Mac extra porting !!!

[mcbob]

Well Steve and Gordon i recall i'm sure that on the old forum the were some comments made about a supercharged Mac Kart that done dirt track oval races and did very well but it didn't last to long motor wise maybe some-one else may recall these comments or story i don't think it would have be related to the pic i put in this thread but i'm not sure.



Mc Bob.

[Bill Johnson]

Mark Bergfelt of the UAS is running a leaf blower hooked to his 125cc Sudam on dirt ovals with sucess. He had to work out the lag issues. You can contact him for info at info@bergfeltracing.com

[Dan Flanders]

Leaf blower induction!!!!!!!!!!
Now that is American ingenuity for you! Leave it up to those dirt kart guys to figure out a way to go faster
Must have one hell of a long extension cord or has he gone cord-less?

Hey Bill, are you headed to Savannah in February?

[Gordon Duax]

Gordon,

Please post the pics
Regards,
Steve O'Hara

Here you go....

Over all length is 7.25"
Width is 5.375"
Height from inlet to outlet 4.3"
The 4 bolt inlet & outlet flanges makes it easy to fabricate custom mounts for manifolds, and carbs.

The drive pulley diameter is 2.18"
But could be changed out to a cog belt drive quite easily.
Max input rpm = 15,000
Should not be a problem since it is way larger than the typical kart / saw engine engine,
and would have to be under driven (turned slower than crank speed).

[Bill Johnson]

Dan, Yes... you will find me at the track or Ed's S Bar & Grill

[Tom Davis]

Gordy,
Does the Outlet bolt pattern match a T72 reed block, Or is that just a optical illusion??
TD

[Gordon Duax]

Gordy,
Does the Outlet bolt pattern match a T72 reed block, Or is that just a optical illusion??
TD

Don't know, never had a T72............
But I doubt it.

[steveohara]

Gordon,

Forced induction increases HP by introducing a charge into the cylinder that is at a higher pressure than atmosphere. The design works in a 4 stroke due to the cylinder being closed except for the intake tract which is under pressure. Reeds or no reeds, high exhaust or low exhaust... none of that matters if you can't trap the pressurized intake charge in the cylinder. A straight exhaust pipe connected to an exhaust port that remains open after the intake tract is closed simply renders the boost in pressure null as it will just flow out the exhaust. Raising the transfer ports or scalloping the piston to keep them open longer will let you pump more charge through but they still have to close leaving the exhaust port open and all the extra pressure is lost unless you have a system on the exhaust side to keep the pressure above atmospheric, as an expansion chamber does to a degree. I could envision an exhaust for a supercharged two stroke that is a long straight pipe with a volume tuned chamber on the end that controls the pressure cycle such that it will remain high until the exhaust closes on the up stroke trapping fresh charge in the cylinder at a higher pressure. It would not need to provide the scavenge function that an expansion chamber offers as the scavenging would be accomplished by the force of the incoming charge rather than inertia and pressure drop as we have in the normal two cycle pipe. It would be an interesting project to mess with but I suspect that it has been tried countless times and abondoned because the gain is not sufficient to justify the complexity of the system.
Now, if we wanted to get real creative we would build a two cycle with the exhaust ports at the very bottom of the cylinder that open for a relatively short duration and feed the intake through an intake valve in the head at the top so the supercharger could pump up the cylinder pressure up after the exhaust closed. Of course, I think that someone has already done that..... I just can't remember where I saw it.
Thanks for posting the picture.... it looks pretty neet but it would work a lot better on a Briggs than a Mac
Regards,
Steve O'Hara

[Gordon Duax]

What ever..........
All I know is that the currant 125cc, non-streamlined 125cc bike record is held by a guy using one of my blowers on a 2-cycle Honda............
Nothing fancy, no special porting, pipe, etc..
He just put it on, chose a drive ratio to make 3-5 psi boost, and took the record.........
The only problem he ran into was that on the first attempt, he sucked the float bowl dry.
He added a small amount of pressure to the tank, and the problem went away.

[Rob Voska]

Float bowl went dry probably because he was pushing raw fuel right out the exhaust. The pressurized tank didn’t fix the root problem just covered it up.