RS246.com Forum :: The World's #1 Audi R, S and RS Enthusiast Community

Why have Audi gone from 40 valve V8 in the S4 to 32 valve V8 in the RS4?????

The new 4 valve head flows better.

There's no room in the top of the cylinder to fit 5 valves, a spark plug and a high pressure (FSI-type) direct fuel injector - so they had to remove a valve.

As Dave said

PetrolDave wrote:There's no room in the top of the cylinder to fit 5 valves, a spark plug and a high pressure (FSI-type) direct fuel injector - so they had to remove a valve.

Dave - do you work for Audi?

Dave - do you work for Audi?

No, never have done. I did work for Lotus between 1988 and 1994 though.

In one of my surfing sessions I found a pdf that explains in quite a lot of detail the FSI system on the 1.4 Golf. It's not just direct fuel injection, but there's lots of other clever stuff - the water temperature is different when the engine is in FSI mode, the throttle is opened wide in FSI mode and the engine speed is controlled by the amount of fuel injected (just like in a diesel) - which means that a vacuum reservoir is needed to provide a vacuum for the brake servo and the flap that redirects intake air between 2 or 4 valves per cylinder, it also explains how the fuel injection strategy is different during a cold start and hence why the RS4 sounds MUCH noisier during the first minute or so after a cold start.

I don't know how to post a pdf file here, but I'm happy to email it anyone who PMs me.

PetrolDave wrote:There's no room in the top of the cylinder to fit 5 valves, a spark plug and a high pressure (FSI-type) direct fuel injector - so they had to remove a valve.

That makes sense, never thought of that. Thanks John

PetrolDave wrote:

Dave - do you work for Audi?

No, never have done. I did work for Lotus between 1988 and 1994 though.

In one of my surfing sessions I found a pdf that explains in quite a lot of detail the FSI system on the 1.4 Golf. It's not just direct fuel injection, but there's lots of other clever stuff - the water temperature is different when the engine is in FSI mode, the throttle is opened wide in FSI mode and the engine speed is controlled by the amount of fuel injected (just like in a diesel) - which means that a vacuum reservoir is needed to provide a vacuum for the brake servo and the flap that redirects intake air between 2 or 4 valves per cylinder, it also explains how the fuel injection strategy is different during a cold start and hence why the RS4 sounds MUCH noisier during the first minute or so after a cold start.

I don't know how to post a pdf file here, but I'm happy to email it anyone who PMs me.

Hello

I would be realy happy if you could send it to me, because i'm realy intersted in this techology(student of mechanical engineering).

Here is my email: mihajeraj(a)mail386.com I assume you will figure out the email adress.

Thank you very much.

PetrolDave wrote:

Dave - do you work for Audi?

No, never have done. I did work for Lotus between 1988 and 1994 though.

In one of my surfing sessions I found a pdf that explains in quite a lot of detail the FSI system on the 1.4 Golf. It's not just direct fuel injection, but there's lots of other clever stuff - the water temperature is different when the engine is in FSI mode, the throttle is opened wide in FSI mode and the engine speed is controlled by the amount of fuel injected (just like in a diesel) - which means that a vacuum reservoir is needed to provide a vacuum for the brake servo and the flap that redirects intake air between 2 or 4 valves per cylinder, it also explains how the fuel injection strategy is different during a cold start and hence why the RS4 sounds MUCH noisier during the first minute or so after a cold start.

I don't know how to post a pdf file here, but I'm happy to email it anyone who PMs me.

Excellent Dave