Gidday Guzzla
Heh Ratbag, do you have any info on how Subaru increased the power of the SG engine from 121kW to the 126kW on the SH? Torque went up a bit too. Subaru rated this engine at 127kW in the Liberty when it was introduced earlier but I assume it is the same engine.
Check out the Wikipedia article here:
https://en.wikipedia.org/wiki/Subaru_EJ_engine#EJ253
"
I-Active valves (VVL intake side) on 06+ models which have ISO 173 hp (129 kW) @ 5600 rpm, 166 ft·lbf (225 N·m) torque @ 4000 rpm. Compression ratio 10,0:1"
Keep in mind that all these figures are for the USA market. The engines they got are slightly different from the ones we got for any given model. e.g. the US market Forester apparently didn't get the EJ-253 until the year after we got it. Oz was a big beta test site, perhaps?
ALL of the Owner's Manuals I have downloaded are for US market vehicles. The OM for other markets do not appear to be available electronically. In major practical terms, this means that the term "dual range" never appears in the US market OMs ...
As for how Subaru changed the EJ-251 performance specs into those of the EJ-253, the answer is simple at an obvious level - i.e. the physical changes. Probably a good deal more complex at the ECU tune level.
Physical changes & Effects:
1) the heads and camshafts are different (the two inlet valves can follow either the same - or similar? - cam lobes, or one of them can be changed to follow a cam lobe with a different lift and profile by the ECU, instead of being identical at all rpm);
2) the valve trains are different (VVLT) - controlled by the ECU. Each of the two inlet valves can have a different valve lift (and presumably valve timing) at break points that are varied by the ECU dependent on engine speed, gear, engine load, etc
3) the inlet manifolds are different. The EJ-253 uses a MAF sensor instead of a MAP sensor, and this allows better control of the fuel:air mixture ratio under all conditions. It also has tumbler valves in the inlet manifolds, giving better swirl characteristics at low rpm, and therefore better and more efficient combustion. The EJ-253 in our SH has longer intake manifolds than the ones on my SG EJ-253. This will increase the torque and engine responsiveness a little.
For a description of the Subaru I-Active Valve Lift System (VVL{ift}T), see here:
https://drive2.subaru.com/Spring07_whatmakes.htm
The turbo engines use Subaru's VVCS (VVT{iming}T), described here:
https://drive2.subaru.com/Win05_WhatsInside.htm
Some manufacturers engines employ both of these in either turbo and/or N/A engines.
All the above physical changes allow the EJ-253 engine to have its torque characteristics optimised for both low revs and high revs simultaneously compared to the EJ-251. Mid-range revs are always "optimised" by default. The EJ-251 torque curve is much more like a classic inverted ski jump shape. The torque curve of the EJ-253 is pretty flat from 1,200 to 6,300 rpm.
What this means in practical terms is that the EJ-253 is getting around 80% of its maximum torque by about 1,200 rpm, and 90% by about 1,800 rpm. This difference is very noticeable in everyday driving situations. The EJ-253 torque curve stays above 90% until it hits its red line at about 6,300 rpm.
My understanding is that the EJ-251 has usable torque by about 2,200 rpm and the torque curve seriously drops away after about 5,000 rpm.
There are differences in the exhaust systems between the series I SG and series II SG, and again between the series II SG and series I SH which also uses the EJ-253 until the middle of 2010.
Are they both called the EJ-253? And if so, what was the EJ-252 (assuming there was one)?
There was apparently an EJ-252 in the US market. See the Wikipedia article. I don't know if this engine was ever in any Oz DM car.
Yes, both are marked EJ-253 on the compliance plates, but with different engine suffixes. The engine block only has "EJ-25" cast into it, but again, the casting is different between the SG and the SH. I understand that the block is the same part number for the EJ-251 and EJ-253, which means that all the modifications are to the heads, cams, valve train, inlet and exhaust systems - and the ECU programming, of course. But if this is so, why are the block castings different between our two EJ-253 engines?
Taza is running an EJ-251 block and heads with an EJ-20 ECU running a piggy-back ECU which has been tuned for the EJ-251 IIRC. Even though his engine is N/A, it requires an ECU tune to fix the incompatibilities between the EJ-20 ECU and the EJ-251 motor. Doing this would also allow shifting the torque curve around a bit, and maybe altering its shape and extent by a little.
However, the things that allow for the ECU programming changes between the EJ-251 and the EJ-253 are all fairly major mechanical changes to the design of the inlet manifold system, the valve gear and camshafts, and probably the exhaust system. I don't know if the changes to the inlet valve lift has caused there to be changes to the exhaust valve timing and overall lift and cam profile parameters. It may have, is all I can say.
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:lol:.
to the ORS forum and its motley crew, mate ... 
