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dyne's 1999 2.5rs - H6 EZ30D swap
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Old 04-03-2011, 07:08 PM   #1
Join Date: May 2005
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Default dyne's 1999 2.5rs - H6 EZ30D swap

Edit: Just to note, I sold my car a few months ago, hopefully it went to a good home.

Donor car: 2001 Subaru Outback LL Bean ed (EZ30D: 3.0L H6 rated at 212 hp/210 ft*lb)

Recipient: 1999 Subaru Impreza 2.5RS (2.5L H4 rated at 165 hp/167 ft*lb)
-I've kept the car is mostly stock up to now (aside from the interior) so this thread will pretty much only be about the engine swap.

A little background info: I've had my car since 2006 and like it quite a bit, so I couldnít just let it go when an idler gear went last summer. The car had been sitting in my driveway for months before figuring out what to do with it.

To my knowledge, this swap has only been done a few times; thereís one guy on NASIOC (Anders8) thatís done it as well as a few by 42 Autosports (who were quite helpful in letting me know what parts I'd need) thatís done a few. There isn't a whole lot of information out there so I kind of just figured it out as I went.

In November I found this guy (along with the accessories, ECU and wiring harnesses) on craigslist from a totaled outback. Turns out the guy's starting a shop in PA named flat 4 subaru or something along those lines. Nice guy.

Hereís my workspace, itís my tiny unheated garage. Before starting work I had to put in some lighting so I could actually see what I was doing.

I couldnít secure the wiring with the car in the garage, forgive me electricians out there.

Hereís the old engine, just before I started removing it. Years of salty northeast winters made this difficult due to nicely corroded nuts and bolts.

Engineís cominí out, woooo.

That big hole in the timing belt cover isnít supposed to be there. My guess is that an idler gear failed, came loose, bounced around before getting caught and spun around until it worked its way through the plastic cover. Just before my car had died on highway, I remember thinking I had hit a large rock. It was the gear.

Eep, broke off an alignment pin when separating the engine and transmission

Fixed with part of a 10mm bolt from home depot and a little JB weld. It seemed to work fine when I bolted the new engine in.

The new engine is a bit larger, but it's a little exaggerated in the picture. Itís 75lbs heavier, 0.8Ē longer, and a bit taller. Despite only being available with an automatic transmission, the old clutch bolts right on.

Hereís a clutch alignment tool I made with a few sockets. It worked well.

And sheís in! That rusty thing is the old AC compressor. I thought I would be able to use it with the new engine, but the intake is in the way of one of the lines. No matter, I have the AC compressor from the donor car.

The donor AC compressor line has a larger fitting than the old one, so it doesnít fit into the evaporator.

20 minutes with a file later, it fits.

At this point I decided to start working on the exhaust. The stock headers wouldnít fit and the only aftermarket headers available were like $250 on ebay. Instead, I decided to buy a Harbor Freight TIG welder and teach myself how to weld.

Hereís the start to my exhaust header flanges. I wasnít confident that I could start off welding stainless so I just went with mild steel (these are 3/8Ē thick).

Some unfinished exhaust flanges are on the left, finished header flanges on the right. The engine uses single port headers with oblong openings. I used my tiny mill to put a couple holes in the plate and milled them as necessary. I really want a larger mill, it was painstakingly slow milling these.

I didnít have a big enough hole saw (and my mill lacked the power anyway), so I cut those holes for the above exhaust flanges on my benchtop lathe. I really would like 4 jaw chuck, so I wouldn't have to bolt the flanges to a jig.

90 degree mandrel bend before slicing it with the dremel

After slicing them. Slow, dusty work.

Looks like itíll work.

After about 15 minutes of practicing with the TIG welder, I decided to make my first weld. Not pretty on the first pass, that required some fixing.

The other side turned out nicer, mostly because I realized I had to remove the mill scale from the hot rolled steel sheet.

I made my own y-pipe, too. That was a pain in the ass.

It almost looks like I know what Iím doing. I decided to weld the flanges to the pipes from the inside because it seemed easier. Though I see all of the professionally welded flanges welded on the outside, these seem to work fine and don't leak. I donít think I took any pictures of the remainder of the exhaust fabrication, just imagine a Magnaflow high flow spun catalytic converter on the end, then a flange, then a midpipe with an 18Ē Magnaflow resonator. Iím using a twin tip WRX muffler that was given to me.

Oh yeah, the smaller pipers are 1.625Ē and the larger one is 2.25Ē, which are roughly the same as the stock exhaust. I probably could've gone a bit larger. This exhaust will probably rust off in a couple years so Iíll make a better one then.

Making the exhaust was kind of a pain because initially I had to redo a lot of my welds. Towards the end I could weld a pipe on in one pass. In addition, the only 220v line I had was in my basement, so I would get under the car, line everything up and mark it, take it down to the basement and tack weld it, make sure it fit back up in the garage, then finish welding it back in the basement. Half the time spent on the exhaust fabrication was spent walking up and down my stairs.

Anywho, onto the intake! I wasnít given the donor intake, and didnít want to adapt mine to the new engine (they had different sized throttle bodies). I elected to fabricate my own intake and finally make my hood scoop functional. You know, to up my street cred.

Cardboard mock-up.

Presto, done! (not actually, I donít have the throttle body connection and vacuum hose barb in those pics). The intake is made of 1/8Ē ABS that is bonded together with ABS sludge (ABS shavings dissolved in acetone). Not pictured is a K&N oiled filter that Iím using; I figure the oiled cotton with repel any water that comes into the hoop scoop. Itís also pink and looks .

On to the wiring! Iíll skip all the pictures I took while disassembling the dash and unplugging everything to get to the wiring harness, I donít think you want to see them.

Oh god what a mess. Thatís the 2.5RS harness with the donor harnesses. Theyíre sitting on a slab of bowling alley lane I got from a guy on craigslist that Iím going to turn into a nice butcherblock countertop for that island when the swap is done. Iíve been renovating my house for the past year and a half or so, and my wife has been kind enough to let me put that on hold for the swap and let me commandeer that counter, the dining room table, and floor. Sheís the best.

I donít have a lot of pictures of the wiring harness merge in progress as itís not very interesting. It was a lot of labeling, then using a diagram to trace which component the wire goes to, finding the component on the donor engine wiring diagram, trace that wire back to the ECU, and soldering the corresponding wires together. Very tedious.

Here's my dog Genny, who interrupted me frequently.

When the wiring was done I decided to push the car out of the garage in order to put the wiring and interior back in.

Callie was not impressed that the car had to be pushed out and couldn't move under it's own power.

The next bunch of pictures is for a power steering fitting that was not included with the power steering pump (which I bought for only $35 from a salvage yard, so I canít complain). Itís made of aluminum with brass fittings.

Again, a 4 jaw chuck would be nice.

Groove for the O-ring cut out and power steering fluid passage drilled. I then milled it to size, hand filed the contour, and tapped the hole for a ľĒ NPT fitting

I think it turned out nice. It works, at least.

After this I put the radiator in, which I don't have any pics of. It was a tight squeeze with the larger engine.

Hereís how the car looks today. I've been driving it around for a couple weeks, and it's a hoot.

The engine bay isnít as tidy as itís going to be when I'm done with it. The power steering reservoir and a nicer looking coolant reservoir are going to be mounted in place of that now useless, rusted bracket on the passenger side. I'm also going to be putting hood struts in because the hood support bar no longer has a place to rest when the hood is closed.

Iím still working through some issues with the wiring. Iím getting a P1507 CEL code while driving, which I think has to do with the fact that itís currently wired so that the ECU thinks itís in neutral all the time. I think going to have to take the interior apart again at some point to correctly hook up the neutral position switch.

That's about it for now, I'm driving the car around and just have more-or-less minor issues to work through. The swap took much longer than I thought it would, probably about 3 months total before I got in on the road. That's partly because I spent all of December and January driving around the northeast for residency interviews (I found out a couple weeks ago that I'm going to be a radiologist, by the way), as well as driving around for family gatherings. I'm just glad I can drive it again.

edit: Here's a short revving video '99 Subaru 2.5RS with an '01 H6 EZ30D engine - YouTube
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Last edited by dyne; 04-07-2018 at 12:35 PM..
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Old 04-03-2011, 07:08 PM   #2
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Issues of note with the swap in case anyone's interested:

The radiator is in the stock location and happens to be much closer to the engine than I think it was supposed to be. The stock 2.5RS fans would not fit, so I ordered a pair of slim ebay fans that fit fine. I’m not sure if the radiator fan wiring is correct, as I haven’t heard them kick on yet (though it’s still quite cold out).

The radiator hoses also needed to be trimmed quite a bit.

The radiator coolant reservoir needed to be relocated. I have an $8 from autozone that works but looks pretty cheesy.

The donor ECU is expecting the car to be an automatic, and will spit out CEL codes if it doesn’t see the automatic transmission. I just emulated the solenoids in the transmission by connecting the transimission control unit to some resistors.

I was also getting a P1590/P1591 code for neutral position switch voltage high/low. I did not wire the NPS correctly when I was doing the merge so I’m going to have to go back and take the dash out again at some point. I need to get the car inspected, so I decided to just give the ECU the signal it wanted to get rid of the CEL: ECU pin B134-8 should be 0V in neutral or 5v when in gear. Neither of those voltages alleviated the CEL.

This was fixed when I made the transistor circuit posted later in this thread

I’m getting a P1507 CEL code while driving, which I think has to do with the fact that it’s currently wired so that the ECU thinks it’s in neutral all the time. I think going to have to take the interior apart again at some point to correctly hook up the neutral position switch.

edit: Solved! - It was just a wiring issue.
edit2: Unsolved! - It may not be just a wiring issue. I have the ECU and TCM wired to be in gear all the time and am still getting this code. I think it stems from the ECU having a hard time idling before the engine warms up when I push the clutch in.
edit3: Solved! - Just had to make the signals going to the ecu think its in neutral when the transmission is in neutral or if the clutch is in. A transistor circuit is posted later in this thread

For the air conditioning, the 2.5RS ECU takes an input from the evaporator thermoswitch and throttle to control the AC compressor. This isn’t how it works with the donor car, so I’m going to take over the 2.5RS ECU’s job with an arduino sometime this summer when I decide I need the AC.
edit: Solved (kind of, my condenser is clogged) Didn't need an arduino or anything. I'll write it up if someone needs it.

The tachometer signal needs to be adjusted; I believe it’s currently sending out 6 pulses per rotation, while my tachometer is expecting 4. I think I’m going to use an arduino to accomplish this.

edit: Solved! - Built a simple frequency converter using an arduino, it works pretty well.

I’m not sure if it’s a problem, but there are 3 vehicle speed sensors (front, rear, and torque converter turbine) that are supposed to be hooked up to the EZ30D transmission control module. The 2.5RS VSS can be hooked up to the EZ30D ECU so the ECU at least knows how fast it’s going. I don’t know if it’s worth using an arduino to try and emulate the 3 speed sensors, as I don’t know if it’s necessary and I don’t know what the signals are supposed to look like.

edit: Solved! - I'm just ignoring the EZ30D vehicle speed sensors and wiring the 2.5RS VSS directly to the ECU. The TCM isn't complaining.

The car will seemingly randomly stall when the clutch is pushed in. My theory is that the engine normally uses the momentum of the engine to keep from stalling, and isn’t compensating well when the transmission is disconnected. Dunno what I'm going to do about it.

edit: Solved - The car hasn't had this stalling issue since wiring up the ECU and TCM to be in gear all the time
edit2: Car still stalls occasionally when coming to a stop when it's warm out. It happens pretty infrequently and doesn't bother me much

Last edited by dyne; 09-27-2014 at 07:13 PM..
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Old 04-03-2011, 07:20 PM   #3
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Awesome work! Came a long way from changing oil and brake pads.

Have to say, the welding/machining you did is very impressive. Really like how the header turned out.

Btw, there are a few here who've done this swap (or very similar) and I'm sure they'll chime in to assist with the unsolved issues.

Last edited by danimprs; 04-03-2011 at 07:23 PM..
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Old 04-03-2011, 07:28 PM   #4
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wow man impressive work!

solid build man, a bit of real solid custom work i'd never do lol

keep it up
I know it's not an impreza...
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Old 04-03-2011, 07:33 PM   #5
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Hey, very nice work
i reckon you should do a DIY on the intake. I'm quite interested of it too, since i'm getting a wrx bonnet soon and wanting better intake for the motor.

keep up with the good work,
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Old 04-03-2011, 07:36 PM   #6
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great job on the swap. estimated cost? if u dont mind me asking. thanx
Ready to party, but keepin it classy!!!
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Old 04-03-2011, 07:37 PM   #7
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AMAZING EXHAUST WORK!!! I'mma gonna keep an eye on this thread. Nice work fella!
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Old 04-03-2011, 07:42 PM   #8
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Veryyyyyyyyyyyyyy niceeeeeeeeeeeee
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Old 04-03-2011, 07:42 PM   #9
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Old 04-03-2011, 07:55 PM   #10
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Thanks for the kind words everyone.

Originally Posted by SuperTu View Post
i reckon you should do a DIY on the intake.
Unfortunately, I forgot to take pictures of the intake construction. However, it isn't particularly complicated and most of the difficulty is just getting everything the right size (which is just trial and error with the cardboard). ABS is easy to work with.

Originally Posted by firme rs View Post
great job on the swap. estimated cost? if u dont mind me asking. thanx
My excel spreadsheet is at $2050 not including tools, $2100 if you count fluids and add a few bucks for nuts and bolts I didn't account for. The engine, AC, alternator, ECU, and wiring was $1300 including gas to pick it up.

I spent about $400 on the welding equipment and other tools. I never really count tools towards a project cost.

Last edited by dyne; 04-03-2011 at 07:58 PM..
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