P38 Stainless Exhaust

I was thinking of getting a stainless "sports" exhaust for my RR,
something like the Janspeed or Rimmer Bros offerings. What kind of BHP
increase could I expect, if fitted along with a K&N or similar filter?

What is the best value (ie biggest increase per £) way to increase
horespower on a 4.6? (Don't say "take the air filter out" !!!). I
love my RR but it feels a bit slow sometimes.

Cheers,
Chrisall.

<[email protected]> wrote in message
news:[email protected]...
I was thinking of getting a stainless "sports" exhaust for my RR,
something like the Janspeed or Rimmer Bros offerings. What kind of BHP
increase could I expect, if fitted along with a K&N or similar filter?

What is the best value (ie biggest increase per £) way to increase
horespower on a 4.6? (Don't say "take the air filter out" !!!). I
love my RR but it feels a bit slow sometimes.

Cheers,
Chrisall.

The std exhaust system isn't really that bad, any restriction that there is
will be in the cats and rear sections. The std manifolds are of a very good
design, I would advise against replacing them with aftermarket items as they
work very well and have been used on engines producing way in excess of the
std power figures.
I'd imagine a sports system connected to the std front end, coupled with a
k&n filter, may give 5 or 6 bhp more at the top-end, BUT how often is the
engine being used right at the top-end? My preferred option would be to fit
a mild-road spec camshaft, a bit of gas flowing work on the heads, then a
re-chip from Mark Adams of Pharmhouse Marketing, hopefully getting another
20 or so bhp with a useful boost in midrange torque. Mark is THE guru with
remapping/chipping these ecu's, he actually does the chips that just about
everyone else sells. (I've used other people's chips, and there's no
comparison!)
Badger.

"> The std exhaust system isn't really that bad, any restriction that there
is
> will be in the cats and rear sections. >

I would concur with the badger. Exhaust design usually involves solving some
2D second order patiral differential equations. In the words of my maths
lecturer, "these bunnies are not your friends." Usually these have to be
solved numerically and this requires cunning software and much forethought.

You will also notice that most newer vehicles headers/manifolds are not
riddled with 90deg bends, folds, creases and other such piffle, as used to
be the case in years gone by, so usually these are pretty close to the
optimum design.

The other thought that enters my noggin, "How can a 4.6V8 not be powerful
enough?!" Are you drag racing with the chavs? Apart from badgers suggestion,
might I suggest flogging the RaRo and getting somthing more suited to the
task, like a Jag XKR or similar.

Regards
Stephen

<i>The other thought that enters my noggin, "How can a 4.6V8 not be
powerful
enough?!"</i>

Because 221BHP through an auto box trying to shift 2 & 1/2 ton is never
going to give spectacular acceleration is it!!!

<i>The std exhaust system isn't really that bad, any restriction that
there is
will be in the cats and rear sections</i>

I would say the standerd rear section was dire myself. After the
centre box the pipe comes to more-or-less a perfect T junction,
90degrees either left or right to the back boxes.

Cheers,
Chris.

On Fri, 18 Aug 2006 12:48:32 +0100, <[email protected]> wrote:

> <i>The other thought that enters my noggin, "How can a 4.6V8 not be
> powerful
> enough?!"</i>
>
> Because 221BHP through an auto box trying to shift 2 & 1/2 ton is never
> going to give spectacular acceleration is it!!!

depends on the definition of 'spectacular' I'd guess.

/any/ measurable acceleration in such circumstance is a marvel of modern
engineering <g>

--
William Tasso

Land Rover - 110 V8
Discovery - V8