If you open the throttle, the vacuum will go down. At wide open throttle the vacuum level is zero and the intake manifold is at atmospheric pressure. Diesel engines have no throttle body to restrict the air flow, so a normally aspirated diesel engine's intake manifold is always at atmospheric pressure. At part throttle, the engine is literally choked off. This reduces the amount of fuel going into each cylinder.
At idle, most gasoline engines develop about 18" of vacuum. That is 18" of mercury on a manometer. Since air pressure at sea level is about Airplanes with gasoline engines use manifold pressure as a measure of engine output.
Of course you have to understand the difference between manifold vacuum and manifold pressure. Just realize vacuum is the absence of pressure. Super Moderator. But, how does a home vacuum work, with an electric motor? I have been looking at the Mazda 3 model , are these any good? I'm looking to replace my Citroen C5 Tourer. I do about 15, miles per year now and want a medium size, reliable replacement with reasonable performance and economy. Value my car , miles buy or sell?
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This might be better-placed in Tech Matters, but Motorprop has inspired me to ask a question I've often wondered about. As I understand it, a petrol engine develops a vacuum on the intake manifold when its running. Page of 1. Filtered by:. Previous template Next. On gasoline engines the brake booster gets it's vacuum from an intake pipe or the intake manifold correct me if i'm wrong.
So my question is, why is that not working on a turbo diesel? And how does it work there? Tags: None. Diesels regulate engine power by how much fuel is injected, they don't have a throttle body. It's the drawing of air past the restriction of a throttle body that creates a partial vacuum in the intake of a petrol car.
Turbos can help to over come this Last edited by 97ED; at PM. Originally Posted by 97ED. It's funny how people think of vacuum or "suction" Yep it is I thinks it's water presure that build at that rate every 10 meters or something I forget. Actually we would still That's a good one gota think about that one And we would be fighting to over come the increased air resistance. The drag Coefficient increases with the sq of speed. Four time the drag on a car doing 40 as doing 20 not twice as much.
But what the heck are we talking about View Photos By: rg Some new diesels are now throttled, but not to the same extent as a gasser. Fuel mixture is now just as crucial as a gasser for emissions. They throttle the intake to create some vac to pull the EGR gasses through. You know, its interesting, the No other real differences other than firing order and timing of course to account for the 5th cylinder.
Now heres the interesting part, my 80 had a throttle plate, the I put in doesnt. They both share the same kind of injector pump operating in the same manner, so whats the point of the throttle on the ?
Or was that some kind of emissions brainstorm?
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