Here is a photo of our Mocal 44 row oil cooler with diffuser. A K&M Streamline into a wedge.

Not sure of the dimensions of hand. The Mocal web site will have specs so you could get a rough idea of size.

I tested this one recently with a leaf blower approximating 100 knot air flow and in that test it was very even.

Having said that, I tested our water radiator wedge diffuser when I built it years ago and had it reasonably even 

measuring pressures across the exit face, but now instrumenting it in flight its flow is vastly uneven.

I have found that the flow is dependant not only on getting the diffuser shape right according to the various papers (eg. K&W, London, Oblique Flow Diffusers - Streamline )

But importantly the environment it ends up in. The papers share data for ideal conditions with for example unobstructed exit air paths.

My thoughts now are that this has a significant impact on the performance and therefore the advantage of instrumenting in flight and reshaping for actual conditions.

The data I collected yesterday of our H2O diffuser reveals that the air flow in various points across the face are very different.

Simplified, if I average the pressures at the five points I measured, then comparatively the back is up 20%, the centre up 25% and the front down 60% from that average figure.

I’m figuring a 20% difference is probably OK, but my front to back/middle difference of ~80% down in the front top of that radiator may hold significant room for improvement.

Further, my data suggests that as IAS rises those differences are amplified. 

So I am now targeting the modifications for our worst case conditions of WOT sea level ~200hp and initial climb numbers of 115KIAS.

Cheers.

Steve Izett