S&J Boxer Engines
have been rebuilding and developing Subaru EJ20 engines since 1998, by 2000
we had begun stroking and using oversized pistons/sleeves, and then in 2003
with the ease of access of the EJ25 we found ourselves building and race
prepping many different combinations of the famed 2.5L Subaru Boxer engine.
Many people may say an "engine is an engine", but the flat four turbo
Subie motor certainly holds a great number of "tricks and traps", some of
which we have had to learn the hard way, and others that we have picked up
by being partnered with the likes of MRT Performance in Sydney, our
resources and testing grounds have been almost limitless.
Most importantly when investing in something as large as an engine
replacement or rebuild, it is extremely important to make the right choices
of internal components and services to suit your needs. It would be easy to
be miss-advised and waste money in one area and overlook something more
important that would match the desired outcome of the project. For example
money is often more wisely spent doing mild port work/matching to the
cylinder heads than replacing the con-rods with stronger ones, the reason
for this is that by increasing flow throughout the heads, power is made
easier and pumping losses are reduced on the exhaust stroke, therefore
con-rods and bearings are far less venerable to fatigue and stress
of an engine is sometimes a term that is used a bit loosely, but the
following points will briefly explain some of the areas that we "Blue-print"
during an EJ build!
Blue-printing Crankshaft, a labour intensive process that is
carried out during the early stages of machining. Here we are
eliminating "nominal" sizes (which means they have a + or " tolerance).
The engine block which supports the crankshaft at its main journals is
closed up to correct tensions without the crankshaft, the tunnel is then
checked for trueness, taper and ovality, if any defects are found within
0.00025" they are rectified by a tunnel boring process. Following the
trueness of the engine block, the new "race series" main bearings are
installed, the block is re-tensioned again without the crankshaft, then
each bearing internal size is measured and recorded. Now the 5
crankshaft main journals can be ground and linished precisely to achieve
the exact clearance that we are after, all 3 of the + or " tolerances
are now removed. This process is extremely critical for any high
performance or track application.
Con-Rod to Crankshaft, just like the 5 main bearing journals on the
crankshaft the 4 con-rod bearing journals go through a similar process.
In this procedure the con-rods are tunnel bored to an exact size, then
fitted with the new "race series" bearings, re-tensioned, measured and
recorded, and then the crankshaft is ground and linished precisely to an
exact clearance for each con-rod bearing. Con-rod bearing failures are
extremely prevalent for the Turbo Subaru engine, and it is our belief
that the nominal clearance processes during the mass production often
leads to the short life of these bearings, once again for high
performance or race applications, this is another critical step in the
building of an EJ engine.
clearances, as with any engine build the machinist will aim for a
specific piston to bore clearance, we take it a step further and
finalise the boring process with a "torque plate" fitted to each block
half. A torque plate is a billet of alloy that is the same thickness and
density as the cylinder head for that model, this plate has 2 large
holes machined into it to allow the boring equipment to pass through.
The torque plate is bolted to the block half in the same manner at the
same tensions as the cylinder head would be, this distorts the cylinder
walls exactly as they would be when the engine is assembled, so once
again precision takes the place of tolerance (+ or -). This process is
used for gains in power as well as reliability, as is the final finish
"Plateau Hone" that we use in the cylinder bores, this is Nascar
technology from the US, which is only available from limited engine
Head Porting, all standard EJ cylinder heads have one exhaust port on
each side of the motor that flows 15-20% less than the port for the
cylinder next door, the flow matching of these ports is just one area
where power and reliability can be gained from a "port job". Many hours
on the flow bench have proven worthy for both inlet and exhaust port
flow improvements, and an extreme amount of data has been recorded for
each model with each capacity and level of mods. As with any port, the
short radiuses, diameters and finish are crucial to a worthy outcome.
Camshafts, valves and springs are a consideration at the time of the
cylinder head re-work, again good advice and correct choices are
paramount here. Also port matching to intake and exhaust manifolds is
not to be overlooked at this time, we can't stress enough how important
flow is to power, torque and reliability!
Camshaft Dialing In, it is a fact that even standard camshafts in a
standard engine can be up to 6 degrees
from their ideal rotating relationship with the crankshaft, when you
factor into account that a Turbo Subaru engine has 4 camshafts that is a
lot of give or take tolerance. Many people also don't realise that the
machining of heads and block halves plus the altering of head gasket
thickness has a major influence on the precision of camshaft timing, and
in turn relationship between the valves and pistons. The addition of
aftermarket camshafts, will also further the need for a precise Dial-in
of all 4 camshafts to the crankshaft. We have seen gains of over 20kw
ATW from simply removing an engine and Dialing-in the cams correctly. As
you can see, this is another worthy process to carry out during any high
performance street or track engine build.
all of the above in mind and the correct choice of hardware and tuning 300kw
at the wheels is not a difficult target to achieve, but "horses for courses"
as always, so if the time comes for a rebuild of your EJ we can help advise
you on the package that will suit your needs.
We are extremely passionate about our engine builds, our attention to
detail does not stop on the inside, every engine is detailed to a degree
that matches its application and the appearance the client is after, have a
look below at some of the engine bays that we have worked in recently!
Please Feel Free to inquire about any level of EJ engine build, and we
will see that you get the right advice!