Porker928

This has probably been asked before but......

Why is it necessary to draw hot stale air in from the cam-belt covers into the cold air intakes?



Thanks for any sensible explanations.

Ben

IcemanG17

Ben
The picture is not complete.....the cold air intake tubes that attach to the airbox and run forward have little holes in them where those vents attach.......so only ambient air could be drawn into those...

Heres a pic

SQLGuy

I would guess that it's crankcase gas scavenging and reburning for anything that might be blown by the cam or crank seals and into the timing belt cover, but I don't know for sure.

atb

The vaccuum created inside the belt covers creates a less dense atmosphere around the rotor making it easier for the spark to jump the gap to the distributor contacts resulting in a larger spark, more efficient combustion, and hence more power.

Fabio421

These responses are hilarious.

SQLGuy

So, what's the real reason?

Jim Chambers

Have to say I was just wondering about the same thing today as I installed the tubes after re-tensioning by T belt.

928 at last

If I get to play too, my guess would be that the toothed belt acts like a fan in it's own right, (much like a snowmobile drive belt) and the vents provide both a source of cooler air flow or at least allow circulation in some capacity, helping to keep the temps down.
Just a WAG though...

928 at last

And for Fabio, and running with the previous thought,
Once the intake tubes are firmly attached to the vents, the toothed belt acts as mild form of supercharging, so if not properly assembled, the engine will invariably run rich at any point over 900 RPM.

RKD in OKC

I've gotta get in on this. Let's see...Alternator cooling, brake cooling, Those temp controlled flap things, well I would say they were to help keep the air in and around the t-belt from getting too hot.

Mrmerlin

the intake tubes actually suck the air through the belt covers to remove any hydrocarbons that may be ejected from the cams crank and oil pump seals , this is also a good system to monitor the belt system as any errant belt particles will be neatly sucked into the air cleaner and give a warning that something was amiss, if the air cleaner was routinely removed and tapped out on a clean piece of white cardboard, belt particles would be easily seen.
I suppose that the suction of the tubes may reduce the pressure in the belt run and add to the efficiency of the spark system

atb

FTW!

GregBBRD

You guys are funny.

Actually, there is ozone created from the spark jumping from the rotors to the caps. Without the intake system drawing off this, the timing belt would deteriorate at a much, much faster rate, as rubber and ozone are not friends.

The 944 models used a plastic cover that kept the ozone out.

tailpipe

And here I thought it was just the dungeon to the mouse house

Vilhuer

Fuel cooling...