No no, don't worry yourself, I was just thinking to put a link to it in the archives, :)

That book is referred to so often. I just ordered my copy.

One of the Chalmers articles that I printed out says that engine cooling contributes 5% to 9% of total vehicle drag. My Civic has only a 4" x 4" opening in the front of the grill block and so far I have have no overheating problems even in 100F temps and when climbing up the NC mountains in 85F heat. I have complete underbody panelling so I exhaust the cooling air out through my front wheel wells and a small amount exhausts out through my exhaust pipe tunnel to keep it and the cat converter cool.

Found another reference to a concept car with an active grille - Ford's Prodigy PNGV concept, 0.199 Cd:

The "front breather" reference is a comparison to the GM precept car which had a rear engine layout that permitted even more streamlined front end design (no grille) as well as venting cooling airflow into the vehicle's wake.

source: https://www.findarticles.com/p/articl...59035635/print

It seems the grill block is the time-honored solution to reduce radiator air drag. Most radiators are apparently oversized enough to prevent overheating even when the grill is blocked off. If this is true, then why shrink the radiator? It might raise the risk of a boilover. If anything, I'd be tempted to make it bigger in order to enable me to reduce airflow even more (additional weight not withstanding).

I've been incubating the idea of an active grill for a few months and I think there may be a simple solution to minimize the grill air flow w/o risking an overheat.

As for the speed of warmup, isn't that what the thermostat is for?

I mainly want to reduce its size because most people I talk with that've seen my wire tuck give me hell about how big my radiator is. It's really really really too big!

Anyway, you're right about warmup, Iono what I was smoking when I thought that.

ah, now I see. Someone else suggested diy movable louvers. That would certainly work.

I was thinking about an even simpler mechanism: a sliding shutter in the grill block. It could either be moved manually when the car is stopped or even linked by cable for real-time adjustment. I should get some of that cloroplast stuff. What kind of glue works? Is it made of PVC? 'jes wunderin'

The formula one boys are the ones to ask how much radiator is needed.
F1 cars have radiators only just big enough to prevent boiling at their average speed.
That is often why when they have a too long pit stop that about 5 laps later they often have an engine blow up.
To cut drag the radiators are too small and they cant bing the temp down if it climbs too high - Kar-Boom

"Gaping maw". :D Laughing.

I was going to use that exact same phrase to describe the gi-normous combined grille opening area on my car.

https://www.lubedev.com/smartgas/quickies.htm

"Imagine a 50-percent reduction in the use of automotive fuel in the U.S. THIS IS INDEED POSSIBLE and it could be implemented very quickly. In our own cars we have exceeded 50-percent reductions. Neon went from 26 to 62 MPG. Mazda went from 13 to 44 MPG. Olds went from 12 to 30 MPG."

This is with NO aero mods and NO driving techniques. Straight highway mileage.