Talk:Manifold vacuum

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I redesigned the entry, and "the basics" and created appropriate links regarding air pressure. As a gasoline engine expert, I don't agree with everything beyond "the basics". But, I didn't want to stomp on the work of other's, and there is value in all that discusson for whomever wants to read it. Sattyam 17:29, 8 October 2005 (UTC)

I reworked much of the article for tighter organization -- like Sattyam, I don't mean to stomp on anyone's toes. Some of the paragraphs seemed to confuse manifold vacuum (inherent in the use of throttles) with venturi vacuum (inherent in the use of carburetors), so I corrected that too. Cheers, zowie 18:34, 25 October 2005 (UTC)

It's not true that the engine in the Toyota Prius has no throttle. Certainly it should throttle less, due to the valve timings and low-power engine, but the throttle is still there. --KJBracey 23:39, 23 November 2005 (UTC)

[edit] Doesn't manifold vacuum reduce the effective compression ratio?

For example, if you have an engine with 10:1 compression with 1/2 bar of manifold vacuum, isn't the effective compression ratio only 5:1?

If so, could a flexible fuel engine be given a nominal compression ratio appropriate for the highest octane fuel (e.g. ethanol), avoiding detonation with other fuels by limiting throttle opening and thus preventing effective compression from reaching a value that supports detonation? 76.80.9.100 22:20, 21 March 2007 (UTC)