An S4, GT cams and an x-pipe are good for 320+ rwhp with a 5-speed.

 

I live/work in a "no x-pipe allowed" location, so I have no "real world" experience with these items.

However, what you have said means that simply installing a X-pipe on a S4, (also equipped with only GT cams), turns a S4 into having as much rear wheel horsepower as a GT has flywheel horsepower?
(Negating the fact that a GT has hand selected heads, slightly higher compression, match ported intake manifold to the heads, and different tuning.)

What happens when GT gets an X-pipe?

 

You must have "Angst" (fear) to open the driver door and start the car!

Btw, aren't GT cams nla?

Edit: Rose Passion has them, a set near 3.000 €

 

Greg an X pipe from Motorsport in UT. installed on a S4 will give it 25 more HP .
Its clearly a noticeable increase.
I was working their when they were developing them with the blessing of Louie Ott ,
yes I have one for my yellow car,
I could break the rear wheels free in Drive with the X installed and 265 35 / 18 pilot sports installed,
Stock cats not really a chance.

 

Only one way to know..share the data.

 

Bonjour,
I get the exact same result than Mrmerlin on my S4. She goes from 320hp (mesured with the accelerometers of an Iphone with an app that calculate power based on the measured weight of the car) to 340HP.
It is the only real significant improvement I get with my car so far. Since then, no matter what I tried to improved, I get globally stuck at about 340HP for max power for my stock car.)

I remember the first day I drove the car with my custom X pipe : the engine was like telling me «thank you so much »… he was like breathing much much more easily. It does like if something pop out and the air in the engine was not blocked anymore… I remember this obvious difference and the engine like breathing normally for the first time!

Best regards,
Raphael

 

Bonjour,
Here are the data I gathered.
The black curve is Stock power curve>
Orange is my first testing, before I get my X pipe and before I tried anything on the car. At that time I did not realized that my S4 was fitted with a LH of a GT car. I bought the car like this. I discovered this after I installed the X pipe. When I tried a correct LH (for a S4), the top end of the power curved was improved so I exchanged my LH with another 928 owner that needs a GT LH. I think it is normal to get the top end drop because of incorrect fuel map (too rich).
In green is the best I get with all kind of improvements I tried. I get the same results with Ken, John or my shartuned experiments on ezk map with E85.


When I will get my regrind camshafts, If they are significantly improved, I will verify if it really improve something.
I know it is not dyno testing but so far results look consistent.
Best regards,
Raphaël