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Author Topic: Talbot Express (Autohome) Calypso power socket  (Read 15278 times)

Geoff_T

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Re: Talbot Express (Autohome) Camelot power socket
« Reply #30 on: January 19, 2012, 12:58:02 PM »
Hi

My comments re two stroke anything were based on personal experience. At the very dawn of my motocycling days I owned most of the models of BSA Bantam... most had a semi-circular speedometer that went up to 55mph and you would not reach that on the 125cc unless down a vertical descent. Even the 175 with the 80mph speedo had trouble reaching 60mph. I believe the 125 motor struggled to reach 4bhp.
Years later I bought a Suzuki F50 as a runabout. It had a reed valve engine with the carb next to the reed valve and pushed out a commendable 4.5bhp (90bhp/litre). The performance was also surprisingly sprite for a 50cc.
Years later still I bought an MZ ETZ250 that produced 21bhp and enormous torque... I could give a Honda 250 4 stroke a demo of faster acceleration. That ended my motorcycle era but showed how the technology had advanced.
Then, as I had owned Commer motorhomes I was interested in the fate of Commer/Dodge/Talbot and discovered the opposed piston TS3/4 engines that I recall, years earlier, trucks and fire engines fitted with the TS3 and their distinctive exhaust bark. I still feel that two stroke technology is a way forward, especially with fewer components and one firing stroke per revolution per cylinder.

 :)

Geoff and Sally

Lou Schneider

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Re: Talbot Express (Autohome) Calypso power socket
« Reply #31 on: January 19, 2012, 01:26:14 PM »
Firing once per revolution, two stroke engines have twice as many power strokes as an equivalent 4 stroke engine, thus they have effectively double the usable displacement in the same package and should produce twice as much horsepower and torque per CC.

The classic 2 stroke problems have been emissions and long life.  If the engine is a pressurized crankcase design where the bottom side of the piston pressurizes the next charge in the crankcase, you have to mix oil with the fuel because it's doing double duty as both fuel and lubricating oil - and doing neither very well.  The lubricating qualities are diluted by the fuel, while the oil burning in the cylinder greatly increases the engine's emissions.

You can get around the fuel and oil mixture problems by using an external charger to pressurize the charge instead of sending the fuel-air mixture into the crankcase, but this still leaves the problem of fuel blowing straight through the cylinder and out the exhaust port as the engine tries to charge and exhaust the cylinder at the same time.

Unburned fuel in the exhaust contributes nothing to the engine's output, lowering it's efficiency (mpg) while also increasing the unburned hydrocarbons (smog) in the exhaust.

By contrast, 4 cycle engines have their input and exhaust cycles separated by the power stroke where the raw fuel is consumed.
« Last Edit: January 19, 2012, 01:44:12 PM by Lou Schneider »

Geoff_T

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Re: Talbot Express (Autohome) Calypso power socket
« Reply #32 on: January 19, 2012, 01:43:35 PM »
Hi

Both the Suzuki and the MZ used a separate oil tank and no oil/petrol mixture like the earlier Bantams. The TS3/4 opposed piston didn't use the crank case as part of the combustion path... here's a link to the operation... http://www.oldengine.org/members/diesel/Rootes-ListerTS3/TS3.htm

My father used to work for De Havilland engines at Leavesden, it was also close to my school... we certainly could hear the Fairey Rotodyne when it landed there and, at the same time, Dr Joe Erhlich (sp?) had a 125cc two stroke motorcycle tearing up and down the main runway as he experimented with producing more bhp from the two stroke engine. I believe he used reed valves like the Suzuki.

Memories...

Geoff and Sally

Lou Schneider

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Re: Talbot Express (Autohome) Calypso power socket
« Reply #33 on: January 19, 2012, 01:49:43 PM »
Right - using an external blower eliminates the fuel contamination of the oil and vice-versa. But you still have the emissions problem of unburned hydrocarbons in the exhaust caused by raw fuel blown out the exhaust port while the intake and exhaust ports are open simultaneously - see figure 5 in your link to see this.

When you need less than a few parts per million of unburned HC in the exhaust, it doesn't take much cross contamination to exceed this.  California's current HC limits are 250 PPM at idle, 200 PPM at speed.
« Last Edit: January 19, 2012, 01:58:48 PM by Lou Schneider »

Geoff_T

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Re: Talbot Express (Autohome) Calypso power socket
« Reply #34 on: January 19, 2012, 02:51:50 PM »
Hi

I just hope sufficient brain cells are applied to the issue... I believe the rewards would justify it.  Four stroke engines now have things like variable valve timing and other enhancements unheard of years before. When SAAB used to race their three cylinder two stroke cars (yes, the were poluters) they won races because they were unburstable and the cars were driven with the accelerator permananently on the floor.

There has to be a future there for the simpler engine, adapted to meet current specs.

Geoff and Sally


Lou Schneider

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Re: Talbot Express (Autohome) Calypso power socket
« Reply #35 on: January 19, 2012, 03:48:06 PM »
I could see something like a fuel injected 2 stroke eliminating the blow-by problem.  Blow the cylinder clear with fresh air then inject fuel after the ports close and the piston is compressing the mixture.  Or even at the top of the compression stroke, like a diesel.

 

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