cooling question - hypothetical

[lawyerbob]

ok, maybe this is a dumb question / idea, but here goes. Why are head cooling scoops always mounted above the head? Heat rises right? so what if you fabricated side pods with ducting in them, forcing the air up from under the heads? Wouldn't the convection of the heat actaully help pull the air through?

I'm not an engineer, but I did stay at a Holiday Inn once.

[Bill Bonow]

Bob,

Many a car/cooling systems have been built this way (bottom up flow) and work just fine. First FV I saw with upflow cooling was built in '79. Ed Womer's cars are all up flow (see photo)



The scoops are black and under the heads.

[rickjohnson356]

The original VW design uses a fan housing and fan that pushes air down thru the cooling fins of the cylinders. On the bottom of the cylinders there is a diverter between cyl # 1 & 2 and also on the underside of cyl #3 & 4. The diverter forces the cooling air thru the fins on the bottom of the cyclinders so that more even cooling is obtained. One clue to check when high cyl head temps are present is to look for the diverter. if it isn't there, then the air may not be effectively cooling the whole cylinder.

Since FV doesn't use fans/fan housings any more, one could duct air up from the bottom if desired, but then you need to be careful of how you divert the air to get to the tops of the cylinders. Also need to consider how to get the hot air out of the engine compartment, too. don't want to suck hot air into the carb intake either.

my suggestion would be to keep the cooling flow as originally designed.

[lawyerbob]

Thank you both - as I said it was mostly hypothetical - trying to learn. Very interesting stuff - thanks!

[Bob VanDyke]

Bob,

With my converted Womer we used Ed's FV scoops and had no cooling issues at all. Granted, the races I did were Watkins Glen and VIR in October and Road America in November, so they ambient temperatures were too high to begin with. Ed did talk about coming up with some type of deflector to go on the top of the cylinders, but I sold the car before I got that far.

[veefan]

I purchased the Womer from Bob... and added Ed's updated engine cover... the diverters are totally removed. The bottom ducts pull the air up over & thru cylinders, the top ducts pull the cool air across the top of the cylinders and out of the car. I have run the car with a temp probe on several areas of the cylinders and they are kept very evenly cool.

Although most people have told me, it's over kill, and the additional drag is bad... I could also argue that a cooler engine bay is also better.

FYI... Just to keep the rule mongers in check, the top ducts also have a 90 bend..

[S Lathrop]

The original Zink Z12 had reverse cooling. We worked with the system over several years. The problem is that you have to change the baffel between the cylinders and the push rod tubes restrict the flow. We still use the bottom up ducts, installed backwards, to extract the air from under the engine.

[Hardingfv32]

1) veefan... Having a top and bottom duct is not going to cool the area between the cylinder. What is the incentive for the air to travel through this space if you have high pressure top and bottom? You need a pressure differential. You would be better served with one duct facing rearward.

2) Steve... It seems to me you are stuck with the same quality of obstruction from the push-rod tubes no matter which direction the air is flowing.

Brian

[veefan]

The bottom ducts are tight fitting and handle the cooling between the cylinders, no different then the typical top fitting formula vee ducts. The top ducts function similar to a standard vee setup forcing the air coming thru the cylinders out toward the back of the car. Flip the picture in your mind upside down of how a standard vee works, the top ducts are open in the back and do not force the air down. If that was the case you'd be right they would just cancel each other out. The top ducts again offer the added benift of keeping the engine area cooler.

Bottom ducts have a vertical 90 degree air flow, top ducts contain a 90 degree horizontal air flow which can not be seen in the drawing.

[Hardingfv32]

Yes, this would provide a pressure defferential, but I would argue that the defferential is not as strong as it could be if the top duct was only open to the rear.

IF in fact you are getting enough cooling air, it could be done better. You could provide the same cooling with less aero drag (wasted hp).

Say something like this:

That is the oil cooler near the left axle boot (below exhaust) almost closed off. That was good for 180 deg oil on a 70 deg day. Still learning about the system.

[S Lathrop]

2) Steve... It seems to me you are stuck with the same quality of obstruction from the push-rod tubes no matter which direction the air is flowing.

Brian

The tubes work to you advantage when they are on the bottom. One of the critical issues is getting the air to flow around the bottom of the cylinders. The baffel between the cylinders and the push rod tubes cause more air to exit from the bottom center of the cylinders. On the air cooled FSV engines we had baffels that forced all the air to exit under the cylinders.

The engine cools well enough both ways, but our feeling was that we had better power. Proof was that we could eliminate the oil cooler and still keep the oil temperature well within limits and we were very competitive on both long and short tracks.

[Hardingfv32]

Yes, I noted that from old NACA air cooled engine studies after WWII. They developed very precise baffles designs regarding the clearance and opening size for the exhaust side baffles. I still need to massage that part of my system.

Brian

[provamo]

Brian i thought you had your oil "cooler" in the nose?

[Hardingfv32]

That was the 2008 model car. With that car I was shooting for 49/51 weight distribution. EVERYTHING the rules would allow was up front. For 2010, I went with something simpler regarding the oil cooler. There really is not much space available in the raised nose with the battery and rocker style steering already there.

Brian

[Turbowerks9]

I would imagine the cooling of the engine is number one and however you do it with good results is the main endpoint. Not sure upper vs lower cooling is the concern. I think most designs do well and if the engine stays at the right temp without having to do frequent rebuilds and performance is not reduced then go with it. Never hurts to experiment with an aero package as long as you do one at a time.