BangShift.com is proud to be working at Westech Performance Group on a variety of Engine Tech stories in 2011, and some are going to be in depth and others will be interesting facts or fun tests to perform. This week’s test is to see how much horsepower a mechanical water pump really costs you. With hot rodders always looking for the most out of their power plants, a lot are turning to electric pumps like the ones we use from Meziere. But for a guy with a typical Camaro with accessories and such, who is still running all his accessories, a mechanical pump may seem less daunting. We’re using Weiand’s Action Plus 9240 Aluminum Mechanical Pump on our 372 cubic inch Dart SHP test engine, to see just how much power the mechanical pump will need, and the results might surprise you. We’ve got video and the dyno sheets from our testing, so check them out.

You often hear bench racing going on at any given car show, drag race, or cruise night, and more than once I have heard folks talking about electric vs. mechanical water pumps. Here at BangShift, we believe that both have their place. In fact, we have mechanical pumps on some projects, and electric on others. The usual argument while bench racing is that one makes more power over the other, that one cools better, or that there is no other option because of fitment issues in a particular project. Personally, I find it convenient to be able to bolt on a mechanical pump to my 1966 Bel Air Wagon and not have to deal with alternator, power steering, etc. that may need some trickery in order to run with an electric pump. On my 1972 Nova drag car however, I can’t think of anything simpler, and love not worrying about throwing belts. I also love the fact that I can control engine temp in the staging lanes and the pits by leaving the water pump and fans running while waiting for the next round. The point is, they both have their places, and we’ll continue to use them both. 

But how much power does it take to sping your mechanical water pump? Well, we decided we needed to test it. On our Dart SHP 372, which baselined at 525.1 horspepower and 481.1 pound feet of torque on Westech’s Superflow 902 engine dyno running a Meziere electric pump, we bolted up a Weiand Action Plus 9240 Aluminum water pump and went to town. We expected to find that the engine made more power everywhere with the electric pump, but that didn’t happen. After 3 pulls in both configurations we came to realize that the mechanical pump was virtually identical to the electric pump, with regards to power numbers, up until about 5100 rpm. At that point the mechanical pump was working hard, and started to cost us some power. But very little.

At peak, the engine made just under 7 horsepower less while running the mechanical water pump, with a maximum difference of just over 8 horsepower at 6000 rpm. Weiand’s Team G waterpump is said to use even less power with even more flow. Which one to run on your combo is going to be up to you, but we say you should carefully consider what you are really going to be doing with the vehicle. 

Check out the dyno plot and video below. 

To find out more about Weiand’s mechanical water pumps for your vehicle, click here.