Can I Add a Turbo to My Non-Turbo Subaru?

Can I Add a Turbo to My Non-Turbo Subaru?

Subaru engine with Blouch turbo

"Can I install a turbo on my <insert non-turbo Subaru model here>?" This seems to be a common question I'm fielding lately, so I'm going to gather my thoughts here, then just be like "Read this link."

So you've got a non-turbo 2006 Subaru Legacy, or 2018 Impreza 2.0i, or 2012 Crosstrek. You see these cool turbo Subarus rolling around and you think, "Why can't I get some of that? Subarus have interchangeable parts, right? It's like a Lego kit, right?" Well, as with most everything else in the world, the answer is that it's a little bit complicated.

Basically, in almost every case, it's going to cost WAY more than your car is worth to turbocharge it. You would be better off just selling your non-turbo car, and purchasing the equivalent factory-turbocharged model. I know, you have grown attached to your existing car, and you added those custom Hella Supertones horns, and you don't want to do that all over again, but trust me on this.

Let's pick an example just so I can prove my point. The 2006 Legacy owner wants to turbocharge his car. On the one hand, we know this is possible to do because Subaru offered a turbo version of the car in 2006, the Legacy GT. So the parts exist, and it could be done. 

Now let's go through what you would need to do it. At the bare minimum, you would need these components:

  • Turbocharger
  • Boost control solenoid and plumbing
  • Intercooler and charge piping
  • Exhaust manifold and up pipe
  • Exhaust downpipe
  • Intake manifold
  • Turbo inlet
  • Intake/airbox
  • Turbocharger oil plumbing
  • Turbocharger coolant plumbing
  • Higher-flow fuel pump
  • Higher-flow fuel injectors
  • Hood with hood scoop
  • Hood scoop ducting

Probably the turbo model car has additional oil cooling that the non-turbo model does not have, but we'll ignore that for the moment. This is already thousands of dollars in parts, and we haven't even tallied up any gaskets, miscellaneous clips and trim pieces, plugs, clamps, nuts and bolts, and other random bits. "I'll get all these at the pick-and-parts place for cheap," you say. Sure you will. When's the last time you saw a Legacy GT in the salvage yard? Yeah, I thought so.

Oh, and your non-turbo clutch is probably not going to be happy with the increased torque, so plan on installing a higher-strength turbo car clutch.

But anyway, let's say you DO assemble all this hardware, and you bolt it all to your existing non-turbo block. That 2.5i block has a compression ratio of 10.0:1, which is much higher than the equivalent turbo block, which was 8.2:1. The higher compression ratio will make the motor more prone to detonation under boost, meaning you will have to run less-aggressive boost/fuel/timing settings than you otherwise would be able to, so the maximum power will be lower than the turbo motor would generate.

Oh, and speaking of ECU calibration, how are you going to accomplish that? The easy way would be to use an Accessport and a turbo-car ECU, and have it custom-tuned on the dyno, but then you'd have to acquire a turbo ECU (more money), and is the ECU wiring harness identical between the two cars? They are almost certainly not, so you would need to re-wire the ECU wiring harness. That sounds like a lot of difficult work, fraught with the possibility of difficult-to-diagnose errors. Okay, so let's stick with the non-turbo ECU. Can that even be programmed to handle a turbocharged motor? How would we even program it? There is no Cobb Accessport for the non-turbo ECU. You probably could have an expert program it using open source tools, but the number of people who can do that (or want to) is small, and they charge a lot.

"My local JDM importer place has all these EJ20X motors for pretty cheap. How about I use that?" The EJ20X is a dual-AVCS JDM (Japan Domestic Market) motor that was never offered here in the U.S. (AVCS is Subaru's variable cam timing system. Dual AVCS means both the intake and exhaust cams are adjustable.) The only ECU in the U.S. lineup that can run dual AVCS hardware is from the 2008+ WRX STI, and that's not going to be plug-compatible with your 2006 Legacy 2.5i body harness, nor would the US ECU work directly with the JDM cam sensors. Again, it COULD be done with custom wiring and/or sensor mods, but it's not simple or cheap. We have seen these engines installed with the AVCS locked out, but the result is LAG, since the cam is extra peaky. It was designed have a tall torque peak that can be moved around as the engine goes through its RPM range. If you can't move it around, you get a very weak low-end and an unusually fast fall-off after the torque peak.

Now let's go back to the value of the car, and what you might purchase instead on the used market. Looking at a standard used-car value site, I show a ballpark value of a 2006 Legacy 2.5i manual-transmission sedan at something like $3800. If I change it to a 2006 Legacy GT manual-transmission sedan the value goes up by something like...$300. I know what you are going to say, "I can't find a Legacy GT to buy." They are out there, but they were never common, so be patient and you should probably cast a pretty wide geographic net. Also remember that the Outback XT was also available for that timeframe. You could even get a manual trans Outback XT.

So my point is for a whopping $300 difference in value, you could just upgrade your existing Legacy 2.5i to a factory-turbocharged car that is ALREADY BUILT. Why would you bother spending $5000 (or more?) converting your non-turbo car? The whole car is not even worth $5000.

Now I've offended that reader out there with the 2018 Impreza 2.0i. That person is saying, "Hey, my Impreza is worth way more than that! It's gotta be worth it to turbocharge this beauty!" My point still stands. Just eyeballing used car values, let's say you can get $19,000 for that Impreza on the used market. You can get a decent 2018 WRX for maybe $23,000. There is NO WAY you could turbocharge the Impreza for $4,000. Even if you did or could, the WRX has SO many other factory upgrades -- wider bodywork, bigger brakes, bigger wheels and tires, performance suspension, the list goes on. 

Of course these swaps have been done, and you can find examples of WRX-swapped Crosstreks, STI-powered base Imprezas, and other fun projects on the internet. Trust me, those projects MADE NO FINANCIAL SENSE. Sure, if you love a challenge, have tons of free time, and you hate money, jump right in. Otherwise, if you are a sane and rational person, just sell your existing car. Buy the closest Subaru factory-built performance variant, and start your project from there.


6 Responses

Mach V Dan
Mach V Dan

October 21, 2021

Henco Phyfer, it is certainly possible to swap in the engine from a turbo car, but the wiring, in particular, can be complicated. Does the body harness on your car mate to the engine harness and ECU from the donor car? If not you are looking at either a LOT of labor in re-wiring, or a good bit of money spent on a custom wiring harness to make it work. If your labor is free it might be worth considering…

Henco Phyfer
Henco Phyfer

October 21, 2021

Gr8 post man, just have a question can you do an wrx or sti engine swap ? wouldn’t that be cheaper?
Obviously you need to buy everything that goes with it ecu, intercooler, transmission and front end of the exhaust etc.
Reason for my question is for instance here in SA where im from the WRX or STI is way more expensive. 6837.00 USD more or less and those engines sell here for more or less a 1000 USD second hand and they have a 6 month warranty so its not like they sell you scrap. I know it is posible like you mentioned above with the right amount of money and time, im just wondering if it would be cheaper to do an engine swap rather than waking up a turbo on my 2005 Impreza rs.

w

luis artiga
luis artiga

October 21, 2021

Totally agree with the article taking a N/A Subaru and trying to turbo charge it is not really a good financial decision. Take for example the truck I had before my WRX. I had a 2003 Nissan frontier and as many people know they offered a supercharged version. I thought to myself the N/A model and the supercharged model have the same engine so all I had to do was buy the supercharger. That was not the case as I continued my research I found the compression ratio was not the same, it didn’t use the same ECU it didn’t use the same transmission either. The supercharged model had a different transmission to handle the psi of boost. So by the time I added the price of all the parts it was coming out to be more than the truck was worth.

The Line Crusher
The Line Crusher

October 21, 2021

It took me years of waiting for the prices to drop on the wrx to finally get one. I knew I would eventually and did. Case in point is be patient, don’t buy shitty knock off cheap shit parts, do your homework, take your time, and save your money. IE: stop eating fast food all the time and use that money for car parts. Eating a $20 meal every other day costs you $300 a month which can go to either car parts or that turbo car you wish you had bought in the first place.

Andrew
Andrew

October 21, 2021

I wanted to do a turbo swap on a Crosstrek. I did some research and now I own a new WRX.

Here to agree
Here to agree

May 09, 2021

This is one of the best breakdowns of why it isn’t worth turboing a naturally aspirated car that I’ve seen. I used this same logic when I passed on a newer crosstrek- no stock turbo = not worth trying unless you have more cash than common sense…

Leave a comment

Comments will be approved before showing up.