Subaru conversion- is it worth it?
Well, yes and no. If you don't like VW's and are living in a location that costs a lot of money to seek VW parts or mechanical repairs then yes its worth it. Lets look at the old school Subaru engines, the pro's and the cons.
The ea series engines seen in the Loyale/Brat/Brumby cars and pick ups eventually got to 1781cc. All alloy built and compact. Light enough for aircraft and heaps of torque for that size engine. In fact maximum torque came in at 2400 rpm. Few engines had maximum torque at such low revs. This ea81 engine weighed less than the VW 1916cc engine I once had in my trike. Maybe a little over the weight of the VW engine when including radiator, coolant and such parts, but not by much.
The ea81 was a 8 valve engine with internal camshaft unlike the ohc of the ea82. The latter has front cam belts,idlers and the like and for the little hp advantage the ea81 is often much preferred. The ea81 therefore has much less width, handy when designing an exhaust system.
Depending on your global location the ea81 come out with a standard Hitachi carb, twin carb, SPFI (ea82) and turbo charged. Twin carb manifolds are scarce now. SPFI for example didn't come out in Australia.
The most common conversion with these engines is the weber 32/36 progressive carb. Early this year I had a 38/38 carb on it but wasn't suitable. It was virtually untenable and not matter what the dtno tuning guy could do he could get it to run well. A 32/36 conversion with adapter plates is readily available. When properly jetted it is a good increase in power over the stock carb. SPFI conversions are popular too. Off the ea82 the SPFI has a much larger manifold diameter. The trouble is that the sensors like MAF and TPS are over 30 years old now and often faulty and expensive to replace.
The stock ea81 with carb is a good engine. Later models had an electronic module in the distributer needing no maintenance. Valve clearance checks were done every 20,000 miles a huge improvement over VW.
This Subaru engine has an ignition system that fires on cylinders on one side first then the other side. This means a cross over exhaust pipe is preferred just after the exhaust outlet of the heads. An adapter plate is required of course to mate with the VW transaxle. When you do this the timing marks for the engine go to heaven because the timing marks are on the flywheel...discarded and replaced by the adapter. The crank pulley on the front of the engine has a notch at TDC and you can use this to time your engine. The pulley usually 350mm circumference means one degree equals nearly 1mm. Add a weber carb and its common to advance timing from 8 degrees BTDC to 12 degrees.
By far the biggest issue of this engine is the manifold. On the bottom of it runs the passage of heated coolant from one head to the other. The air/fuel mixture enters the carb and makes many twists and turns before leaving the engine as fumes. There are twin port heads available from SUB4 but they are very expensive. You can modify a VW engine to have an output in power way beyond what this ea81 engine will ever get (in general terms). The ea81 is smooth and quiet in good condition. These babies can run to 250,000 miles without drama or even more with modern oils. If you are in your 50's and want an engine that will last all of your riding days then get one, recondition it and ride till you drop...its that reliable. Main advantages are just that- reliability, torque and simple easy to maintain design.
The later series engine, the EJ series I know little about except they weigh much more, have ECU computer systems and are much larger. Effectively double the output of the ea81 engine. It depends what you are after. If you want heaps of power and torque the EJ series is to go for. But even these engine are getting to the point of needing reconditioning so factor that in.
Finally radiators. I started off using a new Toyota MR2 radiator behind the passenger, effectively on top of the engine, then a Alfa 33 radiator, a little smaller in size in the same location. That location didn't work, too much vacuum. Finally I placed it up front. Work a dream. A bonus is you get warm legs in winter. 30mm stainless steel pipes carry the coolant.
I've had various versions of the ea81. The weber 32/36, a supercharged SC12 version I made myself (fuel guzzler) and SPFI. I ride up a small mountain near my home here in Oz. Everytime I change the trike mechanically I ride full throttle up it to gauge its performance. This will give you and idea of its output. I have a VW auto transmission.
VW 1916cc top speed 40mph
EA81 supercharged 65mph
EA81 weber 38/38 50mph
EA81 weber 32/36 60mph
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EA81 being reconditioned. Total 1820cc
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Exhaust with cross over pipe
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The EA81 with supercharger
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cheers
