Porsche Patents a Variable Compression Ratio - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

Captain Snooze · 04-30-2015, 05:33 AM

Interesting concept.
http://www.extremetech.com/extreme/2...uel-efficiency

serialk11r · 04-30-2015, 05:58 AM

No. Variable connecting rods is a horrible idea. The connecting rods are the components that see the greatest stress, why would you want to add moving gadgetry to them?

Lotus' moving puck idea is probably the best. For a 4 stroke engine, place the spark plug in a moving piston for a bit of compression ratio adjustment.

Calum · 04-30-2015, 09:08 AM

Quote:

Originally Posted by serialk11r

No. Variable connecting rods is a horrible idea. The connecting rods are the components that see the greatest stress, why would you want to add moving gadgetry to them?

Lotus' moving puck idea is probably the best. For a 4 stroke engine, place the spark plug in a moving piston for a bit of compression ratio adjustment.

Not to mention the weight.

strat61caster · 04-30-2015, 02:33 PM

VW's were just getting too dang reliable after they fixed the exploding fuel pump.

At first glance nifty, anything that prolongs the viability of combustion engines is a-ok in my book, while the article focuses on reducing turbo lag I immediately take this as a way to create a truer modern atkins cycle with an intake stroke shorter than the expansion stroke, maybe not at first but it's possible.

rice_classic · 04-30-2015, 02:53 PM

Like most German designs that are ahead of the curve: It will work brilliantly...briefly. (also: see "Alfa")

serialk11r · 04-30-2015, 04:52 PM

Quote:

Originally Posted by strat61caster

At first glance nifty, anything that prolongs the viability of combustion engines is a-ok in my book, while the article focuses on reducing turbo lag I immediately take this as a way to create a truer modern atkins cycle with an intake stroke shorter than the expansion stroke, maybe not at first but it's possible.

You don't want that thing to be moving around much...lol

There is absolutely nothing wrong with the valve timing implementation of Atkinson cycle right now. Displacement is cheap and not hard to add.

The reason you want variable compression ratio is because when at part throttle, the combustion chamber temperature is going to be pathetically low and efficiency is horrible. So ideally you'd be able to adjust compression ratio up to like 30:1 at idle and reduce it to 10 at full throttle to keep burn temperature up.

Having a higher static compression already helps low load efficiency quite a bit as can be seen with Mazda's Skyactiv line, because 13-14 vs. 10 is quite a huge difference already.

cdrazic93 · 04-30-2015, 09:25 PM

They used turbo lag as a reason to keep compression down alluding to the fact that as boost is low, comp will be raised up.

Doesnt make sense when they use VGT's. The article also never mentions DI either, which the new corvette ZO6 uses at a 10:1 ratio.

Increasing the ratio is a complicated idea, since as soon as your past idle, the compression is dynamic not static.

Poodles · 04-30-2015, 11:21 PM

The Germans have never understood the KISS principal. "German engineering" simply means over-complicated and costly to replace when it inevitably fails.

04-30-2015, 05:33 AM	#1
Captain Snooze Because compromise ® Join Date: Jan 2012 Drives: Red Herring Location: australia Posts: 7,741 Thanks: 4,003 Thanked 9,388 Times in 4,139 Posts Mentioned: 60 Post(s) Tagged: 0 Thread(s)	Porsche Patents a Variable Compression Ratio Interesting concept. http://www.extremetech.com/extreme/2...uel-efficiency __________________ My car is completely stock except for all the mods.

04-30-2015, 02:53 PM	#5
rice_classic Senior Member Join Date: Jun 2012 Drives: Nevermorange FRS Location: Seattle, WA Posts: 4,160 Thanks: 755 Thanked 4,200 Times in 1,803 Posts Mentioned: 77 Post(s) Tagged: 1 Thread(s)	Like most German designs that are ahead of the curve: It will work brilliantly...briefly. (also: see "Alfa") __________________ SCCA T4 - FRS

04-30-2015, 09:25 PM	#7
cdrazic93 Junior Join Date: Aug 2013 Drives: a car Location: Probably at school Posts: 4,341 Thanks: 3,184 Thanked 2,512 Times in 1,502 Posts Mentioned: 20 Post(s) Tagged: 0 Thread(s)	They used turbo lag as a reason to keep compression down alluding to the fact that as boost is low, comp will be raised up. Doesnt make sense when they use VGT's. The article also never mentions DI either, which the new corvette ZO6 uses at a 10:1 ratio. Increasing the ratio is a complicated idea, since as soon as your past idle, the compression is dynamic not static. __________________ "Ah! What music! They could have never imagined, those pioneers who invented the automobile, that it would posses us like this, our imaginations, our dreams. Men love women, but even more than that, men love CARS!"-Lord Hesketh

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04-30-2015, 11:21 PM	#8
Poodles Senior Member Join Date: Oct 2013 Drives: 2015 Series.Blue Location: Fort Worth, TX Posts: 1,781 Thanks: 88 Thanked 781 Times in 481 Posts Mentioned: 16 Post(s) Tagged: 0 Thread(s)	The Germans have never understood the KISS principal. "German engineering" simply means over-complicated and costly to replace when it inevitably fails.

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