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2008 Subaru Wrx
(EJ20x Swap with STI ECU)
For all of your Performance needs
This is my 2008 Subaru WRX. Originally this car came to me with the intention of simply flipping it but having put so much work into the car it makes it difficult to let it go.
It started is life as a simple 2.5 Liter turbo boxer engine, while I was not there to experience it with the previous owner I could tell he had cared for the car, at some point maybe; bad advice, bad parts or a bad tune, something went catastrophically wrong and the engine now had an “inspection” window. I found it in a Copart auction in Georgia looking sorry for itself.
Almost a month after purchasing it It finally arrived at the shop in good albeit broken shape, surprisingly it still ran despite having an inspection port and a very mangled rod. The most mind boggling part is the fact that the engine had MANLEY H beam connecting rods supposedly good for around 400 wheel horsepower besides the obvious it also had Manley pistons and some sort of Aftermarket valves that were surprisingly unscathed. Around the engine I found a bigger turbo by the looks of it the compressor side seems to be made out of a billet piece of aluminum for faster spool up and a much bigger Process West intercooler to aid in cooling Intake air. While these performance modifications might sound like a car that is pushing 400 WHP it really seems the car in its 2.5 shape could not have made any more power than around 350 WHP, I say this because the car now makes around the same with a more efficient engine and the injectors are maxed out in the flowing capacity, meaning if the car at some point made more power the injectors were likely removed.
See this year Subaru has one key disadvantage (besides its weak piston crowns) and that is that the Air Fuel sensor (the sensor responsible for reporting to the ECU the air fuel mixture after combustion) is placed before the turbo and that creates a problem under high boost, the sensor cannot accurately read fuel mixture and thus the ECU has to some guess work so anything past around 5k rpm and full throttle the car will read 11.0 AFR (this is a good reading for these boxer engines under high load) In the higher RPMs, this in stock form is really no issue as the car has been extensively tested by Subaru at the time of making the car but once performance parts are being added and the car is being pushed, an aftermarket Air fuel sensor Post turbo is recommended.
My suspicion is the owner was tuning the car and without knowing anything better kept pushing the car further and further seeing the AFR (air fuel ratio) at the perfect 11 while in fact the car was running much leaner (and thus hotter) broke a rod in half, either due to detonation or heat (or both)
My plan was to make this car better than it was and I played with the Idea of putting an STI engine in but anything (even broken) was nearing the neighborhood of 2-5k dollars and that simply made no financial sense. Luckily for me (maybe you too) they call Subaru Lego cars for their ability to be put together from a wide list of engines, most 6 cylinder engines are direct copies of their 4 cylinder counter parts and the rods pistons and even valves are completely cross compatible.
The engine I found was actually from JDM Orlando and they had an Ej20x with less than 55k miles for $1500 local pick up which I thought was a great deal considering the alternatives, before continuing Id like to explain why these engines from japan are so prevalent here in the US. In Japan strict regulations favor newer more fuel efficient cars, when a car gets to be a certain age (not sure what the range is) it gets exponentially more expensive to own in the form of yearly taxes so owners simply trade them in or seller to avoid such fees, furthermore japan is known for its great public transportation system and densely packed cities which makes owning a car more of a leisure activity than an everyday need so every week hundredths of engines arrive in shipping containers with extremely low miles for the year for us to enjoy.
The Ej20x is a great engine for the sole fact that its not a 2.5L these 2.0L engines are better balanced (wont get into it too much but Conn. rod stroke ratios matter) they are not as robust as they are an open deck design as apposed to the semi deck on the 2.5 but the fact it has forged crowns and a similarly heat treated crankshaft as the 2.5L sti motor makes this a great alternative.
The engine has two potential downsides and they are that in this configuration they came with a Twin scroll turbo which relocates the AFR sensor after the turbo and if using a stock ECU (one for a USDM 2.5L) the computer is going to apply the same correction as if it was before the turbo, for this reason It becomes increasingly hard to use the stock turbo, while it would have made an amazing Low rpm torque monster the 2.5L turbo looked better and provided better top end torque. The second “issue” is that these motors are dual AVCS (Subaru’s version of VVT) and the WRX is only single AVCS. Two options came from this source a JDM ecu but this ECUs don’t have the Emission OBD standards in the US to pass SMOG so selling the car to anyone outside of a SMOG free state limited my buyer pool. The second option is to use a STI ECU, everyone told me that it was not possible because of the 2008+ Subaru CAN BUS protocol that allowed all modules to communicate using a two line connection, they said the different ecus would make the computer go bezerk and leave me in limp mode. While researching the can bus protocol I found that these messages are cryptic by design so there is no easy way to know what each message means and modify it because every manufacturer uses a different system to name them, It did not make sense Subaru would change the codes across such similar platforms. I decided to try anyways, I had to clone the EEPROM (chip used to save key data) from the WRX to STI ECU to make the car start but low and behold it all worked out. A few minor tweaks to the wiring that can be found on my YouTube video here and it all works like factory.
The finishing touches were simple in comparison, differential bushing to stop the big CLUNK when shifting aggressively (the diff hitting the car from so much torque)
1320 Equal length headers because I fell in love with the sound of the EJ20x videos I saw (also ELH aid in spool time and the bigger turbo needs it when paired to a smaller engine)
LC-2 wideband O2 Sensor for proper tuning (placed behind the turbo)
MST 18×8.5 wheels to take care of the cracked wheels I received the car with
The end goal was an Amazing car on the highway it really kept pushing and the top speed was never found as I ran out of road. The car was a great learning experience, If I could do something different is I would change the transmission for perhaps and Audi box, the Subaru design makes these boxes unreliable after 400whp and even upgraded (5-7k) they are still not ready for awesome AWD launches like we see in GTRs.
The car was sold to a local FL enthusiast on 09/27/2022