Poor man's supercharger :)
#1
Ok, most of you guys are probly gonna thing I'm retar... er, special.. or just have way too much time on my hands. Either way, I thought I'd let ya know about a little project I'm workin on.
The "Turbo 400EX" article in the July Dirt Wheels got me to thinkin about how I'd love to give my EX a little 'boost'. Then I get this brilliant idea (haha) air-tight mount a high-flow electric fan inside the airbox at the air inlet, which would force air into the airbox (granted, this wouldn't create MUCH boost, but it WOULD remove all vacuum, and create a slight pressure increase).
So, tonight I took a 60mm Radio Shack 12v fan I had layin around, which is rated at about 30cfm, and did some figuring. If a 400cc motor had 100% volumetric efficiency, then at 9000 RPM it would suck .4 liters of air 4500 times per minute. That leads to roughly 65cfm of airflow at redline... obviously my cheapy fan wasn't gonna do the trick.
So, I got another bright idea . These fans turn about 4000rpm, not a very impressive number at all. I've got some racing RC car motors (a cheap $25 one in particular) that turn 20,000+ rpm, and have plenty of power to turn the fan that fast. Hmm, five times the RPMs... yeah, that'd probly supply at least 65cfm. So, a couple hours and a little bit of epoxy later, I've got a 20,000 RPM 60mm fan, and BOY does she move some air! It literally 'blows away' my 75cfm 120mm fan(if your wondering why I didn't use IT to begin with, it's too big for the airbox). However, according to the amp meter on my 12v car batter charger (aka DC power supply ), this thing pulls a good 20 amps at 12v, which is way too much for the charging system on the EX. But at 6v, it only pulls 15 amps, which is only 90 watts, which the charging system can probly keep up with for short bursts.
If your still reading this, your either interested, or very bored. Regardless, I applaud your attention span, I'll try to sum up quickly.
Tomorrow I plan to install my 'supercharger' into the airbox, connected to a RC battery pack (about 7.2 volts), with a switch so that I can switch the blower on while riding to see if I'm wasting my time, or if I actually make a power gain.
If the test comes out positive, my next plan is to connect the motor to an RC Car speed control (controlls the power to the motor) and hook that to the EX's battery. Then I'll connect a potentiometer (variable resistor) to the thumb throttle, hooked to the speed control, so that the fan speed will be proportional to the throttle position.
I'll also undoubtably have to rejet the carburetor to who knows what, and I may have to rout the carburetor breathers tubes to the airbox, to kinda equalize the pressure in the fuel bowl (I dunno, maybe that won't be necessary?).
Whoa, way long post there. Anyways, I though you guys might get some good ideas to help me out, or point something out that I've overlooked. Or, if not anything, at least get a good laugh out of this. Let me know what you guys think!
The "Turbo 400EX" article in the July Dirt Wheels got me to thinkin about how I'd love to give my EX a little 'boost'. Then I get this brilliant idea (haha) air-tight mount a high-flow electric fan inside the airbox at the air inlet, which would force air into the airbox (granted, this wouldn't create MUCH boost, but it WOULD remove all vacuum, and create a slight pressure increase).
So, tonight I took a 60mm Radio Shack 12v fan I had layin around, which is rated at about 30cfm, and did some figuring. If a 400cc motor had 100% volumetric efficiency, then at 9000 RPM it would suck .4 liters of air 4500 times per minute. That leads to roughly 65cfm of airflow at redline... obviously my cheapy fan wasn't gonna do the trick.
So, I got another bright idea . These fans turn about 4000rpm, not a very impressive number at all. I've got some racing RC car motors (a cheap $25 one in particular) that turn 20,000+ rpm, and have plenty of power to turn the fan that fast. Hmm, five times the RPMs... yeah, that'd probly supply at least 65cfm. So, a couple hours and a little bit of epoxy later, I've got a 20,000 RPM 60mm fan, and BOY does she move some air! It literally 'blows away' my 75cfm 120mm fan(if your wondering why I didn't use IT to begin with, it's too big for the airbox). However, according to the amp meter on my 12v car batter charger (aka DC power supply ), this thing pulls a good 20 amps at 12v, which is way too much for the charging system on the EX. But at 6v, it only pulls 15 amps, which is only 90 watts, which the charging system can probly keep up with for short bursts.
If your still reading this, your either interested, or very bored. Regardless, I applaud your attention span, I'll try to sum up quickly.
Tomorrow I plan to install my 'supercharger' into the airbox, connected to a RC battery pack (about 7.2 volts), with a switch so that I can switch the blower on while riding to see if I'm wasting my time, or if I actually make a power gain.
If the test comes out positive, my next plan is to connect the motor to an RC Car speed control (controlls the power to the motor) and hook that to the EX's battery. Then I'll connect a potentiometer (variable resistor) to the thumb throttle, hooked to the speed control, so that the fan speed will be proportional to the throttle position.
I'll also undoubtably have to rejet the carburetor to who knows what, and I may have to rout the carburetor breathers tubes to the airbox, to kinda equalize the pressure in the fuel bowl (I dunno, maybe that won't be necessary?).
Whoa, way long post there. Anyways, I though you guys might get some good ideas to help me out, or point something out that I've overlooked. Or, if not anything, at least get a good laugh out of this. Let me know what you guys think!
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Back in highschool we hooked a stihl leaf blower up to the air intake on a 79' F150 with a 302 and 290 gears via dryer vent hose routed to the bed of the truck.. when i nailed the leaf blower wide open at 100MPH the F-150 rocketed to over 120MPH, the carb should flow fuel because the fast moveing air creates a vacume in the float bowl.
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It may be the poor man's supercharger, but definately not the stupid man's! Even though it was about 2:30 in the morning, you were still apperantly able to think. nice job! I was able to understand the electronics of your plan. It sounds like a real good idea! How would you hook up the potentiometer to the throttle? I'm Looking forward to hearing more about this.