Quote:
Originally Posted by Tesla
Diesel Vacuum,
Just thought I'd add, I think the general theory is no vacuum, that would be true at idle, but as air volume goes up, with the restriction of the air filter particularly, there is vacuum in the intake system, that is why they benefit so much from ram air setup.
I discoverd this when I set up a manometer on intake system, and am currently organising a vacuum gauge to set up permanently, this will give me a guide on how efficiently the engine is running using the info from both the vacuum & boost gauges, basically telling me the pressure difference across the turbo, less difference, les power drain by turbo.
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This depends from various of factors, airbox design, intake sound muffler design, what kind of air filter there is (there can be even more), I believe that there can be even restrictions between filter and cylinder, even intake valve can cause some restriction so it depends from engine design too with NA diesel engines, turbo of course does overcome restrictions but they still are there.
I think that vacuum gauge setup is good idea to tell if there is restrictions in air intake, but I don't quite see how you could measure power drain of turbo as it is propelled by exhaust and is creating 1 athmosphere even at very gentle driving.
At idle difference would be probably large as there is not much exhaust to propel the turbo and air filter restrictions would make less measurable vacuum, so pressure at intake manifold might be slightly less than what there is after air box. Mostly it would measure just effectiveness of ram air setup over different speeds, but it can be that I have missed something?