<E36><M3) More Incremental Bang for the Buck

["Franklin W. Nelson" <fnelson@xxxxxxxxxxxxx>]

For those of you interested in this project of mine, here are my "interim"
conclusions:

1. Cams sound sexy, but there don't seem to be any cam profiles available
that make and real additional trq/hp below 5k rpm.  Above 5k, however, you
can get about 15hp (at about 6krpm).  Not the way to go for me, though. $2k
(parts and installation) for 15hp I can only use every once in a while
doesn't sound like much of a deal.
2. The reason some tuners (e.g., Dinan) recommend high-flow injectors with
their euro hfm setup is that, with this setup, in the high-rpm ranges, the
injectors are operating at 100% duty cycle.  If the car is being driven at
high rpms for extended periods (e.g., at the track) the injectors will
eventually overheat and performance will degrade.  This means that high-flow
injectors don't increase performance, but merely ensure maximum performance
under extreme conditions.  It also means that if you don't track your car,
you probably don't need them.
3. It's starting to look like the reason there's nothing available for my
car to improve low-mid trq and/or rpm is that the motor's already making as
much as it can in its current configuration.  This means that the only way
to improve low-mid range acceleration is to either increase the displacement
(via stroking and/or boring - not an option for me) or to reduce rotating
mass and/or improve the mechanical advantage of the drivetrain (i.e., change
gearing)
4. Lightening the flywheel appears to be by far the cheapest way to reduce
rotating mass.  About $1,100 (parts and labor) will reduce rotating mass by
about 15-17lbs.  Testimonials confirm that this produces noticeable results.
Methods to further reduce rotating mass are pretty expensive (lightened
crank, rods and pistons).  If I buy the flywheel from Turner, I can also buy
a modified chip which will bump idle by 100rpm, thereby reducing/eliminating
(in theory) the transmission rattle associated with this mod.
5. Replacing the stock 3.15 differential with a lower (numerically higher)
ratio is the simplest way to improve the mechanical advantage of the
drivetrain. 3.46 is the ratio recommended by Korman and that sounds about
right to me (a little less than 10%). Korman also offers a Quaife
differential, which is "infinitely variable" as opposed to the 25/50/75%,
etc. lock offered by traditional clutch-type differentials, and it's also
stronger.  Sounds good to me, but it's also expensive at $1,600 (not
including installation).  If I'm going to spend this much $, I'm tempted to
buy the Alpina differential cover (about $700) just because it looks so
cool.

Based on the above "interim" conclusions, it looks as if

1. Opening up the induction side of things the way I did (open element
filter, euro hfm, software to make it all work) did indeed provide the most
initial "bang for the buck.  It cost me about $1,200 (including labor) but
netted me 28 hp, and a lot of it at reasonable rpm levels where I can use
it.
2. The next step (unless you're a track jockey) would be the lightened
flywheel, mostly because it's the next cheapest.  For about $1,100 I'll get
quicker throttle response throughout the rpm range and improved
acceleration - particularly in the low/mid rpm ranges.
3. The final step would be the Quafe limited slip, which will further
improve throttle response and low-end acceleration, and will also make me
faster out of the corners.

The strangest part about all of this is that a modified exhaust doesn't seem
to be in the picture at all.  Near as I can tell, aftermarket exhausts may
sound neat, but they don't really offer any real performance increases.
Yet, this is the first modification most people seem to choose.

Once I get all of this installed, I may not SOUND fast, or LOOK fast (no
///M badges on my car), but I should BE fast, which is where I wanted to go.

If anyone has comments/suggestions/objections to my conclusions, please let
me know (hopefully BEFORE I start writing checks!)

Cheers!

Frank Nelson
BMWCCA Los Angeles Chapter
'95 M3, JC chip, euro hfm, Dinan cold air intake, and more to come

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