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Old 06-15-2009, 07:45 AM   #2 (permalink)
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Join Date: May 2008
Location: Ireland
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De Yaris - '04 toyota yaris T2
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* What the vacuum in an engine is for,
To provide assistance to the braking system. It reduces the amount of effort to stop the car

* Is it the same for gas and for diesel,
No. Diesel engines have no throttle plate and therefore have no vacumn in the intake system. Brake assist is then done by a vacumn pump. Mine runs off the camshaft from what i can see. It's in the same position as the distributor in the honda civic.

* How strong should it be,
Not sure. Someone else may chip in with that.

* What kind of pump is better - belt driven or electric,
Direct drive to the engine would be safest but.... Ideally electric as there will be no belt losses incurred in driving the pump. Better control can be had over the pump if it's electric. You could combine it with a vacumn resevoir and pressure switch to switch it off when not needed. Good savings to be had while on the open road there!

* What does a vacuum gauge measure and how does this help me,
In a gasoline engine, it is a measure of how much throttle you are giving and how much load is on the engine. (i think!?) How it helps is by giving you feedback as to how hard you are on the throttle and can therefore ease off a little on the uphills and generally drive with as much vacumn as possible. I'm open to corrections here!

* What (and how) should be tweaked/changed for better engine operation,
Not sure what in particular you mean there Piwo. If it's vacumn then as i said above: Electric vac pump with resevoir and pressure switch to cut out unnecessary use.

* Will this help FE and why...
Should help a bit. Less work for the engine. Stick a solar panel on somewhere and you may drive it for next to nothing. If only solar panels were cheaper...

Hope this is of some help. If anyone wants to modify this then fire away.

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