Engine explaination?

[Porka944s]

I was looking at my 2.5 16v engine today and i wast hoping someone could explain in laymans terms why it is so?
I was looking at the inlet manifold and the air box. Why is the inlet manifold so large, and why does it bend under itself? i followed the airbox back to the throttle body(is that the name) then it goes back on a pipe. I couldnt see, at a glance, where the manifold links to this? Whats down there?
I only ask as most cars ive looked at have simple inlet manifolds that meet up at one end (if you know what i mean) and the throttle body sits at the end of it with the box directly there. I guess it just looks a bit over complicated to me, and seems it could just be smaller and simpler.

Take into account i dont know loads about engines, im just interested? Cheers!

Mark

 

[Diver944]

I don't think I've ever looked closely at a 2.5 16v engine as I always thought it looked the same as the 3L version. There are not many around so hopefully one of our few owners will pipe up soon, in the meantime have you got a pic we could look at?

 

[MRGT]

I have no idea, although I am a mechanical numpty []

 

[zcacogp]

The inlet tract route for the 2.5 16v is particularly tortuous - I looked at one last summer, and it's very different to that of the 3.0 16v (S2).

I concluded it was like that for one of two reasons: a) Such a design gave best resonant tuning and hence better performance (which may explain why the S is notoriously peaky), or b) because it allowed the re-use of as many parts-bin parts as possible, thus keeping the cost down.

I can't believe that anyone would design something that fiendish for the fun of it.


Oli.

 

[TTM]

I'm not sure the S intake was carried over from another engine.
Would be interesting to try a S2 intake on an S.

 

[MRGT]

Im willing to give it a go if someone would care to donate the parts []

(oh, and add some funds so I can pay my 'man' to get dirty)

 

[Porka944s]

Ill get a picture and post it, it is odd, unecessarily so...

 

[Tam Lin]

ORIGINAL: TTM

I'm not sure the S intake was carried over from another engine.
Would be interesting to try a S2 intake on an S.

Having owned examples of both engines, I've wondered about this..I seem to remember reading a Rennlist thread about swapping intake manifolds from an S2 to an S/one of the S cams into an S2 to get more overlap..both seemed inconclusive.

The S intake seems designed with one eye on tuned charging, something Porsche took more seriously with each successive attempt (equal lengths on the S2, twin path on 968), and one eye on filter location. On the S2, they gave up and put it in the least convenient place possible, just because this gives the best air-path, but they clearly weren't feeling that brave on the S, and left the filter path compromised (that S bend) but accessible.