Nothing fancy, but I just did a thorough job of exit ducting out of 3 of my 4 coolers. Intercooler, oil cooler, right coolant radiator. I didn't do an exit duct out of the left rad due to it's close proximity to the turbo. I just couldn't realistically make anything that would fit and be efficient and I figured it wouldn't hurt to have a little airflow over the turbo.
Actually there is more to it as well. I spent a lot of time ensuring the cowl is well sealed to ensure that no air gets in there that hasn't done some work for me by passing through a cooler first. This included the diffuser inlet seal to the cooler face, but I believe the greatest gain was made around the prop spinner. I believe that Ed had warned of the pressure behind the spinner causing undesirable airflows into the cowl. I couldn't remember the details, but it didn't matter, I just knew I needed to block it. So while I was doing other fiberglass work I extended this face of the cowl by 3/8" to a closer tolerance with the back of the spinner. Then I made a lip seal on the top & bottom halves of the cowl opening around the PSRU to seal tightly here. This second part can be easily done on any completed aircraft, but the first one is much more work, however for those of you that have not yet reached that part of your project, I recommend that you pay attention to this detail.
When I built my engine mount, I only had the engine but no PSRU and no cowl, and no idea what prop I would use so with the data I could get from Tracy and Vans I did my best to build a mount that would put a prop spinner close to the face of the cowl. In any event, at that time I had no idea of the importance this would be later in improving airflows through the coolers.
One other change I made that I've been meaning to bring up in another thread, that really only applies to those of us using 2 coolers (evap cores). Way back when, there was extensive discussion as to whether series or parallel plumbing would be best for cooling. The consensus at the time was that the less restrictive flow through 2 parallel rads would be best. Since I was also using an EWP (DaviesCraig) and many thought it would not have enough flow to adequately cool the rotary (just ask Paul Lamar, he'll tell you!), I figured I'd better go with the parallel rads. To do this I had to make some compromises in my flow routing and with everything else being equal, one of the rads will always have more flow than the other. But I was never quite sure that I had made the right choice as a series configuration would ensure all coolant goes through both rads for a maximum delta T.
So with the opportunity during this rebuild I revisited this idea. My desire to include the Mocal Laminova heat exchanger pushed the scales over to the series configuration as trying to install it in any sort of parallel configuration that I could dream up would involve way too many ugly compromises. But a series install just fit beautifully and greatly improved upon the original plumbing.
But will it work???? I gotta admit I'm holding my breath on this one, but so far it looks promising with all the ground runs. But so many other things have changed as well that I still won't be able to say definitively which way is better.
Here's a pic of the right rad exit duct. Rather crude but it works.
Here's a pic of the cowl exit louvers that seal to this duct
Here's a few pics that show how I had to extend the face of the cowl to close the gap to the spinner
Here's the small but challenging intercooler. Unfortunately I don't have a pic right now that shows the backside of this exit duct where all the work was. But I made it from aluminum because of its very close proximity to the turbo. The crude fiberglass box seals tightly to the face of the intercooler and to the exit. So air takes a bit of a convoluted route.
Old Oil cooler inlet
New oil cooler inlet
Oil cooler exit duct. This seals tightly to the bottom of the cowl to use the stock RV outlet. I used aluminum here because of the engine mount it would be extremely difficult to do any sort of fiberglass molding. Aluminum I was able to bend and twist to get it into place then straighten it out.
Todd -- sorry for the long winded reply, now my fingers are sore... :-)