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Old 14th December 2005, 15:37   #1
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Default Variable compression ratio engine!

Hi

Long time since i started a thread.

A friend of mine sent me a link to an article that explains an engine developed by Saab that can vary its compression ratio from 8:1 to 14:1 depending on the load on the engine! As per the article, Saab says that it reduces fuel use by 30 percent and the engine is as powerful as an engine twice its size. However, this is still under R&D phase and still long way away from production.

Here is Ze Link
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Old 14th December 2005, 19:11   #2
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From 8 to 14 on a petrol engine???? What kind of fuel will you have to fill to run a 14:1 compression engine?

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Old 14th December 2005, 20:34   #3
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Same fuel. It will run 14 under part throttle and 8 under WOT with max boost.
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Old 14th December 2005, 21:39   #4
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Quote:
Same fuel.
I know that but, what octane fuel?

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Old 15th December 2005, 01:48   #5
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87-89 octane should be OK.
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Old 15th December 2005, 23:32   #6
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Default Variable Stroke Engines

According to my information variable stroke engines are used to measure the knock tendency i.e. cetane and octane numbers of fuels.

If you want to have a look, generate contacts and visit Themodynamics laboratories of IIT powai or Naval College of Engineering, INS Shivaji, Lonavala
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Old 20th December 2005, 14:31   #7
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I dont get it. Do you mean like changing the compresion on the fly without opening the hood? If not it's not so impresive( an A series toyota can do that 9-15 last check).
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Old 20th December 2005, 14:45   #8
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see here
http://en.wikipedia.org/wiki/Compression_ratio
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Old 20th December 2005, 21:01   #9
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Quote:
Originally Posted by samcore
According to my information variable stroke engines are used to measure the knock tendency i.e. cetane and octane numbers of fuels.

If you want to have a look, generate contacts and visit Themodynamics laboratories of IIT powai or Naval College of Engineering, INS Shivaji, Lonavala
Right and wrong.

The engine your talking about is the CFR (Co-Operative Fuels Research) engine which can vary CR from 4:1 to 18:1 through a movable cylinder head. Obviously it is not practical in an automotive installation due to its single cylinder and purpose.

The engine designed by Saab also uses a movable cylinder head but it works in conjunction with a Rootes supercharger to maximise volumetric efficiency.
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