re: Cold Air Intakes/ + dyno numbers

[jkerouac@xxxxxxxxxxxxx]

re: Cold Air Intakes

Cold Air intake snouts as sold by many tuners are misnamed.
They are not cold air intakes as much as they are
'not as hot' air intakes.

What they do is decrease the amount of hot ambient air from the radiator

that gets to the intake.  This is accomplished by a snout that:
+  picks up air lower and further away fromthe radiator
+  may include a separating partition to block hot radiator airflow to
the intake opening.

Is this necessary?
how effective is it?

The mechanical fan is a big contributor towards hot ambient radiator air
being directed outward to the inlet of the air intake.  It is easily
removed, improves throttle response,and costs nothing.

Snout alternatives:
The tuners who show dyno charts always use the stock factory airbox and
counter-aerodynamic shaped accordion intake tube from the radiator
support.

The accordion zigzag tube, due to its mounting position, actually picks
up heat from the radiator.

But can the factory airbox be improved at zero cost?  You bet it can.
Inside that airbox is what BMW calls an "intake noise silencer".  It is
an airhorn that considerably restricts the intake airflow.  It is the
most commonly removed 'cheater' item in stock class competitions.
     I call it choking the chicken.
By simply removing both the airhorn from inside the airbox, and the
accordion zigzag tube to the radiator support, you will increase your
acceleration by at least one tenth of a second from 60 to eight in
third, roughly .2 on a zero to sixty.  (on a 318ti, the airhorn removal
gave a repeatable quarter second faster consistently.)

     Drawbacks?  The big open hole does help increase power, however
being right in the front of the airbox is too open and too close to the
air filter.  So you get too much drone and not enough air velocity to
take best advantage of the bigger opening.

     Next step is to make a better inlet for the airbox.  This is the
Home Depot modification.
What you want:
1x 4 to 6 inch straight flexible rubber plumbing coupler, like toilet
bowl drain pipes in houses are connected with.
1x 3 inch curved right angle flexible rubber plumbing coupling. (only if
outside air feed is desired)

Clamp the 4 inch side of the flexible rubber coupling to the hole in the
front of the airbox.
Reinstall the airbox.
     The rubber will need to bend to the right clear the inside of the
headlight assemble.  The bending is actually better for air velocity
than an open straight shot.  If you have ellipsoids you need to make a
small cutout to clear the electrical connector plug.  Then you also get
a better inlet due to how the rubber will bend to behid the high beam
bulb cover too.

What does this setup due compared to the $400. carbon tubes and
'special' computer remappings for them?

Here's the results of a dyno testing day that Bay Bimmerz conducted
recently.  It was hot and all numbers were on the low side compared to
known cars and benchmarks.  So your exact dyno numbers may vary, however
your results relative to other modification will tell you the value of
what you have done.

All cars had a free flowing exhaust, either Dinan, AA, or Supersprint.
All cars had some sort of computer remapping.
     My car has the most recent remapping that BMW will give you, it is
typically installed with the crankshaft position sensor recall.  I found
that was not measureable with repeated stopwatch runs to what the Dinan
mapping ran like.

Results of several cars:
all peak torque around 4200.  All peak HP with standard AFM @61/6200

Tops HP
1995 3.0 liter, with Dinan snout and Euro afm, 225hp @6500 209 torque
Tops TORQUE
1997 3.2 liter, with airbox as described above, and fan removed. 218 hp,
213 torque
others:
All Dinan:
 3.2 liter, Dinan Snout, stage 2 ECU, Dinan exhaust  221hp, 211 torque

There were several other //M3 with Conforti or Dinan snouts, chips, and
exhausts, all which
dynoed at under 213 hp and under 209 torque.

So it seems I can argue a valid case for the factory airbox as altered
above, with the
freebie remap from BMW, as an equivalent for $750. wortih of hardware
and remapping from Dinan, and as superior in acrual performance.

While my total cost was under $20. to Home Depot.

Enjoy,
'jk

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