Larry, thanks for bringing this back up as I had forgot about it. Here is my take.
I covered the louvers with speed tape and it made about a 5-10 degree increase in temps. While I haven't done an accurate speed test it does seem that my cruise speeds for my typical setting have also gone up about 2 maybe even 3 knots.
My long term thinking is to still put cowl flaps in their place. The louvers absolutely are not needed during the winter or any weather relatively cool. However, hot summer day climbs I can see why Van's put them on. I also don't find they are needed on hot summer cruising.
Also, there seems to be a lot of negativity surrounding cowl flaps. In short, yes the RV does not NEED them but to be honest I don't think the stock setup is optimized for climbs (if it was the speed would be lower at cruise). So a guy has 3 options:
1. accept higher than 400 CHTs on the climb on hot days, especially if you want to climb below 115 knots indicated.
2. go to lengths that Danh does on baffles (it obviously works really well)
3. install cowl flaps, open them during climb and close for the rest of the flight and take a small weight penalty
Timing also matters, if I didn't have a Pmag my CHTs would be insanely low. Pmags are well known to raise CHT 20-30 degrees from a stock setup.
In summary, I have good baffles, not Dan good but pretty dang good, like to climb below 115 KIAS initially, and want to close some area during winter at all times. Sounds like cowl flaps will fit my bill. Hope this helps.
RV-7A Flying as of 03/2021
Last edited by jcarne : 01-25-2022 at 07:03 AM.