just noticed something that i thought i should confirm before going any further. i have begun to set up my radiator under my car so that the lowest point is to the rear of the car, with the intention of scooping air onto the face of the radiator, then having the air go up through the rad and out the back (see diagram) with a fan to help suck through when necessary (hopefully never). i thought this made the most sense as it exposed the maximum area of the radiator to the oncoming air (protected my scoops and mesh of course), allowed the air to rise as it heatede through the rad before being passed out a large opening out the back.

i am worried now because i have just noticed that vwtyp2's setup is almost the exact reverse, with the lowest part of the rad at the FRONT and the air going DOWN and out through the largest part of the rad.

what direction do other conversions take? is there something fundamentally wrong with my design (it made the most sense to me but now i am worried)?

forgot to add diagram

The second design would work very well if you have a Baja bus with a raised front beam. There would be a 100mm gap above the beam the air can flow well through. On a standard beam bus the beam would probably restrict the flow at higway speeds.

what direction is yours pete, air going in the bottom exiting the top or visa-versa?

Air going in from the bottom and fan drawing up and out the top. The radiator is flat, not angled.

cool, feel better now, Ive just got a minor angle on mine as its sitting at the moment, just thought Id better check i was on the right path before i finished mounting it properly

Why not just put it where they belong?

South American style

hey mat, those spotties could look good if they had chrome rings to match the headlights

Whether the radiator is upflow or downflow is not terribly important. What is important is what the inlet does with the air.

The purpose of an inlet is to take high speed air (the slipstream around and under your car) and slow it down (relative to the car). By slowing it down, you raise the pressure, courtesy of that Bernoulli fellow. The pressure is what moves the air through the radiator.

If you just hang a radiator between the frame rails with the leading edge down, you have created a crude scoop that stops the air above the radiator. The stopped air will have more pressure and will tend to move through the radiator. This is not a particularly good design, though.

If you hang it with the leading edge up, you don't really trap the air, so you won't get much pressure difference or flow through the radiator. This is a really bad design!

However, if you add a bit of ducting by boxing in the frame rails forward of the radiator the radiator orientation issue becomes moot. The air will come to a relative stop in the duct and pressure will be generated to move air through the radiator no matter what its orientation. The duct will also serve to prevent easy air recirculation when not moving. It is also important to make sure that the area around the radiator is well-sealed so that precious pressurized air goes out only through the radiator. If it goes out through a gap somewhere else it won't help cool your bus!

My preference is to keep the radiator flat between the lower edges of the frame rails and blow the air downward through it from a duct above. The duct will extend most of the way to the front axle with a scoop at the front end, the size of which I have not determined. Not tilting the radiator reduces air-trapping issues and simplifies the bracketry. The down-flow arrangement also eliminates the blowing of hot air against the floor, which would probably make the back seat rather uncomfortable in the summertime!

Note that these words are coming from someone who _hasn't_ done a conversion. I am still in the planning process. I do have a piece of paper that says "mechanical engineer" and I've worked on various aircraft air inlet and ducting systems so I am fairly confident that what I say is valid.

George

[ Edited on Feb 10, 2006 by GeorgeL ]

[ Edited on Feb 10, 2006 by GeorgeL ]

thanks george, very informative.

The stretch has a similar set up, this is a customer's bus.