|
There is no real math you can use. It depends on too many variables some of which are ambient air temp, driving speed, opening size, how much air coming through the opening actually goes through the radiator, engine temperature, engine load, rolling resistance, altitude, wind speed, and I'm sure more. Add to it that all of these variables are constantly changing and you can't say X opening is good for Y temperature.
The best way to go about it is really guess and adjust it as needed. I'd start with a ~6"x6" opening and if your fan comes on open it up a bit more. It'll be oversized for winter, but it'll still help out a good amount. You can adjust it for winter as well if you wish.
|