951Porschiste

I know, I know, I know. It's a dumb question. But I am not a mechanic and after three years of 951 ownership and countless hours working on the car, there are basics I still don't understand.

So please, if someone could be kind enough to explain tha basics, I would be very grateful.

TIA

Chris White

its becasue they suck.

streckfu's

But if you stand behind them, don't they blow?

adrial

Engines wants to GOGOGO but the throttle body is saying NONONO. Your engine (an airpump) is pulling air through a tiny restriction....so it draws vacum. Engines dont need vacumn it is just a side effect that can be measured to check the working condition of the engine. Some of the accesories like the brake booster in particular need vacumn to function properly.

Diesels never see vacumn because they have no throttle body...interesting tidbit.

Chris White

Now for the real answer –
They don’t “need” vacuum, in reality it is a byproduct of the control function. An engine is basically an air pump. It is always trying to suck air in and expel exhausted air out. In order to control how much air it ingests a throttle in included in the system. The engine is still trying to suck in as much air as possible but the throttle plate is restricting the intake. Sucking against a restriction creates a pressure drop (or a partial vacuum).

So it is because they suck.

Chris White

Chris White

Actually if you remove the throttle the vacuum goes away and then they blow (up)

Chris White

streckfu's

I was trying to imply the exhaust, but yeah.

Trucho-951

The basics of the four cycle internal combustion engine: 1-Suck, 2-Squeez, 3-Bang, & 4-Blow

Chris White

Hmmm.....sounds like the dating cycle too...maybe 3 and 4 are reversed...

Keith E.

Chris, it depends on what kind of load you have....

951Porschiste

So, a vacuum leak reduces the engine's ability to suck in air and that is why leaks are detrimental to an engine's performance?

tommye

Well, the vacuum/boost level is used for many things, it indicates the load level of the engine which is used to control various things like fuel pressure and operation of the BlowOffValve just to mention a few. So, a slight problem will have serious impact on how the engine is running.

Cheers,
Tommy

RKD in OKC

You are correct, a leak reduces the engine's ability to suck.

The air and fuel mixture sucked into the cylinder is asploded to make power.

More power takes more air and increases sucking.

If there is a leak between where the air being sucked in is measured and where the air is sucked into the cylinder then the air fuel mixture is incorrect, (or sucky) and the motor does not make as much power, (also sucky). If the motor is not making as much power it sucks in less air and that sucks.

streckfu's

jacklet

chris LMAO!!!!