Why does the WRX use a smaller displacement, instead of a 2.5L? What is the gain on smaller displacement? Wouldn't the gains be linear with a similar equipted 2.5L?

It's got a shorter stroke than the EJ25 (which is about the only size difference in the engine), and having a shorter stroke allows a higher redline. That, and the closed deck design, which supposedly allows for higher psi when forced induction

It may also be due to WRC class rules, ie. 2.2l displacement max. I don't remember for sure though.

Nigel

but doesn't the evo have a 3.0 litre engine anyway? Besides, the WRX uses 2.0L, not 2.2L. But to really say why they decided on that size, i'm not a subaru engineer, so i can't answer that http://www.i-club.com/ubb-files/smile.gif

The max displacement for WRC is 2 litres, so the WRX engine actually displaces 1994 cc, if I remember correctedly.

It's been pretty well determined that the EJ20 is no longer closed deck - since the WRC regulations mandate certain power limits, there was no need to make the engine closed deck.

The Evo uses a 2 litre engine as well.

Another reason is that in Japan and Europe cars are taxed by engine size. 2.0L is usually the point at which the taxes start to really get ugly. The easy solution is to make turbo 2.0L cars. That's why the rest of the world gets awesome lightweight turbo cars and we get Mustangs http://www.i-club.com/ubb-files/rolleyes.gif

Tony

Basil is correct, and Tony too.

However, the reason for the early 90s Legacy Turbo (2.2L) was because at that time Group A allowed 2.2L displacement. Remember the original Audi Quattro? 2.2L for the same reason, but it was a turbo inline 5 instead of a flat four.

[This message has been edited by ColinL (edited November 03, 2000).]

Can they not have say a 2.0l flat 6 turbo? How come no Superchargers? I would think superchargers would provide quicker response in WRC applications where TQ is king.

GVTEC, how the heck are ya! Long time no hear. The reason we use a 2.0 litre is because thats all we need to stomp butt! hahah

Just kidding, what these other fellows said was spot on. Its cool when racing drives the production models. Its true what they say, Rally on Sunday, Sell on Monday..

Later..

SCRAPPYDO
stephen

Gambit-- the Group A regs specifically call for a turbocharged four cylinder of 2.0L maximum displacement. They are also fitted with an inlet restrictor (34mm I believe) that limits peak horsepower to around 300. Clever tuning can make considerably more power down low though.

ummm, the WRX has like, 89 mm pistions (can't remember exactly), the 2.5L has 99mm, the stroke is NOT the only difference.

92mm http://www.i-club.com/ubb-files/smile.gif

You guys are correct in relationship to regs.. engine size...etc..

J.

yeah, i know it's not the only difference, but it's the biggest... or so i thought...

The EJ25 and the EJ20 have the different stroke, different bore.

EJ25: 99.5mm x 79mm
EJ22: 96.9mm x 75mm
EJ20: 92.0mm x 75mm



[This message has been edited by scooby5 (edited November 03, 2000).]

The EJ25's stroke is in fact 79mm. The EJ22 shares the same 75mm stroke with the EJ20.

[This message has been edited by ColinL (edited November 03, 2000).]

ColinL, I stand corrected.

Actually, there's a lot of wrong EJ25 specs out there that list EJ22 bore/stroke.

one of them: http://www.virtualroadtest.com/SubaruImprezaRS/RSspecs.htm

yeah, cause i also read somewhere that the EJ25 is just a stroked version of the EJ20. That seemed a bit odd when i read it, but i never saw anything contradicting it, until now http://www.i-club.com/ubb-files/smile.gif

Thanks guys; I wasn't thinking along those lines.

SCRAPPYDO: Always expanding my ******* knowledge. http://www.i-club.com/ubb-files/wink.gif

g'lord! How do you guys know all of this? and my friends call ME a Scooby fanatic. Y'all put me to shame. (that's a good thing, I gotta keep up!) =)

don

g'lord! How do you guys know all of this? and my friends call ME a Scooby fanatic. Y'all put me to shame. (that's a good thing, I gotta keep up!) =)

don

Well guys the real reason is pretty simple. In Japan there is a restriction for engine displacement. Anything over 2.0L(1999.99999~ to be exact) has special charges. Anything over 2.0l is often called the 3no. cars(they use the no. 3 on the licence plate, don't ask no why). So the Jap. gov. charges extra money on cars above 2.0l engine cars. And so it cost more money to have cars over 2.0L in Japan. THat's the real reason!!!!

Don: it's in the service manual. http://www.i-club.com/ubb-files/wink.gif

A comment about the WRX and closed deck comments near the top:
The WRX has been open deck for a few years now( as mentioned because of the restrictor) but has continued to be made closed deck in the STi versions.
The WRX is an EJ20G
The STI is an EJ20K
And then there is this new EJ20..It is a semi-closed deck?
Not exactly answering the question, but adding some more insight into the engines out there.

Matt,

Thanks for the info. Always wanted to know the slight differences between EJ20T,G, and K. Mine's "EJ20KDW6PR".

However, seems like the STi's EJ20K are open deck as well:

From Mike Shields a few years ago: http://www.toad.net/~rrubel/turbo.html

quote...

The 1997 year model change over date, "96.6.6", saw a major internal and

external redesign of the engine. It is now the EJ20K series with re-routed,

resized and repositioned turbocharger, repositioned larger intercooler,

lower compression 8.8->8.0, bigger valves, more (relative) boost, and

slight cam changes. After this time, all production engines are open deck

design, including the STI and RA versions. This permitted a great cost

saving by changing all engines over to open deck die-cast cases while

keeping the basic strength for a 300hp design limit.



[This message has been edited by scooby5 (edited November 03, 2000).]

The letter after the EJ20 denotes the version of engine for the Sti models.

94-96 Sti - EJ20G
97-98 Sti - EJ20K
98-00 Sti - EJ207

There is also additional letters and numbers on the engine vin that classifies the differences.