Therefore, in fourth gear, the car with the 2.93 set-up will probably be ahead. If we throw drag radials or slicks into the mix, it would be the other way around.
For us, the overall improvement is enough to call this upgrade worthwhile. As long as the car relies on street-tire traction, it's faster with the 2.93 rear end. The increased speed versus revs also provides better fuel mileage for cruising and a new top speed, given the 7100 rpm cut-off as controlled by the AEM EMS computer. Of course, with this much power and the heavy-duty Ferrea valvetrain we could easily set the EMS to a 7500-rpm rev limiter and do over 190 mph, but that would be unnecessary, if not lunacy.
This month also sees upgrades in the car's cooling systems for both water and oil. Victory Product Design, known for its BMW high performance and racing products, has a trick oil cooler set-up, which, at $650, will save bundles over the European-spec system and is easier to install. It's also good for an average 20 to 25 degrees F in oil temp reduction at the 200-plus F range, and now it's offered with an even larger heat exchanger.
With everything Project M3's got helping the cooling system-including the Fluidyne radiator, hood vents and all the exhaust coating and wrapping-we knew we couldn't go wrong with a heavy duty water pump. EMP Stewart Components has a stock replacement high performance water pump with a stainless steel (and much heavier duty) impeller. The flow is about 20 percent higher for a given pump speed, and the redesigned impeller housing is supposed to reduce cavitation (where water flow exceeds the impeller's flow capacity and potentially damages the impeller blades) at high rpm. Anyone driving a 1991 to 1995 BMW is probably relying on a plastic impeller water pump and there's no telling when those will fail. Owners of cars that see the occasional track weekend or severe summer heat should look into one of these right away. We're curious to see what the improvements of the oil cooler and high-flow water pump will be for us this summer.
Will the Project M3 series ever end? Actually, the car is finished and has been for some time. The project finale will be coming soon.
| Project M3 differential comparison (two-run averages) |
| Power level tested: | 465 whp (15 psi) | |
| Differential gear: | 3.15 | 2.93 |
| 60-ft: | 2.25 sec. | 2.24 sec. |
| 0-30 mph: | 2.49 sec. | 2.43 sec. |
| 0-60 mph: | 4.85 sec. | 4.78 sec. |
| 0-100 mph: | 9.5 sec. | 8.95 sec.** |
| 0-120 mph: | 12.28 sec. | 12.19 sec. |
| 110-125 mph: | 2.28 sec. | 2.28 sec. |
| 1/4 mile: | 12.45 @ 123.0 mph | 12.32 @ 123.5 mph |
| Top speed*: | 164 mph | 180 mph |
Rev Limited Reached In Third Gear
At 465 wheel-hp-a slightly above-average power level for turbocharged M3s today-the differential swap proves numerically beneficial on street tires by basically improving traction, bettering the previous set-up by over 24 feet at the finish line. At higher power levels, the 2.93 rear end becomes more beneficial. Next time, we'll try a rip at 20 psi with this set-up and see what happens.
Special thanks to House of Power for the installation of the 3.64 on Lawson's car. Although HOP normally specializes in Mercedes-Benz go-fast tuning, the shop also installed Jon's cam kit and has helped us tremendously behind the scenes with Project M3.