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Old 01-31-2004, 05:14 AM   #1
andys
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Default 1.8 -> 2.5 questions......

From what I have read it seems like it is possible to swap the 1.8 with the 2.5 as far as sensors and ECU functionality goes. What I would like to know is:

1) Will the 1.8 exhaust manifolds bolt up to the 2.5?

2) Will the 1.8 intake manifold bolt up to the 2.5?

3) Will the MAF and ECU etc. run the 2.5 at the proper mixtures?

4) Will the 1.8 rad provide enough cooling?

On a separate issue:

Which OBS models have a hrdro clutch? What is the earliest model impreza to feature the hydro clutch?

thanks!
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Old 01-31-2004, 09:24 AM   #2
atabert
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yes that would be good swap for you, as far as your questions go; #1 & #2- no, the 1.8 was a single port, and 2.5 were dual, unless you were to use the 1.8 heads with 2.5 block, and the intake configuration is different also, (unless you use the 1.8 heads, which i wouldn't do)---#3- im not sure if the maf's are the same, but you could run it off you current ecu, im not sure if you might have lack of power issue due to the bigger bore----#4- the cooling system is no different from 1.8 to 2.5l cars, so i wouldn't see a problem there. last one, i beleive that subaru introduced the hydraulic clutch systems in 1997-1998 and i think it was put on all manual trans cars since, hope this helps
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Old 01-31-2004, 02:37 PM   #3
Hawk296
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That is not entirely correct. THe EJ18 is a dual port head just like the EJ25. The exhaust manifolds are completely interchangeable between ej25 and the EJ18.. its the same part. so #1 yes.

#2- you wouldnt need to, use the 2.5 manifold and swap over waht you need.

#3- as long as you use the 1.8 MAF with the 1.8 ECU it will be close. Its not 100% accurrate but its pretty close, if anything it will run slightly rich.

#4- yes
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Old 01-31-2004, 10:58 PM   #4
andys
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ok cool - thanks for the input so far.

Couple more questions:

Do you think the 2.5 would run rich enough on the 1.8 ecu to interfere with emissions testing? Actually, speaking of emmisions testing.... if you live here in Vancouver all you need to do is put studded tires on you car and you can bypass the load test. You only have to pass the idle test !! Studes are allowed Sept to April - I think. Studs are cool.

For people who have driven it - how well does it drive? Could you rally it all day have good performance?

I want to go out and get another car to grab the 2.5 from but I don't know what the best bet is. RS coupe? RS sedan? 98? 99? Is there anything I should know? I don't want to go newer than 2000......... my preference is for something 4 door with the turbo hydro clutch. (Is that what you call it?) I'd even get a 2.2 four door or wagon car if it has the hood scoupe and hydro clutch. Any ideas?

Sorry if this is a bit basic - I have done my reasearch but still have some of these nagging questions. I'll post all my findings as this project progresses to share the wealth.

A

PS for those who are wondering - I want to put a yet unaquired 2.5 (or 2.2) with my RA tranny in to my 93L so I can go and eat some tires in the woods. Then I am thinking about putting my VIII motor into the 2.5 donor and driving to work Initially I wanted to put the VIII into the 93L but I now I can't justify all that wiring work just to give my POS 'rebuilt' 93L some rally beats. I only want to put the VIII motor in one car once! In any case I think the 2.5 and the 4.44 RA tranny will make for a pretty solid and easy to install combo for the ol 93L..... we'll soon see I suppose.

Any suggestions from the wise out there?
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Old 02-01-2004, 12:40 AM   #5
Kostamojen
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Use the EJ18 throttle body and MAF with the rest of the EJ25. Theres some wiring involved, and theres a whole post here somewhere about it... I test drove a L with that exact setup the other day, drove very well (although with the 1.8 ECU it will have a 6000rpm redline)
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Old 02-01-2004, 12:51 AM   #6
Hawk296
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cool, whos did you drive? what did you think?

good point about the 6k redline. although the phase II SOHC 2.5s only had a 6,250 so its not a huge deal. there really isnt much wiring. THere will be some with a phase II but a Phase I EJ25 literally plugs right in.

As far as driveability, I drive mine daily and drive it hard. I have several hard track events on it too. where ide be out on 30 min sessions between 4,000 and 6,000 RPM the entire time. held up great.

Its not running all that rich. I am actually getting better mileage than with my 1.8. ANd emissions i dont know, i dont get tested in MI. Also i am running catless.
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Old 02-01-2004, 01:39 AM   #7
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I drove mike from MPJ's car, its the blue one with the hoodscoop that someone back east put together and painted rally blue. It was pretty beat up, but it had some version 2 STI seats which kicked arse

Definatly alot faster, I was impressed... Although the lack of a tach was annoying.
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Old 02-01-2004, 12:56 PM   #8
Hawk296
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cool, if youre ever in the midwest, you can take mine for a spin.

mine has a tach
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Old 02-01-2004, 06:55 PM   #9
garface
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andys, pm'd you
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Old 02-02-2004, 01:33 AM   #10
Kostamojen
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Quote:
Originally posted by Hawk296
cool, if youre ever in the midwest, you can take mine for a spin.

mine has a tach
LOL! I will have to take you up on that some day
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