using microcontroller to control choke

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Mike Hunt

New Member
Jun 9, 2009
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Toronto, Ontario
so i got a basic stamp 2 microcontroller lying around collecting dust and i want to put it to good use.

the other day i was thinking about how on my first ht i had an intake leak that made it run really lean, which is bad for the engine in the long run, but made it run better for a while (no fourstroking when accelerating to full speed, and it went a bit faster)

what if i was to rig up a servo motor to the choke, and set up the carb so its really lean like when i had the leak, and then use the microcontroller to tell the servo to set the choke so its at a normal mix, but when i want that extra boost i could press a button it opens it up more so its leaner then usual. if i use this sparingly i don't think i should have any problems with overheating. once i get this first part done i could add temperature sensors on the engine and program the bs2 to adjust the choke to the temperature automatically, put an index wheel inside the throttle and fine tune the program so it makes it leaner or richer depending on how far i twist the throttle and how hot the engine is.

ive worked with this microcontroller for a good year and a half in college, so the wiring and programming wont be a problem, the thing works off a regular 9v battery and i can get all the electronics to fit in a box slightly larger than a pack of smokes.

the question is, will i be able to squeeze out a decent amount of power by doing this or will it be a waste of time?

also i haven't been riding or been on the forums since the beginning of summer, whats new in the ht scene?
 
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breno

breno

New Member
Aug 19, 2010
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Syd. OZ
can ya throw cruise control in there?? If u think u can make it work why not give it a shot you said it yourself it tends run/feel quicker when u lean it out a tad..
Being careful u could probly have abit bit of fun with it motors are cheap anyway I say go for it..
 
BarelyAWake

BarelyAWake

New Member
Jul 21, 2009
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Maine
Well... the concept is intriguing but there's a couple problems w/it - the main one being is that an excessively lean engine won't run "better" than a properly tuned engine as it's be simply starving for fuel. Also, adjusting a choke doesn't provide more fuel, it reduces the amount of air by restricting the passage, resulting in it "starving" for air... and for maximum performance any restriction is exactly the opposite of what's needed, thus the concept behind turbos & superchargers, to cram more of both fuel and air, as much as possible - even to the point of blowing out head gaskets lol

So... while there's obviously advantages to having variable fuel/air amounts "in flight" so to speak, to compensate for environmental changes and engine operating temperatures, short of a computer controlled EFI unit - with these primitive carbys, simply setting your fuel/air mix via jets & needle clip adjustments where it runs best on average is really the only viable option - you shouldn't be "four stroking" under acceleration/load in any case, it's a symptom of an excessively rich condition.

Generally, it's a neat idea I give ya that - but unfortunately the opposite of what's needed for "maximum performance" which is usually more of everything, not less. As tinkering with random whirly bits & electronics is fun no matter the practicality - you could I suppose take that microcontroller & servo and do the reverse of your idea, making a semiautomatic or even fully automatic (req a temp sender/probe) choke for cold starts?
 
MarkSumpter

MarkSumpter

New Member
Nov 27, 2010
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Ohio
Have to agree with BA that there is no actual advantage to running a lean engine and the detrimental side is that even running lean for a short time can begin metal transfer (gaulding) to the piston and jug. Once it starts it only gets worse till the engine is no longer repairable without replacing the jug and piston if you dont seize it up first. And he is also correct that an engine that is getting the proper air fuel ratio produces more torque than a lean engine, many people think lean produces more power but that is incorrect.

I see no advantage to trying such an experiment unless you just want to buy a new engine after this one is trashed.
 
Goat Herder

Goat Herder

Gutter Rider
Apr 28, 2008
6,237
20
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N.M.
Fuel injection done up with O2 sensors. Problem tho... O2 sensors will never get along with the oily exhaust of a 2 smoke..Very unforgiving
 
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motorhead419

motorhead419

Member
Jul 6, 2009
63
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ohio
Mike Hunt said:
over a hundred views and only 1 reply? is my idea that bad?
Click to expand...
You are beating a dead horse.. The choke's purpose is to richen your lean engine to make it start easier..Other than that the choke is worthless..You may need some basic carb adjustments. .shft.
 
B

Black_Moons

New Member
Oct 25, 2010
205
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Canada, Bc
Well, First off, you'll need a carb with a proper choke circuit that adds fuel insted of takes away air. (Like the CNS racing carb)
Second.. It Could work.. But honestly, a handle bar mounted choke like the CNS carb lets you tweak it as need be, Up steep hills I used to get the odd sputter, but now I just crack open the choke a little and it resumes 2 stroking nicely, then close the choke again at the top of the hill or it bogs a little at higher RPM.
 
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