S-type R engine update

[PhilC]

I read in Jaguar World that the power of the S-type R was increased in the later versions (ie prior to the installation in the XF-SV8 where power is quoted as 420 bhp). Can anyone confirm if this engine was installed in the later S-type R and from what engine number.
Phil Cheetham

[Montana5]

Hi Phil, I really think that this is one of those myths that go about, If the article you refer to is the same one I saw when the Magazine did a 'Supercharged Special' feature, they said it was uprated by 20 BHP with the 2004 facelift. It took me over 16 Months to find my Car and I looked at 2002 to 2007 model year Cars when searching, yet never came across any 420 BHP versions. (there were a few oddballs that claimed 450 BHP etc)
I reckon this was a mistake by the magazine.
In the Jan 2011 edition, Jaguar World did a head to head test between the S Type R and the XJR, the STR used for the report was a 57 plate, it was definitely 400 BHP.
I believe to get the 420 BHP you needed to fit the smaller Supercharger Pulley Kit and additional Airbox, like as you say in the early 4.2 XF SV8, hence the saying 1 Airbox = 400 BHP, 2 Airboxes = 420 BHP.
I tend to keep an open mind about these things so quite happy to stand corrected.

Doug.