Negative Steve. Van the man wrote a series of articles on this back up by test. Now I kind of agree but we WANT ram pressure. If the scoop is designed well than external drag minimized. And to agree with you the RV7/8 no scoop intake van sells (Horz air box) has less drag, est about 1 or 2 mph by Van, while still getting good pressure recovery. As you know it takes the air from the left cowl intake. The air as already slowed and there is pressure recovery there. Further there is a nice bell or trumpet shaped plenum. The problem with most FWD facing inductions is lack of room to develop a good diffuser, a place to slow air down and make pressure. We want pressure. Last an engine does not SUCK continuously like a jet. It starts and stops. So the plenum volume acts like a reservoir.
Mooney's used to have "ram air". Which basically allowed you to open a door (which looks very much like the carb heat door on my 9A) which opens to the front, bypassing the air filter.
I am familiar.
Opening the ram air on my 1966 M20E would increase MP by about 1". On my 1981 M20J it was less than about 1/2". The difference, I think, was improved cowling on the newer airplane.
You have been tricked. The 1" is more a "relative" indication of how poor or less than optimal filtered path is, than how great the RAM air is. If the filter is not a low loss type like K&N than bypassing the filter can help. I am not saying having a unfiltered fwd facing throttle body does not help, but its not the panacea or pot of gold. Part of that 1" is just relative to a so so filtered system. The change from Vans filtered air box and RAM is only may be a few 1/10ths. I think Dan said he got 0.30" more? Part of that was he had to compromise his existing Van's system to install a valve to select between filter and RAM. It's like everything in aviation, there are trade-offs and No free lunch. The KISS method says HAVE one good filtered system. However if you want a two way filter/RAM system, than go for it. But the corollary to the wisdom of KISS is not KISS-ing will tend to add weight, cost and time. Is the benefit worth it. You decide.
The newest Mooney's don't have ram air at all from the factory. An after market cowling for Mooney's (LoPresti) has significant RAM air
I am not sure what you mean by "significant RAM" air", and I am familiar with both. I am not saying ram air has NO benefit, just the benefit is relative to how good or bad the filtered system is. If you have poor mediocre filtered system then RAM air will look pretty good. If you have a Van's filtered system you will not see that much difference. Also a 1/10th or two more MAP is worth a HP or so? So is it worth it. Do you have a separate RAM scoop, that will add a little drag all the time, negating the benefit? For (most) RV'ers I say leave it off, since the gain is small over the stock system. Also no filter and a straight can CAN and has brought down planes from blockage, like a bird (unlikely but documented) and even wet snow. Of course Mooney say close the RAM air in precip.
You name dropped Roy LoPresti, who passed a number of years ago. I have long admired his career; he was a very talented aero designer. His Son is running the company now. I talked to him once. More significant than some of LoPresti's aftermarket cowls having RAM air, is they used round inlets, like the Barnard/James cowl, both based on the NACA funded Mississippi State data. Not a put down of LoPresti's design only that they had to certify it and sell it commercially to General Aviation pilots, so they could not push the envelope. The theories & concept of the "round inlet"(1) are better exicuted on with the Barnard/James cowl/plenum. RAM air or not. [(1) there is a lot more to it than just a round, as discussed else; see NACA / Miss-state reports.]
Its all about design, fit, form & function. If you have a filtered system like Van's FAB, adding all the RAM stuff adds complexity, weight and cost, for little return. Again how much is 0.10" hg of MAP worth? 0.30" hg MAP? A HP or two. To get that will cost you. How much speed does 0.20" hg buy? 2/3 rds of a MPH. How much will a NASA / Miss State cowl buy you? +6 mph
I think the ram air effect on my 9A is significant, but next time I fly I'll give it a try. at cruise speed I'll pull the carb heat and see what happens to MP.
Depends on your definition of significant. IF you want to test you need a DATUM a standard to test from. The datum should be ambient pressure. The problem with doing test at altitude is you only have an est of ambient so here is the test (I got from Van in RVator article):
Read baro on the RAMP, in-hg. With engine off the MAP gauge and Baro should match, say 29.92" hg. Now start up, take off and make a LOW HIGH SPEED PASS OVER THE RUNWAY, wide open throttle (WOT). What is the MAP? This is where you can brag you had 0.10" over ambient. If you have VERT induction and Van's air box your MAP will be at ambient baro. THIS IS FANTASTIC, because it means the RAM air + Air Box is overcoming the rest of the loss in the Carb/FI-TB and induction and cylinder head, which we est. to be 1" to 1.5".
My opinion is, fwd facing induction is more pain and cost than worth. However if you want want it, than its the right choice, but folks with vert induction should not have Horz induction or RAM air envy, the stock setups are pretty good. I will say the Horz set-up that Van offers (no scoop cowl looks good) is a TAD better than the FAB for Vert induction over all. However there are trade offs (as always). The down side is you need to use the stock cowl. I like the James/Barnard cowl which adds 6 mph, more than making up for 0.10" more MAP and a mph less drag the Horz air box gives.
Good luck, fly safe.