Engine Drivetrain 3rd Gen Most liked posts in thread: Introducing the Helix DDCâ„¢

Today I'd like to talk about the development of this specific intercooler and more on why we developed the DDC.

We actually are on our version 2 of the F56s intercooler. We designed, modeled and prototyped our first version last summer. The design was based upon what had worked in our past coolers, with improvements in end tank design. Here's a redacted PDF of version 1:




Once we installed the prototype in the test car, we were a little disappointed with the results. They were an improvement over stock, especially in higher boost conditions, repeated use and at high RPM, but not the dramatic improvements that we had seen in the R series MINIs. Part of that was due to the bigger stock core, but a big part of it was due to an inherent design limitation: our fin density through the core was too tight, dropping pressure between the ferrules more than we wanted. This is very difficult to measure utilizing OBD-based datalogging software, since the factory engine control management operates using what are called torque targets. The DME (the engine's brain) asks for certain levels of boost, based upon the condtions. When you are in sport mode, at wide open throttle (giving it the ol' stick!), the DME asks the turbocharger (By controlling the wastegate) for as mush boost as possible until it reaches a pressure threshold. Then it starts bleeding boost to maintain the target pressure. If you have an intercooler that is very thermally efficient (drops temps well) but also creates a larger pressure drop from end tank to end tank, the DME has to keep the turbo on the roil for longer. Spool up is slower, meaning that your initial burst of torque is slower to happen after you stomp on it, and you're working the turbo harder. Here are some of the data we collected on our version 1 cooler.




These two third-gear pulls were done on subsequent days. The first day was the stock cooler, the second day, our prototype. Weather conditions weren't perfectly consistent, unfortunately. The second day was several degrees higher with 30% more humidity. As you can see the boost levels are pretty consistent, but if you saw the wastegate duty cycle numbers (not shown on this graph) the turbo was working harder with the prototype, which raised the intercooler inlet temperature). Both pulls were the first of a series of 4, so this graph represents the least heat soaked runs. The prototype's greater thermal mass and increased frontal area kept it consistent run-to-run.

So what we had was a cooler that performed well enough, but didn't solve the problem of pressure drop. Back to the drawing board it was. We came up with two tricks to increase efficiency through the core: end tank design, and fin density. To be continued in a later post...