!"
Especially true for the Skyactiv engine. The exhaust is tuned to get the best possible performance from the engine. Swapping the wrong parts just to make more noise almost always ends up a losing proposition. :smile2:
 

·
Registered
Joined
·
106 Posts
I have a carbureted V-twin as well ('05 Kawasaki Vulcan 750) and although I have rejetted and added pod air filters, I don't even think of modifying the exhaust because of what you mentioned:

LOW END TORQUE

That is the number one thing that makes a vehicle driveable IMO, because it's what gets you off the line
 

·
Registered
Joined
·
266 Posts
Yeah...learned all that back in the late 60s...my hearing is paying the price for those loud bikes...same principles apply today.

Beware, you young 'uns! :smile2:
 

·
Registered
Joined
·
49 Posts
I grew up in the 60's when hot rods were cool and the sound of a V8 with open headers really was the sound of power.

The sound of an unmuffled or fart-canned 4-cyl rice motor is just laughably annoying.
 

·
SpeedySpeedBoy313
Joined
·
52 Posts
These yungins like me tend to drive fast and use upper half of the RPM's anyway, so low end torque isn't really an issue except when I go to the drag strip.
 
1 - 6 of 6 Posts
Top