NEW WRX STI TYPE RA S209 SHORT BLOCK ENGINE

This engine block is identical to the newest ones, labeled “705.” It features the same full-counterweight crankshaft, treated with nitriding, as seen in earlier EJ25 models. However, this crankshaft lacks the extra oiling ports present in some special edition EJs. Up to this point, the bearings and clearances fall within the usual specifications for late-model EJ257 engines.

Type RA Piston Differences

At first glance, both the Type RA and STI pistons seem to be machined cast items. The volume of the dish in each piston is very similar, and the depth of the valve reliefs matches as well. Unfortunately, the Type RA does not come with forged pistons, which some had hoped for. However, we haven't completely ruled out the idea that the materials used for the Type RA pistons might be a different alloy that is more resistant to breaking (more ductile), given that they are produced by Hitachi instead of Aisin. Additionally, it looks like the Type RA pistons have crowns that are about 1 to 2mm thicker than those of the STI pistons, although this is difficult to see in the image.

When observing the pistons from the side, a few distinctions become evident. To begin with, the top ringland coating on earlier STI pistons reaches the crown, likely due to variations in manufacturing methods (less or different tooling), rather than indicating any notable performance changes. Additionally, the Type RA piston has significantly more material around the wrist pin for support.The compression height, positions of the rings, and other measurements seem unchanged. This indicates that neither the position nor the thickness of the ringlands has altered. The gaps for the top rings were measured at 0.010″, 0.010″, 0.011″, and 0.011″, while the lower ring gaps were recorded at 0.014″, 0.014″, 0.014″, and 0.015″.

From the base, you can observe the increased material around the wrist pin area (marked in red) and the decreased size of the large center support (highlighted in green). The Type RA structure excels in piston strength because it lessens the cantilever effect and provides enhanced support for the wrist pin.Previously, STI pistons had a weight of 414 grams, whereas the Type RA pistons come in at 424 grams. This additional weight of 10 grams is negligible considering the advancements in the piston’s design. For reference, forged pistons designed for the EJ257 generally fall within the 370 to 400 gram range, varying based on bore size and construction. Both engines use wrist pins of the same weight.

Type RA Con Rod Differences

From what I can see, the Type RA rods seem to be exactly like the rods found in the GR STI. This isn't shocking since the rods are certainly not the weakest part of the engine. However, there are some changes in the later models compared to the earlier EJ257 and EJ207 rods, particularly with the closed channel inside the big end's bore and the absence of a straight support rib.

There are no visible differences between the GR STI rod and, in reality, the rods from the 2018 STI and Type RA have the same part number.

Part Number:

Type RA Engine Assembly (Shortblock)
10103AD020

Warranty Disclaimer: Parts that are installed by a CERTIFIED Subaru Dealership are the only ones covered by Subaru of America. Additionally, the part must correspond with the vehicle's VIN. For example, if you put an STi block into a WRX at your friend's garage, don’t assume you’ll be able to file a warranty claim if it fails! It’s important to use your best judgment.

 

Fits: 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014 Impreza WRX

Fits: 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021 Impreza WRX STI

Fits: 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Legacy GT

Fits: 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Forester XT

Fits: 2005, 2006, 2007, 2008, 2009 Outback XT

Fits: 2004, 2005, 2006 Baja Turbo

Fits: 2005, 2006 Saab 9-2X Aero