Supercharging a 4 stroke cart motor
- Thread starter Jerry57
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JTSpeedDemon
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Haha, I've actually been thinking about thismyself! Unfortunately, my research shows that there have been very few supercharged small engines that I can find on the web. What little there are share almost no info. To make a forced induction go kart, it'll take a WHOLE LOT of custom work, and there's no guarantee it'll work and give you the performance you want. Unless you're extremely confident in your fabrication and small engine skills, I would recommend against it until you feel ready. The simpler solution to HP is to get a high stage kit from GoPowerSports or the likes to build a screaming high RPM small block. They can make some MAD power! Somewhere around 20 HP with a kit.
Also, we need a lot more details about what exactly you want to do, what engine, and your plans in general. But I will agree that a draw through slide carb setup is probably the way to go.
Also, we need a lot more details about what exactly you want to do, what engine, and your plans in general. But I will agree that a draw through slide carb setup is probably the way to go.
JTSpeedDemon
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My suggestion is to get a few books on the topic and read up, I got a really nice one yesterday at Half Price Books. When I figure out how to get a blower, I'm basically going to be winging it, building the system around the blower. You could look for motorcycle blowers maybe?
From your posts you seem to be mostly asking about the actual carb itself? Almost no one around here will have firsthand experience, but I would guess it would want more fuel due to the increased air throughput. Probably some other tuning intricacies I'm missing, but like I said, it's a rather obscure topic, it'll have to be all DIY.
From your posts you seem to be mostly asking about the actual carb itself? Almost no one around here will have firsthand experience, but I would guess it would want more fuel due to the increased air throughput. Probably some other tuning intricacies I'm missing, but like I said, it's a rather obscure topic, it'll have to be all DIY.
karl
Well-known member
At least in my draw through turbo experience, with slide valve mikuni, nothing really special with the carb.
Fattened it up a tad, thats it.
Blow through is where things get complicated.
I would be more worried about what engine, what blower, what drive ratio, and how will it idle.
OPmini
moo
I have done something similar to a 196cc honda clone. I designed and 3d printed some adapters for a FRAM air filter to a small rc motor (with a fan shaft slide-on that was wired to a battery and switch), then the adapter went to the carb. (supercharger)
But to do this without specialized tools you would need a carb air filter adapter some large PVC tubing to connect the blower to carb air filter adapter and a way to connect the air filter to the blower. In short, you'll need a lot of duct tape PVC pipe, and epoxy.
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I remember seeing a couple videos as well on turbocharged 212s and it seems like they don't work well for a number of reasons. One being that you don't have enough exhaust pulses to keep pressure and another being that the intake valve is never open while the turbo is being powered by exhaust gasses. On those setups as well the carb would never give enough fuel for some reason so they needed to go with an efi fuel system which is super expensive. Much like everyone else I havent seen much online about supercharged 212s but from the videos I have seen draw through seems to work just fine even with the stock carb on there. As far as blowers go I have heard that the 68-69 vw smog pumps can put out more than enough pressure to blow a 212 up around 18lb so that could be somewhere to start. I also saw a video on red beards garage yt where they supercharged a 670 with a small roots supercharger but I cant remember the model number for it. Good luck though with your cart it sounds like a really cool idea.
JTSpeedDemon
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Be careful with high boost, these small engines aren’t made as tough as car engines. When I super my kart, I’m planning literally 3 lbs of boost or so
65ShelbyClone
Active member
One thing I never, ever see on those builds is enough intake plenum. Actually, I never see an intake plenum at all. The only one I can think of was part of the Hansen supercharger kits.
Single-cylinder turbo setups do work. The problem is that people doing it to $99 engines are usually turbocharging a single (or anything) for the first time. Singles do have their own nuances that make it more difficult with carburetion than a multicylinder engine , but there are ways to work around them if you know how.
Im actually working on a 350cc motorcycle motor. Im actually more of a car guy but im in to cool different projects. This ones a 64 cushman silver eagle omc motor. Dont want to go the vanguard route they make great power just not the look i want. Thought that supercharging this motor would be cool. Thxs
65ShelbyClone
Active member
The Eagle's OMC appears to be built a lot more like a single-cylinder automotive engine than a bike or utility engine. That's good though; it has pressurized oiling that would make it simpler to turbocharge if desired. If it has a steel connecting rod like many other OMCs, then it should be reasonably strong enough for some boost. Just be conservative on the tune to avoid knocking ring lands off the cast piston.
To address your original question, nothing needs to be done to a draw-through carb except jetting. Even blow-through carbs can often be used without modification, they just needs to be setup differently to get pressure/vacuum signals where they wouldn't normally be so the fuel circuits work correctly.
To address your original question, nothing needs to be done to a draw-through carb except jetting. Even blow-through carbs can often be used without modification, they just needs to be setup differently to get pressure/vacuum signals where they wouldn't normally be so the fuel circuits work correctly.
JTSpeedDemon
2019 Build Off Winner!
Good to know. Out of curiosity for my own project, how would that affect a diaphragm carb on a draw through setup? The intake I've got on the way has a pulse fitting on it, and I'm wondering if I'll have to block that off and use a different pulse fitting. So basically the pulse fitting will be just "upstream" of the blower, and I'd assume that the supercharger would pull a more or less constant airflow, nullifying the pulses. Am I overthinking it?
65ShelbyClone
Active member
A diaphragm carb with no float bowl like a Tillotson or Mikuni BN that relies on the manifold pressure signal, I don't know, but I think it would be a problem of getting a strong enough pulse. A two-lobe Roots blower is going to have some pulsing of its own, but I don't know how much or if it could drive a pulse carb properly. Float bowl carbs would be far and away easier to use because they don't need any special considerations for draw-through use.
JTSpeedDemon
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Ok thanks for the input. I'll see if it works, but if all else fails there are modified breather plates. Could run the pulses off there.