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What's the difference between- wrx and sti engines in classics?

Old 01 November 2009, 06:07 PM
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pistol
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Default What's the difference between- wrx and sti engines in classics?

Sorry im new, unsure if this subject has come up before, im sure is has, can anybody give me some links so i can read it myself?

Or if anybody knows, please fill me in.

Cheers
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Old 01 November 2009, 06:13 PM
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sorry, little more info, got an wrx without an engine, thinking maybe better to fit an sti engine so it's a little stronger basically.
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Old 01 November 2009, 06:43 PM
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On the pre '96 there is not much difference between the 2 at all.

All the pre 96 heads have hydraulic valve lifters.

On the 97/98 (v3/v4) the sti's had forged pistons as standard and under bucket shims on the heads/valves, with better cam profiles.

The 97/98 WRX and Uk heads had large above bucket shims.

On the 99/00 the heads were revised again with different castings, cams and inlet manifolds, with low compression pistons and rear thrust cranks.


If buying a second hand complete engine there is no way to tell from the outside whether the engine has forged pistons, unless you had access to a bore scope type camera.
For heads/valves/cams the rocker covers will need to be removed to check.

Reliabilty wise they are all the same as its the big ends that go normally, before pistons/heads on the lower/medium powered cars.

All the cranks, conrods and bearings on the classic engines are the same except for v5/v6 which had rear thrust blocks and cranks, but not really improved reliabilty.

Correct me if I am wrong.

Last edited by Brett_555_Sti; 01 November 2009 at 06:54 PM. Reason: added info
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Old 01 November 2009, 06:53 PM
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pistol
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oh right, i was told the rods were stronger aswell, mines a N plate, not sure which year yet.
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Old 01 November 2009, 07:00 PM
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Originally Posted by pistol View Post
oh right, i was told the rods were stronger aswell, mines a N plate, not sure which year yet.
No difference to the rods on the classics AFAIK, that only came in on the later newage cars. Yours would be the version 2 '96, so should have hydraulic lifters with ribs and DOHC 16 VALVE on the rocker covers, if its the original engine.
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Old 01 November 2009, 09:52 PM
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As Brett has said, rods are all the same, these normally are one of the first things to let go when going for big power, nice hole in your block as a result big end bearings are due to several issues, oil starvation being the biggest due to oil pumps/incorrect oil filling procedure.

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Old 01 November 2009, 10:39 PM
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pistol
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interesting, so changing the oil pump maybe an idea on a engine that's already out?

what's the correct procedure in filling with oil then? maybe disconnecting the crank sensor and priming it by turning the engine over?
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Old 01 November 2009, 10:52 PM
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checking the screws on the back of the pump are tight is always a good thing
they tend to work loose ans bye bye engine. two of mine were loose when i had my cam belt changed.
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Old 01 November 2009, 11:39 PM
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Originally Posted by pistol View Post
what's the correct procedure in filling with oil then? maybe disconnecting the crank sensor and priming it by turning the engine over?
Pretty much what you said there, ensure the filter is correctly filled first, one without oil in isnt really recommended

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Old 02 November 2009, 10:12 AM
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ok, so i may aswell get myself a wrx engine to keep me going, instead of paying out more for an sti one, only want 300bhp tops.

this wont be my everyday car, so would this be achievable safely?
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Old 02 November 2009, 10:27 AM
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I believe taht the loom/ecu is different as well so probably bets to stick to wrx engine. 300 is easy peasy
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Old 02 November 2009, 07:20 PM
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Originally Posted by Fat Boy View Post
I believe taht the loom/ecu is different as well so probably bets to stick to wrx engine. 300 is easy peasy
The original intake manifold/wiring from a pre 96 engine will also bolt onto a 97/98 heads, its only from 99 onwards that the stud pattern on the manifolds changed.

So it does not matter if you get a complete 97/98 engine just use your old wiring and coil packs, it all fits straight on.
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Old 02 November 2009, 10:27 PM
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Just out of interest if pre- 96 sti and wrx's have the same heads, how come the sti /wrx ra , has a higher rev limit , just i have a pp chip/ecu from a wrx ra with the higher rev limit, fitted in my 95 wrx and was told not to rev it past 7000rpm as the hydraulic valve lifters can't keep up past 7000 rpm, not that i want to rev it past that , just wondered whats different , cheers
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Old 02 November 2009, 11:11 PM
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Originally Posted by jeffwrx View Post
Just out of interest if pre- 96 sti and wrx's have the same heads, how come the sti /wrx ra , has a higher rev limit , just i have a pp chip/ecu from a wrx ra with the higher rev limit, fitted in my 95 wrx and was told not to rev it past 7000rpm as the hydraulic valve lifters can't keep up past 7000 rpm, not that i want to rev it past that , just wondered whats different , cheers

As you said, Hydraulic lifters can pump up at higher sustained rpm's but the Early STi's with Hydraulic heads have lightweight hydraulic lifters fitted - each one is approx 10g lighter (when stripped and cleaned) than the WRX one's - that makes for a nice weight saving on the valvetrain.
STi Version 2 RA had Top hat Inner shims instead of hydraulic lifters.


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Old 03 November 2009, 07:44 AM
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i've got a version 1 sti wagon(no.120/200).it is a s.c.b with standard pistons but uprated rods and uprated head's(lifters etc.) to allow for the higher rpm(has a different ecu to the wrx) and it boosts .2 higher than a wrx,that's standard from the factory(apparently also the engines were hand built there).also there is something about the gearbox that isn't wrx aswell(according to the mechanic at subaru)
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Old 03 November 2009, 01:54 PM
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ok thanks all, just a quick one, how do you tell the difference between sti and wrx heads?
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Old 06 February 2013, 04:57 PM
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so what gives the sti more power than the wrx if there are no differences?
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Old 06 February 2013, 10:35 PM
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Originally Posted by vtecsti View Post
so what gives the sti more power than the wrx if there are no differences?
If you're talking v2 1996 .It's the forged pistons and ecu tuned for an extra 10ps .I'll have to double check my cam profile data I can't remember if the cams had more duration and less lift on the sti. It's the sti v2 ra engine you want. If you can find one.

Intake Manifolds on V1/2 can't directly interchange with v3/4 directly as the tps and idle valve are different but could be used if modded

Last edited by jason_2013; 06 February 2013 at 10:37 PM. Reason: typo
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Old 06 February 2013, 11:00 PM
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V2 sti and wrx cams are the same. Sti Ra cams are better.

So best choice would be to fit a v3/4 sti engine and modify the inlet manifold to fit= headache or use your V2 intake manifold which restricts you using a front entry turbo without modding again and also the slanty intercooler ain't too good. Or find a genuine sti V2 ra engine whIch is closed deck block and better heads. Remembering also that changing things can lead to a remapped ecu = more money.
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Old 03 August 2015, 03:18 PM
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Hi guys,

I know this is a very old thread, but I've just got a version 2 wrx wagon.
The person I got it off, said it seems as if the engine has been rebuilt at some stage of its life.
The side covers say 4 cam 16 valve on them, and the inlet manifolds have a fifth injector hole ( so I was told & shown )
I just want to try and get some idea about the engine, as it didn't come with much history.
It's a jdm, so all the pre uk service history is in Japanese.
It's also fitted with a z4 ecu, and a td05 turbo.
Any help and advice would be much appreciated, as I also own a hawkeye Sti spec d.
But I know what's what with that one.
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