….or a history of VW engine conversions, and why Subaru engines are most commonly used:
From when they were new, rear engined VW’s were always quite widely tuned, with all sorts of carburetor swaps, capacity increases, sportier cams and supercharger kits, etc available. Until the 1980’s or 1990’s, the objective was always to increase the power output – the engines were economical enough relative to everything else at the time. The VW flat 4’s – especially the air cooled models are very tunable. Tuning them used to be relatively inexpensive up to the late 1990’s, and you can get far more power out of them than they were ever intended to make. But it’s almost always at the expense of reliability.
As VW’s flat 4’s were used for so many years with relatively few changes, by the 1990’s other more modern engine designs were getting a lot more economical, making older VW engine designs relatively uneconomical. But with the build quality of VW’s in general and the cult following meaning far more rear engined VW’s were still on the road than a lot of their contemporaries, some owners started to want a more economical engine, not just a bit more power. In fact what most want is a bit of both – a bit more power than their VW engine, with better economy too, plus better reliability without the constant need to tweak air cooled engines that they are renowned for especially as they get old and worn. This sounds like ‘having your cake and eating it’, yet thanks to other manufacturers developing their horizontally opposed engines far beyond where VW got to, this is totally achievable.
In the 1980’s and early ’90’s this lead some to experiment with converting to Alfa Romeo flat 4’s. These conversions were never very common, and seemed to largely be based on the engines from the Alfasud and the Alfa 33, which had overhead cams. The narrow range of capacities and similarity in power output to some of the VW models means their were not very advantageous, and them still using carburetors meant they didn’t provide the economy and reliability available with injection or engine management either (if that’s possible with 1980’s Italian injection!). Alfa did develop their horizontally opposed engines a bit further, with the injected versions of what were effectively the Alfa 33 engines in the 145 and 146 up to the mid 1990’s, but these hardly seem to have been used in VW conversions at all.
By the time VW stopped building flat 4 engines and rear engined models (outside the South American market) in 1992, their flat 4’s were showing their age. The last horizontally opposed car engines to be pushrod rather than overhead cam. Even the water cooled models were heavily based on design of their air cooled predecessors, which ultimately date back to the late 1930’s. Lots of other newer engine technology had come along in that 50+ years which VW never applied to the flat 4’s, which were still restricted by 2 valves per cylinder and a 3 bearing crank. If VW had continued horizontally opposed engine development, overhead cams, 4 valves per cylinder and a crank bearing between each rod journal would have been the obvious improvements, along with a built in water system rather than the wasserboxer’s external, afterthought mess of a cooling system.
Subaru had been developing their EA series of horizontally opposed engines since the 1950’s, and by the mid 1980’s, like Alfa they were ahead of VW in terms of adding newer technology. By 1984 then new EA82 engine had overhead cams, with carburetor injection or turbo variants, but still a 3 bearing crank like VW’s. All were 1781cc. These did get used in VW engine conversions, but were never very common. Like the Alfa engine conversions the narrow range of capacities and similarity in power output to some of the VW models means their were not very advantageous. Unlike VW though, Subaru were also working on the next generation of their flat 4’s, and it was a new design from scratch, superseding the EA series and with no common parts. These became the EJ series engines, introduced in 1989, for the 1990 model year. They have 5 bearing cranks, so significantly higher rpm limits, and were all overhead cam, with multiple SOHC and DOHC variants over the next 30 years. If VW had continued development of horizontally opposed engines, they would almost certainly have come up with something very similar. Subaru made EJ series engines with a very wide range of different capacities and power outputs.
Subaru’s range of horizontally opposed water cooled engines have become by far the most commonly used engines for transplanting into rear engined VW models for many years now. The first we heard of Subaru parts being used in VW’s was in 1992, with Peter Harrold’s awesome turbocharged 4wd rallycross Beetle and it’s VW engine with Subaru turbo DOHC cylinder heads. It was the late 1990’s before complete Subaru engines started being used for more conventional VW applications though, when they quickly took over from the Alfasud flat 4’s as being the most commonly installed alternative engines (at least here in the UK).
Another appealing feature of the Subaru EJ series engines is that they are still relatively easy to work on. Almost all of the subsequent horizontally opposed engines such as the Subaru EZ, EE, FA and FB series, and Porsche M96 engines (Subaru and Porsche being the only two manufacturers to stick with horizontally opposed engines after the late 1990’s), are anything but simple to work on. The early versions of both the Subaru EE series and M96 both had significant problems too, not that they required work on the engines to fix – the problems often wrote the whole engine off! (snapped cranks in the early EE series, and failed intermittent shaft bearings in the M96).
Also, the EJ series engines fall into a very nice ‘sweet spot’ in terms of the engine management used. On all of the pre CAN bus models, it is sophisticated enough to give the reliability and economy that many considering changing their VW engine for something more modern desire, but also easily separated from the rest of the car (i.e. not reliant on being connected to many other systems which will not be in the VW. It is not impossible to use some of the CAN bus engine management systems in VW’s, however you should put considerable thought into this before purchasing one. It is considerably more complex and expensive than using a pre CAN bus model, and often comes with a lot of mechanical complications which don’t exist with the earlier engines too
We have been involved with Subaru powered VW’s since 2002 – longer than anyone else except one company in the UK. There are quite a few ways that Subaru engines can be installed in VW’s, some better than others. Our objective has always been to make products to do the job to the highest standard possible. There have been plenty of others out there with the rather opposite objective of investing the absolute minimum about of money in making a Subaru engine run in a VW, cutting every corner you can imagine (plus plenty that few would ever imagine), while charging an awful lot for them. Therefore not all Subaru engine conversions are the same. A lot are installed to very very low standards. The worst ones in the UK at least are generally not amateur DIY attempts, but the work of ‘specialists’. So do your homework up front if you’re looking for someone to do installation work for you in the UK.
If you’re looking for products to install Subaru engines into VW’s which have been continuously developed by professional engineers for over 20 years, you’re at the right place.