Oj's Thread Of Newbie Questions

[oj 89]

Totally a thing.

Okay! Since my knowledge of the boxer engines, and Subaru's in general are limited to 'I know why the engine works, why they do it, and where the turbo is,' I have a habit of thinking outside the box. However, the things I'm thinking have probably been thought of before and not done for a reason. Its those reasons I have yet to find out.

Hence this thread. I'll be posting my questions in here that come to mind and most people can probably see a flaw in my seemingly sane plan.....

So, 1: Headers are the first part of the exhaust, connected to the block, correct? So, unequal headers means one bank of exhaust is longer than the other. I've also read that there is a performance loss through this. Would that show on my n/a, and/or would the burble change/come back? Also; Would 2.0/2.5 unequal Headers even fit my engine?

2: How much space is there under the TMIC/ air intake? Would a cold air intake be of any use back there if an airbox was fabricated to utilize the bonnet scoop? As I say, these are outside the box ramblings, so if there's something I've missed, please shout them at me.

Edited January 16, 2014 by oj 89

[mctwistuk]

looking forward to seeing the answers and just sorry I am not any good at technical stuff to give advice ?

[oj 89]

As am I. With the n/a's relative lack of power, I'm slightly shocked that no one seems to have found a good way to manufacture a CAI other than a second pipe to the existing airbox. The only flaw in the plan is the MAF, which surely can be relocated to a new airbox with relative ease, I would assume.

[thebigfelly]

Yeah gona keep an eye on it. Look forward to developments

[lewisscoob]

So, 1: Headers are the first part of the exhaust, connected to the block, correct? So, unequal headers means one bank of exhaust is longer than the other. I've also read that there is a performance loss through this. Would that show on my n/a, and/or would the burble change/come back? Also; Would 2.0/2.5 unequal Headers even fit my engine?

2: How much space is there under the TMIC/ air intake? Would a cold air intake be of any use back there if an airbox was fabricated to utilize the bonnet scoop? As I say, these are outside the box ramblings, so if there's something I've missed, please shout them at me.

1. Headers are bolted to the heads - you could argure this is the 'long' block but I would disagree Chances are the headers and crossover and collector will fit but the uppipe I imagine (dont know for sure) is different, since there is no turbo.

2. Your gains from doing this will be absolutely minimal. I personally would put the saved money to other things.

[bmwhere?]

The Scooby or boxer 'burble' comes from the unequal length headers and the resulting time difference it takes for the sound to travel through the exhaust system from either side of the engine - The bigger the difference in length, the more pronounced the burble will be, with equal length headers you'll get no burble

1---2---3---4---1---2---3---4--- <= Engine firing timing equal

--1---2---3---4---1---2---3---4- <= Exhaust sound timing with equal headers

-1-----2-3-----4-1-----2-3-----4 <= Exhaust sound timing with unequal headers

There is a performance gain in using equal length headers, but its so minimal, you'll only notice if you really need an extra couple of tenths on a lap of the ring! You'll get a bigger performance gain driving in the rain!

[t5nyw]

I agree with BMWwhere

the gains are approx. 25bhp through unequal headers and 35l[bs of torque, so the equivalent of PPP

IIRC

Tony

Ps thought was going to as where the bright switch was LOL

Edited January 21, 2014 by t5nyw

[ccrien]

I think OJs original question was for a non turbo so gains really minimal if any, but also need to bear in mind cost of unequal headers for non turbos is around a grand ! Lot of money for a burble.

[The Don]

OJ,

Your 2.0R is probably already running unequal length headers.............

Borla headers were alway a good upgrade for the N/A's but the above later style OEM setup replicates that now.

As with anything N/A in the Scoobie world you would be best to look at some of the US Forums as they have much more advice on tuning non turbo versions as they've had the 2.5L N/A for years and (relatively speaking) only just got the turbo models.

One mod that was advocated to improve power/response was the throttle body spacer but there is some differences of opinion on this.

Lots of threads on this an example being.............

http://www.rs25.com/forums/f5/154318-show-me-quantifiable-throttle-body-spacer-gains-3.html

and just an example of one

http://www.sparktecmotorsports.com/nts11521.html

[oj 89]

1. Headers are bolted to the heads - you could argure this is the 'long' block but I would disagree Chances are the headers and crossover and collector will fit but the uppipe I imagine (dont know for sure) is different, since there is no turbo.

2. Your gains from doing this will be absolutely minimal. I personally would put the saved money to other things.

Ty for the info on 1 Lewis. As for the second: I realize any 'gains' would be minimal. I'm more of a 'wonder if this will work,' kind of person. And I like fabricating/doing things that haven't been done before, necessary or not. When you consider the cost of a WRX bonnet + fabing my own airbox, its not a lot of money to see if it'd work.

That and functional bonnet scoop so no one can complain about my having a bonnet scoop on an n/a

The Scooby or boxer 'burble' comes from the unequal length headers and the resulting time difference it takes for the sound to travel through the exhaust system from either side of the engine - The bigger the difference in length, the more pronounced the burble will be, with equal length headers you'll get no burble

1---2---3---4---1---2---3---4--- <= Engine firing timing equal

--1---2---3---4---1---2---3---4- <= Exhaust sound timing with equal headers

-1-----2-3-----4-1-----2-3-----4 <= Exhaust sound timing with unequal headers

There is a performance gain in using equal length headers, but its so minimal, you'll only notice if you really need an extra couple of tenths on a lap of the ring! You'll get a bigger performance gain driving in the rain!

Right, to Unequal headers make such a small difference, hence why Subaru took so long to change it. This makes a lot of sense, thanks.

OJ,

Your 2.0R is probably already running unequal length headers.............

Borla headers were alway a good upgrade for the N/A's but the above later style OEM setup replicates that now.

As with anything N/A in the Scoobie world you would be best to look at some of the US Forums as they have much more advice on tuning non turbo versions as they've had the 2.5L N/A for years and (relatively speaking) only just got the turbo models.

One mod that was advocated to improve power/response was the throttle body spacer but there is some differences of opinion on this.

Lots of threads on this an example being.............

http://www.rs25.com/forums/f5/154318-show-me-quantifiable-throttle-body-spacer-gains-3.html

and just an example of one

http://www.sparktecmotorsports.com/nts11521.html

Ahh, ty on all counts Don! I'll have a look at the exhaust next time I'm under the car. And as for looking at US forums, thats not something I'd considered before. *toddles off to scour NASIOC*

[MarkJHarris]

The headers in that picture look equal length anyway.

Here's the headfuk though.....

If the cylinder numbering order on a EJ is like any other 4 cylinder and the crank is also the same, there are some interesting comparisons to an inline 4 to make. You can imaging a four, then move it so that Cylinder 2 and 4 are pulled round 180 degrees and 1 and 2 therefore produce an opposite motion of pistons both reaching TDC at the same time. Same for 3 and 4. The Firing order therefore has to reflect this with the two front cylinders firing 360 degrees apart. Itmust therefore be a firing order of 1-3-2-4. The headers are paired like this so you get Front Left, Back Left, Front Right, Back Right. A Normal in line gives 1243 so adjacent firing is NOT on a paired header. as usually on a branched manifold 1-4 and 2-3 are paired. Interesting. If you were to pair the left and right pair on an inline four you'd have a similar effect. This I believe gives some of the lumpy sound nature on it's own.

Now, a N/A car needs exhaust scavenging to make its power far more than a Turbo. Equal length primaries (headers) help and the odd pairing will give differing frequencies and possibly more of the benefits of a 4 into 1 than a 4 into 2 into 1 give. It's a science of its own an well beyond my poor old brain.

The Yanks will know more I guess.