Two-stroke catalyst?

Some austrians try to take over the market for catalyzed IC driven generators for hybrid cars.

Two stroke range extender.

It is a two-cylinder two -stroke but not like the famous Trabant where crankcases blew the cylinders with fresh charge.

It is claimed that exhaust can only be catalyzed ,if fresh charge come from blowers separated from crankcase.

Crankcases are full of oil and slidebearings like fourstrokes .

Why?

..because unburnt fuel / oil in catalyst can cause damage from exothermic reaction, maybe?

Total scavenge is necessary?

Post reunification, aftermarket catalyic converters were made for Trabants. IIRC they had a working life of around 50,000 Km

Hello Diogeness and MZ-adorer mgnbuk.

I forgot to mention that it is a three-way catalyst with a Lambda senor.

The philosophy is they run the thing with a pme of only 6 bar or ca half theoretical full charge.

With longitudinal scavenge no unused oxygen escapes during scavenging and cannot disturb lambda measurement.

Unburnt fuel is low on both scavenge schemes and with no fuel in crankcase the oil content in exhaust is not vastly different I think?

As far as I can tell, it has some kind of blower instead of crankcase induction, and exhaust poppet valves instead of ports in the wall so you get better scavenging. It should work, but whether it's better than a 4 stroke is beyond my pay grade. It has swapped 2 inlet valves for a blower, so is it that much simpler?

Maybe the blower /catalyst statement is just marketing speak, if you are going to make a 'green' engine you cannot oil it by total-loss, it has to re-circulated, and if if it has to be compact and look 'clean' under a modern bonnet you will want to wet-sump it - and if you cannot squeeze the charge under the pistons you need a blower - maybe they just think this is too long-winded and prosaic to explain to customers..

..'though all this will have occurred to you already maybe, Niels..?

Edited By DiogenesII on 30/06/2023 06:36:33

Somewhere it is written that they intend the twin 2-stroke to run at a mep (mean effective pressure) of 6 bar and have a maximum pressure of 45 bar.

A fourstroke with well engineered inlet tract can run 12 bar mep and ca 75 bar maximum.

Same power from same cylinder volume.Which is lowest mass?

You have some points.

It is also complicated by being two-cylindered with a lot of gearwheels ,whirling counterweigths,camshaft etc.

I have tried to compare size for a valveles VeloSolex with a coresponding sidevalved version and both crankcase scavenged.

One sealing ring will do

The Austrian need many more to seal two separate crankcase pumps from oil for gear and cams and bearing.

Edited By Niels Abildgaard on 30/06/2023 08:25:11

The crankcase scavenged has a volume/packaging advantage

Crancase versus blower

Edited By Niels Abildgaard on 30/06/2023 08:38:31

MZ-adorer mgnbuk

Guilty as charged, Niels !

Though I did actually sell one last year (an ES150/1 ) that I finally admitted to myself would never get rebuilt by me. That means that I only have 5 at the moment - and a couple of those may be getting moved along to someone more likely to put them back on the road than I am. I did have a Trabant at one point & got it running without too much difficulty after it had been stood outside for many years, but at the time didn't have the time sort it's many structural body issues - the non-corroding Duroplast panels were only the outer cosmetic panels - so that found a new home as well.

The return of "modified" 2T engines has been mooted before & seemed to hold great promise at the time - remember the Orbital engine ?

Two stroke motorcycles are actually still available today - see KTM motocrossers And until fairly recently Aprilia (Piaggio Group now ) were working on a direct injected small two stroke for scooters, but that seems to have gone quiet.

Nigel B

Edited By mgnbuk on 30/06/2023 14:43:47

2 strokes with improved scavenging and external blowers are not new, see split single, and of course the wonderful Deltic engine, not forgetting the TS3

Three dead ends

Edited By Niels Abildgaard on 01/07/2023 05:45:28

I guess this make 4 dead ends as well?

Lotus omnivore efficient two-stroke engine | Motoring ...

Dec 11, 2009 · Lotus omnivore efficient two-stroke engine - DP Ford were working with a company called Orbital in the early 90's on a 1.2 litre two stroke, three cylinder engine for the Fiesta and...

Cheers Michael

I didn't say they were a lost opportunity, just that the Austrian proposal that started this thread off is nothing new. The EMD diesels beloved of USA railroads were blower charged 2 strokes, but they had exhaust valves in the cylinder head. I think even they have moved to 4 strokes

The Austrians claim that they can make a two stroke spark ignited than can use a three way catalyst.

This is done by longitudinal scavenge and around half the possible charge.

Doing this using valves in head has been tried by most. car makers

but not with sidevalves that make a very compact layout possible.

I try to find prior writing than my describtion in dec 2014 HMEM

to convince my daugthers in law that they have not married completely useless no brainers.

There are other possible explanations when grandchildren underperform.

Edited By Niels Abildgaard on 01/07/2023 18:20:28

Blown two stroke engines could be a very good idea in modern vehicles. With current technology they could be turbocharged, with an AC motor driving the blower at low loads and extracting surplus power from the turbine at higher loads.

Stepped piston two strokes also offered a conventional bottom end whilst avoiding the complication of a separate charge compressor. Bernard Hooper Engineering

Brian G

The ford Ka was intended originally to have a very innovative two stroke engine, but legislation insisted that they put a catalyser on it. They couldn't get it to work effectively and blew their budget and time constraints, so the antique kent engine went into it instead. Apparently an overhead valve engine wouldn't fit under the tightly sloping bonnet.

Source; ex-ford designer at a Haynes Museum display.

Comparasion of packaging

Left

One way oil crankcase scavenging

Rigth

Wet sump lots of oil

Upper Austrian with electric blower

Lower Hooper stepped piston

Edited By Niels Abildgaard on 02/07/2023 09:33:35

Edited By Niels Abildgaard on 02/07/2023 09:35:27

The Kadenacy patent engines come to mind whenever two strokes without crankcase scavenging are mentioned. Petter reputedly came across the concept whilst testing the diesel version of their established two strokes with crankcase scavenging, the diesel was test running but with lower power output than previously when it was realised the crankcase inspection door was not fitted. This gave rise to their Harmonic engine range of two stroke diesel naturally aspirated engines. However General Motors threatened legal action as they already held patents for that system, so a settlement was reached where Petter took a license for supercharged two stroke ( linear) inlet in cylinder lower end and exhaust valves in head, as GMC Detroit Diesels were. All this was pre war. Wet case non scavenging two strokes are very long established. The surprise is being a side valve, compromising the combustion chamber shape normally reduces thermal efficiency, but perhaps an affordable penalty for the sake of installation. Certainly, using valves allows a degree of internal exhaust gas retention helping emissions. Perhaps the loss of controlled inlet valves ( allowing variable induction stroke or compression pressure) is made up for by combinations of hybrid transmission allowing the engine to operate at constant load, and the exhaust valves retaining measured quantities of exhaust gas to maintain compression rates with lower induction capacity when required. Certainly an interesting engine.