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Author Topic: Quietest New Car for HF  (Read 13819 times)
M6GOM
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« Reply #15 on: July 14, 2014, 09:02:47 AM »

With direct injection gas motors becoming main stream here diesel is loosing luster and soon we will see wider use of Atkinson Cycle engines to which will offer diesel like MPG without the noise or smell and cold weather quirks.

Wow, your automotive industry is improving, its only just over a decade behind us now instead of being 20 years behind. We've had direct injection gas engines for quite some time. Certainly the 2003 VW Golf I owned with the FSI engine had direct injection.

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One reason for Priuses high MPG is not only Hybrid but also Atkinson Cycle engine with 13 to 1 cr.

BWAHAHA...Prius is high MPG. Its fuel economy is a joke here. Its a hybrid with worse fuel economy than both gas and diesel engines. It averages about 50MPG (UK Imp gallon). There's a lot of petrol engined cars that beat that. Hell, the 1989 Vauxhall Cavalier mid-sized sedan I had 15 years ago with a 2 litre gas engine managed 45MPG and it had over 180,000 miles on the clock.

And you're going to high compression gas engines just as we're ditching them and going over to forced induction as standard meaning we can have a 1.4L engine that generates 160BHP with maximum torque generated at a far more usable 1500-1750RPM instead of up near the redline where few people actually rev their engines up to. That means we can have cars like a Ford Focus with a 3 cylinder 1 litre engine that generates 123BHP, will return 56MPG (Imperial) and still do 11 seconds 0-60. Hell Ford even put these 1.0 litre eco-boost engines in MPVs such as the Ford Grand C-Max and still have it return 54MPG (Imp)

You'll catch up one day, maybe.

« Last Edit: July 14, 2014, 09:07:52 AM by M6GOM » Logged
G8YMW
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Posts: 239




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« Reply #16 on: July 14, 2014, 10:36:48 AM »

Actually an Atkinson engine has a lower compression ratio than an Otto cycle engine because the inlet valve is held open longer to give "Atkinson like" behaviour. ( The engine is not a true Atkinson as all four strokes are not in one turn of the crank) Blowing air back through the inlet manifold.
13:1? I think a petrol engine would have problems with detonation at those levels
The reason I question the compression ratio is that two strokes back in the old days was quoted as 11:1 ish but that was from bdc to tdc. My Yamaha 350 quoted (IIRC) 7.4:1 which was from when the exhaust port closed to top dead centre
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73 details Tony
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W8JX
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« Reply #17 on: July 14, 2014, 12:19:19 PM »

Actually an Atkinson engine has a lower compression ratio than an Otto cycle engine because the inlet valve is held open longer to give "Atkinson like" behaviour. ( The engine is not a true Atkinson as all four strokes are not in one turn of the crank) Blowing air back through the inlet manifold.
13:1? I think a petrol engine would have problems with detonation at those levels
The reason I question the compression ratio is that two strokes back in the old days was quoted as 11:1 ish but that was from bdc to tdc. My Yamaha 350 quoted (IIRC) 7.4:1 which was from when the exhaust port closed to top dead centre

Compression ratio works two ways but in a Atkinson Cycle its main function is on EXPANDSION and converting maximum amount of energy to crankshaft. While you loose some volumetric efficiency in HP per cubic inch you increase thermal efficiency of engine and get more work per lb of fuel burned. It end of expansion stroke the pressure in cylinder is closer to ambient and temperature of gas is lower too because more energy has been caught or captured from burn. 

M6GOM does not have a understanding of engine efficiency as seen in his comment of turbo charged engines. In order to tolerate low octane fuel and not self destruct via detonation the lower CR and use enhanced spark management (knock sensing and spark retardation) all of which reduces thermal efficiency. I you want maximum efficiency you runs as high a mechanical compression/expansion ratio as possible. If you want max HP per lb you turbo or supercharge a gas engine. Do not confuse higher HP per pound with higher thermal efficiency.

Furthermore, the consumer is sold on hype like Fords Eco Boost which has proven to be very thirsty in real world due to reduced thermal efficiency under load in larger vehicles which many has found out the hard way. Also E85 is poorly utilized in a flex fuel engine because it has a octane of 108+ and would thrive with CR ratios of 13 and above but this is not possible when tolerance to 87 octane is needed. If 87 was removed from market auto makers could ratchet up average CR in use but that not going to happen because public is fixated with using they cheapest fuel they can find even though using at least 89 would allow for more aggressive times and improved MPG. To suggest needing more than 87 in a manual is a sales killer to many so myth continues.

In next few years you will see wider use of Atkinson Cycle engine and may see turbo charged one that will make more power than stock but yield better MPG than turbo charged Otto Cycle engine.
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K0BG
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« Reply #18 on: July 14, 2014, 12:46:01 PM »

I guess this info on Mazda's Sky technology is incorrect!

Premium, 91-octane fuel is required for the Sky’s not-so-staggering 163 hp at 6000 rpm and 155 lb-ft at 4000, but Mazda is proud of its exceptionally wide torque band for enhanced real-world drivability. To enable running on regular gas, the U.S. version will have a compression ratio of 13:1,
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W8JX
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« Reply #19 on: July 14, 2014, 01:08:14 PM »

I guess this info on Mazda's Sky technology is incorrect!

Premium, 91-octane fuel is required for the Sky’s not-so-staggering 163 hp at 6000 rpm and 155 lb-ft at 4000, but Mazda is proud of its exceptionally wide torque band for enhanced real-world drivability. To enable running on regular gas, the U.S. version will have a compression ratio of 13:1,

The Mazda engine uses forced EGR in design. The exhaust valve is held partially open during intake cycle diluting mixture and reducing amount of free oxygen in cylinder and requiring a leaner mixture than normal for volume. This also slows the speed of flame at ignition reducing tendency to knock. they raise CR to increase thermal efficiency. It is a interesting concept but I do not see it as a long term viable solution. They have played with this concept in past for emissions purposes and abandoned it. They had a tendency to develop hard carbon deposits in ports and combustion chambers after many miles of use. Time will tell on this application. Because of modified cycle it does not relate directly to limitation of a regular Otto cycle but still not as efficient as a Atkinson Cycle.   
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K0BG
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« Reply #20 on: July 14, 2014, 03:35:46 PM »

In all due, and great respect, I think you need to do a bit of research on the Mazda Sky system.
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W8JX
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« Reply #21 on: July 14, 2014, 04:51:55 PM »

In all due, and great respect, I think you need to do a bit of research on the Mazda Sky system.

In all due respect I have followed IC engine design for over 40 years and even wrote a few papers on it in college. I have see many many developments and false starts. Mazda is a small player but they also use a Atkinson Cycle engine in a mini SUV. Subaru is planning on using them around 2016 model year. Future MPG requirements will require more than current Otto Cycle can deliver.

While you are accomplished with your site on some Ham info you are not even remotely in my league on auto theory and design. I read on trends and engineering developments almost daily and I have seen the sky concept/design before and I was not impressed. It looks like one of those designs that look good on paper but do not pan out long term. Using EGR to retard knock and improve emissions is nothing new and sometimes under right conditions it can even improve economy but results were never consistent. Toyota is developing a new design with no crankshaft and uses a integral generator to extract power and can crack the 40% gas efficiency barrier that has only been closely approached by Atkinson Cycle engines to date. Otto Cycle cannot compete here.
« Last Edit: July 14, 2014, 05:39:34 PM by W8JX » Logged

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K1DA
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« Reply #22 on: July 17, 2014, 08:30:37 AM »

British Leyland products fill junk yards all over the world.  Many of us in the states have met the "Prince of Darkness".  If Britsnobs are now touting the quiality of their cars it's because they are German or Japanese. 
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N6AJR
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« Reply #23 on: July 17, 2014, 09:32:47 AM »

I don't have one yet, but the next vehicle will be a ford flex.  lots of room and well made.  check it out.
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W8JX
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« Reply #24 on: July 17, 2014, 10:26:14 AM »

I don't have one yet, but the next vehicle will be a ford flex.  lots of room and well made.  check it out.

The Eco boost engine is not living up to its ratings. Ford bet the farm on it and it is not panning out real world.
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G8YMW
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« Reply #25 on: July 18, 2014, 03:41:34 AM »

K1DA what was your diatribe about? If you were trying to get a reaction, sorry to tell you "no chance"
In the 70's, British Leyland was a byword for the worst of British.
Incompetent management and bolshie union leaders was the order of the day.
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73 details Tony
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W8AAZ
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« Reply #26 on: July 26, 2014, 03:58:14 PM »

Was reading this thread until it became a discussion of other than HF radio and became an episode of "Car Talk" with contentious claims and counter-claims about anything but mobile radio.   
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W8JX
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« Reply #27 on: July 26, 2014, 04:17:35 PM »

Was reading this thread until it became a discussion of other than HF radio and became an episode of "Car Talk" with contentious claims and counter-claims about anything but mobile radio.   

Well cars are technology and not simple like they once were. I changed plugs on a Jeep compass today that uses a coil module mounted on each plug so it "should" be quieter than cars with plug wires. Its a Dodge/Chrysler motor so it would be same in their cars using same or similar engines.
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