[Hankscorpio]

I was scanning through the cover article of the most recent issue of "drive" titled the ultimate performance STI so Subaru built a race car with pro drive to set an Isle of Man record. here is what confused me, they supposedly used a STI block with custom internals and reduced the displacement from 2.5 to 2.0 liters. I'm no race engine builder but why reduce the displacement? I haven't needed to get deep into Subaru engines, is the engine like old VWs where the block is seperate from the cylinders allowing significant modifications to the displacement?
It sounds suspiciously like they modified a WRX FA20 and are calling it an STI for PR.

Which brings me to a symantics question. What makes a WRX a STI? If pro drive and Subaru Tecnica International started with a factory STI but put an FA20 and prodrive transmission and diff in is it a STI race car or does the New power train Make it a WRX? Inversely if the car left the factory a WRX is this a WRX race car or does the STI division's hand in it make it rightfully an STI despite not having any production STI components in it. (Yeah I know it's really whatever Subaru wants to call it.)

 

[zax]

Are you not aware of the EJ207 that had been the golden standard for JDM STis over the last 18 years? This is the engine typically chosen for motorsport over the last two decades for homologation and rulebook reasons.


Allow me to do your homework for you.

https://en.m.wikipedia.org/wiki/Subaru_EJ_engine


What makes the STI an STI is what Subaru calls that model. What makes the Mustang GT a GT and not an LS?

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[XJman]

People cut displacement at times when they destroke an engine to get higher rpm. But the 2l that Subaru uses in race engines is typically the ej207. They have advantages, but from some inquiries I've made around to my local performance shops it's getting harder and harder to find quality import JDM stuff. There are companies that will label shortblocks as new and sent you reman engines.

I've also read from various sources the lower torque of the engine make it less engaging to drive as a daily commuter. However that's subjective.

I've actually been putting effort I. Researching the engine as to figure out why they wouldn't choose a closed deck block across the board for forced induction engines over Simi closed.

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[Hankscorpio]

In my defense I did plead ignorance to Subaru engines
The article doesn't use engine designations and heavily implies they started with a 305hp 2.5L. This implies they started with an export market EJ257. There is nothing to suggest they started with an ej20. Which still begs the question why not maintain the 2.5 displacement?
Also can you swap out cylinders on an EJ crankcase to change displacement? (Are these really Lego car?)

I do concede that it does make more sense to use a race proven already developed EJ20 engine rather then building a 600hp FA20.

 

[EJ257]

I've been intrigued by the destroked EJ257 for a while. From what I've seen, the biggest names in the destroked engine build world talk more people out of those builds than into them. If you're not road racing the vehicle, you are generally better off with a standard engine build, unless you want something unique.

By destroking the engine, you allow it to spin out further, but by shifting the powerband to the right, you are not able to use the power like you would on a standard engine build. Basically, you need a turbo big enough to be continuing to make power > 7500, and want a car you can rev out. You sacrifice every day usability, but gain hearing the engine roar at higher speeds.

 

[zax]

Because prodrive has far more experience with building Ej207s.

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[XJman]

It also requires gearing changes to make the most use of it I would think.

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[Hankscorpio]

the article is slightly extended on the website with Q&A (or maybe I just missed this) that supports that this was an old race EJ20 configuration
Subaru Drive Performance - Oh, Man: The Ultimate Subaru WRX STI (dp13.3)

How long did the design, development and production process take?

Prodrive: The whole process from agreeing on terms to completion was 10 months; for a project of this nature you would normally allow two years. We had to use a lot of our resources internally to meet our targets and carry over elements. Albeit substantially updated from our World Championship-winning Subaru cars from the late 2000s, this was the only way we could meet our goals.