Not trying to be a dick, but please (pretty please) answer just my specific question because I am old, I don't understand all these numbers, and I want to start shopping.

What is the biggest, most horsepower, turbo, gas, Subaru engine that easily ( no drive by wire or anti theft stuff) can be swapped into the car?

Biggest and baddest? That would be the STi 2.5 liter EJ engine with 300 hp, but Rich, you say you're really old? And feeble? Then that might be too much power for an old guy, so next up would be a later 2.5 WRX turbo EJ with 230 hp, or the later EZ30 six cylinder (gear driven cams) naturally aspirated with about that same power or more. There's a Wikipedia article that lists them all by year, engine model numbers, displacement, hp, etc. (HERE)

Just a point, though. The immobilizer and drive by wire stuff only comes into play if you use the OEM Subaru ECU, if you go aftermarket it's a non-issue. There are plusses and minuses of aftermarket vs. OEM ECU's, but going aftermarket gives you a lot of flexibility with all the different systems. Using a later engine with an OEM ECU gets you past the drive-by-wire and immobilizer issues but then locks you into a lot of stock systems that need to be brought over from the donor car.

https://en.wikipedia.org/wiki/Subaru_EJ_engine

EJ207 would be my choice...then swap out the pistons with forged..new injectors, turbo and your 400-450 HP capable.

98'-2000 JDM WRX STI

There is just nothing,simple about this .

EJ207 with a rebuild is not simple....

300 HP,EJ STI motor, what year and number is that?
I have seen the wiki, it's not an easy read.

Simple would be go with the ez30 & aftermarket ECU. No turbo to deal with. Great power in the 220-240 range realistically. We are still talking about an engine conversion though. It is not simple or easy. If you want something turnkey buy a completed car. BigKat was selling one of his ez30 driver's a while ago though I am sure it sold. NA is going to be less things to worry about conversion wise. Still doing the motor you should do a suby tranny. By the time you deal with adapter plate's for the 901. You can do the suby tranny for only a little more. Plus have nice smooth shifting. I would recommend you talk with Bob (BigKat). He's done multiple conversions. I think he could explain everything in the way you'd like.

Thanx

IIRC, they're up to 330hp on the STI now. I'll 2nd Jamie's nomination for the EZ30. Nice steady power curve, nice 6 cyl sound and only an inch and half longer than the 4cyl 2.5. If 300hp ain't enough then twin turbo an EG33 for double that.

dont know much about the EZ but the EG33 from an svx is bigger, cheaper, guaranteed at least 225 hp and in my experience in my swap simple and easy to work on. ez30 also has a weird head with only one exhaust port and iirc makes 175 crank in the cars its in, not saying it wouldn't make more but I just dont remember it making 230.
don't know what year mass has cut off smog req but Im in CA and I took off all emissions gear on my engine and am using a megasquirt ecu. Hoping for 225 whp..

its not a turbo, but I think it'd be easier and cheaper so maybe that helps.

Mitch

edit: as aforementioned heard on some forum that people have taken the eg to 400 hp stock internals with turbos..

the Tribeca subie engine(2005-2009) or EX30D 3.6 make 250 HP but only 217 torque,..but it comes on at 4200 RPM,..that is suppose to fit easy aswell,..!!,..???,..

any engine can have nice ratings but over time Iam sure they have lost pwr the true HP/TQ would not been known unless Dyno'd..

Having just torn down my EG33, I must say it's a COOL engine. Simple, the EFI is bulletproof and after 180000 miles, it looks like it's in great shape. I'm doing the head gaskets as piece of mind, but cams and cylinders look pretty good to me. They're by far the cheapest Suby engine per HP. It was rated at 240 from the factory. Not sure what it makes now, but it sounded amazing when I had the donor car running. Examples can be found in the $600-800 range. There was a guy in the classifieds selling one with the harness and ECU fairly cheap and the hard part is already done!

The EZ engines with the black plastic intake manifolds have three exhaust ports per head, not one siamesed port, and make from 217 to 260, if I remember correctly, depending on model. Not a bad deal, especially for the compact size and weight. Firing order the same as a Porsche six, too, so with a Porsche sport muffler the same sound.

One other issue with the later motors is the variable valve timing. There are aftermarket ECU's that can control them, and I seem to recall that Megasquirt has a channel that will as well but am not sure. Alternatively you can get Delta re-grinds pretty cheap to make the engine into a fixed cam. Lose a bit off the low-end torque curve, but other than that it's a pretty simple, cheap and painless alternative. Your choice.

Oops, dopple post. Don't know how that happened, sorry.

Yes, 2003-2009 had three exhaust ports per side, variable valve timing, etc. Bob recently sold his blue EZ30 car as well as the extra EZ30R engine (250hp) he had. He's neck deep in a 1970 Camaro and his LS car.

I noticed recently we got a JDM dealer in the Chicago area. Selling some nice looking engines for decent prices. They also have engine/trans combos. They have a LOT of EJ20 NA engines. Only 137 hp 2.0L, but at $949 not a bad deal.

Here's an EZ30D with the plastic intake (indicating 2003 or later) for $1499.

EZ 30 JDM

Don't know ANYTHING about these guys, just FYI.

Here's a pic of the ez30 (3.0L) head
ez30

The engine that makes 260 is the ez36, the 3.6 found in the tribeca. I know nothing about it but it does have three exhaust ports and vvt iirc.
3.6 will run you more than the 3.0 i think

Edit: i guess they updated the head for the newer ez's go figure

Edit: all info neccessary is here: subaru eng wiki

The great thing about a turbo EJ motor is the great aftermarket support. Hundreds of companies making parts to support these family of motors and if the urge for more power is there, it is cheap to buy a tune and turn up the boost. I don't really understand the argument for simplicity, as the turbo does not really add much complexity. You still have to fab a custom exhaust on both motors. You just have to relocate the air to air inter cooler to fit, or run a water to air.

This project needs a turbo, and needs to be in the right family of engines so I can boost the power if required over time.

Simplicity for me is to know what motor to buy, a turbo, a 4 cylinder.
As all of these threads go, there are so many opinions that do not answer the initial question, thus why I get confused with all the numbers and give up again....

Six cylinder motor is not an option.
Using a stock ECU would be my first choice to keep the up front costs down initially, but have that option later on.

Rich

OK, real simple, buy an STi motor, U.S. market, any year but the newer the better. You're going to find that those are a bit expensive so the next option would be a U.S. market WRX motor, again as new as possible, about half the price and not much of a step down from the STi.

That's the answer to your question, but I don't think you're asking the right question. The problem will be the drive-by-wire, variable valve timing, immobilizer, etc. If you use late model versions of either of those engines with a stock ECU you'll need to incorporate so much of the donor car's systems into the swap to satisfy what the OEM ECU needs to run that your project won't be simple any more. And those lower "initial" costs will turn into a lot more time, work and expense. I don't want to TELL you what to do, but I'd suggest you consider using an aftermarket ECU, even if only a Megasquirt, to keep the whole thing simpler, and in the end cheaper. And that's going to be simpler/cheaper even after paying someone for a nice dyno-tune at the end.

The next alternative is Matt's suggestion, an older 2003-2005 WRX EJ205 engine that may not be the pinnacle of the monster power map, but is a straightforward engine with 230 stock horsepower that's simple, proven, and well supported by the aftermarket so can be easily modified when you want. It's what I have, and I'm pretty sure it would have more enough power to keep you entertained for a long time. A long long time, you being so old and all ( ). The nice thing about the EJ motors is that they aren't too expensive or hard to find, so once the work to finish the basic conversion part is done you can plug-and-play with lots of different variations if you happen to blow one up, want more power, do some experimentation with E85, stupid big turbos, or whatever.

The WRX motor 2006+ is even the same displacement as the STI motor but cheaper.

The EJ207 I suggested above is just the JDM version of the STI. Both motors great for power. My suggestion on adding forged Pistons is only if you wanted a big turbo and big power. It's not 100% necessary, but at big turbo/high boost the EJ motors have a known issue with ring land failure. My daily driver is an 06wrx and I have been running 15-17 PSI on the engine for its whole life (now at 117,000)

Important to note, that's ring land failure of the STOCK pistons when run with huge boost from bigger than stock turbo. It's no different than any other engine, increase the power a lot and you need to make things stronger so stuff doesn't break. You can increase the power/boost considerably from stock, as Matt and my son (when I'm not looking) have done, but stupid big increases will eventually cause problems unless you upgrade the stock internals. And that's the basic difference between the STi and WRX motors, upgraded internals, bigger turbo and injectors so it can run higher boost for more power.

When did the WRX STI motor start?
Thought it was 325 hp back in the early 2000,s?

Don't want to hijack but... If one was to complete a build using one engine and then decide to switch to another engine down the road for more power.

Is there a resource for which engines fit which transmissions and would the engine/trans mount locations need to be changed if going from an EJ to EZ or EX? Or early to late?

If you're talking about a Subaru transmission, pretty much any 5MT will bolt up to an EJ, EZ, etc. The clutch kit and flywheel are matched to the trans, so you would just move that to whatever engine you swapped to. Engine mount locations are universal too. The only engine that is a tight fit with the universal cradle mounts that are available is the EG33. It fits but nearly touches the front firewall. You could us a spacer to push it back a bit if you wanted. The rest are fine from 2.0 to 3.0L (not sure anyone has completed a 3.6 yet .

The Subaru STI started in 1999 in Japan but didn't come to America until 2004.

Official power output has never been above 315ish on a stock street version.

What is the displacement of the 2006, WRX EJ207?
Also, is a twin scroll turbo an option for fitment?

2.0, not sure if they were twin scroll or not, i dont believe so. But you can always make it happen.

I have run a 1996 JDM V2 STI in a Forster and it was great. I used the harness from that 1/2 cut and ecu. That is the way I will go for my build and I will be using the Subaru 5 speed.

If you want simple run the stock computer, OEM Harness and have Busaru redo the stock wiring harness. They will help you with the immobilizer to as I recall. I did a EJ25 swap this way, super easy. With new exhaust and intake they are like 180hp+.