legacycentral bbs

Hello! looking for someone with a bit more experience than my own.



I'm looking to pick up a 91 Legacy with a bad trans, I was set on turning it into a rally car, problem is its absolutely georgous and would be a crime to race it, SO! My question is I currently own a 97 Impreza L 383k on the clock, perfect rally car. what troubles will i encounter with a drivetrain swap? two cars are as listed:



91 Legacy auto/2.2/awd

97 Impreza 5spd/awd/frankenmotor



my plan is to swap Engine, trans, shifter, rear end(4.11 final drive) pedal box. I'd really like to do a partial harness swap to keep obd2. id also like to swap over the 2.5rs brakes. I'm also aware i will need the trans crossmember.



will my driveshaft work or do i need a manual legacy driveshaft?

will the pedal box carry over?

are the legacy rear axles roll pin or stub style?

will the brakes carry over? id assume yes but want to be sure.

will the impreza seats bolt in as my RA seats would look fantastic in there.



the Impreza on the otherhand is getting a 04 wrx harness, 2L turbo, 4/2 pot wrx tr brakes, 4.44 trans, cage, yada yada



appretiate the advise as I need to make this swap as smooth as possible

You need a legacy drive shaft because the two cars have a different wheel base ..the rear half is the same after the donut but you need the front portion
Yes the pedal box should work just fine you might need to drill a hole for the clutch cable to go through
the rear axles should have a roll pin
yes the brakes are all interchangeable between the two
Im not too sure about the seats but i would say yes as the earlier subarus didnt vary much with 02+ seats you might have fitment issues ( seat height)

Ah, good to know thank you.

I plan on using the impreza pedals as the impreza trans is cable and the jdm 5spd requires me to run hydro for the turbo swap.

Seat height should be ok as the seats came out of a gc chassis, just wanted to make sure it'd be mostly bolt in. And I'm pretty sure I can get a drive shaft out of a 90-91 legacy wagon so that should be simple.

Just had a look at all data And see the ecu is a eaaaaarly style jecs unit so I might have to hold the ecu swapping off for a bit. Hopefully it doesn't get angry about not having an auto in the car. Thankfully it looks like it still has knock control which is a must for the frankenmotor.

Welcome to the BBS.

I'll reply more later, but I would not recommend doing an ECU swap...it'll be a huge pain.

Regarding the driveshaft length. The length has a lot to do with the rear diff style and whether it's the older or newer style rear diff. The 97 should have the newer style diff. You may need to take some measurements under the two cars from the transmission snout to the carrier bearing and then to the diff. I'm not sure whether you'll just be able to use a 5spd Legacy driveshaft with the Impreza rear diff. Take the measurements and see if the Impreza driveshaft would work as is. If not you may need to piece together a front section of the driveshaft from a Legacy and a rear section of the driveshaft from an Impreza (or vice versa).

I had to do that with my 6spd.

http://bbs.legacycentral.org/viewtopic.php?f=7&t=49917

Oh yea about that i forgot to mention that if you use the impreza diff you need to either switch over the diff snout because the bolt pattern is a bit different if you wanted to use the impreza diff on a legacy driveshaft(rear) but since you have the whole car just use the rear portion of the drive shaft off the impreza and the front from a legacy ..some vary in length due to the length of the rear diff carrier but as long as you have that matching rear portion then you should be okay when i did my swap i used parts off a 96 impreza L brighton (coupe) and the only thing that changes lengthwise is the front portion however that is relative to the dougnut bushing..it bolts up in the same position regardless it just needs to match up based on your diff as Legacy777 has stated
however im not too sure how similar our situations are

wait, what? there's two different r160 flanges? huh.

welllllll, on the plus side being an auto it should be 4.11 final drive so itll work with my trans, i would like to update later to regain my lsd. the impreza i don't want to completely pick apart as ill still need the driveshaft.

the ecu on the other hand, to simplify things i was going to break the connectors out of a dead ecu i have and soder a patch harness to more or less pnp, then run a few wires up to the glove box for a obd2 port.

looking between the two ecu pinouts i don't think id really have to add anything as the motor in the wagon is still full 2.2 harness.

so just went fully over the ecu pinouts, i stand corrected. looks like a pita. lol


anybody know how the frankenmotor does with early ecus?

Yes, there are two different style of R160 rear diffs and associated flanges, and as you found out...converting to OBD2 is not a minor undertaking.

The challenge you run into is the TPS signals are reversed for the newer motors and the IAC system can be different depending on how new you go. Same thing with the crank & cam trigger setup if you go with a phase 2 engine setup.

Do you have more specific details you can share about your desired engine setup?

Well, basically the engine in my impreza is a

Ej251 bottom end
ej253 pistons
single port ej22 heads
Cam and crank signal intake everything is 97.

So the 91 ecu should run my engine with swapping the intake over if the idle control is ddifferent. My concern is what is it's logic on knock control? The motor I put together wants to knock, it's really on the limit of the stock ecu, but it works, doesn't knock and makes great power and due to its increased efficiency gets awesome mpg. So I guess really so long as the legacy ecu can get by without trouble I'll deal with counting flashing CELs if an issue comes along

Mainly because it's solid and I'm not worried of it breaking anytime soon

The 91 should run your motor. The 97 intake should have the same IAC, however the TPS is probably different 3-wire vs. 4-wire. You need to run the 4-wire TPS. I'm not sure if you can just swap TB's as that would be the easiest option.

I believe you can swap the Tb over i used my 94 22E tb on a 97Ej25D to avoid any rewiring other than the two tranny pins once again i did it but it doesn't mean we are on the same boat

first off, I really appreciate the responses and help.

The 4 pin bit makes sense, although if i wanted to be ultimately lazy i could just repin the 3pin connector on the legacy harness. except i'd loose that sweet "POWER" light. If i'm remembering correctly once you ground the MT ID pin the ecu should quit looking for a TCU signal.

should be grabbing the car next weekend. the owner has the title but no keys so i need to pop the passenger door cylinder out and get the code to have a key cut.

couple of random pics to showcase how mint this thing is.... minus the tree sap

I'll trade you a manual legacy driveshaft for that brat lol.

rpholz wrote:first off, I really appreciate the responses and help.

The 4 pin bit makes sense, although if i wanted to be ultimately lazy i could just repin the 3pin connector on the legacy harness. except i'd loose that sweet "POWER" light.

Are you talking about running the 3-pin TPS with the 91 ECU?

That power light is only "sweet" when your car is WOT/5000RPM's +/- a few

Huh, I'll be Damned I assumed it was like an ea82 car where the 4th wire on the tps goes solely to the tcu. Quick check of the wiring diagram and the ecu sees all 4. Weird. This car is half ea82 half new gen.

What is indicating it's half ea82?