A question about this cleaning that I have been pondering over for some time, if I may.
We take off the manifold and clean it, but surely the head inlet ports are also gunked up.
It seems to me that this part never gets cleaned, but surely it to is restricting airflow.
Why does the inlet ports not get cleaned also?
Is it that it is just too hard to get to the ports?
They are gunked up. So too is the intake valve. But 90% of the time they are nowhere near as bad as the intake manifold. There's a few reasons for this. Mostly though, it is to do with airflow and air speed. The injectors also have a lot to do with it.
If you were to think of the manifold as a swollen creek. The creek is wide and deep. There's a heap of storm water in it. Because of the depth and the width, a heap of water can flow through with no problem.
The creek gets narrow as it goes. The speed of the water increases the more narrow the creek becomes. The debris is carried with it.
Same thing happens in the intake of the engine. Where the air enters the intake, the plenum chamber, it is large in volume. The air speed is slow. This air travels toward the intake valve and the diameter of the intake tract reduces, increasing air speed even more as it goes. It travels faster and faster until it enters the combustion chamber.
Back to the creek. With all the flood water comes debris. The debris enters into the wide and deep part of the creek with the slow moving water. It's very easy for this crap to become trapped. One bit lodges against something, it then traps the next bit and so on and so on. It keeps building up. As the water flows through the narrow sections of the creek, the debris that wasn't caught earlier, is carried with the water. It's very hard for it to become lodged against something due to the speed it's travelling at. Sure, a little bit will lodge itself here and there, but most will flow through.
Back to the engine.
The PCV valve and EGR is usually in the plenum. This is where the air speed is slow. So it's easier for the debris to lodge here. As the intake tract narrows the debris is harder to lodge due to speed. Where the airspeed is almost at its highest, is right where the fuel injector Isuzu (petrol engines). In theory, any debris that's in this area, should be suspended in the air travelling stupid fast speeds. To help it pass, even more, there's a stream of fuel being hosed in to be carried along with it, which reduces the chance of that debris coming out of suspension so it can't lodge against the intake tract or port.
You will always find the occasional case where the entire intake port is covered. Usually this is from an oil burning low rpm engine. The oil is often from intake reversion and the build up is often from that oil combined with constant low rpm. (Low airspeed)
Hope that makes sense.
Shane.
