Any Disadvantages of Subaru Engines?
There are some disadvantages of Subaru engines, but there will always be compromises when installing engines designed for one vehicle into another. However, as such cross manufacturer conversions go, you won’t find many much more straight forward than a well thought out Subaru - VW conversion. The following are things you may not be aware of, especially if you are new to Subaru engines:
The main, and obvious, downside to the use a Subaru engine in a VW is the need to install a radiator, unless your VW is type 25 / Vanagon which originally had a water cooled engine. However, there is no mechanically simple way to install a modern engine in a VW which was originally designed to be air cooled – all will require either a radiator, dry sump oil system, major bodywork modifications or more. The complexity of fitting one varies from very little work in a water cooled Type 25 (Vanagon), where the original radiator is compatible, to quite a big job (for a hidden installation on a Beetle, bay window or split screen type 2). However, the water plumbing is very simple compared to some engines. If you’re use to the horrible external water plumbing system in wasserboxer type 25 / Vanagon models, you will be pleasantly surprised by the simplicity of the Subaru system.
A water cooled engine is an advantage if you are converting a type 25 (Vanagon) which originally had a VW wasserboxer water cooled flat four (the cooling system is compatible), or if you want to add a decent heater. If you’re use to the horrible external water plumbing system in wasserboxer type 25 / Vanagon models, you will be pleasantly surprised by the simplicity of the Subaru system.
Despite the Subaru engines fitting into the bodywork of most VW’s very neatly, there is a less obvious downside to the fitting of the majority of Subaru engines into your VW. All Subaru engines mount very high in the chassis compared to VW engines, and have a very deep sump. The deep Subaru sump will mean you lose about 90 mm ground clearance compared to an air cooled type 4 engine or a wasserboxer. The solution is not difficult though – there are various fabricated shallow sumps available to help you regain some or all of the ground clearance. Some are better than others - some just chop the bottom off, reducing the total oil capacity (NOT recommended), while others retain the full capacity, but require a lot of labour to produce. All require sending your original sump away for modification.
We are currently working on a cast alloy sump, which will retain the standard ground clearance while retaining the standard oil capacity. No exchange or modified parts will be necessary - it will simply bolt right on. The sump and our engine mounts have been designed as a system, and so will fit neatly together.
Whilst it is to be expected that a more modern engine will have more complex wiring, there is a less obvious disadvantage to Subaru engines over those from some manufacturers. Whilst Subaru engines are mechanically very self contained, electrically they are far from it. The engine circuit itself is relatively straight forward for most models (no more complex than it would be on any other modern fuel injected engine), but the wiring is all built in to the harness for the rest of the vehicle, rather than there being a separate engine harness, like some other manufacturers (such as GM) use. Separating out the wiring required to make an ‘engine only’ harness is the most common way of getting the Subaru engine management system running in a VW, but this is a big job. Don’t be put off though – because the Subaru conversion is very common (particularly in Australia / America), there are people who can build your harness for you, sell you instructions, or help with any problems you may have. There is also a huge amount of help and information available (on all aspects of Subaru conversions) from internet forums. LINKS
There is an advantage to using engines from 1996 > Subaru’s. They all have OBD II LINK diagnostic systems built in. This does make the wiring slightly more complex, but the system is very useful for fault finding when building your engine harness, as well as throughout the life of the engine. The engine management systems used with OBD II systems are also much more robust in terms of tolerance of being connected up incorrectly.