Air cooling question.

I've had this discussion numerous times over the years with various vw/

356/911 friends, but it usually ends up staying on the drawing board even though if someone had a ratty car with which to experiment, these assumptions could be proven either way. What we wanted to try was this: Remove the fan, replacing it with an electric unit hooked to a temp switch - in theory, this would kick on at low speeds/idle and go off once the car was moving. This would allow experimenting with scoops on the bottom of the motor, hopefully designed to avoid the exhaust pipes. Anyway, it could be a fun driveway project to try. Upside is: Possible cooler running & net HP increase without the mechanical fan. Downside is: Fried motor from failed experiment (LOL)

Unless you want to make a *lot* more than stock horsepower the VW engine is not terribly thermally limited, at least not the later models with the doghouse oil coolers.

Also, don't forget that every Joule of heat energy you are removing from the engine through waste heat extraction is just that - *wasted energy*. Heat removed via the heat extraction system (which on the ACVW engine is a combination of air and oil cooling) is energy that is *not* transmitted through the pistons, rods, crankshaft etc. ultimately out to the wheels.

If this were a more perfect world we'd have high temperature, high strength, non-brittle, easily formed materials to make our engines out of and we'd have -no waste heat extraction- whatsoever. People have tried to do this. Back in the late 70's / early 80's they were looking at making engines out of ceramic materials (at least the engine blocks and pistons). They had some success in that they were able to demonstrate engines who's normal operating temperatures were north of

450 degrees F. But, ultimately they couldn't solve the brittle fracture problem with the ceramics and finding a lubricant that would work at these temperatures proved problematic (I actually think they could solve that problem now). Back in the day they were working on this technology they were going for high efficiency/high gas mileage, but any efficiency improvement can be spun into higher horsepower as well.

Unfortunately, this is not a perfect world and we have to make do with the materials at hand.

I say all this to make this point. When you design an engine the goal for heat extraction is to remove *just enough* heat such that the engine will give a reasonable service life and will require only an acceptable amount of maintenance. If you are pulling heat out of the engine beyond this level you are throwing away either fuel efficiency or horsepower or both. I see lots of guys that get really focused heat extraction and fancy radiators, oil coolers, air ducting, etc. when in fact they are pulling more heat than necessary out of the engine already.

That said, if you're really going to build a large displacement engine with some sort of forced air induction you are going to have to devote some effort at improving heat extraction. The trick is knowing when enough is enough.

You don't know squat about the ACVW and already you are ready to disregard decades of German engineering expertise. Go ahead. Reinvent the system. Don't bother to do any research. Blow stuff up. Be happy.

Stupid, stupid, stupid. The car isn't always moving, you know.

First, you also have a big honkin propellor pouring air across those cylinders. They are not cooled only by forward motion through the air.

Second, one of the great issues is radiated heat which you cannot blow away any more than you can blow aside a flashlight beam.

We did run ACVWs without a fan or any tin. We put them in 60's BMW motorcycle frames. They didn't work very hard, and did not last very long.

The interior gets its heat from chambers that surround the rear exhaust pipes.

Downside #2 - electrics put drag on the alternator, stealing power.

That what a fan is for.

furnaces are routinely installed in attics around here... that said, I run a full cooling system, including thermostat and control vanes... this regulates the operating temperature... we don't always need *all* the cooling available to us to keep the engine in the temperature range it was designed to run in... that said, how can cooling be "better"? cooler does not equal better running/etc... it's really easy to overcool a vw engine without doing all the stuff you describe... now ifyou are just wanting to do something different, for the hell of it.... go for it, but if you are looking for making the engine run *cooler* than the designed operating temperature, you are not doing yourself, or engine, any favors...

I seem to recall a discussion on the amount of air the VW fan produces

it is a significant CFMvalue (more than 1000cfm @4000 engine rpm). So much so that no electricfan comes close (most electric fans are in the 200-400cfm range). Thisis why race motors that use electric blowers are only good for thetrack. You are suggesting that air "scooped" from under the car will replace this volume of air?

I'd think you'd still need an engine driven fan to provide air flow at idle and low vehicle speeds. Only at cruise would the scoop be functional enough (maybe). So you would need a way to switch between air sources.