… not that the stock M5 is a flexy-flier by any
means, but you can always improve rigidity by adding front & rear strut
tower braces:
The stock M5 handles extremely well… for a 4000lb
sedan. However it understeers moderately, especially at low speeds,
and both front tires bear the brunt of any heavy cornering. The Dinan
stage 3 suspension setup replaces springs, sway bars, adds camber plates
for more negative camber in front, and replaces the stock shocks &
struts with adjustable Konis on all four corners. The change
lowers the car about ½”, which is barely noticeable (see picture).
However, the vehicle’s handling is transformed – it is as if 400 lbs had
been removed from the vehicle. It now turns in instantly with near-zero
body lean, and holds a tight line even in slow corners. All this,
yet the ride quality is almost indistinguishable from the stock vehicle’s;
unless you’re actively looking for clues, this could be a stock car… at
least until you turn the wheel. Dinan’s magic with suspension seems
to be the ability to make any BMW handle like an all-out sports car while
still riding like a luxury vehicle. They’ve done it again with this
package.
The stock M5 is a very fast sedan – it leaves the factory
with 330 rear-wheel horsepower, will accelerate from 0-60 in 4.7 seconds and
will cover the ¼ mile in 13.1s @ 108mph. However, your humble editor
is a somewhat jaded horsepower junkie;
my previous car
did the quarter mile in 11.0 @ 131. The M5 isn’t likely to threaten those
figures, but by opening up the intake and exhaust and adding a bit of pressurized
breathing, the M5’s 5.0 liter V8 should be able to make close to 500 rear-wheel
HP. Stay tuned for further developments…
Step 3a - The Exhaust:
As a rule, stock exhaust systems are fairly restrictive. In the case
of the M5, the exhaust system in isolation is not a major bottleneck.
However, swapping the stock cans for a pair of Dinan stainless units added
7 HP, dropped 30 lbs (!), and added a pleasing, Corvette-baiting exhaust
note to an otherwise sleeper car:
With the exhaust and ECU mods, the M5 doesn't pick up any peak horsepower
on the dyno, but horsepower and torque improve 3% throughout the low-to-mid
RPMs. The chart below has my M5 in blue and a bone stock M5 in red.
Note the power increase everywhere except the top end:
Step 3b - The Intake:
Swapping the stock airboxes, hoses & resonators for a pair of beautiful
carbon-fiber Dinan cold-air intakes with K&N filters allows the engine
to breath a bit more easily. Pictures and dyno figures to come shortly...
