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:

[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.