Project M3 Part 8
To date, we've seen a peak gain of around 35whp with the addition of an M50 intake manifold conversion, 3.5" intake system, cat-back exhaust, throttle body, underdrive pulleys and software. Now this may not sound like a lot, but considering it's an OBD2 car with stock cams and headers, it's actually quite impressive. But we must remember that extra power brings extra heat, which puts additional strain on the cooling system.
With most E36 M3s registering high mileage these days, replacing cooling parts has become more of a necessity, regardless of power. What's more, the '95 M3s had a plastic impeller in the water pump that was notorious for breaking before 100k miles, while all E36 models had aluminum radiators with plastic end tanks that are also known to fail. And with 140k miles on Project M3's odometer as well as the extra power, we decided the cooling system should be upgraded as a precautionary measure.
Parts
Our first order was placed to PWR, an Australian company with headquarters in Southern California. It manufactures custom and replacement aluminum heat exchangers, offering two cores measuring 57mm and 42mm thick for the E36 M3. The fat 57mm unit is a racing application that requires some modification to fit, as well as the removal of the stock cooling fan. However, PWR's stock-sized 42mm radiator is a direct replacement and the one we chose.
When we put the PWR radiator next to the OEM part we noticed that, although the widths are the same 42mm, the actual core thickness measured 41.8mm for the PWR unit against 32.8mm for the stock one, giving us a 27% gain in coolant capacity. Additionally, the sturdy aluminum end tanks should last the life of the car.
For the rest of our cooling components we contacted our friends at BimmerWorld. With a trio of E90 330i racecars in the Speed touring car championship, and the majority of employees involved in some form of racing, these guys know temperature management.
We ordered a Stewart Components water pump. Even though our '97 M3 came factory-equipped with a metal impeller, we knew this beefier Stewart would never give any issues. Additionally, it's rated at a 15% increase in flow, with the impeller design providing a steady increase in flow at any given engine speed. Track junkies will appreciate this because it helps eliminate cavitation - drag caused by air bubbles forming near the impeller's tips when it spins too fast, resulting in wear and tear as well as higher temps.
We also used a BimmerWorld silicone hose replacement kit. With the upper and lower radiator hoses being the most common failure points, these were highly recommended since they're sturdier and don't expand. BW offers them in black, red or blue.
When upgrading your cooling system, it's a good idea to replace your thermostat. A cooler thermostat opens earlier to allow coolant to pass through sooner, keeping engine temps down. BW suggested that replacing our original 88C (190F) thermostat with an 80C (176F) would be best.
They also offer colder units for racecar applications, but don't recommend them for stock-DME street cars because it may run so cool that it keeps the car in the fuel-rich warm-up mode, thus adversely affecting fuel economy and power.
We also ordered one of BimmerWorld's Spa Technique digital dual gauges to read oil and water temps. This would not only would this give us important information, but would help us set-up each dyno test more accurately - after all, temps greatly affect horsepower.
Accurate to the nearest 0.1F, the gauges use top-of-the-line sensors and feature a variety of menu options, including reading units in Fahrenheit to Celsius, different back-light colors, peak recall and reset functions, as well as warning light programming.