“At first we wanted to keep it Stage One, which meant just
the supercharger kit with no intercooler and retaining the standard inlet
plenum,” remembers Tony. “With a smaller pulley it made 560hp first time out
like that. But the heat soak wasn’t good and we really wanted to avoid that as
other kits suffer from it. We wanted to develop a kit that could deal with the
extra heat much more efficiently so it could make the same power time and time
again rather than have the figures drop as it gets hotter.”
So the decision was made to add an intercooler to the
equation to cool the charge, but this meant keeping the standard look would be
more of a challenge as usually intercoolers are front mounted and on show to
ensure good airflow. Wanting to avoid that, a smaller intercooler with a more
efficient core was shoehorned in front of the driver’s side arch liner and fed
cold air from the fog light recess. Additional venting was made to the arch
liner so air could freely pass through the intercooler and the result is a neat
fitment with no cutting of the bumper or cross member required.
Supercharger kit
has been carefully designed to integrate perfectly into the engine bay without
disturbing anything too much. It certainly looks at home
Next came further development of the package and after a lot
of testing, the weak link proved to be the standard inlet plenum, as Tony tells
us: “I have done around 16,000 miles with this kit fitted and as the car has
been used as the test mule, it’s done plenty of spirited driving and countless
power runs. It was through playing around with high boost settings that we
eventually cracked the standard plenum…”
Seen simply as the next hurdle to tackle, the answer was to
create a complete replacement plenum setup that was CAD-designed and CNC
-milled from billet alloy. It’s stronger yet still looks factory and was fitted
inside with shorter inlet runners to improve the engine’s throttle response at
the same time. “That made the biggest difference as it went from 595hp to 622hp
but using less boost so the engine and Rotrex aren’t working as hard. It’s on
just 6.5psi on this current setup,” Tony enthuses.
With all that extra power you might think it would feel very
unhinged out on the road, but we’re told the reality is very different. “It’s not
like the leap from naturally aspirated to a turbo where you get a massive
torque spike come in, the supercharger just makes everything feel a bit better.
It’s so linear and there’s torque everywhere, whatever the gear. It’s such a
nice all-rounder and for a 14-year-old car it really is so good to drive. I
find myself driving newer and sometimes even faster cars but they never feel as
good, I’m always glad to get back into this and I think that says a lot.”
The back of BMW M5
At this point, Tony offers to take me for a spin to
experience it for myself and sure enough, it’s exactly as he says. At low speed
it feels virtually like a standard M5, except you can afford to be a gear or
two higher and it still begins to pull from early down in the rev range. But
with the taps fully opened the car gains pace at a tremendous rate, catapulting
you forwards but in an unnervingly calm manner. It picks up speed quickly yet
it’s all very steady, calm and composed. It makes far less commotion than any
other 600+hp car I have been in but it still gains speed furiously and
continues to do so as the needles on both the rev counter and speedo indicate.
The car’s power feels smooth and linear like a standard M5 but it’s as if it
has gained an extra few litres of capacity. And aside from the odd hiss
expelled from under the bonnet, you would genuinely struggle to realise it’s
supercharged other than the increased performance.
Mission accomplished for Tony and the guys at Evolve, then,
as it really does feel like a re-engineered M5 rather than a heavily modified
one. Tony agrees: “From the start I wanted a nice, subtle conversion kit and I
wanted it so you couldn’t necessarily tell there was anything done at all from
the outside. It was never going to be a mass designed kit, we just wanted the
definitive kit, the best you could get if you wanted to supercharge one of
these.”
There are now a few of these converted cars on the road and
Tony’s is one of the most subtle. The vented bonnet is arguably the one
giveaway, but it’s there for a purpose. “Fitting the bonnet actually dropped
temperature in the engine bay by 15 degrees, it actually does work. Although I
do want to swap back to my old bonnet now as you do get a bit more engine
noise.”
As refined and well-finished as Tony’s M5 is, the plan now
is to put the car up for sale, as he has now decided to get back into track
days, and as much fun as the M5 is, it’s no track car. “I love the car but you
can’t get away from the fact it’s heavy. I miss going out on track so I’m now
planning on building a BMW-based track car. I’m thinking a track-focused E46
GTR replica with metal arches and 500hp. The guys at Evolve are on board with
it, too.”
The vented bonnet
actually works well in reducing engine bay temperatures, so it’s staying in place
for now.
Let’s hope Tony won’t regret selling this one as well, but
at least he has a plan in store for a replacement this time. He certainly knows
how to modify a car the right way, which means his next one should be
interesting…
