question for guys who know internals...

[korybobsimpreza95]

okay here's my questions, how does the ej25 non turbo act with sti internals, are the pistons the same diameter? is their any way to hybrid this together? just a thought i guess...im beatin around the bush before i decide to go for the ej20t swap i guess..seems wasteful to swap a motor that only has 70k miles on it...and what about the heads? wrx heads on a 2.5 block? or even sti heads? or are the heads the same with different cams and valvetrain? this is all pertaining to it being boosted that is..just some random questions i haven't really thought completly through yet lol...anyone who knows more about this feel free to "enlighten" me on my quest to learn how compatable the ej series are, compared to the b-series honda motors:P thanks....

[SabreKhan]

I don't know for sure, but I would bet you wouldn't want turbo internals in your non-turbo engine. Turbo internals are designed for high-pressure applications (high air flow and high fuel flow), so without the increase in the air/fuel mixture I'd be willing to bet the STi internals will actually make a non-turbo engine weaker. The compression ratio ratio can't be favorable (yes, I typed "ratio" twice on purpose).

If you want to go turbo, it would be easier by far (and probably cheaper) just to do a motor swap. You can just ship your old one to me, and I'll install it in my dune buggy.

[korybobsimpreza95]

what im trying to say is, i knwo it will lower the compression deffinatly, thats what im looking for...i meant if the 2.5 had sti internals and had the turbo swap..i didnt really make myself clear on that sorry, but an sti had an 8.0:1 compression ratio compared to a stock 2.5 which i think is 9.6:1...i was wondering if i could use sti internals to lower compression and run more boost...or if none of it will bolt to one another...sorry for the unclarity...

[korybobsimpreza95]

also, with the swap from obd2-obd1 motor is the wiring harness a pain to do, or has someone made a diagram for the ej20t in the 2.5rs? i know i have to get a turbo crossmember to clear the downpipe, but i seen on a forum where a company makes aftermarket headers for the turboed 2.5rs, does this eliminate this need for a crossmember or am i still gonna have to go junk yard diving?

[LjasonL]

You can bolt all of that together no problem, it's getting it wired up that's the fun part.

[2turboimports]

Originally Posted by korybobsimpreza95

also, with the swap from obd2-obd1 motor is the wiring harness a pain to do, or has someone made a diagram for the ej20t in the 2.5rs? i know i have to get a turbo crossmember to clear the downpipe, but i seen on a forum where a company makes aftermarket headers for the turboed 2.5rs, does this eliminate this need for a crossmember or am i still gonna have to go junk yard diving?

first things first. For some reason every ej20t made has a different wiring schematic year to year car to car. They're similiar, but unless you know your stuff you'll spend a good 30+ hours on the harness itself. That's with schematics from both current and swapped engine, w/ both harnesses to cut and splice from. More than likely, you'll only wind up w/ a messy mound of wires and pages upon pages of diagrams.

For the cost of the aftermarket headers it'll probably be cheaper to get the crossmember. I don't believe that headers truly make much of a gain on a stock turbocharged engine. Unless they're like $200 I'd say just pick up a turbo crossmember and swap that. But then you kinda have to do a little custom jobby to get the front sway bar mounts to screw to the turbo crossmember. However that is by far the least of your worries.

[korybobsimpreza95]

talkin about bummin someone out on a swap...lol j/k really though ive done alot of swaps in honda's but they are so interchangable everything almost bolts up lol...so i mean experience is not the issue....experience in subarus on the other hand..lol...my buddy that will be helping me with the swap is a certified electrician on residential and small motors so hopefully that schoolin will eventually pay off...sounds like to me its just a good reason to do i wire tuck lol...where can i find the wiring diagram for both the motor being swapped and my car now?

[mr_tw]

Man i don't know much about swaps or anything like this, but kudos to you for not talking the easy way out tuning your car is about having something unique, and you dont see this terribly often

[korybobsimpreza95]

thanks man, its just, i have such a passion for cars that if im going to do something i want it to be done right, hints all the questions, the way i see it, why not do something right the first time, instead of going back and re-doing it over where you half-assed it before...i hate nothing more than to see a car hacked together, its like abuse or something lol...and with your name, if its fast and it diserves respect, give it respect, i prefer imports but i mean if its fast, its fast! and thats what its all about......right? people who build cars are always striving to achieve perfection....

[2turboimports]

It would depend what year your car is. I have the manuals for 00 - 01 Imprezas. I don't know what changes were made past that. You just have to search a lot of forums for whatever car your engine will come from. Nasioc is a good resource. Alot of overseas forums. I dunno really lol. It takes alotta time.

Mechanically easy...technically very difficult. lol

[korybobsimpreza95]

my model is a 2000 2.5rs and the motor im prolly going to swap in it is the ej20tt out of the legacy prolly about a 95 model...before the swap, i might convert it to a single turbo application. so will i have to find the wiring harness out of a 95 impreza and splice it in to my stock wiring harness? i just want to know exactly what i need to do before i start this swap, i dont want to get in the middle of the project and get stumped or caught up on some unforseen problem, and not be able to get my car back on the road on scedule. any ideas?

[2turboimports]

Originally Posted by korybobsimpreza95

my model is a 2000 2.5rs and the motor im prolly going to swap in it is the ej20tt out of the legacy prolly about a 95 model...before the swap, i might convert it to a single turbo application. so will i have to find the wiring harness out of a 95 impreza and splice it in to my stock wiring harness? i just want to know exactly what i need to do before i start this swap, i dont want to get in the middle of the project and get stumped or caught up on some unforseen problem, and not be able to get my car back on the road on scedule. any ideas?

lols, you're not 'might going to convert it to single turbo', you are going to have to. lol. You'd have to do so much custom work to make it fit especially b/c the brake booster of the usdm models sits where the 2nd turbo goes.

[korybobsimpreza95]

that thought crossed my mind one day while looking under my hood, but single is better anyways...more thrill once you meet mr. spool lol!! will the 02-03 wrx cat back fit my application? j/w..any kinda help will be appreciated..

[korybobsimpreza95]

okay after studing up on the wiring harness most of the day and all night now on nasioc, this is the simple conclusion i have came up with.. once i get the wrx motor into my rs, my factory plugs will no longer plug into the wrx motor..thats a given...so practically all im doing is splicing the wrx plugs + a little extra slack, into my stock harness so that the plugs will plug in properly to the new wrx motor correct? then im splicing the facory ecu harness into the new harness with the wrx ecu now...kind of making a home-made conversion harness correct? wow...thats a confusing statement...am i on the right path? in this case from bod2-obd1 the signals lights ect. will also have to be spliced in order for the wrx ecu to read it...err..wait..umm someone straighten me out here cause that would be practically just using the wrx wiring harness and splicing the factory one out of the picture...HELP!?!?!?!