Type Half Baffle & Cooling
For additional information, see VW Type 1 & 2 Baffle & Cooling.
T he VW engine is able to keep adequately cool in automotive installations. However, there have been some problems reported when using it as an aircraft engine.
First, consider that in the automotive installation it had a shrouded fan and close fitting baffle. I had two friends with VW buses (known to heavily exert the engine) in New Jersey that commuted on the turnpike and could go 65-70mph@4000rpm. And yes the engine would occasionally run a little hot - but not dangerously hot. The one thing they both had done was use a larger after market oil cooler. This at least confirms that under the right conditions, the VW engine is a capable engine.
I have rebuilt three type 2 VW four cylinder conversions and one type 2 VW two cylinder conversions and I am confident that over heating is not a problem if extra care is taken. Most of my experience is with 94mm x 82 (2275cc). I rate my engines at 100hp (3900rpm) for 5min, and 75hp (3300rpm) continuous.
Probably the biggest aircraft conversion cooling issue is the differance bewteen the automotive air cooling (top down) installation and how an aircraft does it (horizontal). The auto installation works very well using a center mounted top fan that evenly distributes cold air in a uniform outward direction. The manufacture was able to mount the oil cooler on top of one cylinder and still keep things cool because the air came from the center of the engine.
The problem with an aircraft installation is the air comes from the front and needs to move to the rear of the engine. If the stock oil cooler is used, it will block air to one of the cylinders. Even a 1/2 VW conversion using the stock oil cooler may create a low volume or relative "dead" air pocket in front of the cooler making cooling uneven.
I use the following considerations on my full VW engines...
- 30mm gear oil pump i.e. Schadek 111-115-107ahd (about 2x oil flow)
- oversize oil cooler i.e.(Empi 00-9233-0)
- mount oil cooler below or at the back of the engine so no cyl is blocked
- use proper oil with zinc or extreme pressure additive (EP)
- use case with 10mm oil galley, do not use 8mm
- air scoop to direct air accross oil pan fins
- careful full baffling and tight seal around cowl
- directional baffles between cylinders
- generous cowl inlet & outlet openings
- proper fuel mixture (not too lean)
- minimize ground runup time in hot weather
- conservative climb out in hot humid weather