As you go through this, keep in mind that these are simply my opinions, some valid, some probably not. I do not claim the mantle of "expert," honestly I am not one, nor am I a professional mechanic or a race car driver. These are just the misguided opinions of an M3 fan....
Before you read my ravings, read this write up by Jim Comforti on the subject of software, et al (posted at RoadFly E46 M3 Forum 5/31/03) - If you don't know who Comforti is in regard to tuning BMW's you really should find out.
Folks, I've said it once.. I'll say it again.. there is very
little cheap horsepower (read: from software) to be gained
from the E46 M3.
I'll bet that I've spent more butt time and dyno time combined
than anyone else in America (outside of factory folk) with the S54B32
motor in both of it's forms. In 2 different M3's (my wife's and
Josh MacMurray's) and my M Roadster.
In the M3 form, there are SIX legitimate RWHP to be gained.
Software and HEADERS/CATS yeild about 8RWHP, but a significant
gain in torque midrange (about 10 lb-ft RWT).
See, there are esssentially 5 things you can tune at wide open
throttle on the M3. I doubt if most tuners even mess with
the third one below.. but it does exist.
You can tune the fuel.
You can tune the ignition timing
You can tune the actual opening of the throttle plates (as opposed
to pressing the pedal.. 100% of pedal does NOT mean 100% of throttle)
You can tune the timing/sync of the intake cam VANOS
You can tune the timing/sync of the exhaust cam VANOS
You can do all 5 of those in some happy combinations.
You can spend too many hours on a dyno until you are cuckoo from
the CO and HC fumes you're breathing.
You will gain SIX REAL HP.
Same Day, Same Car, Same Dyno, Same FUEL, everything.
That's it.. SIX.
We've done it.. software is being released THIS week.
(It's real easy to play dyno games with this motor by changing fuels
and then running the ignition timing up to create GOBS of power with
say 110 octane race fuel.. the same timing with 91-94 octane street
fuels will destroy the motor before you can say "Oh sh*t there goes
To gain more you need to change HARDWARE.
To go from the 270something range.. 272-278 or so. to the 295-300
range you need to change:
Headers (and necessarily the CATS), then you need to open up the motor
and using $1000+ of special tools and a LOT of finesse and patience
you need to change the cams.
If you use BIG cams.. say 280 or greater.. you have NO error in the
position/sync of the cams statically. If you screw it up, you WILL
bend valves before the word "GO".
We've done the cam installs.. (No, we didn't bend valves ;)
To gain about 10% in power you will spend around $6,000 in parts alone
(Yes, OWWWCH!.. and just think, we have to buy all this stuff just to
test it.. then pull it off and most times JUNK it because it didn't
work like we wanted.. at least we get to keep the "good" stuff tho)
Note, I didn't include any software costs, and software is absolutely
NEEDED if you goto headers/cams. Those who don't believe me can try
it and report back with the melted motors. (Hint: in one test of cams
without software the vehicle hit the "lean stop" and set a MIL within
a few hours) that ONE test was the last w/o software as we found the
fueling to be significantly leaner than even the "lean stop".
With tuned software, you can get about +8-10 with headers/cats alone
and anywhere from 14-30 with headers/cats/cams.
For those who want to argue.. let me offer you this.. there are quite
a few in this country successfully running cams/headers/etc. They got
their software from a source outside the contintental US. They know
who they are and who I am talking about in a warm climate with very
good Pina Coladas. I developed that software and have been "secretly"
working on this stuff for WELL over 2 years now.
The funny thing is that the numbers they are all getting (300+rwhp) are
coming from experimental software (not finished) of mine.. the final
software gives no more HP really, but you can run cams and not stall.
PS: Now everyone can pipe in how "someone" got 300rwhp from some magic
intake and software.. it's not real people. trust me it isn't.
Ask any REAL tuner out there and they'll tell you.'
If you feel the need to waste money, I'd suggest you find a worthy
church, charity, or even a local watering hole and blow your money
their instead of wasting it on smoke and mirrors.
And now, for my ravings:
- Unless you plan tracking your M3 there is probably very little reason to upgrade your stock brake system. Being in the US, we got short changed on rotors by BMWNA. Other parts of the world get drilled rotors, we get solid ones. Do the Euro drilled rotors do anything to stop the car faster - that's fairly doubtful - but they do look better (but make more noise, eat pads faster and do not last as long). Good basic street and track mod would be to change out the stock brake lines, fluid and pads. Stainless steel lines do not expand from pressure or temperature and thus provide better brake feel in heavy repeated use. Upgrade pads will give a bit more grip and run cooler, especially under heavy use and better brake fluid will resist temperature better providing more consistent feel. Upgrading to Brembo, StopTech or someone else big brake systems is purely aesthetic when used on the street. You will not stop any faster with Brembo big brake upgrades under street conditions. On the other hand, after 10 hard stops you will stop better with Brembo's than with stock. Otherwise, Brembo, etc. will give much better repeatability once the brakes are hot than stock which is rather important on the track but probably not useful on the street. I do have to admit that those big Brembo calipers and rotors look great on the car - but probably not great enough to justify $3000+ (front only) or $5000+ (front and rear). If you are frugal and vain you can always paint you stock calipers and get Euro spec drilled rotors - complete mod would be under $1000.
- Exhaust is a popular modification for E46 M3's. Many understand that an after market "free-flow" exhaust system will simply change the way the car sounds and not provide any tangible performance benefit. The thing with the E46 M3 is that the exhaust is very good from the factory (performance vise at least) and that most after market exhausts do not provide a power gain. Conversely, many after market exhausts actually prove to be detrimental to performance. A quick examination of the already dubious dyno number provided by exhaust manufacturers show that there tends to be a power LOSS at RPM ranges below around 4500 - 5000 RPM and a small gain at 7000 - 8000 RPM. This is actually typical for "free flow" systems and some argue that this is due to a loss of back pressure down in the lower RPM's. My theory is that unless you change the software and make intake (and possibly cam) mods you will make more noise, suffer low end power loss (people describe it as being similar to having your AC on) and gain very, very little at 8000 RPM. My thought on this is that if you really want to make noise then get that exhaust system, if you think you will make more usable power form just an exhaust, you're delusional. A little psychology: The human mind associates noise with speed, just because a car is louder it does not mean that its faster.
- Springs are a popular mod for both handling and appearance reasons. Aftermarket springs typically lower the car and thus lower the center of gravity which is always a good thing for handling. Stiffer spring rates also server to tighten up handling. Its not all good though. If you simply replace springs with HR or Eibach, etc you have to keep in mind that your car's stock shocks will not be matched to them. This will lead to a severe shortening of the shocks' life span (typically reduced to 5-10K miles with springs). Also, since your shocks and springs will no longer be matched up you can expect a reduction in ride quality. If you like the way the car looks lowered, then you will probably be very happy with the way the car looks with springs installed. Remember that it will take a few hundred miles for the springs to "seat" properly so ride height will change a little at first from the original installation height. I really think that this is a stop-gap measure. If you really want to improve performance and retain a good level of ride quality and not destroy your stock shocks then a full coilover system is probably a much better bet. Another thing to keep in mind is that you should have your car's alignment checked about 200-300 miles after the spring instal.
- Strut Brace
- "The cheapest performance mod that you can actually feel!" Or so I think. For $300 or less you can do a mod you can really feel (especially those of you with cabs). The strut brace ties together your strut towers and keeps them from deflecting under hard cornering. When strut towers deflect they also change the camber of your front suspension and thus the amount of rubber you are laying down on the road. The more the strut is deflected, the less rubber you have on the ground - less rubber = bad. Tieing the towers together with a strut brace is very effective in reducing this deflection. Any race car you will ever look at will have significant reinforcement of the engine compartment and while it is impractical to have all of the bracing a race car has on a street machine it makes sense to spend the $300 and 15 minutes to tighten things up. You WILL feel the different the first time you take a hard corner! There are typically two types of strut braces - hinged and solid. Call me crazy but I think that solid bars are better than hinged (which are cheaper to make). Since tieing things together is the main goal using a solid strut brace makes more sense to me. The BMW OEM strut brace seems to be the ideal solution both for price and function.
Review of BMW's Strut Brace | DIY for BMW Strut Brace
- Sway Bars
- Sway bars are another simple and inexpensive mod that you can really feel.
Replacing stock sways with a set of quality sway bars from Eibach or Ground Control will reduce the amount of body roll your car has and lend to greater control and better road feel.
Sways are a fairly simple installation and the results are readily apparent.
Sway bars can typically be adjusted (Eibach: front bar only, GC: front and rear). By changing the stiffness of the bars you can effect the oversteer/understeer tendency of the car.
Some people claim that there is an issue with GC sways with OEM suspensions when placing the car on a lift (the sway sits higher and the half shafts can in theory rest on the rear sway) - is this actually a problem? Probably not - the fear is that the weight of the rear suspension and wheel can strip sway bar brackets. I seriously doubt this would happen and I've never heard of this actually occurring. One end of the sway bar can be easily released before placing the car on a lift if this is a concern. This is not an issue with Eibach sways (at least not with OEM suspension).
Make sure to get sways from someone with a good reputation (GC, Eibach, UUC) as a poorly designed set can accentuate the car's already apparent understeer qualities or go too far the other way and induce serious oversteer and lead to other poor handling issues.
I run Eibach - simply because I got them at an unbelievable price and because they do everything I want them to do - though they do lack some of the adjustability of GC sways. For quality, design and adjustability GC sway are really hard to beat. At around $600 its really hard to come up with a valid reason to pick UUC sways over GC.
Also, start with the recommended factory settings on adjustable sways and work slowly from there.
Adjusting the stiffness of sways can lead to dangerous results to a novice (especially where the rear sway bar is concerned).