The Split Cycle Rephase

[ReycleBill]

Food For Thought

While this could be done with an XS engine I think the easiest way to build such an engine might be to use 2 rear heads on an old Ironhead Sportster engine with the front being the air pump and the rear being the power cylinder. An even better choice might be one of the old Yamaha, BSA, or Triumph triples.

That is, unless you are capable of building entire engines from the ground up. Don't worry about infringing on patents as "The Backus Water Motor Company of Newark, New Jersey was producing an early example of a split cycle engine as far back as 1891." https://en.wikipedia.org/wiki/Split_cycle_engine

Of course, what this effectively does is supercharge the engine using one of the pistons to do so but it supercharges the engine with cool air.

Edited for spelling

 

[650trader]

Heiden tuning built a steam xs that won a new invention contest for top place.
A Blown ( in 1950's) NSU 500cc twin. roadracer could do about 212 MPH and
held a landspeed run OF 223MPH.

 

[ReycleBill]

Heiden tuning built a steam xs that won a new invention contest for top place.
A Blown ( in 1950's) NSU 500cc twin. roadracer could do about 212 MPH and
held a landspeed run OF 223MPH.

I'd like to learn more about both of those bikes.

 

[Ratranger]

I saw this a few years ago, a guy did similar with a GS500 for a school project. Used reed valves on the compression cylinder, and normal on the power cylinder.
https://www.bayarearidersforum.com/forums/showthread.php?t=352579

 

[ReycleBill]

I saw this a few years ago, a guy did similar with a GS500 for a school project. Used reed valves on the compression cylinder, and normal on the power cylinder.
https://www.bayarearidersforum.com/forums/showthread.php?t=352579

Thanks, great read. Page 9 confirms my belief that a V-twin would be a better choice for this engine: https://www.bayarearidersforum.com/forums/showthread.php?t=352579&page=9

Seems he isn't the first to do it either: https://thekneeslider.com/ducati-v-one-twin-to-supercharged-single-conversion/

I wish I knew more about fuel injection.

The biggest advantage of split cycle is that the air being injected into the combustion chamber is cool air. That allows timing to be advanced much farther than ever before without harming the engine.

Another advantage is that the compression cylinder makes boost even when the rider is backing off the throttle. This boost (compressed air) can be stored in an air tank and fed to the engine when needed. It's like having a Nitrous Oxide bottle that refills itself as you ride.

 

[Ratranger]

EFI is pretty simple once you learn a bit about it. Check out the msextra.com forums and the manuals on setting up an ms2 or microsquirt. I've got a micro on my xs running sequential fuel and spark on a rephased engine, not too bad to set up, and it runs pretty good. Need to fix it and get back to the dyno.

 

[ReycleBill]

EFI is pretty simple once you learn a bit about it. Check out the msextra.com forums and the manuals on setting up an ms2 or microsquirt. I've got a micro on my xs running sequential fuel and spark on a rephased engine, not too bad to set up, and it runs pretty good. Need to fix it and get back to the dyno.

I think my biggest weakness may be the computer skills necessary to program the thing.

 

[Ratranger]

Programming a megasquirt is dead easy. I use a program called tunerstudio, you put in your parameters(engine size, no. of cylinders, injector size, trigger set up, oddfire/evenfire etc.) This will set up required fuel, and rough in a map for you. Ignition you have to set up your own map, so I copied the stock advance with a little retard in the cruise area for heat control. Then go for a ride with the laptop hooked up to datalog and tweak the fuel table till it's close and then let autotune do it's thing. No programming skills needed, and there are lots of videos on youtube and support on the msextra forum.

 

[TwoManyXS1Bs]

I'm reminded of the '60s Puch 2-cylinder shared-combustion engine.

https://en.wikipedia.org/wiki/Split-single_engine?wprov=sfla1

 

[ReycleBill]

I'm reminded of the '60s Puch 2-cylinder shared-combustion engine.

https://en.wikipedia.org/wiki/Split-single_engine?wprov=sfla1

I bet those split single shared-combustion engines with 2 cranks were very smooth, albeit a little heavier than most 2 strokes. Though probably no heavier than counterbalanced engines.

 

[TwoManyXS1Bs]

A friend of mine had a Puch. I recall it had a conventional crank, like ours, pistons moving together. Looked like a wide 2-stroke...

 

[grizld1]

Used to be a lot of those Puch 250 twingles running around, Sears sold them under the Allstate label. They were cheap and very, very slow.

 

[gggGary]

Used to be a lot of those Puch 250 twingles running around, Sears sold them under the Allstate label. They were cheap and very, very slow.

Don't forget; ugly as sin.

 

[ReycleBill]

Here's a 2 stroke, opposed piston version of a Split Cycle engine made from an air conditioning compressor.

Not good for anything but learning.