Difference between STI engine and WRX?

[villagehoppa]

Hi all, new to this Subaru stuff!! Can someone please tell me the difference between an STI engine and a WRX please? Is one a 2.0 and the STI a 2.5? And can you fit the big intercooler on the top a of an STI in a FF 818? Sorry if this seems like an idiot question!! Starting to get my head round the 'techi' stuff and wondering about donors?....cheers all...

[Somerset Subaru]

There is plenty different and plenty the same. With the newer STi's over the WRX the major difference is turbo size, intercooler size and suspension pieces. 06 and up WRX has a 2.5L but different blocks are used and different heads. Along with a smaller turbo on the WRX and intercooler. The list would be so big it would be crazy.

[Evan78]

All US STi to date are 2.5L. 2.0L STi was/is Japan and other non-US markets.

US WRX was 2.0L 2002-2005, then went to 2.5L in 2006.

Not a comprehensive answer, but just a little to respond to the displacement portion of your question.

[Xusia]

villagehoppa, perhaps it would be easier for folks to help if they knew the basis for the question. For instance, are you concerned about how much HP those engines can make (comparatively), or??

In case it is HP you are concerned with, I'll say that the STi engine and electronics do come in a more highly tuned state, but that most of that difference can be made up in the WRX engine for less than the difference in cost between a WRX and STi donor.

[Pearldrummer7]

All of the above answers are definitely accurate, here's a little more:

The pics are gone but this has some great information-
http://forums.nasioc.com/forums/showthread.php?t=1667168

Basically, the EJ257 short block (2004-2015 STi) has different pistons than the short block of the EJ255 (2006-2014 WRX). Long block wise, I believe the heads are slightly different, and they come with slightly different turbos and exhaust systems from the factory, and pretty different intake manifolds. Most of the motor is comprable, and if you're building up a block (i.e. pistons, rods, etc.) it doesn't matter which short block you use.


Hope this helps a little!

[villagehoppa]

I've been offered an STI but the website said not to use as a donor?! Did I read it wrongly?

[K3LAG]

I've been offered an STI but the website said not to use as a donor?! Did I read it wrongly?

Some of the STi parts won't fit. I don't remember which ones, if you search around the forum I know there is a list somewhere. You could use the STi if you were willing to get some parts from other sources, but it might not be cost effective depending on your planned budget.

Larry

[Pearldrummer7]

Some of the STi parts won't fit. I don't remember which ones, if you search around the forum I know there is a list somewhere. You could use the STi if you were willing to get some parts from other sources, but it might not be cost effective depending on your planned budget.

Larry


I've been offered an STI but the website said not to use as a donor?! Did I read it wrongly?

Kind of. Formally, it doesn't work to use an STi. They've successfully tested an STi trans on the 818 and that option to adapt them is in the works! My good friend works at FFR and he and I have talked about someday upgrading my trans to a 6 speed (for the diff, mostly). Other parts.... you get aluminum control arms that almost definitely fit (good thing), same radiator, the motor fits, intercooler might not, and probably a few other differences that won't fit.

I'm using an STi motor. Both Frank and Joe Scott see no issue with the motor, as it uses the same mounts as a 2.5 WRX motor.

[villagehoppa]

Cool, thanks for the reply's, I'm definitely getting there, think I'll get back on the phone!!.. Cheers all....

[Xusia]

A big "also" is the wheel hubs. The STi ones are currently not compatible. If you can get an STi donor for a reasonable price though, I would certainly do it. By the time you get your kit, the 6-speed will probably be supported. This would really leave just the hubs, which you could source separately.