Another supercharger post

[Crappy212go kart]

Hey fellas, I am yet again another idiot taking a shot at small engine forced induction. But my situation is a little different from the other guys. So here is my plan. I've got a predator 212 on my go kart with a mikuni clone slide carb and a header with muffler, and I got my hands on a 3d printed centrifugal blower that my friend made. I'm curious as to whether it will hold up to 5-10 lbs of boost. I want to fab an oil cooler into an intercooler, but I'm wondering how the carb system will work out, also wondering where I could mount the pulley system (thinking I'll steal a few alternators from the junkyard). Any and all ideas are appreciated. if all else fails I am willing to use duct tape and jb weld. thanks

 

[Hellion]

What an ambitious project, and I wish you success.
I wanna see that blower, man. The blower!

 

[Thepartsguy]

3d printed blower now that’s something I wanna see! I of course used the smog pump. And the AMR 300’s are $140 cash…

If it does make boost it will suck the slide against the backwall and stick the throttle. YOU NEED A BUTTERFLY carburetor.

We don’t know if you’re using a draw through or blow through. Draw through carburetor being easier.

If this ****er backfires your plastic blower gonna go boom boom. Just use some caution..

 

[Sparkwizard]

I put the carb in a box and pumped the boost into that box. It ran lean because I didn't have any fuel pressure into the box, so I ran a piece of vacuum hose from the pressurized box to the gas tank vent. I actually used a military ammo can for the sealed box, so I could pop the door open to service the carb. That was over 20 years ago, so no pictures. It was on a minibike with a smog pump mounted under the seat and a pulley on the rear wheel. PCV valve on the box allowed idle air when the pump wasn't pumping.

 

[Crappy212go kart]

yeah i don't really know about it being plastic, but the reason is that me and my best friend are in a build off, we both have the same 212s down to the jetting and hes gonna turbo his and I'm supercharging mine. so I got that I need to use a stock style carb, and I don't have the means to build a pressurized box so I'm running a draw through setup. thinking I'm gonna move the gas tank and use those studs to mount this bad boy, what needs to happen carb-tuning wise tho? (and of course I'll get pics ASAP) And what about the pulley system? wanna do it like this guy but I don't have the machine to make the pulley, shave the flywheel, ect...

 

[Crappy212go kart]

ok upon more research I am now going to do a blow through setup with my slide carb, if that doesn't work and the throttle starts sticking then I will swap back to butterfly carb. I've also decided I'm going to mount the pulley to the output side instead of using the flywheel side (less complex). Any good carb hat ideas besides the one mentioned earlier by sparkwizard? and what jetting would I need?

 

[Sparkwizard]

The simplest sealed box I could find is an ammo can. I can send you one if they are not accessible to you. As long as your gas tank is boost referenced to the carb, your jetting should be slightly more rich than normally aspirated. Blow through is definitely easier than draw through, and less throttle lag. I look forward to reading about your centrifugal build!

 

[Crappy212go kart]

what if I ran just a carb hat to the intake where the air filter is currently and a pressure line from the drain vent at the bottom (not trying to be difficult sparkwizard just throwing stuff out there), but yeah your ammo box seems to be a good method. I got the print design from this video and thought that his setup looked relatively simple and clean and was wondering if that could be run with a blow off valve

 

[Grizzlymi]

I put the carb in a box and pumped the boost into that box. It ran lean because I didn't have any fuel pressure into the box, so I ran a piece of vacuum hose from the pressurized box to the gas tank vent. I actually used a military ammo can for the sealed box, so I could pop the door open to service the carb. That was over 20 years ago, so no pictures. It was on a minibike with a smog pump mounted under the seat and a pulley on the rear wheel. PCV valve on the box allowed idle air when the pump wasn't pumping.

Did you notice any improvement with this setup? Did it work enough to justify it? I love the idea of the ammo can as a box for service.

 

[Sparkwizard]

No wheelies off the line, but super accerelation from about 10-30 mph. maybe 50 top speed.

 

[Thepartsguy]

A guy is in the middle of building a nitro twin with two 5hp’s

If you got a junkyard near you then you need a smog pump and alternator bracket from an old Chevy and they will push 30+ psi on a gauge and run great.

The very last two pictures in this post are of my red smog pump setup. Draw through ANY intake carb setup you want to use and a tube from the outlet of the pump to the inlet of the engine. As simple as it gets.

I’m gonna see if my friend will print me that turbo just for display as I love stuff like that!

 

[Denny]

A blow through system is complicated and you will give up some power. With a supercharger you want a suck through system. It helps cool the charge air also.

 

[Crappy212go kart]

well I think these are all good ideas. but this setup really isn't designed for max power, I just want a functional blower (cause who ever gets to say they had a supercharged go kart?). I need to keep the carb in the original spot because there is nowhere to mount it on the blower, and I do think I'm going to need to do a carb hat with boost reference lines and whatnot because there is nowhere to seal a full on box on my setup. I can drill/tap stuff for reference lines, but I need to know what kind of jetting you ran. I will post pics of the blower/my plan to mount it shortly

 

[Sparkwizard]

My old blow thru setup was on a Tecumseh HS50 with stock carb with idle and high speed needles. I do not think I changed the jet, but it was adjusted out pretty rich, like 3 turns. One of those carbs might be worth looking into. I sealed the gas tank vent and ran a boost reference line to pressurize the tank because it would lean out/ run out of gas if left open to atmosphere.
@Denny is correct about the draw through system cooling the mixture and lubing the pump, but with a centrifugal blower, friction shouldn't be a big problem.

 

[Crappy212go kart]

yeah i figured as much, I've heard that the gas will not flow right without a pump but a boost reference line to the tank seems genius. So you had the boost feeding into the tank to push the fuel down into the carb instead of using a like a pulse pump?

 

[Sparkwizard]

That is correct. On my mini, the air pump ran off the rear wheel, so it would block airflow into the airbox when it wasn't moving, so I added an automotive PCV valve to the airbox so it could idle and the valve would close under boost. That made it idle kind of rich, so I just leaned out the idle mixture screw. The high speed screw was adjusted rich.

 

[Crappy212go kart]

thats genius, I can see why they call you the spark wizard. But mine will be hooked up to the output shaft on the crank so it will constantly be turning. for that I believe I will need bigger jets both main and pilot, any idea on what size I need to be running? (at school rn so I will let you know the size when I get home- don't tell my principal)

 

[Crappy212go kart]

ok got some pics of the blower for yall, I knew that @Hellion wanted to see it so here ya go. My buddy just gave it to me today fresh off the printer, the gears sound sooo sick even when turned by hand. its got a 4 to one reduction in the case, I want to run it at 2 to 1 on the pulley so its 8 to 1 from the crank to the impeller. I have a 5250 rev limited coil from EC Carburetors, so at 5000 rpm the impeller will be turning 40,000 +. Yes I know this is dangerous (almost as dangerous as an exploding flywheel if you know you know) so I will be installing a sort of blast shield made from sheet metal behind me.

 

[Sparkwizard]

That thing is bad azz! Boost guage and blowoff valve are suggested.

 

[Denny]

It will explode long before it makes boost. I’m sorry.