briggs 5hp supercharger ideas ?

sparkwizard

sparkwizard

#41
#41
jeffo said:
The set up you talk of seems very interesting. You should make a thread and replicate this system on a mini.

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I guess I'll have to put one on my Doodlebug and show the non-believers. Granted, this is a float carb, and I do not want 12 PSI for my 9 year old stepson, but consider me in on this project.
 
sparkwizard

sparkwizard

#42
#42
texasfabguy said:
what about using the pulse of the crankcase for the fuel pump?
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Oldsalt said:
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.
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If they had put the entire carb in a pressurized box and indexed the boost pressure to the fuel pressure, their problems would have been solved. Think about it.
 
sparkwizard

sparkwizard

#43
#43
Where can I get a 3/4 inch crank for a 4 horse Briggs? I have one with a 6:1 gear reduction on it. with the proper crank, I will build a blown Briggs flathead.
 
J

jeffo

New Member
#44
#44
Does your 4 HP come with a 5/8s crank? You could pry get one on eBay, or post in the classifieds want ads on here. I want to see this happen!!!:D
 
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Bill Ellerby

New Member
#46
#46
Do you know the model/type and code of your motor? It is must likely 80302-????-?? If you know it you can look it up at Partstree.com. Example a 080302-0015-01 motor the crank p/n is 492880 replacing 260257. If you do look up you motor just type in the model ie.80302. For it to work must enter 6 digits so add a zero in front. Good Luck
 
Oldsalt

Oldsalt

Well-Known Member
#47
#47
texasfabguy said:
what about using the pulse of the crankcase for the fuel pump?
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Brilliant idea! In fact it may be the only reasonably inexpensive way of doing it.

Suppose reed valves on one side of the crankcase [hopefully with a good air cleaner] could be fitted to allow 'one way' induction to the crankcase when the pulse was at negative pressure. Then another set of reeds on the other side and a pipe to the carb mounted on the Briggs engine. The whole carb would need to be in a box so that there was the same pressure on the outside as in the throat.

Really hard to say how well it would work based on the fact that the piston, after going down to compress the crankcase volume, then goes up a like amount. Might be possible to 'time' the opening of the reeds by opening and closing a port by the skirt of the piston.

When ya gonna start work on one!

At one time there were a few single cylinder 2-stroke racing bikes that had another 'pumper piston' connected to the crank. It was pure and simple a supercharger.
 
sparkwizard

sparkwizard

#48
#48
back to the blower idea. The reason I scrapped the blown mini back in the seventies was because I could not retard the timing to keep from detonating. Do any of you guys have any ideas on how to retard the timing when the boost gets up there?
 
Oldsalt

Oldsalt

Well-Known Member
#51
#51
I'll bet them little EFI things cost at least a hundred dollars. I'm sure no one in their right mind would put one on a clone motor which also costs about that much too.
 
J

jeffo

New Member
#52
#52
sparkwizard said:
back to the blower idea. The reason I scrapped the blown mini back in the seventies was because I could not retard the timing to keep from detonating. Do any of you guys have any ideas on how to retard the timing when the boost gets up there?
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I would say the only way to do that would be to use a car coil and custom ignition pulses

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Adrenaline

Member
#55
#55
jesse8931 said:
you can make a bracket to advance timing but not sure if you can retard timing the same way.
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you should be able to retard the timing by making a bracket that moves the coil mount foward so the flywheel passes the coil later. but since we're currently speculating could said bracket be made spring loaded so as to advance/retard timing during operation?
 
texasfabguy

texasfabguy

New Member
#57
#57
sparkwizard said:
back to the blower idea. The reason I scrapped the blown mini back in the seventies was because I could not retard the timing to keep from detonating. Do any of you guys have any ideas on how to retard the timing when the boost gets up there?
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Two plug head,two mags.


Pressure switch on the leading magnito that grounds it out when it reaches the set psi. I would think this setup would have a lot of benefits.
 
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Bravin neff

New Member
#59
#59
First time poster, frequent lurker...

Re: adjustable timing

...if you use efi, its fairly straightforward to fashion a 36-1 or 60-1 type of trigger wheel with VR pickup. Then you can just program a completely adjustable timing curve, complete with timing retard as a function of boost.
 
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