Lilchopshop’s Subaru Conversion Project, Making it up as I go Options

[Lilchopshop]

Hi All,
My name is Aaron. I've been lurking on this site for years, learning from all of you who are kind enough to share your projects and the challenges that go along with them. In an attempt to keep me motivated on my project and as a way to create a place for me to ask questions as they come up (which they will, frequently), I decided it was time to start a proper build thread. I’m not a novice when it comes to tools, fabricating and most things automotive, but I’ve never attempted an engine swap before, and most things electrical tend to stress me out. That being said, I love a good challenge and I’m not afraid to fail.

I purchased this car in February of 2020, just before Covid lockdown. I got off to a pretty good start repairing the rust and trying to make a solid chassis for what I thought was going to be a stock-ish restoration (some of that work documented here: http://www.914world.com/bbs2/index.php?sho...ty+jack+points). Then, after watching all the great engine-swap builds on this site, I changed my mind. I knew I wanted more horsepower, but I couldn’t justify the cost of an air-cooled Porsche 6-cyl and I didn’t want to lose the trunk to a big V8. For a while, I was considering keeping the original engine from the car and using a tunable fuel injection package, but for the total cost, the bang for the buck just didn’t seem there. So, I settled on the Suby engine. After some research and some purchasing mistakes, I ended up buying a 2002 legacy outback donor vehicle with an EG25 engine. I harvested the engine, the ECU and whatever else seemed valuable. After selling off the old Porsche engine, transmission, all of the FI components and the saleable parts from the donor Subaru, I probably ended up in the black, financially.

Since buying the car in 2020, I’ve gotten pulled away by many other, more important projects, so I’ve only been able to do little stints of work on the car. I’m optimistic this time, that I will be able to finally dedicate some quality time this winter and hopefully make some real headway. I haven’t been great at documenting the little things I’ve done on the car in the last 2 years, so I’ll start this thread off with some of the things I did actually get pictures of and a summary of where I’m at now.

The day we met:
The first attempt at a Suby Engine (EJ22):
The second attempt (complete donor vehicle):
My crazy, home-built cable shift linkage:
My home-built engine cradle:
Shifter from a boxter (slightly modified):
Some suspension ear reinforcement:

[Cairo94507]

Great; we all love build threads with lots of photos so we can enjoy the ride with you. Good luck this winter. (IMG:style_emoticons/default/beerchug.gif)

[gereed75]

Nice work so far. That shift linkage looks really nice.

[76-914]

Looks great. Will you be able to drop straight down a few inches from the manifold with the exhaust and clear your engine cradle? Now is a good time to weld a few pieces of bushing stock to the cradle so that it will accept some caster wheels. Makes for a quick install or removal.

[Lilchopshop]

Looks great. Will you be able to drop straight down a few inches from the manifold with the exhaust and clear your engine cradle? Now is a good time to weld a few pieces of bushing stock to the cradle so that it will accept some caster wheels. Makes for a quick install or removal.

Good timing Kent. Exhaust is what I was working on this weekend and that was going to be my next post. Here are some pictures of the header I made for the right side. Aside for a few welds that I rushed, I’m pretty happy with how it turned out. I was considering using exhaust clamps of some sort to join the muffler to the header pipe, but I think I’m just going to weld it right on. I’m sure the muffler will outlast my header pipe anyway and the whole exhaust is so short it will be easy to remove in one piece. I plan to weld a hanger on the muffler and attach it to another hanger on the underside of the trunk with a rubber exhaust mount.

Any suggestions as to where I might mount the O2 sensor bung?

[76-914]

Nice looking fab work you have there. Weld the bung within 12" of the flange and somewhere between 9 & 3 o'clock. Moisture is their enemy so stay above the bottom half and keep it accessible for future testing and/or replacement. Looking back I wished that I would have fabricated the cradle to accept hangers for the entire exhaust system. (IMG:style_emoticons/default/headbang.gif) That would have been better than having mounting points on the tub. You're not exaggerating about the short exhaust. I ordered 10ft of 2" tube and it is still sitting in the corner. Nothing but fittings and flanges on mine. (IMG:style_emoticons/default/evilgrin.gif)

[tygaboy]

Do these Subaru engines not benefit from the ol' equal length exhaust runner thing? I'm not picking on the design, it's just that I've seen a few after-market Subbie headers and none of them are anything like what you hear about being designed for optimal performance.
Is it down to available space (totally understandable) or am I missing something?
Your work looks lovely, by the way, so again, not a dig at you.
I'm going to be fabbing a complete exhaust for a buddy's Subaru swap and was planning something equal length - so I'm genuinely curious.

[Lilchopshop]

@76-914 , thanks for the O2 sensor placement advice.

@tygaboy , pick away, by all means! That’s really the whole reason for the thread in the first place!

Below is a picture of the engine end of the stock manifold. (Looking at it more objectively now, I realize that the “runners” are sort of equal lengths)… However, this doesn’t fit with the engine cradle I have. In my mind, I was making something similar that cleared the cradle. If anyone thinks my design is going to cause issues, I’d rather know now! Don’t hold back!

[technicalninja]

Tygaboy is right!

Every cylinder has an "optimal" primary diameter and length for maximum VE at a specific RPM range in the engine.

A primary length for 3-4k RPM will be different than the exact same engine at 5-6K.

If you're racing and always above 5k you need one length, and a streetcar will have better overall performance with something quite different.

How much of an improvement is the real question here. The OEMs break these rules all the time with weirdly different length primaries that seem work OK in real life.

Yours are already built; I'd try them like they sit.

It almost looks like you went slightly larger on the exit tube past where the primaries blended?

I think that will actually function OK.
I think you will be fighting cracks just past the blend from now on...
That area will be getting double the heat versus separate longer primaries.
I'd still want to try it if I was in your shoes.
Sounds like making a dedicated tuned length separate primary header might be a bitch with that engine.

I'd look at a NA Subaru high performance header (if such a beast exists) for primary dimensions.

[Lilchopshop]

Tygaboy is right!

Every cylinder has an "optimal" primary diameter and length for maximum VE at a specific RPM range in the engine.

A primary length for 3-4k RPM will be different than the exact same engine at 5-6K.

If you're racing and always above 5k you need one length, and a streetcar will have better overall performance with something quite different.

How much of an improvement is the real question here. The OEMs break these rules all the time with weirdly different length primaries that seem work OK in real life.

Yours are already built; I'd try them like they sit.

It almost looks like you went slightly larger on the exit tube past where the primaries blended?

I think that will actually function OK.
I think you will be fighting cracks just past the blend from now on...
That area will be getting double the heat versus separate longer primaries.
I'd still want to try it if I was in your shoes.
Sounds like making a dedicated tuned length separate primary header might be a bitch with that engine.

I'd look at a NA Subaru high performance header (if such a beast exists) for primary dimensions.

@technicalninja Thanks for the info! I love the knowledge that everyone brings to this site! I knew about the equal length primary thing, but I really didn’t think it would make much of an impact for my relatively anemic 2.5L NA engine. I like the idea of “just trying it”, but I’m already thinking about how I could redesign. The other thing I should mention, that isn’t obvious from my pictures, is that I am planning to have two separate exhaust runs each with their own separate muffler. I’m going in this route primarily due to available space and to simplify the exhaust pipe construction. So, cylinder 1 and 3 exhaust runs never merge with 2 and 4. Am I asking for trouble with this? Can anyone educate me on the reasons for/agsinst merging exhaust runs on a 4-cyl NA engine? And what about the sound? Am I building something that is going to sound whacked? For reference, the mufflers I picked are flow master delta 50 series. This choice was based primarily on size and cost and had nothing to do with performance.

[76-914]

You could put 3 into 1 and it will still outperform that old air sucker. Just build it. I'll bet you will thrilled with your outcome. I've been waiting for someone to build a NA 2.5. 165 hp won't be anything to sneeze at. (IMG:style_emoticons/default/beerchug.gif)

[76-914]

You could put 3 into 1 and it will still outperform that old air sucker. Just build it. I'll bet you will thrilled with your outcome. I've been waiting for someone to build a NA 2.5. 165 hp won't be anything to sneeze at. (IMG:style_emoticons/default/beerchug.gif)

[technicalninja]

6 cylinder or less should be run through a single pipe.
8 or more should be two that come together after the collectors in either a H pipe or better yet an X.

Look at Tygaboy's LS3 car for example. His stuff is bad assed!

The above is my opinion and it has more to do with the exhaust sound than scavenging.

4s or 6s sound like ass with 2 complete exhaust systems that never meet.

And here's a little dig at @tygaboy (IMG:style_emoticons/default/devil.gif)

You understand this stuff pretty well Sir...

Why haven't you applied 180-degree headers to the LS car?
I haven't read the entire 230 pages yet, maybe I missed that conversation.

Could have made it sound like a flat plane Ferrari!

I see what you did!

Going for that Ferrari shriek the hard way...

[Lilchopshop]

As I contemplate design changes to my exhaust, I decided to knock out something a little more straightforward tonight. I mocked up a hybrid CV axle.

Here’s the driver’s side:

And the same axle on the passenger side. I’ve got about 1/4 to 3/8” of free play when the distance between attachment points is at the shortest.



Got them boxed up with two spare 914-4 CV shafts to use for the new axles and will be sending them off to Dutchman Motorsports tomorrow. (IMG:style_emoticons/default/piratenanner.gif)

[Lilchopshop]

I’ve had more distractions lately than I expected, but I have some updates to share…


First, the hybrid axles from Dutchman showed up. They are really nice!






And, I finished the exhaust! This was definitely harder than I expected! No right angles anywhere and very challenging to find ways to hold pieces in place while I measure/adjust/tack in place. My car has a factory rear sway bar and my engine cradle is kind of clunky back by the rear of the car. Those two things, plus the relatively large muffler that I chose, made it very tricky to find the ideal position for the muffler.

[Lilchopshop]

Couple more pics of the complete exhaust system.

[Lilchopshop]

After finishing the exhaust, I felt like I needed a different type of project. I got out the crusty old rear valence to see if it could be saved and converted (properly) for a right-hand tail pipe exit.

This is what I’m starting with. The big dent on the side opposite the factory tail pipe cutout was the previous owner’s solution to a right-hand tail pipe. (This car had a very clugey turbo and the cobbled-together exhaust exited on the right.)







After scraping a pound of mud and tar off the backside and spending a few hours with a hammer and dolly, I got it reasonably straight. I’ll give it a good cleaning, strip the remaining paint and start measuring where to cut for the tailpipe now that I have the exhaust finished.

[76-914]

Your fabrication work kooks good. Exhaust routing requires a bit of thinking and fiddling. There isn't a lot of room for an exhaust system on these cars. I still have an untouched 10' section of exhaust tubing after doing 2 of these conversions. It's all fittings and mufflers. There wasn't enough room for any piping on mine. (IMG:style_emoticons/default/welder.gif) (IMG:style_emoticons/default/smash.gif) I'm impressed that you were able to incorporate a crossover pipe. (IMG:style_emoticons/default/beerchug.gif)

[East coaster]

Looks good! I just wrapped up my Suby exhaust so I can relate. I bought headers and only had to fab from the header flange back. I like how close you kelp the pipes to maintain ground clearance.

[Maltese Falcon]

Buddy of mine in New Mexico is building "Physco Beetle" and fabricated this exhaust header for the boosted Suby engine; turbo V-band clamp not attached in pic. Smooth transitions, proper od / gauge tubing, and all joints smooth and de-burred, prior to (TiG or MiG) welding are your friends. Unlike n/a engines, "Boosties" are all prone to (unwanted) back pressure as the exhaust pulses tend to slow down at the hot-side turbine inlet >> unlike a free flowing & scavenging collector in an n/a scene. Turbo sizing is already done for you, as you will be using the factory designed OE turbo that came with the engine.