Stihl 029av to 039 conversion
- Thread starter GoBigBlue1984
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Paragon Builder
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Is it necessary to do this or just helps get more power?
Terry Syd
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It is for more low end power, call it torque. It enables more fuel flow through the low speed circuit. And, I've yet to see a limiter jet that wasn't .25mm on either a Zama or Walbro.
If you go back through the 7900 carb thread I explain the two fuel curves of the low and high speed circuits and how they overlap one another to give the total fuel curve for the air flow through the carb. There is even a link to some dyno testing where you can see a 'dip' in the low end torque as the low speed circuit maxes out and the high speed circuit is unable to make up the difference.
EDIT: There is also some links to fuel mixture ratios and power. Although a lean mixture will still burn, it doesn't make as much power as it could (there is extra air that is not being utilised). If anything, making it a bit on the rich side of the curve will not only increase the power, but it will provide extra cooling when you are lugging the engine down.
If you go back through the 7900 carb thread I explain the two fuel curves of the low and high speed circuits and how they overlap one another to give the total fuel curve for the air flow through the carb. There is even a link to some dyno testing where you can see a 'dip' in the low end torque as the low speed circuit maxes out and the high speed circuit is unable to make up the difference.
EDIT: There is also some links to fuel mixture ratios and power. Although a lean mixture will still burn, it doesn't make as much power as it could (there is extra air that is not being utilised). If anything, making it a bit on the rich side of the curve will not only increase the power, but it will provide extra cooling when you are lugging the engine down.
GoBigBlue1984
Right-wing conservative blue collar American
That being said, what mix ratio do you like to use? I've heard some people say regardless of manufacturer instructions 40:1. I've also heard guys say 50:1. Furthermore, I'm pretty certain that I'd have a difficult time distinguishing between the two unless I mixed the fuel myself. This is all very interesting nonetheless. I will also say that your grasp and understanding of exactly and specifically how a carburetor works dwarfs mine at this stage. I will keep learning though and from guys like yourself Terry on this
GoBigBlue1984
Right-wing conservative blue collar American
Very site I've obtained a heap of information. So for that, thank you.
Terry Syd
Addicted to ArboristSite
Have a read of this thread, there's heaps of information on carbs in it - http://www.arboristsite.com/community/threads/dolmar-7900-carb-upgrade.229528/
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Yup. Read it twice. I think I need to start playing with them to really get it...
Terry Syd
Addicted to ArboristSite
Yeah, you'll end up like Rich - try something simple like to make the throttle response better, get some results - and your freaking hooked! Then work out the low speed fuel curve to bring in more torque and you wonder why everyone isn't doing it - free torque without any machining or porting.
Did I mention Fork the EPA?
Did I mention Fork the EPA?
GoBigBlue1984
Right-wing conservative blue collar American
Hell yeah!!!! Fork the forkin EPA
