Common 5V buss on T-leg ecu?

[hankosolder]

I've got a scheme to turbocharge my NA 98 Leg. Outback - it's got a '95 dual port ej22 in it at the moment, so the WRX parts should pretty much bolt up and work for a very low boost setup.

'For engine management, I was hoping to use a T-leg ecu and build an adapter harness to plug into the factory 98 ecu plug. On the '98, looking at the wiring diagram, I notice that the CTS, TPS etc. are tied to a common +5V buss from the ECU. On the '94 T-leg, all the sensors have individual wires which go back to the ECU. Are the +5 supplies for the CTS, MAF, TPS all tied together internally in the T-leg ECU?

I also notice that the T leg ignitor has an extra wire. Will the T-leg ECU run a later style ignitor OK, or do I need to swap that and run an extra wire?

TIA,

Nathan

[Legacy777]

Welcome to the BBS Nathan.

I'm pretty sure the +5v supply on the t-leg ECU is a common +5v supply.

As for the igniter question, I'm pretty sure the extra wire is just a ground. Does the 98 igniter only have 4 wires? You should be able to use the 98 igniter without any issues.

[hankosolder]

Thanks for your reply, Josh. Once I get the ECU (it's on its way) I can check for continuity between the pins I think are all tied together internally to the 5V reference.

As for the igniter, I'm looking at the wiring diagram in the Haynes manual and they are showing a sixth pin on the T-leg igniter which going to a yellow wire marked "Turbo only" tied into the 12V power supply for the fuel pump relay coil. It looks like the NA OBDII igniter has five pins in the diagram. I'm guessing those Haynes manual wiring diagrams are sketchy though. I'm planning on tracking down some better wiring diagrams before digging in....anyway, I'm glad to hear that the '98 igniter will probably work.

Finally, as a reality check-- is my scheme of using a T-leg ecu to control a NA '95 ej22 totally doomed? Supposedly, folks have run 3-5 psi with stock NA engine management. That seems like living close to the edge, so I thought the T-leg ecu might be a better choice as it will at least pull some timing under boost. If it blows up, I guess I can find an ej22T block, or at least some ej22T pistons, but I'd rather not blow it up in the first place.


Nathan

[Legacy777]

You can d/l a lot of factory service manuals from me. This thread in the stuff you need to know forum has the info.

http://bbs.legacycentral.org/viewtopic.php?f=12&t=14485

As for using the tleg ECU. I think it will work, the primary issue is going from OBD2 to OBD1 and making sure all the sensors work appropriately with the tleg ECU. If you can get all that to work, it "should" be ok. The one thing that may cause issues is the higher CR of the 95 ej22. You'll just need to make sure to limit boost.

[BoostedSubie]

Are you sure the Coolant Temp Sensor is tied in with the MAF and TPS? That doesn't make any sense. The Coolant temp only has 2 wires, one to the ecu, the other is grounded. I'm doing a similar swap right now. EJ22t swap into a 95 Impreza LX (OBD 2). On the Impreza, the MAF, MAP, and TPS share a common pin for power like you said but nothing to do with the CTS. I do wonder about that 6th wire coming off the ignitor going to the ignition switch pin at the ecu then the fuel pump relay as you pointed out, I never even noticed that before. I have used the newer Diamond Igniters from the gen 2 Legacys before on my turbo Legacy and never noticed a difference so I wonder why they put that in there on the turbo Legacys.

[hankosolder]

Boostedsubie, I think you are probably correct. There are two ways they could do it... have an internal "pull up" resistor in the ECU tied to +5 and have the CTS tied between the other end of the pull up resistor and ground. Or, they could tie one end of the CTS to +5 and have the other end go to a pull down resistor inside the ECU to ground. (Basically, they are creating a voltage divider circuit one way or the other.)

I have been following your '95 Imp thread and it's been helpful. Also good to hear another confirmation about the later ignitors working with the earlier ECU.


Nathan

[BoostedSubie]

Once i'm done with my Impreza, I plan to do a thorough write up. When I started this project, in doing all my research, I didn't come across any good write ups on the wiring. There were a couple on people doing the swap into the OBD 1 EJ18 Impreza but nothing on the OBD 2 stuff really. I wanted my swap to be as simple as possible. I couldn't understand why no one was using the wiring that was already in the car through a jumper harness or soldering the Legacy ecu plugs in lieu of the Impreza plug. Instead they were merging the Legacy harness with the Impreza. Thats more work and more wiring in the car. I will swap out my harness for a manual harness when I come across one as having all the unnecessary automatic wiring bothers me.

Hope to see your project progress.

[BoostedSubie]

Also, another idea for you motor build would be to use a set of EJ251 heads on your EJ22 block. Lowers the compression to be more boost friendly. MikeyMeyagi has done it with success. Check out his build thread http://bbs.legacycentral.org/viewtopic.php?f=5&t=48934

[BoostedSubie]

Another thing to add if you consider using EJ251 heads on your block. I'm pretty sure the phase 2 EJ22 intake manifold will bolt up to the EJ251 heads. Using the phase 2 EJ22 intake manifold would allow you to run a Legacy IAC vavle with side feed injectors so you could run the EJ22t pink injectors. This way, there would be no need to run an Apexi AFC to scale down the bigger 440 injectors. Or you could get a Robtuned EJ20 ecu and run some 440s injectors or the 550s for his higher tune. Just a couple options to think about.

[hankosolder]

Those are some interesting low comp combos, I kind of like the idea of trying highish compression, low boost. I may cease to like that if it blows up. I'm not chasing ultimate power... if I can get just a bit more output than a stock T-leg I'll be happy.

Where did you get your ej22T ecm connector /pigtails? I'm getting another 98 legacy ECM for the connector, but I'm having no luck with the T leg connectors.

So far, I've got the 2.0 WRX manifolds & crossover pipe, '05 LGT up pipe, a TD04, TMIC from a '07 WRX. The T-leg ECU, '98 ECU for parts, '03 WRX X-member are on their way. Hopefully, that's the last of the $$ items. Still need a down pipe, T leg ecu pigtails, T leg maf, injectors, intake piping, oil and coolant lines for the turbo.

[BoostedSubie]

I work at one of the bigger salvage yards in the US, so I have access to lots of good parts. You can use any 90-94 Legacy ecu plugs as they are the same, the EJ22t just has 5 more wires than the non turbo and the pins for the Cam/Crank angle sensors are swapped.

I'm sure you can find a lot of the parts you need here if you don't find them elsewhere.

[hankosolder]

OK, I received the T-leg ECU. There is no continuity between B48.3 (Map power supply) and B58.3 (TPS power supply.)

On the OBDII cars, there's a shared 5V buss which feeds the TPS, MAP and fuel tank pressure sensors. I think the easiest way to deal with this issue is just to run separate cables to the TPS and the MAP. The 4 pin TPS is going to need that extra wire anyway for the idle switch, so a two conductor wire should do the trick. (Power supply + idle switch.) The ground and signal wire should be OK. A three conductor wire to the MAP would be good.

T-Leg ECU connectors are on the way. I'm REALLY wishing I bought a rustbucket, brakeless T-leg which I saw for $900 a couple of years ago. Could have harvested the ECM, MAF, MAP, wiring harness, crossmember....

Oh well!

[Legacy777]

Thanks for following up and confirming they are different sources.

[hankosolder]

So, I'm making good progress on my adapter harness. I think it might be ready for a crude test late this weekend. (I have ANOTHER '98 Legacy, this one a rustbucket 4EAT... I'll try the T-leg ECU and adapter harness in that just to see if it will start at all- if I damage some sensors or the wiring in the car it won't be a great loss. It'll be running NA, with the NA injectors, the JECS MAF, and a 3 pin TPS, but I think that should be close enough for it to at least start and idle if everything else is OK. I'll ground the extra TPS idle switch pin to fake that out.

A Hitachi MAF is on its way.

BTW, Josh- is it OK to be running on about my project here? I realize that the site is for 1st gen turbo Legacies, so if you like to keep things tightly focused on the 1st gens, I will respect that.

[hankosolder]

Well, I saw some non T-leg projects in the build journal, so I think I'm OK.

Proof of concept! I put my adapter harness in our rustbucket 4EAT 98 Legacy today for a test. Starts and runs!

Walkaround:
http://vimeo.com/66977873

Start and idle:
http://vimeo.com/66977874

Still have quite a few small parts to collect and then I'll take the plunge in the non-rustbucket 5MT '98 Legacy Outback -w- 95 EJ22.

Helpful hint: the diode to the ignition relay is shown REVERSED in the Haynes manual. The FSM shows the correct orientation.

[86BRATMAN]

looking good Nathan, btw that map and wiring looks awful familiar lol

Sent from my ADR6425LVW using Tapatalk

[BoostedSubie]

Are you talking about the self shutoff diode?

[hankosolder]

86BRATMAN- yes, thanks so much for selling me the MAP sensor and the ECU plugs! I might be getting in touch for a few of the other things I need.

BoostedSubie- yes, I am talking about the self shutoff diode. (Well, I think that's what it's called... it is connected to the line which drives the coil for the ignition relay coil.) I think this was discussed in your thread, yes?

[Legacy777]

Nathan,

Yeah, you're more than welcome to post about any subie.

Are you running the JECS or hitachi maf? If you're running the JECS maf, that's why it doesn't run well.

[BoostedSubie]

Yeah I was looking into this on my thread as well. How did you end up wiring yours up? The diagram I have which I'm not sure if its from the FSM or not as it was downloaded awhile back and there is no label on it, shows the yellow wire of the diode going to the starting/charging system and the coil, then the green wire goes to the ecu and the ignition relay. I have seen in so many peoples builds this seems to be a hurdle for most and I haven't seen any straight forward explanations. A lot of people just give up and wire in a switch. Also with the yellow wire going to the starting/charging 12v source, I wanted to confirm whether it was a constant 12v or switched. I would assume it was a constant as the car will continue to run after the ignition is turned off with out the diode but read on another thread that it should be a switched source.

[hankosolder]

I have a line going between the "ignition switch" terminal on the '98 Legacy connector (in my case terminal B85) to B58.12 (the ignition switch terminal on the ej22T ecu.) The anode of a diode is connected to that line. The other end of the diode (the cathode) goes to F47.5 on the ej22 ECU and the coil of the ignition relay. It turns on and off just fine with the key.
In a nutshell, it needs to go to switched power through a diode.

There are significant differences in how the power switching and distribution happens in the OBD II cars. IMO, there's really no way for the later cars to stay running with the key off, as the ignition module is connected to switched power. Of course if it's miswired, anything is possible.

[BoostedSubie]

Great, that's how I have mine setup on the harness. Just wanted to make sure since you had said the Haynes manual was wrong. I have mine in but still need to do some stuff in the engine bay to finish up before I can even try to start it.