Grassroots flat four 2-stroke

The multi-cylinder pressed crankshaft thread brought back an idea/ brain fart I had back in the 80's. Two strokes were popular back in the day of D Sports Racing before LC one liter MC engines came on the scene. I ran a two stroke GT-750 Suzuki Ocelot for a while but flat fours mated to Hewland transaxles were kicking some butt around that time w/ names of IIRC: AMW, Aaen and Kohler based flat fours... and flat sixes in C/SR.

I ran this rough idea of building a flat four two stroke using mostly production engine parts w/ some custom parts past MC engine gurus, machinists and some (non-automotive) engineers... they agreed in theory FWIW.

I kinda left it there after that and upgraded to a FZR 1000 in the D Sport but I always wondered .... what if? Not that it would be competitive in any way but just building it on paper would be fun... a design exercise... or exercise in futility. I still think it would be a good retirement project I could call my own. Being the GT-750 crank was pretty stout, I'd base crank parts from there or similar.

This is it in a nutshell:

Crank and rods: Existing crank pins, bearings, thrust washers, crankcase seals, crank webs. Webs could be indexed to flat configuration and rebalanced or made custom/ lightened for use w/ a flywheel and transaxle instead of the gear takeoff for the bike gearbox. Production or custom rods depending on the stroke and jug choice. Flange take off for flywheel.

Cylinders: Existing liquid cooled single cylinder jugs. Boring, sleeving, modified porting or cylinder jacking. 90% of the work is prolly done here off the shelf, not that there wouldn't be some serious work here.

Pistons: Obviously one-off. Bore/ stroke, piston pin dia. per rod upper end, cyl porting etc.

Engine cases: Billet one-off, entirely depends on crank fit/ dimensions.

Carbs/ induction: Carbs, EFI, MS, custom throttle bodies... prolly the least of concern here but I believe totally achievable

Ignition: First thought was crank trigger electronic four stroke that fires every revolution, re-program for two stroke curve. Prolly a lot more available now than the 80s.

Other: Morse belt driven water pump from the crank. Engine cases adaptable to transaxle. Chambers, build to suit. Engineering... yea, prolly gonna need a lotta that.

Well, there ya go.... Have at it, critique it, add to it, shoot it down... what ya got?

Disclaimer: I have absolutely no intention of ever building this engine... if even possible, so please don't bust my nuts too bad. Just to build it on paper would be a blast.

Something similar has been done. Years ago at a show I remember seeing two stroke mc cylinders on a air cooled vw case. The thing was two stroke, air cooled, but had some sort of weird external water jacket and pump.

I am going to have to do some searching to see if I have any more info.

I'm confused, where are you going to put the turbo now?

I just wanna see the way you are gonna route the expansion chambers. Not to mention the crankcase volume will be kinda large unless each cylinder has its own separate crankcase, so to speak. If they share a common crankcase it'll run but the compression ratio under the pistons will be low, making for poor low end performance (won't be able to force a lot of fuel/air mix through the transfer ports). Once it's wound up it'll be better, but mixing the crankcase pulses would do weird things too.

a six pack

a nest of snakes

In reply to Curmudgeon:

He just needs a supercharger so he doesn't have to bugger with the crankcases at all...

Last month in Racecar Engineering or Race Tech there was a clean-sheet thought experiment of a flat, oppposed-piston (cranks at the outside, pistons sharing a combustion chamber) two stroke using a supercharger. It was a neat idea; no heat wasted through a chamber ceiling, as the "top" and "bottom" of the combustion chamber were both pistons.

Last year at the SCCA runoffs, a DSR powered by a turbocharged 670cc de-stroked GSXR1000 went under 2 minutes. This was the absolute lap record for the runoffs at Road America. I'd expect that this is the future for DSR - and it highlights the immense difference between regional and national cars.

I've heard the development program cost 7 figures, and Level 5 bought the West Car Co. as part of the effort.

I'm using a GSXR1300R Hayabusa engine in my (old, heavy) Radical Clubsport CSR. The advantages are:

• Cheap and easy. Someone totals a Hayabusa every day.
• Good aftermnarket support.
• Durable if you don't go fully crazy making more power.

Plus, next year when SCCA does away w/ CSR/DSR/S2000 in favor of SR1 (current tunnel aero exotic material national cars) and SR2 (flat bottom cars, no Ti, no exotic brake materials, comparatively stock motors) SR2 class weight @1300cc is 1200# - which is reight where I am.

Like this?

Pro Hydro outboard racers have a variety of layouts - very light powerful 2 strokes.

What about one of the Yamaha 200hp 2-stroke marine engines? Modify it to work/mount to a car and boost it. Problem solved.

Use Honda CR250 cylinders, powervalves, pistons, and rods. Have the intakes be at the center of the crankcase facing up, and the exhausts on top.

You'll make 50 horsepower per cylinder. It would be difficult to get much more power from this displacement reliably, let alone match the miniscule size and weight of such an engine.

In reply to Curmudgeon:

Being it's so stout I'd prolly base the crankshaft and separate crankcases w/ seals off the Water Buffalo. Stretching the crank and cases out from 3 to 4 cylinders would prolly make the separate crankcase volumes larger which could be handled by milling less material from inside the billet cases or adding stuffers.

I had 7 spare Water Buffalo engines disassembled and stored in my basement until a house fire, water damage ruined the cranks, scrapped 'em all. That'd been fun to toy around with.

ransom wrote: In reply to Curmudgeon: He just needs a supercharger so he doesn't have to bugger with the crankcases at all... Last month in Racecar Engineering or Race Tech there was a clean-sheet thought experiment of a flat, oppposed-piston (cranks at the outside, pistons sharing a combustion chamber) two stroke using a supercharger. It was a neat idea; no heat wasted through a chamber ceiling, as the "top" and "bottom" of the combustion chamber were both pistons.

You mean like a Napier Deltic?

http://en.wikipedia.org/wiki/Napier_Deltic

Under the new SR rules, you can have up to 1400cc of two-stroke.

That's five CR250 engines, and you'll make 250-270 horsepower.

It'll take dual snowmobile drives to transmit that much power.

Shoot, just put together three CR500 engines. 64hp each (Honda's figures) = poop the pants.

What I loved about the D Sports engine formula was two strokes, four strokes, MC, MC turbo and automotive based engines all could (and have at some point) been competitive. Back in the day most of the engine development was pretty much grassroots.

Curmudgeon wrote: You mean like a Napier Deltic? http://en.wikipedia.org/wiki/Napier_Deltic

Wow! Yeah, it was just the top "row" of that engine in this example, but ain't that some crazy business...

Curmudgeon wrote:

ransom wrote: In reply to Curmudgeon: He just needs a supercharger so he doesn't have to bugger with the crankcases at all... Last month in Racecar Engineering or Race Tech there was a clean-sheet thought experiment of a flat, oppposed-piston (cranks at the outside, pistons sharing a combustion chamber) two stroke using a supercharger. It was a neat idea; no heat wasted through a chamber ceiling, as the "top" and "bottom" of the combustion chamber were both pistons.

You mean like a Napier Deltic? http://en.wikipedia.org/wiki/Napier_Deltic

Napier Deltic FTMFW!!!!

Why stop at only 4 cylinders? http://www.leftlanenews.com/video-the-48-cylinder-motorcycle.html

Chaparral: that was the idea to use existing jugs (CR or otherwise) and their components

motormoron: I've tried to keep up w/ D Sports progress over the years. When $tohr and West came on the scene everything else might as well be a backmarker. Word had it there were a few shops working to perfect the 670 turbo MC engine, Tucker just made it there first, prolly thru pure cubic dollars. I remember the days when D/SR was threatened w/ regional status due to low car turnout... it's come a long way and then some. Tucker's car was said to turn a top speed of 183 mph in closed course testing.

With my limited resources and time these days I'd prolly be content to run a converted formula chassis w/ R1 power in regionals or track days just to scare the E36 M3 outta myself a couple times/ month. AS regional car would prolly work too. Or... build a BMod.

This engine thread was just a grassroots design exercise, never meant to be competitive in todays world. Maybe I'll putz around w/ it in retirement one of these days.

It's nice to know I'm not the only one with such unconventional ideas rattling around in my head constantly trying to escape. I definitely think you should start working on trying to make it work. But from what I hear, pressed cranks are pretty much a waste of time and effort...So you'll probably have to go with a billet crank to make it work.