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Thunder Alley--Question for Rich R.
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Posted by: bigcr---------------------
I've read some positive reviews about the Thunder-alley slip on.
What is a reverse megaphone and what makes it better?
Posted by: Rich Rohrich---------------------
In theory a well designed megaphone system like the Thunder Alley (TA), will tend to improve scavenging due to the stronger finite waves produced with the megaphone. Better scavenging allows leaner jetting, better fuel tolerance, greater intake flow during cam overlap (higher Volumetric Effciency) and overall better charge density/purity as a result of lower quantities of leftover exhaust gases from the previous burn cycle. This all adds up to an increase in available torque.
The downsides:
- megaphones tend to be louder than straight pipes (all else being equal) so it takes a more advanced muffler design to keep it quiet while still producing power
- the strongest wave characteristics are only present over a relatively narrow rpm range. This will be true of any exhaust design that attempts to maximize torque.
From my limited testing on a couple of CRF450s I found the TA to be tuned for low to mid type power, with noise levels greater than stock, but on par with the rest of the aftermarket MX stuff being sold. It complemented the CRF450 powerband really well. It was one of the rare times I felt like I got my moneys worth from the motorcycle aftermarket. :thumb:
Posted by: bigcr---------------------
So if I put one on my CRF, should I go leaner on the jetting?
Posted by: Rich Rohrich---------------------
I don't know anything about your fuel, your riding conditions, your air density, or the way your bike currently responds, so I honestly can't tell you. 
Posted by: bigcr---------------------
I guess what I'm trying to ask is will the TA pipe make my bike run richer?...If
I change nothing else the jetting is spot on for my current riding conditions without it.
Thanks for your input by the way.
Posted by: Rich Rohrich---------------------
Quote:
Originally posted by bigcr
I guess what I'm trying to ask is will the TA pipe make my bike run richer
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Depending on the changes you have already made it could go either way on the low speed circuits (the Honda is pretty lean stock), and you may need to bump the main jet up.
BUT ...
I don't know anything about your fuel, your riding conditions, your air density, the way your bike currently responds, or what YOU consider spot on, so I honestly can't tell you for sure. Once size RARELY fits all when it comes to jetting.
So the best advice I can give you is if you are unsure err on the side of being TOO RICH. You won't hurt the bike by running too much fuel through it. :thumb:
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