Musing a full '93-'99MY Impreza to EJ251/EJ253 conversion

[janas19]

Allow me to skip the fluff and get right to the nitty gritty. I'm actually seriously considering doing this conversion and all the man hours and work it would require. I want your highly valued feedback and don't pull your punches, give it to me straight.

 

I want to know everything I can about an EJ251/EJ253 conversion. The reason is I'm looking for broke-down Impreza hatchbacks from '93 and up. If I find a '93-'95 MY I'm planning on a full OBD-II harness conversion. Since the full harness conversion is on the table anyway, why not look at the EJ253 with AVLS?

 

Looking for your feedback and thoughts.

Edited October 28, 2016 by janas19

[golucky66]

I had a buddy who wanted to do the same thing. So he ended up putting a 3.3L from a SVX in it. Apparently he only had to modify the upper radiator bracket and change the radiator with an aftermarket one.

But that engine produces 240 HP. More then anything you're going to get unless you put a WRX engine in it.

[matt167]

Find a 1999-2001. Will have an EJ251 ( 2000-2001 ) or early EJ253 ( 1999- few early 2000 ).. The real 'hot ticket' would be the 1999 MAF EJ253. Makes later turbocharging easier

 

Then look up Project Lambda for recently released JECS ECU tuning options. The AVCS brought drive by wire, so it's a whole nother ballgame. And nobody supports tuning the N/A 2005+ anymore. Your on your own with romraider anyway

[janas19]

I had a buddy who wanted to do the same thing. So he ended up putting a 3.3L from a SVX in it.

Highway MPG is very important so the 3.3L is out of the question. If I'm going six cylinders I'd rather have a pickup truck.

 

Find a 1999-2001. Will have an EJ251 ( 2000-2001 ) or early EJ253 ( 1999- few early 2000 ).. The real 'hot ticket' would be the 1999 MAF EJ253. Makes later turbocharging easier

True, but I'm using a different approach. The goal is cheap and speedy, so the lighter the better. This official Curb Weight thread over at NASIOC is my bible. Most important is simple availability and price. I'm looking to spend no more than $500 on the shell which likely means non-RS. Hence the necessity of swapping. Edited October 28, 2016 by janas19

[janas19]

The AVCS brought drive by wire, so it's a whole nother ballgame. 

 

What do you mean?

[matt167]

Something that you need to understand.. The Impreza was the same from it's introduction in 1993 until the GD chassis came out in 2002 ( For USDM, other markets 2001 ).. A face lift happened in 1997 and a new dash/ interior happened for 1998. Minor changes other than that.. The minor weight changes are literally nothing, because absolutely nothing changed within the car itself that can't be simply swapped. You want cheap which suggests buy as much as you can use with the car itself to meet your goals.

 

You do want a coupe if you want the lightest BUT, Coupes are not cheap or easy to find.. I did give reference to EJ25's which Impreza's would not have if stock. But they would have EJ222's or EJ223 in that year range. Still the same MAF VS MAP arrangement and JECS ECU's that can be tuned now.. Just swap in a phase II EJ25 with the original intake manifold.

 

AVCS/AVLS  did not come to the USA N/A cars until 2006 model year IIRC, and by 2005 all Subaru's were drive by wire, which is where the gas pedal is a potentiometer, there is no cable..   Also, the N/A USDM AVLS system was for emissions, not HP or MPG.. JDM had an EJ204 which was a DOHC 11:1 compression 2.0L screamer that produces 190hp in stock trim. It has AVCS. It is the only 4cyl N/A swap worth doing IMO... Yes it runs high octane fuel only but you need compression/ octane to get HP out of a small displacement.. High compression, or forced induction does it easier but both work by compression increse

[janas19]

Yes you're right. I don't need the AVLS, I don't have to have it. I will still look for the 04-06 EJ253. Better block and intake manifold, lower mileage = less ring/cylinder wear = longer lasting better engine.

 

I need the 04-06 instrument cluster, full harness, and ECU. What about the steering column? I don't know which dashboard is gonna work. I'm going to tear down the interior to the bare shell and map out each wire on the harness.

 

I'll pay $400-500 for the hatch, and $700-800 for the EJ253 longblock. Might take me a month, even two months to find them for the low. Have to drive to Denver.

 

If I can get a good EJ251 from the junkyard for $300 I'll probably go that route. Problem is I'm 40 miles away and can't drive their everyday to look, plus I have to buy a compression tester for $50

Edited October 28, 2016 by janas19

[matt167]

The intake, block and heads are not 'better'. Up until 2005 they are virtually the same minus different pistons and such. After 2006 came the AVLS.. And actually it's well known, they have weaker pistons than the earlier engines. So if you go with the 2005+ electronics, your going to deal with the more complicated systems for essentially no reason if you plan not to use AVLS

 

Your banking on stuff that just isn't going to work out.. An engine is going to cost $1-1.5K for something good you can trust. The only dash that fits right is the GC or SF specific dashes. others might bolt up, but they won't 'fit'.. You can put a GD cluster in a GC with some work

Edited October 28, 2016 by matt167

[matt167]

dbl post

Edited October 28, 2016 by matt167

[janas19]

Alright, guess it's best to go EJ25D or EJ251. If I get a 93-95 hatch, I'm going to do a full OBD-II harness conversion with knock sensor and full mani swap. I can pull the harness off a rust bucket at U-Pull for $40. I'm estimating around 40-50 man hours for a complete conversion, my first time.

 

Do you have any recommendation on the best MY ECU between the EJ25D and EJ251 heads? 90% of my driving is done under 4000 RPM, so my goal is torque and complete fuel efficiency.

Edited October 28, 2016 by janas19

[matt167]

1999 ecu I would say. It is now tunable thanks to project lambda. Its MAF based which is better for various reasons.. You can go 2000-2001 for the MAP engine which would be ok too. Can come from a 1999-2002 forester also. Map vs maf follows same years in them. Grab whole dash while your at it if you end up with a 1993-1995

 

I would use project lambda to add some timing, and fuel. But it does other cool things now too

[janas19]

I like that. I want to learn more. I'm going to read over the website.

 

So EJ251 MAF is best, then MAP second? Are the MAF ECUs only in 99MY Impreza?

[matt167]

It would actually be EJ223 if MAF Impreza IIRC. You can get the EJ253 ( early 253 not same as late 253 ) MAF based from a 1999 Forester.. The MAP based cars would be workable but they act in a more confined tune.

[Numbchux]

Something wrong with your other thread on the same subject?

[janas19]

 

Something wrong with your other thread on the same subject?

Well the other thread was about swapping a Phase II EJ251 engine into a 95-98 Legacy. I decided to ditch the Legacy chassis and go with the Impreza hatch instead. And I'm looking at a full EJ25D-1 conversion, wire harness, engine, dash and all. Seemed like it warranted a new thread. Is that alright? Not trying to break any rules or piss anybody off :-)

Edited October 28, 2016 by janas19

[janas19]

It would actually be EJ223 if MAF Impreza IIRC. You can get the EJ253 ( early 253 not same as late 253 ) MAF based from a 1999 Forester.. The MAP based cars would be workable but they act in a more confined tune.

Thanks. Sorry if I'm asking too many questions, the Subaru ECUs are pretty new to me. And thank you so much for sharing your knowledge.

 

I'm thinking I'll buy the hatch first and start slowly chipping away at the harness conversion first, because that's going to take the most time. Ideally, I want to make a harness which has the 3 plug connector for the JECS ECU, but can be made to fit either the EJ25D OR the EJ251 on the engine side.

 

I don't even know if that's possible, but that would be the most flexible and sensible solution. The big issue seems to be the MAF/MAP sensor differences. I believe everything else between the two is pretty similar and can be easily modded.

Edited October 28, 2016 by janas19

[janas19]

OK, this is what I'm going to do:

 

Junkyard EJ251 shortblock

EJ25D heads, 04-06 STi MLS gaskets

99-02 2.5RS harness, cluster, and ECU

93-95 GF5 wagon 5MT

 

Any mismatches or big mistakes here? I'll figure out the small stuff myself, but this will be the plan going forward.

Edited October 29, 2016 by janas19

[matt167]

You'll have to adapt the EJ25D throttle body and your going to have an issue with idle control but it should work well enough as long as your willing to tune it.

You can use the harness/ dash for a 1999-2002 Forester. 1999 HAS to come from a SOHC.. Essentially an RS from 1999-2001 shares the same stuff as a Forester from same years... Clusters/ pinouts ARE different but they can be re pinned easilly if you have to have the Impreza cluster. But stock clusters look very much the same anyway.

[janas19]

Mind elaborating on that? I'm using the 25D mani and harness... Why would TB and idle be an issue?

 

Also, it seems to me that the Impreza dash/harness would be easier? The Forester has a different body so the harness and dash dimensions won't match up as easily?

 

The 2.5RS cluster is ugly as sin. I'd rather using anything else than that cheap white monstrosity. I'm going to go to the big junkyard 40 miles from home today and look at every Subaru. I'll be taking notes and preparing for the conversion.

 

No one here is selling a hatch. I might have to go to UT or TX...

Edited October 29, 2016 by janas19

[janas19]

Took a trip to the junkyard today. That was enough to dispel any illusions. This will be a helluva job. I'm estimating 1-2 months, minimum, for a full OBI to OBD II harness conversion on the 93-95MY.

 

First thing is to map and plan everything out. First, I have to do a full walkthrough on the OBD II vehicle and identify every necessary electronic signal. Then I need to get the Impreza wiring diagrams and map out each signal I have to retain.

 

Finally, I'll have to strip both vehicles and find the terminals/plugs of all signals, fuseboxes, relays, and connectors. It will be loads of fun, I'm sure!

 

That's only the beginning. This conversion is going to take a couple of months, at least.

Edited October 29, 2016 by janas19

[janas19]

I found something interesting at the junkyard. There's a 98 Legacy hybrid. It has the DOHC, Phase II block, and a single plug ECU.

Edited October 29, 2016 by janas19

[matt167]

For the most part, the Forester wiring parts will be close enough if not the same as Impreza wagon aside from the dash cluster wiring which is the same connectors pinned differently..

 

If you use a 1999-2002  phase II/ JECS ECU, your harness needs to match that. EJ25D electronics will run on it EXCEPT the idle air control which works different than the earlier EJ25D.. SOHC heads would make everthing plug and play

 

 

The phase II block came in late 1998. A very few 1998's got them since it was just before the model year switch. It could be a swapped car also.

[janas19]

For the most part, the Forester wiring parts will be close enough if not the same as Impreza wagon aside from the dash cluster wiring which is the same connectors pinned differently..

 

If you use a 1999-2002 phase II/ JECS ECU, your harness needs to match that. EJ25D electronics will run on it EXCEPT the idle air control which works different than the earlier EJ25D.. SOHC heads would make everthing plug and play

Thanks Matt. The idea is to go full Forester harness and dash, since 2.5 Imprezas are so hard to find.

 

Nice tip. I'll definitely pick up the DOHC heads off the 99-00 to match IACV, but like I said, it's going on top of the 251 shortblock. Too risky to use the 25D bottom end when junkyard is the source...

 

Are you aware if the 93-95MY 5MT switches match up to the 99-02 Forester harness? That's my primary concern.

 

Thanks.

Edited October 30, 2016 by janas19

[janas19]

Working link to the full 99-01 Impreza wiring diagrams PDF for reference: http://www.mediafire.com/file/ndg4nnm5tvz/Subaru_Impreza_wiring_diagram.pdf.

 

65 pages of wiring goodness mmmm. Going to be parsing through all this next week.

[janas19]

Documentation on 95 L coupe to 98-01 dash conversion: http://www.rs25.com/forums/f145/113716-rhd5280s-1995-l-coupe-2006-sti-swap-widebody-gtx3076r-now-dry-sump-8.html

 

Looks like 4 modifications are required, 3 can be done with drills and grinders. For the last one which requires welding I am going to cold weld the dash mounting tabs using JB Weld, should be adequate.

Edited October 30, 2016 by janas19