Torque, or RPM? (Moped exhaust on 66cc)

Vikingimike01

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Jul 1, 2018
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222
Nope, I have to cut off an old exhaust's part, that I can screw on the engine. I alredy did that, because I have 2 strock and 1 banana pipe exhaust. The tubes are the same size though. My relative is comming over tomorrow, he will show me welding. I'll have to stick weld it. I've never done this before, so I'll practice on some scrap.
 


JerboaJohn

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Jul 29, 2018
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I dont have a welder yet bcs I'm debating if I want a cheap flux welder for the odd job. but I do have all kinds of aluminum billets so I've did a couple blocks kind of like that x block to extend or angle a pipe. I'll try one of these scooter pipes this summer after I finish a 4 stroke bike
 

LewieBike

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May 21, 2014
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431
The flange is for a engine with bigger ports and transfer areas. 50 cc scooter engines as a class of engine stock put out about 3 to 4.5 HP stock These HT engines aren't set up with the volume of gas flow that a 49cc scooter engine moves. Which is why these scooter exhaust systems are IMO a waste of effort for the casual user looking to get more torque out of them. You're already doing a tuned pipe on an engine specifically set up to operate with a broad amount of RPM and torque band as set up stock. Sure you may get more power out of this, but you'll kill what ever wide power band the engine had previously. There is no such thing as increasing the torque of these engines at lower RPM's by messing with a tuned pipe.
 

CrazyDan

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Jul 9, 2016
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1,465
The flange is for a engine with bigger ports and transfer areas. 50 cc scooter engines as a class of engine stock put out about 3 to 4.5 HP stock These HT engines aren't set up with the volume of gas flow that a 49cc scooter engine moves. Which is why these scooter exhaust systems are IMO a waste of effort for the casual user looking to get more torque out of them. You're already doing a tuned pipe on an engine specifically set up to operate with a broad amount of RPM and torque band as set up stock. Sure you may get more power out of this, but you'll kill what ever wide power band the engine had previously. There is no such thing as increasing the torque of these engines at lower RPM's by messing with a tuned pipe.
You can easily tune an expansion chamber for low rpm torque by shortening the header length (maybe I am backwards). Header length dictates at what rpm it "gets on the pipe"
 
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JerboaJohn

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Jul 29, 2018
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longer header for low-end,, gives each pulse more time to reenter the cylinder, and like with a longer intake, optimum flow happens at lower rpms at the expense of peak power.
 

Frogslayer

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Jan 20, 2019
Messages
207
Good luck trying to ARC weld exhaust. It's an art. It will look way better with a MIG welder.
 

Street Ryderz

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Oct 14, 2016
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2,837
The flange is for a engine with bigger ports and transfer areas. 50 cc scooter engines as a class of engine stock put out about 3 to 4.5 HP stock These HT engines aren't set up with the volume of gas flow that a 49cc scooter engine moves. Which is why these scooter exhaust systems are IMO a waste of effort for the casual user looking to get more torque out of them. You're already doing a tuned pipe on an engine specifically set up to operate with a broad amount of RPM and torque band as set up stock. Sure you may get more power out of this, but you'll kill what ever wide power band the engine had previously. There is no such thing as increasing the torque of these engines at lower RPM's by messing with a tuned pipe.
WTF are you talking about?Scooter pipes carry their band width over twice the rpm range of a dirt bike pipe and 4x that of the available aftermarket bolt on's except for the MZ 65 witch act's more like a dirt bike pipe.To say our engines don't flow the volume of a 50cc is whacked just the pumping efficaintcy difference of the added 16 to 19cc is huge and with proper porting and carb/pipe wicth alot of these guys are doing we far exceed the flow rate of the 50cc scooter engines and make the same or more output,8 hp is not that hard to get from these and it's at a lower rpm witch means they are making more torque!The next good point to the scooter pipes is that they are 2 staged witch is also why they power band is so broad,you can have it pull from 4-8k no problem and that makes a huge difference on the street and doesn't sacrifice the very bottom end because under 4k it still flows much better than any aftermarket pipe!
 

Vikingimike01

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Joined
Jul 1, 2018
Messages
222
Ever since he's seen one of my pictures of my bike, he's been "hating" on my saves, and trying to drive me away from experimenting.

Even though I know that a 66cc produces more exhaust gasses than a 50cc, I don't want to argue, because I think even he knows that it makes no sense. I think he's jealous ;)

Anyways. I'm practicing welding now with a welder that needs the sticks, with the coating on them. I'm still pretty bad. I was thinking: I either practice a lot first, then try my best, and if it doesn't work out I grind the stuff off, OR, bring it to my mechanic welder. He has a MIG welder. I'm not sure if he will do it or not, but hopefully yes. I would want it done professionally, and he has been doing this for 20+ years (Car mechanic, motorcycle mechanic, he loves motorcycle racing, has been in 4 accidents too..)

I'll report back soon.
 
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