2 strokes 1

[MrWFO]

i was wondering if anyone on here knows 2 cycle engine.

could you perhaps suggest some books, i'm reading 2 stroke tuning by a.graham bell, & when i finish would like another good book to cloud my views a bit.

i'm building a motorized bicycle using a 66cc 'happytime' chinese engine & believe a pressurized oiling system combined with direct fuel injection i could come up with a way to bring these amazing engines back.

but, my primary reason behind studying the design is to optimize the intake length, port shape, & expansion chamber.
the last of which i'm not too worried about.

imagine what kind of economy a cvt-equipped 500cc v4 direct injected 2-stroke could pull off. especially if the expansion chambers were adjustable to also increase low-rpm effiency.

 

[dgallup]

Look for "Two Stroke Tuners Handbook" by Gorden Jennings. It's out of print but possible to find. Lots of info on port shape & duration. I used it 35+ years ago to increase power & narrow the powerband of my dirt bike to the point it wouldn't pull the gap between 1st & 2nd gear on a hill. Seriously, it's a good book but like many novices I quickly found out there is more than peak power in making a good engine.

Lots of 2-stroke direct injection engines have been tried with varying success. The TESI killed motorcycle company Bimota. The Ficht injection system contributed to outboard boat engine manufacture OMC going bankrupt but it has been reborn by Bombardier as ETEC. Mercury outboards use Orbital direct injection, Yamaha has a different "HPDI" system. Lots of others have come & gone. The best can compete with four strokes if emission requirements are not too stringent.

Good luck on that fuel economy.

 

[Metalguy]

I've got that book, so if you need any specific info I can look it up.

In the meantime, try this:

http://microcarproject.tripod.com/html/expansion_chamber_design_softwar.htm

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[Tmoose]

Looks like some scooter engines may be reed valve equipped.

http://ep.yimg.com/ca/I/yhst-12208756820499_2116_6079786.gif

I'm not sure intake length beyond the reed does much positive. Articles by Boyesen and others seem to favor placing the reeds close to the piston face/crankcase as possible, but that's for "performance" not for economy. I think if you cruise with throttle openings below 50% or so sonic or inertia tuning would get pretty muted too.

One Part of 2-stroke "economy" requires not wasting any intake charge by losing it out the exhaust port. A well done expansion chamber can help power by tucking the good stuff back in just before the ex port closes, but some of the "best" 2 strokes have had short port timing events, crude exhaust systems and ports seemingly sized so tiny as to barely allow mixture to seep in and out of the engine.

http://www.britishseagull.com.au/featherweight.php

http://www.saving-old-seagulls.co.uk/images/sophie 00037.jpg

 

[dicer]

Bring them back? They are still here.

 

[TCAir]

The Evinrude ETEC is the most modern 2 stroke set-up. They are not forced inducted but achieve better fuel economy and emission standards than their 4 stroke counter parts. These engines are not FICHT engines but a new design (obviously with lessons learned from FICHT)

The big issue now is legislative. I believe 2 strokes have been outlawed over a certain displacement for highway use.

I agree modern engine controls can/should bring the 2 stroke back but there are too many pre-conceived ideas that will have to be overcome to make them commercially successful again.

Good Luck

Engineering has always been my love, but it ended up being my second career...

 

[dgallup]

There are no laws against spark ignition 2 strokes for highway use, they just can't play in today's ultra low automotive emissions marketplace.

Spark ignition two strokes can only compete in certain niche markets like outboards where the emissions requirements are not too stringent. Look at how little emissions controls are on the four stroke outboards, just fuel injection. No EGR, no cats, no direct injection. It might be possible for the DI two strokes to meet the relatively lax motorcycle emissions but since non of the major (or minor) motorcycle manufactures are currently making or racing 2 strokes I doubt we will see one any time soon.

Whether they call it FICHT or ETEC is just a matter on marketing semantics. The ETEC system is just a refinement of the FICHT system. There was nothing fundamentally wrong with the FICHT system, they just rushed it too much & did too little testing. Gave themselves a bad reputation so they had to change the name. Bringing completely new fuel injection systems like that to market is a much bigger job than most companies realize.

 

[TCAir]

Dgallup:

The legislature failed to get the 2 stroke banned, but you are right on the emiissions issue.

ETEC has received the highest rating from the EPA for an outboard engine. Ultra-Low Emissions status.

The only thing Ficht and ETEC have is common is computer controlled direct injection. OMC purchased the rights to FICHT. When gross corporate mis-management (not FICHT) caused the company to become weak enough to be purchased by BRP the system was completely redesigned, (ETEC). To say they are the same is the equivalent to comparing the OMC Ficht system to Yamaha's HPDI. The systems are different. BRP also owns Rotax a very respected engine manufacturer in it's own right.

Just because and engine doesn't have cats doesn't mean it is not low pollution. The new outboard standard is very tight and most I/O engine manufacturers are borderline on their compliance with their engines (engines over 500 hp gas do not have to meet emissions), and Evinrude is exceeding the current standard by a wide margin (for outboards)

BRP has done a great job on that engine family.



Engineering has always been my love, but it ended up being my second career...

 

[dgallup]

I'm a big fan of BRP, I owned a CanAm MX motorcycle back in the day, have a SeaDoo & I would love to have an Etec on my new boat (but it came pre-rigged with a Yamaha). We manufactured the Ficht nozzles & made suggestions to OMC for improvements, some of which are in the Etec injectors.

The fundamental operating principal of both the Ficht & Etec injectors is identical & completely different from the Yamaha HPDI (or any other DI system). Both the Ficht & Etec use a pressure operated outwardly opening poppet valve. Both use individual solenoid drives to generate the pressure to open the poppet valve. Sure the Etec has a lot of improvements but that is to be expected in an improved design.

Compare the marine "ultra low emissions" regs to the automotive "ultra low emissions" & you will see they differ by an order of magnitude.