I decided to use a remote electric water pump for the cooling system. I chose Pierburg, the same company that makes my intercooler pump. I initially purchased a CWA200 from Agile Automotive. They spec it on all of their SL-C and Aero builds and they’ve proven it at the 24-hour Thunderhill race and other endurance races. It allowed them to move the engine forward an inch or so and to relocate the pump’s weight to the nose box. Apparently the CWA200 has also been used by several GT2 teams. While the race credentials are nice to have, it’s been proven in many BMW and other OEM applications which is more applicable to my use case.
My engine builder expressed concerns about using an electric water pump. Seven or eight years ago he was retained by GM to test electric water pumps and he burned up a bunch of engines trying to find one that worked when a forced-induction, high-HP engine was pushed hard. Interestingly, the issue wasn’t flow rate. Rather the pumps didn’t create enough pressure to force steam pockets out of the rear of the block. This caused hot spots around the two rear cylinders (i.e., 7 and 8) which scorched their rings.
This need to have enough pressure to force steam pockets from the rear cylinders is why he advised me to leave the rear steam vent ports plugged. He strongly disagrees with the aftermarket steam vent kits that up-size the vent hose because they reduce pressure where you need it the most in an LS motor. Given that he’s been retained by GM for multiple R&D projects and he built the engines for the SL-C national champion after the team had a spate of blown engines from their prior marquee engine builder, it’s worth listening to him. That said, the tests were done a while ago.
To ensure that I would have enough pressure in the block, I upgraded the CWA200 to a CWA400 because its differential pressure rating is 1.9x higher (its flow is also ~40% higher). As can be seen in the comparison table, the CWA400 is marginally (i.e., ~1%) larger and while its max current rating is 2.2x it has an integral motor controller which is driven by a PWM signal. So, I gain ~2x increase in performance for a ~1% increase in size and a ~2x increase in power consumption (but only if I need it). In the end, the upgrade was a no-brainier.
In the pictures below, the CWA200 is on the left and the CWA400 is on the right. The primary physical difference is that the mounting tabs are on opposites sides of the outlet (i.e., they are 180 degrees apart).
The cap on the CWA200 can be easily removed via four Torx screws, but it can’t be clocked. It took me a while to figure out how to remove the cap on the CWA400. It’s held in place by a split ring. To remove it, I used a large flat screwdriver to compress the ring between a bump on the body and a notch in the lid while twisting the screwdriver between the bump and the edge of the lid. It takes a couple of tries because an o-ring makes everything tight. When putting it back together you want to ensure that the split in the ring is 180 degrees (i.e., opposite) to the notch.
There’s a notch that’s machined in the edge of the lid which fits around the aforementioned bump. The sole purpose of the notch is to prevent the top from rotating and putting strain on the inlet and outlet hoses. The top can be easily clocked to any position by machining or filing a new notch.
Fortunately, the CWA400’s outlet orientation is perfect for my application and I didn’t need to make any modifications. The CWA200, whose cap can’t be clocked and is 180 degrees different, would have been a real pain in the ass to mount in my configuration. This was one of the other reasons why the upgrade made sense.
The next step is to mount the pump.