You've drifted way of the mark here. I was only pointing out that for like installations, the size of the radiators that I have seen are not greatly different between diesel and gas engines. You implied that there is a substantial difference and based on my observations I respectfully disagree.
As for the size of an intercooler on a certain engine, who cares? If you really want to see a big one go look at a large marine diesel. I have seen AIR TO WATER intercoolers the size of big dog houses. Of course I could also crawl through the cylinders. The SMA unit you describe is relatively tiny. For what it is worth, I have also seen much smaller air to air intercoolers than the SMA, installed on even higher hp diesels.
As we have discussed previously, the principle reason for an intercooler is to increase the density of the intake air and thereby provide increased power capacity. Even more so for a diesel, were detonation is essentially the ignition system. Higher temperatures aid evaporation and increase combustion speed, which are beneficial in terms of power and efficiency. Since detonation is not an issue for a diesel, its combustion chamber temperature limits are defined by material properties alone. At high altitude, you might want to close all cooling airflow to the intercooler. While the mass flow through the engine would be reduced, at least there would be adequate energy in the combustion chamber to keep the engine running.
As long as we're on the subject, what is the typical cooling drag as a percentage of the total airframe drag? My memory from undergrad aerodynamics is fading but it seems like it is in the 5 to 10% range. For the moment lets assume it is 7%. If a diesel engine rejects 10% more heat through its cooling system than a similar otto cycle engine, this would result in an increase in total airframe drag of just 0.7%. If the x hp diesel engine gets 6% better fuel economy at 60.7% cruise power than the x hp Lyconental does at 60%, then which engine would likely go the farthest on 100 gallons of fuel?
The big downsides of the diesel compared to a similarly equipped and power capacity otto cycle are its preference for consistent mass flow through the engine and it's increased mass, which effects both center of gravity and payload. If the airframe presently has excess payload capacity and your goal is to fly it farther at moderate altitude and the same part throttle speed, yet maintain short runway performance and short climb times, the diesel may be the way to go. If you want to win races at Reno, I suspect there are better alternatives.
Fundamentally, diesels make a lot more sense in cars than they do in aircraft. But, given the right flight profile requirements, a diesel may be the best choice for a specific airframe.
It's kind of like putting a turbine in an LIV. With the TSIO 550 you have a fast vehicle that you can fly half way across the U.S. with your wife and all of her luggage. Replace the TSIO with the turbine, add larger tanks and you and your brief case can fly just as far in about 45 minutes less time. Of course your better half is PO'd, but maybe you're happier. There are always trade offs.
Rob