.se domain is SWEDEN. There's a pretty simple explanation about all this. And that explanation is different countries use different measuring standards, and the numbers they yield, on the same identical engine, may look different but is in fact, the same. For example, the original spec for European S54 engine is rated in Kilowatts for power, and Newton Meters for torque. Standard metric measurements that us 'Merkins don't use. To convert it to imperial measuring units (Horse Power and #ft) is a simple process. The confusion comes from differences in international measuring standards and differences between a British yard and American yard (literally). Let's take the base European power rating on the S54 of 252 Kilowatts. 252 Kilowatts converts into 342.62 Metric Horse Power (PS), or the common 343HP that we often see quoted by European publications. The same 252 Kilowatts converts to 337.94 standard Horse Power as measured by DIN standards, the common "standard" measure in Europe, which is the 338 number often quoted by British magazines (because Standard measures like pounds, inches, and yards is what British "imperial" measuring units are). To complicate the matter more, U.S. measuring standards, SAE, differs from DIN measuring standards. 1 SAE HP = 1.0139 DIN HP. 337.94 DIN horsepower as quoted by European standards = 333.37 SAE HP, which is what's commonly referred to as the standard HP output here in the United States for the S54 output on E46 M3s. This is the HP as measured by BMW at the crank of an S54 engine capable of revving up to 8,000 RPM. Now, horse power as measured at the wheels is a lot different. A dyno machine usually takes a measurement and then a voodoo formula applied to the number to adjust for atmospheric conditions, parasitic driveline loss, final gear ration and gear ratio as tested. Dyno numbers from car to car, from dyno to dyno, of the same brand, can vary as much as 10%. The numbers quoted above from the Swedish company that makes dyno testing machines seems to read much higher than typical result, most of the dyno readings on the MZ4 S54 engine seems to fall between 280-290 rwhp, and the 335i N54 engine seems to fall between 260-270 rwhp. At least the dyno is off by a fairly consistent basis. Also keep in mind that production tolerances may account for up to 5% difference in actual engine output. I've once witnessed two nearly identical E46 330Ci produce a pretty dramatic difference on the same dyno ran back to back. Somebody correct my math above if it's wrong.
also you need to account for the US emission restrictions that reduce the HP we get on our cars compared to euro versions.
Why would US emissions be that much more restrictive? The engine block is the same, the only major difference is the catalytic converter is on the header in addition to the mid-pipe. The stock software is tuned to the engine with or without the catalytic converter present on the exhaust header. The "emission restrictions" that reduce HP? Amounts to 3 HP on the MZ4. 333hp vs. 330hp. The days where U.S. emissions robbing us of major HP is long over. EU emission standards are just as tough, if not tougher than California emission standards. Most of the HP difference you see quoted between HP for overseas market and US market is now simply down to the difference between DIN and SAE measurement standards. Take the only other engine in the Z4 both markets share. 3.0Si output is quoted as 265 PS in Europe, 255 HP in US trim. 265 PS = 261.5 DIN HP = 258 SAE HP. The "Euro" spec engine has only 3 more HP than the US trim.
RE your reference to that 3 HP difference from emission differences between euro and US versions.... it has been reported that the 3 HP difference between the e46 M3's 333Hp and the MZ4's 330 HP is attributable to a slightly more restrictive exhaust system, (toned down/ less "raspy") all other things being equal (both US versions).
Those are just the manufacturer's stated "crank" numbers. They are as much marketing as anything else, and often times BMW likes to manipulate them typically to underrate the motors. Ultimately, the dynos show a 10 to 11 hp difference between the US and Euro exhaust systems. What else really matters? Who says the software is different? It could be, but I don't want to assume that. Interestingly, the same guys that dyno'd the Z4 M at 317 whp only got 299 whp from a E46 M3. They have different transmissions I understand. But that's a big difference if the gearbox is costing that much power loss. Ultimately, I'm willing to mount the Euro header to gain back some torque and horses, but as Steve Dinan says, the final gear change (3.91) is the biggest bang for the buck.
interesting info. i always like to hear this stuff about my car. 300+ at the wheels is impressive, doesn't matter how you slice it really. thanks
What's more impressive is the average whp. For daily driving, compare average whp from 2,000 rpms to redline and you get the following: 335i = 222.9 avg whp Z4 M = 236.6 avg whp E92 M3 = 250.7 avg whp For aggressive driving and/or racing, only the upper half of the rpm range matters. Here you get: 335i = 243.4 upper avg whp Z4 M = 271.2 upper avg whp E92 M3 = 329.9 upper avg whp Considering power-to-weight, you get (upper-half rpm range average whp per 1,000 lbs.): 135i = 72.2 upper avg whp per 1,000 lbs. 335i = 68.2 upper avg whp per 1,000 lbs. Z4 M = 84.0 upper avg whp per 1,000 lbs. E92 M3 = 89.1 upper avg whp per 1,000 lbs. Suddenly our out-of-production Z4 M's don't seem so obsolete! Our cars are just a 3.91 final drive ratio change from out accelerating a new M3! Not that it matters (as it's impossible to keep the car at the exact peak power rev in all gears at all times), but here's peak whp-to-weights: 135i = 83.8 peak whp per 1,000 lbs. 335i = 79.1 peak whp per 1,000 lbs. Z4 M = 98.0 peak whp per 1,000 lbs. E92 M3 = 100.6 peak whp per 1,000 lbs. This is why you don't want a N54 in a Z4 M!!!
