im going to smog pump supercharge my predator 212cc for kicks

Bump for boost

Bump for improvised frag bmb.

>>1182204
No you won't.

>>1183102
It's been dun befo bub

>>1183130
Yes I will. Parts are on the way.

>>1182204
What are you using it for? I believe blow-through will give you better throttle response, so if response is important with your application you may want to do that. If you do draw-through you'll probably want to step up to a larger carb, depending how much boost you're actually using. Doesn't matter how much magic you've got going on downstream, a choked carb will only allow so much CFM (and thus power) drawn through it.

>>1183217
It's going on a minibike so instant throttle response isn't exactly necessary however having an excessive hang when you gas it is undesirable as well. I'm stepping up from the 6.5hp 200cc carb to the 13hp 390cc carb (19mm to 27mm bore) so that definitely won't be a bottleneck.

>>1183220
Whoops, meant 22mm bore not 27mm.

>>1182204
Isn't draw through the only real way to get a carb to throw enough fuel in? Or am I confusing it with turbo chargers.

The carburetor only responds to amount of volume of air that travels through, and going on boost will drastically change the mass flow (and thus fuel needed). If drawn through, the air is accounted for by the amount of increased flow (if .5 bar gauge then it would be 1.5x of air flow at atm). If your blow through, the carburetor sees no extra volume flow. With any forced induction survival is dependant on eliminating knock (retard ignition, keep boost low if no intercooler) and ensuring you're not leaning out and overheating.

>>1183238
No with blow though and a blow though carb it acts the same was as draw through except it doesn't put fuel inside the compressor (to prevent it from washing the bearings or detonating when compressed) or any tubing or intercooler (so that it doesn't pool and explode if the car backfires).

>>1182204
>how about how much boost do you think a stock 212 can take before undergoing unplanned rapid deconstruction?
Depends. What's the compression ratio? What fuel will you be using? Do you plan to use some sort of intercooler or charge cooler?

>>1183635
8.5:1
91 aki
No

>>1182204
Cool

I would try a simple blow through first. idk how those predator carbs are built but they shouldn't need a pressure box, just some kind of blow off valve. Usually carbs don't need a lot of adjustment to work as a blow through. The jets on that fucker are probably fixed so I wouldn't even mess with it until I tested it. Go full rich on the needle if that's adjustable.
>how much boost
there's only one way to find out. just keep an eye on the fuel mixture. too lean and it will detonate and it's life will be quickly shortened.

>>1182204
Dumb question.
Can a el cheapo air cooled engine like that operate at reduced rpm for longer engine life or will it overheat since it won't be sucking air in as fast?
Thinking 1800 for a alternator battery charger.

>>1184048
It should be fine unless it's running at full throttle for a long time

>>1184032
I guess I can try to hook it up blow through but I don't think it'll work because I've tried using an air compressor to blow air into it for shits and giggles at always stalls, but that could just be because it didn't have enough fuel to compensate. The Jets and emulsion tube are replaceable, I have an upgraded emulsion tube and .038 jet in there right now which is much bigger than stock. Doesn't have a mixture needle though unfortunately, hopefully the GX390 carb does.

>>1184048
That's what they're made to do. They're mechanically governed to 3600, but you can remove the governor and they'll rev to 5500 where the valve springs will float. They have a fan hooked up to the flywheel that sucks in air through that Grill part on the front where the pull start is and the case serves to direct the air across the engine to keep it cool. I've actually made a generator myself using a 212 predator and 200 amp alternator hooked up to a 1500 watt inverter. Of course that's not really a whole lot of wall power, but it still bogged down pretty heavily when I completely loaded the inverter (which max draw is 157 amps at 12 volts) but did work as a battery charger when I needed to charge my car in my driveway and I didn't have another way to start it.

>>1184052
What rpm did you run it? I want to slow the engine down so it will last longer and be quieter. I could do 2700, best fuel consumption.

>>1184060
I geared the pulleys at 1.61:1 so that at 2500 (max torque output) the alternator spun over 4000 which should give full current without multiplying too much to have to fully load the engine just to spin it freely

>>1184048
Monitor oil temps, install an oil cooler in needed.

>>1184060
Rev that bitch up. Govern it right before it has valve float. If you blow it up then you have another fun project. You can rebuild it with upgraded parts and see how much more power you can squeegee out of it.

>>1184629
*if

Meant to ask, what's the difference between draw through and pressure box? The only way my brain sees it is that boost goes through the carb where it then mixes with fuel and from there goes strait to the intake valves

File: 1466692859508.jpg (108KB, 600x535px) Image search: [Google]

108KB, 600x535px

>>1182204
>smog pump supercharge

Is this actually capable of that kind of flow rate? Have you done the math?

>>1184634
Draw through is where you just hook the carb to the inlet so it just sees all of the suction of the engine plus the extra suck from the super/turbo. This is simplest but holds the danger of the fuel charge exploding in the super/turbo when it gets compressed and if you have a full piped intercooler system it will leave fuel all over the inside and all it takes is one backfire and kaboom.

Pressure box is like all of the positives of using blow though without actually having to use a blow though carb. It pressurizes the whole carb so it doesn't just push air back into the Jets and stuff.

>>1184635
No, however it has been done multiple times (with little documentation of course) and even if it doesn't work out the parts are cheap enough for me to not care if it's a failure.

>>1183641
In that case I wanna say somewhere around 10 psi.
https://www.youtube.com/watch?v=TJTQ_XO3NK0
This guy says he's running 16-17 psi on a stock 212 but I think he runs race gas (he says so in another video with a different bike, anyways).

I'd recommend trying to get a few different pulleys and experimenting... listen carefully for knocking and if you hear it then quit before something breaks and step down to the next lowest ratio you have.

>>1184672
Sounds like a good place to start. I'll have to get a thing that measures air flow so I can figure out it's cfm curve and not overboost the engine.