Lawson's 818C

The Complete 818 Coupe Documentation

Engine and Trans

Subaru WRX EJ05/EJ257 Hybrid Engine Teardown

Here is my donor car’s engine as I received it. It was a poorly running hybrid build with leaking fuel injectors, number stripped holes, poor painting, and issues just about everywhere you looked. In hindsight, I should not have bought the donor I did but I consider it a learning experience.

I quickly knew a full rebuild was in order for this one. And the story starts there…

Donor Engine Rebuild: My First Engine Build

I began the rebuild process by determining which parts were usable, which parts weren’t, and cleaning everything up to make it nice and shiny.

Washed all the engine parts in purple power degreaser. Then I found a great trick for cleaning parts- a rental apartment dishwasher! It gave the aluminum parts a really good final cleaning.

The parts I ended up using in my rebuild:

  • OEM STi complete gasket kit
  • JE Hybrid Pistons (for reducing compression of the EJ257/EJ205 “hybrid” engine)
  • King Bearings rod and main bearings
  • OEM STi 11mm oil pump
  • OEM water pump
  • Gates Racing timing belt, pulleys, and tensioner
  • ARP head bolts
  • Used STi OEM oil pan, pickup, and baffle.
  • Used STi side-feed injectors, TGVs, and fuel rails.

I painted the intake and valve covers in VHT wrinkle paint. They added a nice touch to the whole engine.

I cannot stress how important tolerances are on the rebuild! Make sure that the bearing tolerances, valve shim tolerances, piston ring tolerances, are all spot on. I think this is what contributed to my engine failure on the dyno and that was with me attempting to be careful but clearly I missed something. Read along on my “Updates” using the engine rebuild tag to see just how much work went into this rebuilt. It’s no small task!

They say you learn the most from making mistakes. And boy did I make my fair share of mistakes on this one!

Unfortunately my engine build had very short life. I took it to the dyno tuner, and once they began doing the high rpm tuning it developed what sounds like rod knock. I still haven’t taken the engine apart to figure out exactly what happened. I’m planning to part out the good bits as soon as I find the time to disassemble.

JDM Version 8 EJ207 Swap Into My 818

Being burnt out from the exhaustive and unsuccessful first engine rebuild, I had no desire to do another. I knew I was looking at finding a motor I wouldn’t have to work on. Something stock, unmodified. Which is hard to find in the world of Subaru WRXs it turns out! As I did more research, the JDM import engines seemed like a great option. Specifically, the EJ207 – the JDM WRX STI 2.0L Engine- appeared to be a good fit for the 818. More power and higher revving than a USDM WRX 2.0L. It has variable intake timing and a twin scroll turbo.

This being my decision, I bought a V8 JDM EJ207 to be my replacement engine. The only modifications required were that I would need to wire in the AVCS system which was done using a wiring kit provided by iWire. I also had to modify my exhaust because the turbo has a different downpipe flange.

I’m really happy with this decision! The engine runs great and is the perfect power level and character for a car like the 818. I think a high horsepower NA build would be ideal, but this is as close as you’ll get with a turbo 4.

Transmission Rebuild

Intake Plenum

I custom built an intake plenum out of sheet aluminum so that air from the roof scoop would flow through the factory intercooler. The 818 does not come with any provisions to do this, but it is likely necessary if you want to make sure that sufficient air is flowing through the intercooler. It gets hot back there! I cut the metal out on a waterjet, but the shapes are not terribly complex can could be cut using other means or even hand tools.

My intake plenum CAD: