Found this there think was written bye a NASIOC Member 
This is not an FAQ for the EJ207 thread, but a collection of info that I have, which will allow those that are interested in these awesome engines to be informed more efficiently and not to have to go and re-ask the same questions in the said thread over and over again.
My style has been to clearly differentiate what I hold as fact (supported by backup) from what I have seen others post.
I will point out facts and mention some of the more interesting things that I've seen people post, again describing them as such.
What is an EJ207?
It is an engine that has been in production (wikipedia) since 1999.
It is still in production today and used for Sti and Sti Spec C cars for the Japanese market.
In time, this engine has equipped Subaru Impreza Sti cars in many countries, in Asia, in Europe, in Australiaand New Zealand and maybe in South Africa.
I think I saw a ROM for a South African market version.
It was never made available for the US market.
It is considered a 2.0 (1994 cubical cm) and has the following main measurements (factory brochure):
BorexStroke 3.62"x2.95"
Compression ratio 8.0 +_0.2
It is semi-closed deck.
To be noted is that the latest EJ207 for Spec C models has a configuration of sleeve support that can be called better than semi-closed deck.
Some versions have had forged pistons and some have had cast pistons.
Some versions have had equal length headers, most of these with twinscroll. The differences will be reviewed below.
Why was the EJ207 engine not made available for the US market?
Facts:
In 2003, Mitsubishi created a site with a countdown clock for their upcoming Lancer Evolution launching for the US market.
Subaru was at the time a competitor of Mitsubishi in the WRC and had similar vehicles in their line-up for sales.
Both companies were emphasising sportiness, handling and AWD.
Theory:
Subaru wanted to create a vehicle that would upstage the Lancer Evolution. The terms of the upstaging were never "which could be modded to produce more HP", but "which is more enjoyable stock".
Subaru may have felt at the time that the 2.5 provides more torque and more HP than the Lancer and that at the time, it was showcasing quite a number of technologies and gadgets making the EJ257 equipped Sti more desirable/enjoyable than the Lancer.
Brief history of the EJ207
Begins in 99 with semi-closed deck and coil pack over manifold.
The subject of AVCS for early EJ207 has been debated in the past on this board.
With the appearance of the "New Age" Impreza, Subaru dropped the "Version" designation for the Impreza Sti, they differentiate the Sti by the factory designation "revision" A-G.
The talk of versions, which continues, is only a fan-club talk and we are trying to put some order into what we are describing:
Factory revisions A and B, amounting from 02/01/2000 to 10/31/2002, are called V7
Factory revisions C and D, amounting from 09/01/'02 to 05/31/'04, are called V8
Factory revisions E, F, G amounting from 03/01/'04 to 04/30/'07, are called V9
GRB bodystyle EJ207 are called V10.
As information, UK guys call a revision F and G a V10 and I think I've seen Australians call a rev F V10 and a rev G V11.
Both UK and AUS, due to being RHD, are better environments to have complete JDM cars on the street and under my opinion, there are a lot more of the complete cars on the road, than there are in the US.
Once you discuss complete cars, it becomes useful to have a conversation based on factory code number (It's the code that begins with GDB) and it can be useful to discuss V10 and V11 in GDB. However, in US, with only having engine, or only engine and transmission, there will be too few differences between a rev E, F, and G and it is suitable to call all of these a V9.
Also, discussing code numbers does not seem to be productive, when the engines of the two codes are actually identical and the difference between the two codes is a set of stickers that one car had and one did not have. If you will never see the donor car, it's a waste of time, I think.
I will focus this information on engines that start with V7.
The Gentleman's Agreement (jishu-kisei)
Wikipedia/Theory: Sometime in 1988 there has been a meeting between the top executives in the Japanese automobile manufacturing industry, regarding the production of cars for usage in the Japanese Domestic Market.
At this meeting, a more or less verbal agreement had been reached, to the effect that no Japanese maker will make available for the domestic market a vehicle with an output higher than 280 HP (crank).
Now, understand that the definition of the HP differs from US to Japan to EU, so you will see numbers anywhere from 280 to 275, depends on who's horses we're counting.
As time went by, nobody wanted to be second in domestic car magazine reviews, so rumor had it that all makers continued to advertise 280 but beefed up the power significantly....
The agreement never was intended to cover one-off vehicles or limited series, therefore the S 202, 203, 204 were advertised always at full potential. Also, I have never seen anything suggesting that the torque was going to also be limited, so the advertised torque could have been realistic.
The agreement was said to have been widely considered invalidated in 2004, so it is an interesting exercise to locate factory specs for a 2006-2007 Sti and compare them with earlier advertisements.
The importance of the Agreement is going to become clear when I will start to list advertised engine output below..
Involvement in Motorsports
According to Wikipedia, the Rally engines were develloped beginning, at the base, with an EJ207. Of course, a rally engine is a very-very expensive engine, well beyond the resources of .. your common guy.
Why would I want an EJ207 in my car, what can it do for me?
Theory:
What has been said about the EJ207 is that is the genuinely "under-rated Japanese engine", maybe due to the Gentleman's agreement, they were laying the hardware foundation to keep quietly increasing the power every year, to stay ahead of the competition.
Basically, this is best suited for someone that does have a relatively tight budget and wants to avoid the constant horror stories about ringlands of the EJ257, the constant horror stories about spun bearings of the EJ205 and the constant sories about lower-end-power built engines still needing refresh/rebuilds every so often.
My personal opinion is that a built EJ207 is not any more reliable than a built EJ257, I think this reliabillity is only for the factory put together engines.
Basically, the hope with an EJ207 is that you reach a power level that allows you to enjoy your car and still run without a rebuild 100K miles or maybe even more.
The power levels will differ based on driving style, quality of mods and quality of tune.
Special versions of the EJ207 engine
Type RA Sti Rev A (Version 7 engines)
People usually refer to these wrongly as V7 Spec C. Spec C did not exist as a designation right away, when the bugeye Sti began.
These engines were the only ones to have different and bigger ports on the inlet ports of the heads. The ports are bigger due to extra 0.5mm smoothing of the port radius on the narrow side of the "pear" shape. Also, these had the shoulder removed by the valve guide in the casting of the head, at the intake port.
All the following years Sti and Spec C have the same size ports on the intake.
Sti Spec C Type RA Rev B (Version 7 engines)
These engines were the only ones to receive dedicated internal engine parts in GDB. They got only for '02 special springs and special cams. The cams were then used on all Sti for the next year. Different turbo, with roller bearings, VF34, the ROM reflected this.
To recap: Rev A, is not called Spec C yet, gets slightly bigger ports. Rev B, is called Spec C type RA, gets run of the mill JDM big ports, but gets upgraded cams and springs.
V8 Spec C engines
The V8 Spec C received a different turbo, the VF36, with roller bearings. Some sources indicate it has titanium aluminide turbine and shaft. I tried to check mine with a magnet, but it's not a good test unless you remove the housings, which is not that easy on VF ballbearing turbos.
There is an intercooler autowash feature that can be activated from the ECU that stabilizes the intake temperature, using tables in the ECU.
The intercooler received a redesign, compared with a V7.
There are two possible spec C engines, with all years: there is a model with A/C and one without. The one without gets a different front belt cover, metal. The Type RA designation that some Spec C carry may or may not be related to this.
V9 Spec C engines
The V9 Spec C also received the VF36 turbo. An optional package became available for the Spec C engines, for Air-to-Air oil cooler. I like to call it oil radiator, to differenciate it easier from oil cooler. The oil radiator package, replaces the oil cooler with an oil manifold, that then is connected via rubber couplers (no ordinary rubber), to a metal oil riser that takes the oil behind the right side headlight and in front of the coolant radiator where some more rubber couplers connect it to the oil radiator.
The oil manifold is thermostatic and there is a group N option for braided hoses adaptor.
There is an intercooler autowash feature that can be activated from the ECU that stabilizes the intake temperature, using tables in the ECU. This engine received a more advanced intercooler than the V8, but still not so advanced as a GRB Sti intercooler.
S202 Engines
I have separated this engine from the other S engines, because I have read from some sources that it came with a special exhaust manifold, equal length. The turbo was a VF34, like the Spec C. It got OEM the expensive sti turbo inlet. It did not get an immobilizer. It did not receive separate assembly line ballancing. The ROM reflects equal length headers and the settings differ from even the Spec C. The engine speed limit is still 8000 rpm.
This engine received a separate oil cooler package with braided stainless hoses. There was no version for the Spec C V7 for oil radiator.
S203-S204, RA-R Engines
These engines received the VF42 turbo. I have seen one picture of this turbo with a compressor wheel speed sensor port. All sources indicate this turbo as having titanium aluminide turbine and shaft, with 9 turbine blades.
If Ti-Al has a affinity for bright-red oxidation, then this can confirm that this is the material for the VF42. VF36 also does bright red oxidation.
The ROM is different for these, notable the AVCS more aggressive and timing map different.
They came from the factory with oil radiator, the same one as the Spec C.
The S204 had immobilizer for sure. The S203 may have had it too.
I have seen no evidence of hand porting of the inlets of the heads on these.
The internals have been separately ballanced for the S203 (official info), The internals have been select weight ballanced and crank manually ballanced for S204 (official info).
The RA-R was not ballanced (official info).
It has been said that the ballanced engines have marks by the flywheel.
The Ra-R below has no marks.
The speed limit for these engines is still 8000 rpm.
Other special engines
There could also be a yet different category of engines, that the factory provides for privateers. These are not the super-expensive Rally engines, nor the Prodrive engines. You can get an idea by looking at the WRSpares inventory.
I arbitrarily have decided to call these "inbetween engines" "group N engines".
These may sometimes show up in a batch of imported used engines and some of the guys that look into these engines see features that they then extrapolate to the whole line of JDM Sti engines.
Differences between standard Sti engines V7-V9
Internal differences
I think the best available info about differences in V7-V9 and Spec C versions can be found in the work of Jeff Sponaugle, a compiled huge list of all part numbers of all JDM and export Ej207.
This image has been resized. Click this bar to view the full image. The original image is sized 1234x896 and is 811KB.
This image has been resized. Click this bar to view the full image. The original image is sized 1345x911 and is 792KB.
It is to be noted that the models for '05 are wrong in that they should be designated (By Ex.:GDAD4HD should read GDAE4HD). Rev E has E in 4th position. This will not affect anything else.
In short:
V7 pistons are different, universally said is that these are forged, evidence below.
I found information at the APS site, comparing a USDM Sti piston with what had been the standard before it, a forged piston.
http://www.airpowersystems.com/us_sp...ns/pistons.htm
Forged piston is 12 grams lighter, but the pin is 10 grams heavier, with most weight distributed around the centre.
V8+ pistons are cast, hypereuthectic.
Here is a link to a photo of part number 12006AC430, the piston for V8-9
http://www.rallyandracing.biz/subaru...on.html?lang=1
In the link, at the sides of the piston, by the wrist pin bore there are casting marks where the forged pistons are smooth.
V8 and V9 receive an updated block, and crankshaft and heads. The crankshaft is said to be doublecrossdrilled.
V9 receive updated rods, these rods are backward compatible, are the same part number as the USDM rods.
V8 use the V7 spec C cam, without those V7 Spec C springs
V9 get updated cam
Overall, V9 is a completely different engine from the V7, with different part numbers for all main parts, except valve springs. Those they only briefly tried to upgrade back in '02.
Important Note
EJ207 for other than JDM, continued with forged pistons beyond V7. It was discontinued with the arrival of the EJ255-257 in 2006. The V8 export (UK, AUS, EU, SA), was likely not twinscroll, different than JDM turbo.
Other Differences
V7 are single scroll, AVCS, throttle by cable, topfeed injectors, engines.
The TGV are deleted from the factory, but the TGV partition wall inside the TGV body is not. The factory deletion is incomplete, even on the Spec C and even on the Type RA.
The exhaust is compatible all the way to the downpipe to the USDM WRX/Sti.
The oil pan is like the USDM WRX 2.0
The Turbo is the VF30.
The ECU has the same number and shape harness plugs as the USDM WRX 2.0.
There is no immobilizer.
The engine speed is limited from the factory at 8000rpm
V8, 9 are twinscroll, AVCS, throttle by cable, topfeed injectors, engines.
There are no TGV's, the intake manifold is one piece.
The spark plugs are specified one step colder, compared with other Sti.
The exhaust is completely different/incompatible with the USDM WRX/Sti, all the way from the header to the downpipe. It can be replaced by a USDM exhaust, the USDM does bolt up to the block.
The oil pan is like the USDM Sti.
The turbo is a VF37.
The ECU has the same number and shape harness plugs as the USDM WRX 2.0
There is no immobilizer for V8 and for some V9.
The V9 known so far to not have immobilizer have been early V9 Spec C (revision E engines).
The engine speed is limited from the factory at 8000 rpm
When compared with the USDM A/C Compressor, the JDM Sti is of a different part number and smaller in size. It is possible that the losses while using it are smaller.
Many have an additional intake air temperature sensor by the throttle body. It's function has been discussed but not completely clarified.
The power steering pump is different. The JDM cars included some Spec C with 13:1 steering rack. The pump remained the same, so it is designed to handle a fast rack.
The com protocol is not canbus for any of these.
Some of the Sti engines don't come with provision for cruise control. It's next to impossible to tell which had it.
The ROM settings are quite different from a V7.
The turbo inlet has one less connection in it and most likely is of a larger diameter than the USDM, from the factory.
The front Oxygen sensor has been relocated after the turbo, in the downpipe. Some people on the forum (including me) feel that with this location the readings are accurate enough, down to the limit of this unit. It is still not a wideband, you won't have readings in the 11 range and below.
Advertised Engine Output
Sti 2002 (internet source)
Horsepower (PS/rpm) 280 / 6000 [206kW/rpm]
Torque 394N.m/rpm(Kgm/rpm) 40.2 / 3500
Meaning: 290.5 ftlb @ 3500 RPM, 276.1 BHP
Comments: the single scroll provides the fastest spool, stock.
Sti Type Ra Spec C 2002 (from press release)
Max. torque output 384 Nm
Max. Power "Enhanced power"
Meaning: 283.4 ftlb
Comments: there was really no figure on power and neither on the RPM at which the torque was reached. This was with those special valve springs too.
2004 Sti Spec C (internet source)
Max. Power 205.8 kw / 276 bhp @ 6400 rpm
Max torque 412 nm / 303.9 ft lbs @ 4400 rpm
Meaning: 303.9 ftlb @ 4400 , 276 BHP
Comments: the twinscroll arrives, bringing higher torque, but slowing spool down. I have to revisit my stock JDM ROM collection, but I think that the boost went up a bit like 1 PSI.
2005 Sti (internet source)
Horsepower (PS/rpm) 280 / 6400 [206kW/rpm]
Torque 422N.m/rpm(Kgm/rpm) 43.0 / 4400
Meaning: 311.2 ftlb @ 4400 , 276.1 BHP
Comments: V9 arrives, with the completion of engine internals updates and they are confident to increase the torque at this point.
2005 Sti Spec C (internet source)
Horsepower (PS/rpm) 280 / 6400 [206kW/rpm]
Torque 422N.m/rpm(Kgm/rpm) 43.0 / 4400
Meaning: 311.2 ftlb @ 4400, 276.1 BHP
Comments: The ROM shows an earlier spool designed for the Spec C and a higher boost designed for the Sti, the maximum numbers don't tell the whole story.
2007 Sti Spec C (internet source)
Max. Power 205.8 kw / 276 bhp @ 6400 rpm
Max Torque 422 nm / 311.3 ft lbs @ 4400 rpm
Meaning: 311.3 ftlb @ 4400, 276 BHP
Comments: no more changes in performance at this point. This is another reason for which this is also called a V9.
S202 (from official page)
Max. Output (net) 235 kW (320 ps) / 6400 rpm
Max. Torque (net) 384 Nm (39.2 kgm) / 4400 rpm
Meaning: 283.2 ftlb @ 4400, 315.6 BHP
Comments: the RPM at which this is reached suggests the equal length headers.
S203
Max. Output (net) 235 kW (320 ps) / 6400 rpm
Max. Torque (net) 422 Nm (43.0 kgm) / 4400 rpm
Meaning: 311.2 ftlb @ 4400, 315.6 BHP
Comments: Twinscroll arrives to the S engines. Increased torque is reached.
S204
Max. Output (net) 235 kW (320 ps) / 6400 rpm
Max. Torque (net) 432 Nm (44.0 kgm) / 4400 rpm
Meaning: 318.6 ftlb @ 4400, 315.6 BHP
Comments: V9 arrives, with internals updates completed, they are confident to reach a higher torque.
Type RA-R
Max. Output (net) 235 kW (320 ps) / 6400 rpm
Max. Torque (net) 432 Nm (44.0 kgm) / 4400 rpm
Meaning: 318.6 ftlb @ 4400, 315.6 BHP
Comments: while this engine has the same performance as an S204, the car is faster, because it also combines Spec C lightness into the mix, something that the S cars did not have. The difference in weight of the two cars is signifficant.
source http://sub-machina.blogspot.ie/2012/08/so-i-decided-to-put-together-some.html
This is not an FAQ for the EJ207 thread, but a collection of info that I have, which will allow those that are interested in these awesome engines to be informed more efficiently and not to have to go and re-ask the same questions in the said thread over and over again.
My style has been to clearly differentiate what I hold as fact (supported by backup) from what I have seen others post.
I will point out facts and mention some of the more interesting things that I've seen people post, again describing them as such.
What is an EJ207?
It is an engine that has been in production (wikipedia) since 1999.
It is still in production today and used for Sti and Sti Spec C cars for the Japanese market.
In time, this engine has equipped Subaru Impreza Sti cars in many countries, in Asia, in Europe, in Australiaand New Zealand and maybe in South Africa.
I think I saw a ROM for a South African market version.
It was never made available for the US market.
It is considered a 2.0 (1994 cubical cm) and has the following main measurements (factory brochure):
BorexStroke 3.62"x2.95"
Compression ratio 8.0 +_0.2
It is semi-closed deck.
To be noted is that the latest EJ207 for Spec C models has a configuration of sleeve support that can be called better than semi-closed deck.
Some versions have had forged pistons and some have had cast pistons.
Some versions have had equal length headers, most of these with twinscroll. The differences will be reviewed below.
Why was the EJ207 engine not made available for the US market?
Facts:
In 2003, Mitsubishi created a site with a countdown clock for their upcoming Lancer Evolution launching for the US market.
Subaru was at the time a competitor of Mitsubishi in the WRC and had similar vehicles in their line-up for sales.
Both companies were emphasising sportiness, handling and AWD.
Theory:
Subaru wanted to create a vehicle that would upstage the Lancer Evolution. The terms of the upstaging were never "which could be modded to produce more HP", but "which is more enjoyable stock".
Subaru may have felt at the time that the 2.5 provides more torque and more HP than the Lancer and that at the time, it was showcasing quite a number of technologies and gadgets making the EJ257 equipped Sti more desirable/enjoyable than the Lancer.
Brief history of the EJ207
Begins in 99 with semi-closed deck and coil pack over manifold.
The subject of AVCS for early EJ207 has been debated in the past on this board.
With the appearance of the "New Age" Impreza, Subaru dropped the "Version" designation for the Impreza Sti, they differentiate the Sti by the factory designation "revision" A-G.
The talk of versions, which continues, is only a fan-club talk and we are trying to put some order into what we are describing:
Factory revisions A and B, amounting from 02/01/2000 to 10/31/2002, are called V7
Factory revisions C and D, amounting from 09/01/'02 to 05/31/'04, are called V8
Factory revisions E, F, G amounting from 03/01/'04 to 04/30/'07, are called V9
GRB bodystyle EJ207 are called V10.
As information, UK guys call a revision F and G a V10 and I think I've seen Australians call a rev F V10 and a rev G V11.
Both UK and AUS, due to being RHD, are better environments to have complete JDM cars on the street and under my opinion, there are a lot more of the complete cars on the road, than there are in the US.
Once you discuss complete cars, it becomes useful to have a conversation based on factory code number (It's the code that begins with GDB) and it can be useful to discuss V10 and V11 in GDB. However, in US, with only having engine, or only engine and transmission, there will be too few differences between a rev E, F, and G and it is suitable to call all of these a V9.
Also, discussing code numbers does not seem to be productive, when the engines of the two codes are actually identical and the difference between the two codes is a set of stickers that one car had and one did not have. If you will never see the donor car, it's a waste of time, I think.
I will focus this information on engines that start with V7.
The Gentleman's Agreement (jishu-kisei)
Wikipedia/Theory: Sometime in 1988 there has been a meeting between the top executives in the Japanese automobile manufacturing industry, regarding the production of cars for usage in the Japanese Domestic Market.
At this meeting, a more or less verbal agreement had been reached, to the effect that no Japanese maker will make available for the domestic market a vehicle with an output higher than 280 HP (crank).
Now, understand that the definition of the HP differs from US to Japan to EU, so you will see numbers anywhere from 280 to 275, depends on who's horses we're counting.
As time went by, nobody wanted to be second in domestic car magazine reviews, so rumor had it that all makers continued to advertise 280 but beefed up the power significantly....
The agreement never was intended to cover one-off vehicles or limited series, therefore the S 202, 203, 204 were advertised always at full potential. Also, I have never seen anything suggesting that the torque was going to also be limited, so the advertised torque could have been realistic.
The agreement was said to have been widely considered invalidated in 2004, so it is an interesting exercise to locate factory specs for a 2006-2007 Sti and compare them with earlier advertisements.
The importance of the Agreement is going to become clear when I will start to list advertised engine output below..
Involvement in Motorsports
According to Wikipedia, the Rally engines were develloped beginning, at the base, with an EJ207. Of course, a rally engine is a very-very expensive engine, well beyond the resources of .. your common guy.
Why would I want an EJ207 in my car, what can it do for me?
Theory:
What has been said about the EJ207 is that is the genuinely "under-rated Japanese engine", maybe due to the Gentleman's agreement, they were laying the hardware foundation to keep quietly increasing the power every year, to stay ahead of the competition.
Basically, this is best suited for someone that does have a relatively tight budget and wants to avoid the constant horror stories about ringlands of the EJ257, the constant horror stories about spun bearings of the EJ205 and the constant sories about lower-end-power built engines still needing refresh/rebuilds every so often.
My personal opinion is that a built EJ207 is not any more reliable than a built EJ257, I think this reliabillity is only for the factory put together engines.
Basically, the hope with an EJ207 is that you reach a power level that allows you to enjoy your car and still run without a rebuild 100K miles or maybe even more.
The power levels will differ based on driving style, quality of mods and quality of tune.
Special versions of the EJ207 engine
Type RA Sti Rev A (Version 7 engines)
People usually refer to these wrongly as V7 Spec C. Spec C did not exist as a designation right away, when the bugeye Sti began.
These engines were the only ones to have different and bigger ports on the inlet ports of the heads. The ports are bigger due to extra 0.5mm smoothing of the port radius on the narrow side of the "pear" shape. Also, these had the shoulder removed by the valve guide in the casting of the head, at the intake port.
All the following years Sti and Spec C have the same size ports on the intake.
Sti Spec C Type RA Rev B (Version 7 engines)
These engines were the only ones to receive dedicated internal engine parts in GDB. They got only for '02 special springs and special cams. The cams were then used on all Sti for the next year. Different turbo, with roller bearings, VF34, the ROM reflected this.
To recap: Rev A, is not called Spec C yet, gets slightly bigger ports. Rev B, is called Spec C type RA, gets run of the mill JDM big ports, but gets upgraded cams and springs.
V8 Spec C engines
The V8 Spec C received a different turbo, the VF36, with roller bearings. Some sources indicate it has titanium aluminide turbine and shaft. I tried to check mine with a magnet, but it's not a good test unless you remove the housings, which is not that easy on VF ballbearing turbos.
There is an intercooler autowash feature that can be activated from the ECU that stabilizes the intake temperature, using tables in the ECU.
The intercooler received a redesign, compared with a V7.
There are two possible spec C engines, with all years: there is a model with A/C and one without. The one without gets a different front belt cover, metal. The Type RA designation that some Spec C carry may or may not be related to this.
V9 Spec C engines
The V9 Spec C also received the VF36 turbo. An optional package became available for the Spec C engines, for Air-to-Air oil cooler. I like to call it oil radiator, to differenciate it easier from oil cooler. The oil radiator package, replaces the oil cooler with an oil manifold, that then is connected via rubber couplers (no ordinary rubber), to a metal oil riser that takes the oil behind the right side headlight and in front of the coolant radiator where some more rubber couplers connect it to the oil radiator.
The oil manifold is thermostatic and there is a group N option for braided hoses adaptor.
There is an intercooler autowash feature that can be activated from the ECU that stabilizes the intake temperature, using tables in the ECU. This engine received a more advanced intercooler than the V8, but still not so advanced as a GRB Sti intercooler.
S202 Engines
I have separated this engine from the other S engines, because I have read from some sources that it came with a special exhaust manifold, equal length. The turbo was a VF34, like the Spec C. It got OEM the expensive sti turbo inlet. It did not get an immobilizer. It did not receive separate assembly line ballancing. The ROM reflects equal length headers and the settings differ from even the Spec C. The engine speed limit is still 8000 rpm.
This engine received a separate oil cooler package with braided stainless hoses. There was no version for the Spec C V7 for oil radiator.
S203-S204, RA-R Engines
These engines received the VF42 turbo. I have seen one picture of this turbo with a compressor wheel speed sensor port. All sources indicate this turbo as having titanium aluminide turbine and shaft, with 9 turbine blades.
If Ti-Al has a affinity for bright-red oxidation, then this can confirm that this is the material for the VF42. VF36 also does bright red oxidation.
The ROM is different for these, notable the AVCS more aggressive and timing map different.
They came from the factory with oil radiator, the same one as the Spec C.
The S204 had immobilizer for sure. The S203 may have had it too.
I have seen no evidence of hand porting of the inlets of the heads on these.
The internals have been separately ballanced for the S203 (official info), The internals have been select weight ballanced and crank manually ballanced for S204 (official info).
The RA-R was not ballanced (official info).
It has been said that the ballanced engines have marks by the flywheel.
The Ra-R below has no marks.
The speed limit for these engines is still 8000 rpm.
Other special engines
There could also be a yet different category of engines, that the factory provides for privateers. These are not the super-expensive Rally engines, nor the Prodrive engines. You can get an idea by looking at the WRSpares inventory.
I arbitrarily have decided to call these "inbetween engines" "group N engines".
These may sometimes show up in a batch of imported used engines and some of the guys that look into these engines see features that they then extrapolate to the whole line of JDM Sti engines.
Differences between standard Sti engines V7-V9
Internal differences
I think the best available info about differences in V7-V9 and Spec C versions can be found in the work of Jeff Sponaugle, a compiled huge list of all part numbers of all JDM and export Ej207.
This image has been resized. Click this bar to view the full image. The original image is sized 1234x896 and is 811KB.
This image has been resized. Click this bar to view the full image. The original image is sized 1345x911 and is 792KB.
It is to be noted that the models for '05 are wrong in that they should be designated (By Ex.:GDAD4HD should read GDAE4HD). Rev E has E in 4th position. This will not affect anything else.
In short:
V7 pistons are different, universally said is that these are forged, evidence below.
I found information at the APS site, comparing a USDM Sti piston with what had been the standard before it, a forged piston.
http://www.airpowersystems.com/us_sp...ns/pistons.htm
Forged piston is 12 grams lighter, but the pin is 10 grams heavier, with most weight distributed around the centre.
V8+ pistons are cast, hypereuthectic.
Here is a link to a photo of part number 12006AC430, the piston for V8-9
http://www.rallyandracing.biz/subaru...on.html?lang=1
In the link, at the sides of the piston, by the wrist pin bore there are casting marks where the forged pistons are smooth.
V8 and V9 receive an updated block, and crankshaft and heads. The crankshaft is said to be doublecrossdrilled.
V9 receive updated rods, these rods are backward compatible, are the same part number as the USDM rods.
V8 use the V7 spec C cam, without those V7 Spec C springs
V9 get updated cam
Overall, V9 is a completely different engine from the V7, with different part numbers for all main parts, except valve springs. Those they only briefly tried to upgrade back in '02.
Important Note
EJ207 for other than JDM, continued with forged pistons beyond V7. It was discontinued with the arrival of the EJ255-257 in 2006. The V8 export (UK, AUS, EU, SA), was likely not twinscroll, different than JDM turbo.
Other Differences
V7 are single scroll, AVCS, throttle by cable, topfeed injectors, engines.
The TGV are deleted from the factory, but the TGV partition wall inside the TGV body is not. The factory deletion is incomplete, even on the Spec C and even on the Type RA.
The exhaust is compatible all the way to the downpipe to the USDM WRX/Sti.
The oil pan is like the USDM WRX 2.0
The Turbo is the VF30.
The ECU has the same number and shape harness plugs as the USDM WRX 2.0.
There is no immobilizer.
The engine speed is limited from the factory at 8000rpm
V8, 9 are twinscroll, AVCS, throttle by cable, topfeed injectors, engines.
There are no TGV's, the intake manifold is one piece.
The spark plugs are specified one step colder, compared with other Sti.
The exhaust is completely different/incompatible with the USDM WRX/Sti, all the way from the header to the downpipe. It can be replaced by a USDM exhaust, the USDM does bolt up to the block.
The oil pan is like the USDM Sti.
The turbo is a VF37.
The ECU has the same number and shape harness plugs as the USDM WRX 2.0
There is no immobilizer for V8 and for some V9.
The V9 known so far to not have immobilizer have been early V9 Spec C (revision E engines).
The engine speed is limited from the factory at 8000 rpm
When compared with the USDM A/C Compressor, the JDM Sti is of a different part number and smaller in size. It is possible that the losses while using it are smaller.
Many have an additional intake air temperature sensor by the throttle body. It's function has been discussed but not completely clarified.
The power steering pump is different. The JDM cars included some Spec C with 13:1 steering rack. The pump remained the same, so it is designed to handle a fast rack.
The com protocol is not canbus for any of these.
Some of the Sti engines don't come with provision for cruise control. It's next to impossible to tell which had it.
The ROM settings are quite different from a V7.
The turbo inlet has one less connection in it and most likely is of a larger diameter than the USDM, from the factory.
The front Oxygen sensor has been relocated after the turbo, in the downpipe. Some people on the forum (including me) feel that with this location the readings are accurate enough, down to the limit of this unit. It is still not a wideband, you won't have readings in the 11 range and below.
Advertised Engine Output
Sti 2002 (internet source)
Horsepower (PS/rpm) 280 / 6000 [206kW/rpm]
Torque 394N.m/rpm(Kgm/rpm) 40.2 / 3500
Meaning: 290.5 ftlb @ 3500 RPM, 276.1 BHP
Comments: the single scroll provides the fastest spool, stock.
Sti Type Ra Spec C 2002 (from press release)
Max. torque output 384 Nm
Max. Power "Enhanced power"
Meaning: 283.4 ftlb
Comments: there was really no figure on power and neither on the RPM at which the torque was reached. This was with those special valve springs too.
2004 Sti Spec C (internet source)
Max. Power 205.8 kw / 276 bhp @ 6400 rpm
Max torque 412 nm / 303.9 ft lbs @ 4400 rpm
Meaning: 303.9 ftlb @ 4400 , 276 BHP
Comments: the twinscroll arrives, bringing higher torque, but slowing spool down. I have to revisit my stock JDM ROM collection, but I think that the boost went up a bit like 1 PSI.
2005 Sti (internet source)
Horsepower (PS/rpm) 280 / 6400 [206kW/rpm]
Torque 422N.m/rpm(Kgm/rpm) 43.0 / 4400
Meaning: 311.2 ftlb @ 4400 , 276.1 BHP
Comments: V9 arrives, with the completion of engine internals updates and they are confident to increase the torque at this point.
2005 Sti Spec C (internet source)
Horsepower (PS/rpm) 280 / 6400 [206kW/rpm]
Torque 422N.m/rpm(Kgm/rpm) 43.0 / 4400
Meaning: 311.2 ftlb @ 4400, 276.1 BHP
Comments: The ROM shows an earlier spool designed for the Spec C and a higher boost designed for the Sti, the maximum numbers don't tell the whole story.
2007 Sti Spec C (internet source)
Max. Power 205.8 kw / 276 bhp @ 6400 rpm
Max Torque 422 nm / 311.3 ft lbs @ 4400 rpm
Meaning: 311.3 ftlb @ 4400, 276 BHP
Comments: no more changes in performance at this point. This is another reason for which this is also called a V9.
S202 (from official page)
Max. Output (net) 235 kW (320 ps) / 6400 rpm
Max. Torque (net) 384 Nm (39.2 kgm) / 4400 rpm
Meaning: 283.2 ftlb @ 4400, 315.6 BHP
Comments: the RPM at which this is reached suggests the equal length headers.
S203
Max. Output (net) 235 kW (320 ps) / 6400 rpm
Max. Torque (net) 422 Nm (43.0 kgm) / 4400 rpm
Meaning: 311.2 ftlb @ 4400, 315.6 BHP
Comments: Twinscroll arrives to the S engines. Increased torque is reached.
S204
Max. Output (net) 235 kW (320 ps) / 6400 rpm
Max. Torque (net) 432 Nm (44.0 kgm) / 4400 rpm
Meaning: 318.6 ftlb @ 4400, 315.6 BHP
Comments: V9 arrives, with internals updates completed, they are confident to reach a higher torque.
Type RA-R
Max. Output (net) 235 kW (320 ps) / 6400 rpm
Max. Torque (net) 432 Nm (44.0 kgm) / 4400 rpm
Meaning: 318.6 ftlb @ 4400, 315.6 BHP
Comments: while this engine has the same performance as an S204, the car is faster, because it also combines Spec C lightness into the mix, something that the S cars did not have. The difference in weight of the two cars is signifficant.
source http://sub-machina.blogspot.ie/2012/08/so-i-decided-to-put-together-some.html
