We are using a 227hp EJ205 motor that is rated at 250hp in Japan. The Japanese version EJ205 has way more low end torque and throttle response. However,  it has different ECU, different cams, variable intake valve timing heads, and an approximately 95 octane gas to run on. The following paragraphs will lay out this difference in detail. But the biggest differences in power are better fuel, no mandated fuel economy regulations and slightly relaxed emissions regulations in Japan. Japan has pretty much frozen emissions regulations to equal our 1988 Federal standards. Gas is $5 or more a gallon, so fuel economy standards take care of themselves.

It is VERY important to realize from the start that we do not have a detuned 280hp STI EJ207 that is now only available in the STI versions. This is significant for a number of reasons. Most important our engine lacks forged pistons and the much better valve materials. But the EJ205 WRX engines also have smaller injectors, smaller runners, a different block, cams, and pistons and some other differences that lets the STI EJ207 motor live at high power and high rpm levels for a long time. Going for broke with a stock US WRX engine may be just that.

All WRX were pretty much the same until 1996. These were all EJ20G. There were also STI V1, V2 and V3 versions of this engine. By the time US enthusiasts began paying attention to the WRX, everyone knew about the 280 hp EJ20K motor  introduced in the 1997 WRX and fitted to all 97-98 WRX. The STI versions of this engine simply had different ECU, turbo, forged pistons, better valve materials and in the STI-WRX RA, different cams. On good gas the STI RA models made upwards of 320hp. In the mean time, the 5-door model in Japan and export WRX models continued on with earlier type WRX EJ20G hydraulic lifter motor with  a 9.0 compression ratio up rated to 250hp. For 1997 this hydraulic lifter motor was modernized with the new style intercooler and intake runner of the EJ20K. The export version of this EJ20G motor were 218hp through 1998.

1999 was an important year for Subaru engines. It saw the WRX and STI models with a revised EJ207 280hp motor and the 5-door with a newly designated 250hp EJ205. The EJ205 became the world motor and with improvements, it is what we have now. I will repeat that the much higher rated EJ207 has a different and stronger internal components.  This is very important to remember. We have put crate 1999-2000 EJ207 STI engines on a dyno with 100 octane gas and pulled a very easy 340hp with no modifications. The non-STI engines would eventually fail at this power level.

For 2001 there was bad news for Japanese WRX fans. The new style Japanese WRX model is no longer fitted with the 280hp EJ207. The EJ207 is now reserved for and only produced in STI form. Too many stock 1999-2000 WRX cars were trashing STI cars at the stop light, running the STI owner's image. So, the 250hp EJ205 became the basis of the standard Japanese market WRX and the export engines from 2001 on.  It is expensive to take the EJ205 motor to the reliable power levels of the EJ207 STI engine. Many loyal Japanese WRX owners do not want to replace their earlier 97-00 WRX with the new car for this reason. Their $24,000 WRX is just as quick than a new $32,000 STI WRX. This difference also limits our ability to make a true fire breathing WRX, despite magazine articles and promises of aftermarket parts makers.

The physical differences between the Japanese 250hp EJ205 and the 227hp Export EJ205 mentioned in the first paragraph have more to do the significantly higher octane of Japanese gas and their less rigid emissions regulations than any other factor. The Japanese engine can make a lot more midrange torque with the relaxed emission standards and better gas. We will constantly discuss the engine differences with reference to 91/93 octane fuel we burn. It limits our choices, and we have to constantly remember this fact.

The 227hp export spec EJ205 motor is tuned to run on 91 to 93 (US rating method) octane gas. In closing this section, I want to point out that the 250hp Audi 2.7T motor chips to a safe and easy 315hp. If we do a little math and factor the displacement difference between the 2 liter Subaru and the 2.7 Audi, we discover if the Subaru were 2.7 liters it would have 306hp as delivered. So off the showroom floor, the stock Subaru WRX engine has roughly the power chip tuners can get out of the Audi 2.7. It points out that the American WRX is in a relatively high state of tune already, when our fuel octane is taken into account. A 2.7t Audi v-6 with modified parts installed can be tuned to the ragged edge for about 365hp and the WRX can just touch 280hp on 93 octane. But this would be on a cool, damp day, and I would hesitate to thrash the motor at the track unless it had full detonation control and EGT limiting software of the factory ECU unit still working. More on this in the two sections one level down.