Can you extend an expansion chamber exhaust?

[ApacheHelicopter]

Hi all, sorry for the potentially noob question, but I haven't found anything about this browsing around so I thought I'd ask myself. I'm looking to do a high compression head+performance cdi+expansion chamber upgrade on my 80/66cc once it's well out of break in, and I was wondering if welding a pipe to the end of an expansion chamber exhaust would result in any performance loss. Thing is I'd like an exhaust that blows out the back so it doesn't do it on my shoes like the stock one does, but the EC ones I've seen so far all have a similar shape, they're short and they blow downwards. Do any of you guys know? Thanks!

 

[extremeodd]

From the sounds of it you've been looking at the fake expansion chambers on the market.

The only expansion chamber worth it's salt is the MZ65 which is this:

They typically run roughly $100 shipped and only come up about once per year (this is that time of year mzmiami on ebay has them). They will roughly double your engines power output and will accept a generic cheap amazon exhaust silencer without any welding.

If your looking at these "expansion chambers"

Literally nothing you will do can hurt the power output of one short of simply welding it shut. They are essentially a "prettier" factory exhaust and have no added benefits other than being louder.

 

[ApacheHelicopter]

From the sounds of it you've been looking at the fake expansion chambers on the market.

The only expansion chamber worth it's salt is the MZ65 which is this:
View attachment 90338

They typically run roughly $100 shipped and only come up about once per year (this is that time of year mzmiami on ebay has them). They will roughly double your engines power output and will accept a generic cheap amazon exhaust silencer without any welding.

If your looking at these "expansion chambers"
View attachment 90340

Literally nothing you will do can hurt the power output of one short of simply welding it shut. They are essentially a "prettier" factory exhaust and have no added benefits other than being louder.

Thank you for the insight! Sorry for the late reply, I only just saw your post. One of those banana pipes is exactly what I was looking at good to know they're not the real deal. I have one more question. Ideally I'd like to do an expansion chamber and a sprocket upgrade since I'm not looking to turn it into a rocket ship and spend more money on it than the whole bike cost stock, but I'd also like more than the 38kmph top speed I'm currently getting (plus going above 35 makes it vibrate a lot, so more power at lower rpm's would be great, ideally a 45kmph cruising speed). However I read on a post that expansion chamber+cdi+high compression head should be a package because they compensate for each other with regards to the changes they make in the engine, and you shouldn't do them individually. Is that true? Would just adding an expansion chamber cause problems? Thanks a lot!

 

[GreasyChris]

You can run an expansion chamber only but you'll probably need to retune the carb. What head and cdi were you thinking of using? Alot of the Ebay Chinese heads actually don't increase performance they just help out with the cooling. The Chinese heads have a bigger combustion chamber and cause lower compression and some don't let the spark plug down far enough into the cylinder to fire properly. The MZ pipe is probably the best direct bolt on expansion pipe however dirt bike pipes and scooter pipes work really well if your able to cut and weld.

 

[extremeodd]

Most of the info on CDIs isn't really relevant anymore for the most part. There used to be big gains to be had by swapping over to a Jaguar CDI but that was mostly due to poor magnet positioning from the factory. For 99% of people, the stock CDI is more than good enough.

You can do mods like a high compression head, pipe, etc all seperate without issues. Every time you change something on the engine, you will need to adjust the carburetor to compensate. All an engine is is an air-pump, it pumps air from one side to the other. How much power you get depends on how much air/fuel you can pump from one side to the other. Any time you increase the amount of air (better pipe, better intake) that can flow, you must increase the amount of fuel to compensate. Small changes like going from a stock pipe to a cheapie expansion chamber (banana CDH66) should only require a small change, usually just adjusting the needle clip position. Larger changes like a stock pipe to an MZ65 or better, or a cheap pipe + better intake typically require also changing the jet to a larger size.

Basically you can run any bolt-on on its own for a minimal gain, or if you mix several bolt-ons their gains will play off of each other for a greater gain than either item would give on its own.

If you just bolt on the pipe and don't adjust the carb, you may see an overall loss of power since your throwing off the optimal air-fuel ratio.

Overall, if you want to keep the same low end grunt and gain some top speed you're kind of stuck doing a good pipe + head + carb tune + sprocket. If you want some more top speed but lose your low end do just the sprocket or do just the bolt ons but not both. Without spending a fair bit of money you won't be able to get both more low end grunt and more top end speed, that is the curse of a 2 stroke engine.

 

[ApacheHelicopter]

I

You can run an expansion chamber only but you'll probably need to retune the carb. What head and cdi were you thinking of using? Alot of the Ebay Chinese heads actually don't increase performance they just help out with the cooling. The Chinese heads have a bigger combustion chamber and cause lower compression and some don't let the spark plug down far enough into the cylinder to fire properly. The MZ pipe is probably the best direct bolt on expansion pipe however dirt bike pipes and scooter pipes work really well if your able to cut and weld.

I was looking at the gt6 high compression head, since it seems to have good reviews and be pretty popular. Since the mz65 is out of the question now since it's out of stock, I was thinking of getting a 36t sprocket and a high compression head to compensate for the loss of low end torque. Honestly if I can get a comfortable 45kmph cruising speed out of it that's enough for me, more that that would be too fast for what it is I think. But as it stands anything over 35kmph gets pretty shaky and feels bad for the engine, and as soon as I hit 40 it acts like it's limited, power cuts out, slows down, then starts pulling again, then cuts out again when it hits 40. That's a bit slow for me, I lose a lot of time on longer commutes.

 

[ApacheHelicopter]

Most of the info on CDIs isn't really relevant anymore for the most part. There used to be big gains to be had by swapping over to a Jaguar CDI but that was mostly due to poor magnet positioning from the factory. For 99% of people, the stock CDI is more than good enough.

You can do mods like a high compression head, pipe, etc all seperate without issues. Every time you change something on the engine, you will need to adjust the carburetor to compensate. All an engine is is an air-pump, it pumps air from one side to the other. How much power you get depends on how much air/fuel you can pump from one side to the other. Any time you increase the amount of air (better pipe, better intake) that can flow, you must increase the amount of fuel to compensate. Small changes like going from a stock pipe to a cheapie expansion chamber (banana CDH66) should only require a small change, usually just adjusting the needle clip position. Larger changes like a stock pipe to an MZ65 or better, or a cheap pipe + better intake typically require also changing the jet to a larger size.

Basically you can run any bolt-on on its own for a minimal gain, or if you mix several bolt-ons their gains will play off of each other for a greater gain than either item would give on its own.

If you just bolt on the pipe and don't adjust the carb, you may see an overall loss of power since your throwing off the optimal air-fuel ratio.

Overall, if you want to keep the same low end grunt and gain some top speed you're kind of stuck doing a good pipe + head + carb tune + sprocket. If you want some more top speed but lose your low end do just the sprocket or do just the bolt ons but not both. Without spending a fair bit of money you won't be able to get both more low end grunt and more top end speed, that is the curse of a 2 stroke engine.

I see. Well the mz65 is out of stock now which sucks, it's basically double the price factoring in transport and import fees and I won't have the money to spend on it for another couple of weeks. So you're saying anything else that pops up when searching mz65 on ebay is fake? Also Amazon? Granted they're much cheaper... What about the zeda88? Not worth it? I see feedback saying it gives gains but others say it's a crappy copy...

 

[GreasyChris]

Sorry I bought the last mz65 yesterday. Unless it's from mzmiami it's probably not the real deal.

 

[gary55]

Your best bet is to get one for a 65 to85cc dirt bike or one like Chris and Spare Parts use and have a welder fit it to your bike.
As far as lengthening the stinger goes, page 64 Jennings: Two-Stroke Tuner's Handbook - tuners.pdf

 

[ApacheHelicopter]

Sorry I bought the last mz65 yesterday. Unless it's from mzmiami it's probably not the real deal.

Haha no worries. Yeah I figured. Guess I can try finding a two stroke bike or scooter pipe that could fit, I read that's another option