Originally Posted by
Loner
If your VW engine is; 1) retaining stock fan and tins, and 2) a 1600 with the offset oil cooler in the tin, then I doubt that you would ever see any overheating so long as the trailer is a nominal weight (<1000 lbs). Remember that you've dropped about 1500lbs of the vehicle weight by converting to a trike. Also the VW gearing is quite low so the fan speed will normailly be kept reasonably high.
If you want to build in that little bit of extra cooling, you could add an external oil cooler that will bolt on to your existing oil cooler base and adds a small oil radiator that you'd mount in a high airflow area (like over the fan inlet on back of the stock housing). That is an affordable (under $100) bolt-on mod that will add a lot of extra cooling for the oil system. You might also add a spin-on oil filter base while working on that area. That won't add any noticeable additional cooling, but will be a worthy investment for your motor maintenance.
I've pulled lots of heavy towables with VW trikes - including a wooden 16 ft Chris Craft boat - and never had any overheating issues so long as I was using some type of stock cooling tins. Don't get suckered in to the myth that a trike can run without cooling tins - it can't and will overheat at some point.