When you line up at the lights next to a BMW it’s
always wise to first look at the badges on the boot lid. If you can see the
letter M you’d better be careful – M3, M5 and M Coupes have the grunt to well
and truly ruin your day. But numbers like 316, 320 and – to a lesser extent –
325s are pretty easy prey. You can dump the clutch with confidence.
But beware of this 325ti owned by Sydneysider
This compact Beemer maintains a classy, smooth
look and there’s nothing to hint to its performance. It's quiet, it
idles smoothly and everything seems fairly sedate. But when Michael flicks his
way up through the gears using the M3-style paddle shifters, you’d better be
prepared to be dealt a blow from its imported supercharger kit. BMW badge theory
goes down the toilet...
This 2002 E46 BMW 325ti was purchased second-hand
by Michael a couple of years ago after he was impressed with the style and
finish of his previous 733i. The ti provides that same satisfaction of ownership
but Michael felt that the 2.5-litre engine could do with a little more poke. And
here enters Bavariacars Motorsport.
Herbert Gattermeier of Bavariacars suggested the
fitment of an Infinitas SK Stage One supercharger kit – one of the first in the
country. So what on earth is the Infinitas SK supercharger kit? Well, at the
heart of the system is a compact and quiet ASA TM1-12 centrifugal supercharger
which is mounted on a CNC-machined aluminium bracket. The kit also comprises all
necessary pulleys and belts and, interestingly, the ASA blower must be
integrated into the engine’s lubrication system using a T-piece at the oil
pressure sensor and a return fitting in the sump. The compressor draws air
through a K&N pod filter.
In the entry-level SK Plus kit you don’t get any
form of charge-air cooling but in the Stage One kit (as chosen by Michael) you
receive a 12-row air-to-air intercooler that nestles into the nose without any
cutting or grinding. The core has been painted matt black to ensure a stealth
installation. The intercooler plumbing is TIG welded stainless steel equipped
with twin Bosch blow-off valves and maximum boost pressure is a conservative 0.4
Bar (6 psi).
Erik Gattermeier from Bavariacars recalls that the
standard 325ti maintained a stoichiometric air-fuel ratio at WOT to about 5000
rpm, at which point it richened into around 12.5:1. By installing the supplied
ASAtronic controller (which modifies the airflow meter output) and a new fuel
pressure regulator with modified lines, the car now holds stoichiometric to
around 5000 rpm and richens to 11.8:1 near full power. The injectors and fuel
pump remain standard.
With the off-the-shelf blower kit fitted and
tuned, Michael’s 325ti was elevated from its standard output of 101kW at the
wheels to 161kW at the wheels (a gain of 59 percent). Infinitas claims 199kW at
the flywheel along with 320Nm of torque. In addition, Michael has recently added
an Eisenmann high-flow exhaust which has been modified for extra noise
suppression. The new exhaust should theoretically release around 10kW for a
total output just over 200kW. (Incidentally, the Stage 2 Infinitas SK blower kit
comes with an upgrade exhaust, slightly more boost and accompanying tuning
changes to deliver a claimed 213kW.)
The supercharger gave the 325ti a much greater
power output but there were a couple of other mods necessary to help make this
newfound extra grunt more accessible in normal driving. First, the standard diff
ratio was shortened from 3.25 to 3.46:1 to sharpen response without causing
excessively high cruise rpm on the highway. We’re told that a limited selection
of compatible diff centres prevented employing an even shorter ratio. The next
step was the fitment of a US-sourced M3-style paddle shift system which
integrates with the standard Steptronic transmission and wiring loom. A M3
steering wheel is also included as part of the upgrade. The paddle shift system
makes it much easier to drop the engine back a ratio or two and bring the engine
Braking performance has been massively boosted
using E46 M3 discs teamed with Porsche GT3 4-pot calipers mounted on custom
machined brackets. Braided stainless steel brake lines are also included.
Subtle styling changes distinguish Michael 325ti
from other examples. A Rieger body kit gives a M3-like appearance thanks to
front and rear bumper extensions and side skirts. The standard wheels are also
replaced by 17 inch BBS jobs wearing Continental tyres. These give extra grip
while an aluminium tower brace improves front-end rigidity. The M3 steering
wheel and paddle gear shifter is the only change to the standard leather-lined
This is one of Bavariacar’s first experiences with
the Infinitas blower system and they’ve come away impressed by the quality
construction, ease of fitment and performance. Herbert Gattermeier says the car
now offers straight-line performance that feels similar to the expensive M3
(which is slightly heavier than the 325ti). At present, Michael has no further
plans for modification as there are some concerns regarding the strength of the
transmission. But if the transmission were to fail Michael wouldn’t be too
disappointed – he’d probably switch to a high-strength manual gearbox and pursue
even more power.
But we don’t think that’d be fair without some
reorganisation of the numbers on the boot lid!
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