In the mid seventies, I put a smog pump (positive displacement, vane type air pump) under the seat of a minibike. I put a pulley on the back tire to run the pump, ran 1 inch rubber to the carb inlet, added a piece of vacuum hose from the tank vent to the rubber hose. This brought the tank (fuel pressure) up to my boost pressure. Centrifugal clutch on the engine to the rear wheel, and a PCV valve in the rubber hose for idle air when the blower wasn't moving. It worked GREAT! Sorry oir the simple description. Ask me, I'll help you.
briggs 5hp supercharger ideas ?
- Thread starter Wideopenthrottle
- Start date
- Tags 5hp briggs smog pump supercharger
I remember back about '67 a company named Judson made a small roots type blower for the VW Bug(36hp)...... that was to be mounted on the ex.side to suck the charge out of the cylinder,kind of the same way a tuned pipe will help scavenge the burnt waste and fill the cylinder with a cleaner air/fuel charge....well I seen one in an old cycle mag,and sombody mounted one on a 5hp briggs,belt drive off the starter cup,It had a lake injector on it for a carb...just had one pic...Has had Me dreaming for ever about one....Scootercat....
Any engine with a poor induction track, which every flat motor has, is greatly benefited by forced induction. Even more so than its better breathing OHV cousin. That's one of the reasons that a flattie Briggs would be fun to force induct.
The other good thing is that the stock compression ratio is very low; I don't recall what it is but it is no more than 7 to 1 which is good for a blowermotor; More boost can be safely used if the engine does not start with a high compression ratio. On blowermotors the exhaust track needs to be more refined than the intake side because of the forced induction. Induction can me more sloppy and still not be a big detriment; Not so the exhaust side which, when blown, requires a much greater amount of exhaust gas to be handled without outside help.
As I understand it these are general considerations. My hat is off to anyone willing to make a serious effort to supercharge a Briggs. A guy would be the only kid on the block with one. I have one of them engine evacuation pumps that Neck mentions and I sorta get the idea after dealing with it that it would not produce the required air volume. But then it has only been put to it's intended use.
I heard a smog pump can be used but the RPM has to be really high.
Another consideration is that the carb really should be a 'pull through' set up. Like you see on a Jimmy blower on a hot rod or dragster. The 'belt driven intake manifold' sucks on the carb. If the carb is on the engine and the blower pressurizes it there is going to be a LOT of carburation problems. For a number of reasons that won't work. So anyone trying to puff a Briggs should consider having the carb 'pulled through' from what I understand.
The other good thing is that the stock compression ratio is very low; I don't recall what it is but it is no more than 7 to 1 which is good for a blowermotor; More boost can be safely used if the engine does not start with a high compression ratio. On blowermotors the exhaust track needs to be more refined than the intake side because of the forced induction. Induction can me more sloppy and still not be a big detriment; Not so the exhaust side which, when blown, requires a much greater amount of exhaust gas to be handled without outside help.
As I understand it these are general considerations. My hat is off to anyone willing to make a serious effort to supercharge a Briggs. A guy would be the only kid on the block with one. I have one of them engine evacuation pumps that Neck mentions and I sorta get the idea after dealing with it that it would not produce the required air volume. But then it has only been put to it's intended use.
I heard a smog pump can be used but the RPM has to be really high.
Another consideration is that the carb really should be a 'pull through' set up. Like you see on a Jimmy blower on a hot rod or dragster. The 'belt driven intake manifold' sucks on the carb. If the carb is on the engine and the blower pressurizes it there is going to be a LOT of carburation problems. For a number of reasons that won't work. So anyone trying to puff a Briggs should consider having the carb 'pulled through' from what I understand.
I know I'm new here, so nobody saw my reply. I am an older guy with alot of fabrication experience and have been a master certified auto tech for 25 years. smog pumps pump more air than a 5 hp can consume, They do NOT need to be overdriven. If the fuel tank is at the same pressure as the carb, there is no carb problem. The air/fuel ratio will be the same as if normally aspirated. The blower does not need to run at idle, so running it off f the rear wheel is ideal. since you cannot draw air through a smog pump, you need a vent in the system so the engine will idle. I used a PCV valve for this.
that does sound like the most workable system spark. put a boost guage in there and your set. id run another chain off the jackshaft to it as they suck alot less power than belts. and you can fine tune the gear ratio to it if you need more boost. i would think even 3 or 4 pounds would make a significant difference like oldsalt said. I was thinkin of building a hot briggs for my next bike but i might try that 
Hansen makes a kit for it already and cheap for all you get :shrug: It works quite well.. I spent the better half of my adult life every day all day on the dyno and building superchargers doing R&D for various mfg's its not rocket science, but a whole lot of fun!!!!
Hansen Supercharger Corporation
Hansen Supercharger Corporation
Cool but it takes up some real estate, it would be cool for a custom build though. I've seen it before and thought it was very cool. I like the rear wheel driven smog pump idea, seems live the most efficient way to drive it and the fact it only turns while underway is cool. Someone needs to try some of these and let us know if the juice is worth the squeeze.:thumbsup:
that does sound like the most workable system spark. put a boost guage in there and your set. id run another chain off the jackshaft to it as they suck alot less power than belts. and you can fine tune the gear ratio to it if you need more boost. i would think even 3 or 4 pounds would make a significant difference like oldsalt said. I was thinkin of building a hot briggs for my next bike but i might try that
In 1957 Ford offered as an option a 'axial flow' supercharger. Around that time there was such a thing as a Studebaker Golden Hawk. Same deal but as i recall the supercharger was a Judson. In any case the boost for both was around 5 or 6 pounds. That is about a third of an atmosphere and will produce useable HP. The reason that the boost had to be limited to such a low number is that both were 'blow through' systems. In other words the air was compressed and then introduced to the intake of a carburetor in its normal position on top the engine. Easiest way to do it but a carburetor will not function very well unless the ENTIRE carburetor sees the compressed air. All metering circuits are fooled and tuning becomes a big problem if the boost gets any higher. That is why all supercharged engines that have carburetors the carburetor is 'pulled through'. Unless of course the engine was intended to run at one RPM and was tuned for that narrow performance band.
I have grave doubts that a Pulse-Jet carb would work at all even if it was a pull through system. The diaphragm that pumps/meters the fuel would not move back and forth if nothing but negative pressure was available. It for sure would not work if it was a blow through system. Again, the diaphragm would not move back and forth because it would only see positive pressure.
A float bowl type carb would be the way to go...especially if the intended boost was 10 or 12 pounds. But the system would almost certainly need to be a pull through.
Have fun,, play with it. This is how things get started.
Fuel will be the issue; guess you would need to set the" fuel jet"up for full time boost. With the larger jet it may not run when the boost ie off.
Have fun.
Strap a leaf blower in the back. Lol
A wet shot of nitrous is easy to add fuel and cold air at the same time. A small dry shot would cool air intake temps and give great power. Sneaky pete kits are cheap.
Note nitrous is just cold air and is very safe.
http://www.dynotunenitrous.com/store/scripts/prodView.asp?idproduct=141
I put a 90 cc head and just a piston ring on a 70cc eaton 4 wheeler one time. Took about 20 mins and man did it helped a ton. I was shocked. Would spin the tires and picked up alot on the top end
Fuel will be the issue; guess you would need to set the" fuel jet"up for full time boost. With the larger jet it may not run when the boost ie off.
Have fun.
Strap a leaf blower in the back. Lol
A wet shot of nitrous is easy to add fuel and cold air at the same time. A small dry shot would cool air intake temps and give great power. Sneaky pete kits are cheap.
Note nitrous is just cold air and is very safe.
http://www.dynotunenitrous.com/store/scripts/prodView.asp?idproduct=141
I put a 90 cc head and just a piston ring on a 70cc eaton 4 wheeler one time. Took about 20 mins and man did it helped a ton. I was shocked. Would spin the tires and picked up alot on the top end
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I wish I could see more statistics and numbers instead of opinions. bring on the video's!!! How much CFM does a 5HP Need to make boost? How many CFM does the smog pump put out? how many RPM's does it take at the input shaft to make that boost?
Nitrous oxide,What about jetting? how much fuel pressure? what kind of nozzle?what size solenoids?what will power them?
Also,has any one thought of what needs to be done to the engine to handle the extra power? Horsepower is horsepower so you need the engine built to handle the intended HP no matter how is is made.
Let's put some numbers down.
Nitrous oxide,What about jetting? how much fuel pressure? what kind of nozzle?what size solenoids?what will power them?
Also,has any one thought of what needs to be done to the engine to handle the extra power? Horsepower is horsepower so you need the engine built to handle the intended HP no matter how is is made.
Let's put some numbers down.
