Karl Snarl
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I'm in. lets do it. I was wanting to do pulse jet, but hell lets take this nitropropane and put it back to it's original use as ROCKET FUEL!!!
What's the next step for performance?
- Thread starter noah9988
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I'm in. lets do it. I was wanting to do pulse jet, but hell lets take this nitropropane and put it back to it's original use as ROCKET FUEL!!!
noah9988
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That's exactly what I did. I took a spare cylinder and started cuttin' it up. I wanted to raise the exhaust for more rpm... but I went wayyy too far. It gets up to 6k and it's done. It's not in the powerband until at least 7k and it just doesn't have enough torque to get there. Going down a hill and getting to 7.5k makes it go like crazy but as soon as you're on level ground it goes back to about 6k.
Since I mostly bricked it, I freehand cut a boost port. It actually made a difference, after that it turns up to 6.5k under its own power, and low end feels better.
I'm not afraid to experiment (burn $30). I don't recommend it of course, but it's in the pursuit of knowledge. ¯\_(ツ)_/¯
DieselTech
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Well spoken there! Sometimes hands on experience is the best. I'm getting ready to carve on another 1 of my cylinders. I cant believe your engine dont pull in the lower rpm range, mine sure does. Top speed on my bike with a 44 tooth sprocket is only 40mph thou.
noah9988
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As I understand it, a ported reed valve 66cc won't have much low end, and I don't expect it to. I'm also using a 36 tooth.
Karl Snarl
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My low end is just fine. It's all about how you port, where you want the power to come on. Pipe has a big say, as well as the opening size, etc. It's all up to you though. I usually port and pipe for lower rpms( slightly wider, and slightly taller to keep velocity up, but enhance flow volume). My peak I try to keep between 5500-6500 rpms. I try not to go above 7k, no need for me to need much over rev. I do believe these engines will handle 7k, even 8 k happily all day long. I know for sure they can handle 10k bursts if your engine is in good shape.
I wanna say thick on gear side and thin on magnet side. My latest engine had all 4 seals the same, thick.
Chop-chop
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At some stage you will need to draw the line and just sit back and enjoy the ride, or rip the donk out and do a KTM swap...
My point is - u need to decide when u've reached the developmental limit of the engine and simply stop. Once u reached that point, the more $ u throw in the less gain u'd get in return....
My point is - u need to decide when u've reached the developmental limit of the engine and simply stop. Once u reached that point, the more $ u throw in the less gain u'd get in return....
All4-1
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All4-1
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My brother is a machinist and ex hot rod builder.
Now anytime I bring it up he says the same thing
"Drag racing is just a game of who spends more money
Speed costs money so how fast you want to go"
Chop-chop
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I've participated in the performance development of several projects over the years and this is what I've noticed -
Say it costs $20k to get a particular car to run 12 seconds down the quarter,
It would cost another $25k to get it to run a 11 sec quarter,
These are the cheapest seconds you will gain in the performance envelope,
Because it will cost another $30k to take the car down to a 10 second machine,
To get into the 9 second bracket, you'll be looking at investing another $35k - $40k etc
I think you see the picture here ...
The spending curve is of a exponential one where the amount spent increases the faster u go ....
Don't take the figures here as gospel but rather an example.
This rule applies until, obviously, when you reached the development threshold of that particular platform as every vehicle design has it's limits of how far you can take it in the scales of trade-offs in getting it to do what u want it to do..
Having said that - the 'development threshold' of these china girl 2 stroke engines are relatively shallow, meaning they're not designed to be taking very far in terms of performance if any at all. If someone wants out-right 2 stroke 'POWER' then they wouldn't be looking at China girls but rather something more performance oriented like a watercooled KTM65 clone...
How far something can be taken depends hugely on what that something was originally designed for in the first place...
