Wednesday, October 31, 2012

A million zany ideas

Since the advent of water cooled engine conversions for the VW, there has been the perennial problem of where to put the radiator. There are three generally acknowledged places to put it:

The Brazilian T2c imported to the UK with the radiator
disguised by a faux wheel cover.
The Brazilian T2c put a new nose on the Bus and gave it a proper radiator grille, but it is prohibitively expensive in the USA to lay hands on all of the Brazilian components needed to convert an original German bus. That and once you start carving up the front of the vehicle, there is no going back. You're either going to finish, or pictures of your vehicle are going to show up in the 'backyard abortions' gallery on the air-cooled VWs websites.

At this rate, its unclear what the vehicle is,
so much of the front is covered.
One of the most consistent difficulties in adapting a radiator to a T2b is trying to produce a solution that work consistently below freezing as well as in Death Valley that is not, frankly, butt-ugly. Mile after weary mile when you're in the middle of nowhere, or every day around the city from stoplight to stoplight. Many cooling solutions will work, in a certain confined seasons or circumstances. But a proper solution must work in all of them and have enough spare capacity built into it that there can be a modest problem and you can still limp to the next village for help.

The first solution is to put the radiator up front, bang slap against the airflow, just the way they did it in Brazil, but without going to all of the panel beating required to graft it in. Unfortunately, radiators hung off the front look like...radiators hung off the front. They ruin the classic lines of the vehicle and no matter how well decorated, (and how wonderfully functional the radiator is in cooling the engine) they still look like a hack job. Those who have gone to the trouble to source the radiator fascia from Brazil certainly have a better looking product. But this gets very expensive, very fast unless you have considerable fabrication skills to also do the body work required to graft in the grille.

Not only does it look like they left
the rear engine hatch somewhere back on the motorway,
also note the size of the extensions on the
 intake vents at the top rear.
Others have attempted to replace the rear engine door with a radiator...and it looks like it. This is based on the idea that the small air intakes on the top left and right rear of the vehicle are sufficiently large to pressurize air through the engine compartment to drive this back-door radiator. This is patently ridiculous: such a design would need to have the space between the engine and the body sealed as the aircooled engine was, to force all of the incoming air through the radiator. The air will always take the path of least resistance if given the opportunity.

Not only do you have a scalding hot radiator out where it can burn you and others, how are you going to get TO your engine in an emergency if the principle access is over 200*F? So this one loses for practicality, aesthetics and cooling.
Engine shown with radiator partly covering
 the battery at the rear, at the bottom of the vent stack.
In this installation, there are small radiators
 on both sides which have been plumbed together in series.
The next to last solution starts to get the idea nailed down: move the radiator inside the engine compartment. Usually two radiators, one at the bottom of each intake vent. With fans, the radiators breathe in from the vents, and out to...where?

Well, down. Down around the space between the body of the engine compartment, and the engine itself. This is probably a workable solution...as long as you keep moving. But when you hit stop and go traffic, or are creeping past an accident in only one lane on the freeway, you won't have enough ram air to move heat from the radiator. So your fan comes on...do we overheat? Maybe.

One successful variant of this design is to seal the radiators to the area around the bottom of the vent stacks. That way all air that passes down the vent stack cannot 'go around' the radiators; it must pass through them. This would dedicate the vent stacks to the radiators, and translate any forward movement to pressurizing the air through the radiator.

But it turns out that performing this kind of seal up is really, REALLY hard. The radiators must fit precisely, and where they don't, they need to have cladding added so that they are both mechanically secure and reasonably airtight. Making all of this ready to go bouncing and rattling down a dirt road is a dubious prospect because of a few fundamental problems remain:

  • There is an enormous amount of fitting, cutting, and perhaps welding required to seal both vent stacks.
  • The vent stack on the right cannot be permanently sealed, or the battery (which lives there) must be relocated, possibly inside the vehicle under the rear seat, or possibly suspended from the roof of the engine compartment. Regardless, the main power harness would have to be modified or extended to the new location.
  • Heat rises. In the air cooled engine, the sealed engine compartment means that hot air coming off of a stopped engine rises up and out of the vents, drawing cool air in from beneath the vehicle, pulling it, in reverse, through all of the fins on the heads and cylinders. But a stopped liquid cooled engine would be trying to use its fans to cool the engine by pulling air down the vent stacks, through the radiators and then down (again) to be pushed out from under the vehicle. This is fighting the heated air's natural tendency to rise and draw in cool air from beneath it. Perhaps not a problem at speed. But three hours of stop-and-go traffic through downtown Atlanta when it is 110 in the shade....your fans would need to be running almost constantly.
  • You had not only best have an almost hermetically sealed air intake, you'd better have very very good radiators that can move a LOT of heat. This means ducting and really stellar fans.
There are two enormous benefits to this arrangement, however:

Radiators are kept in engine country instead of body country (the front, the rear, the top) or chassis country (beneath.) Radiators are fragile, and don't react well to rocks, fallen branches, road kill, and other sundries crashing into them at speed. They are well protected, unlike ANY OTHER SOLUTION.

The engine compartment solution answers the 'ugly' problem, and we've seen some pretty bug-ugly example above.

Keeping our cool is the challenge there.

So to sum up, the three radiator placement solutions proposed so far are:

At the front, which is either expensive in terms of body work (if you fit a Brazilian grille) or ugly (and dangerous) if you just mount the radiator on the front bumper.

At the rear, replacing the rear engine hatch. Ugly, also dangerous, and ultimately ineffective because of insufficient throughput.

In the air intake stacks. Only effective with great gobs of fabrication effort to ensure a good seal of the radiator bodies. And it requires either access provisions for the battery, or relocation of the battery. Lots of work, and great reward if done right. If done wrong...baked engine.

There is only one universal place left: beneath the vehicle.

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