86MLR 2017 LE From stock to not

[MCTeeJ]

Nice detailed thread!

[RayRay88]

Originally Posted by 86MLR

Cold start was still to loud


So, now, my current exhaust is a Tomei UEL header, Ultrex 2.5" overpipe, OEM front pipe back.

Going to the smaller pipe isn't a worry as calculations say that 2 1/4" will flow more than enough NA.

And the OEM front pipe will flow the power its making without much of a issue and will save the kittens and frogs for future generations, which is a bonus.

In all honesty I wish I just did the header and overpipe to start with.

Or, stayed with the decat OEM header, 2 5" catless overpipe and 2.5" cat back, the only issue with that is the trail of dead kittens and frogs in my wake.

Like all things it was a lesson, albeit a slightly costly one.

Dooh.

So what's the verdict on power vs the decatted stock header?


Are you still running the same tune as the decatted header?

[86MLR]

Originally Posted by RayRay88

So what's the verdict on power vs the decatted stock header?


Are you still running the same tune as the decatted header?

Stock decat header flows well, I made 198hp, with no cats

Yeap, till on same tune, will retune in a month or two, this time with stock exhaust from overpipe back.

It will be interesting to see what I now have power wise.

Until then the jury is out.

The car doesn't really "feel" any different power wise, only real noticable change is it isn't as loud.

In all seriousness, it's only a 2 ltr that revs to 7isk k rpm, the 2.25" OEM exhaust should flow 200hp easily, the cat in the header and front pipe is the only real restriction.

The OEM header actually has larger diameter primaries to the Tomei headers, both EL and UEL.

I would like to see what a twin makes with a full decat on the OEM exhaust, with a proper tune of course, not a quick flash or 1 or 2 remote edits.

I would hazard to guess you could easily get close to 200hpatw, all for the cost of some hammer time, gaskets and dyno time.

[new2subaru]

Originally Posted by 86MLR

Cold start was still to loud


So, now, my current exhaust is a Tomei UEL header, Ultrex 2.5" overpipe, OEM front pipe back.

Going to the smaller pipe isn't a worry as calculations say that 2 1/4" will flow more than enough NA.

And the OEM front pipe will flow the power its making without much of a issue and will save the kittens and frogs for future generations, which is a bonus.

In all honesty I wish I just did the header and overpipe to start with.

Or, stayed with the decat OEM header, 2 5" catless overpipe and 2.5" cat back, the only issue with that is the trail of dead kittens and frogs in my wake.

Like all things it was a lesson, albeit a slightly costly one.

Dooh.

This may be obvious, I don't know, but why is the UEL so much louder than a decatted stock header. I thought both would be close to the same and it was the CAT that suppressed noise.

[86MLR]

Originally Posted by new2subaru

This may be obvious, I don't know, but why is the UEL so much louder than a decatted stock header. I thought both would be close to the same and it was the CAT that suppressed noise.

I assume it's the very short runners on 1 and 3.

[new2subaru]

Originally Posted by 86MLR

I assume it's the very short runners on 1 and 3.

Thanks man

[86MLR]

Originally Posted by new2subaru

Thanks man

From a quick look:

Exhaust gas will create a boundary layer inside the exhaust, in effect lowering the ID.

The longer the exhaust, the greater the effect, the other effect, apart from reduced flow is noise cancellation.

The UEL header has about 1/5 (rough guess) the pipe length on 1 and 3 to the collector at the overpipe.

The thing is you need to try and keep the exhaust port and primary faily typical, until the collector, the primary length should be so the exhaust pulses follow each other through the collector into the secondary or collector, and finally to promote and increase scavenging.

Hence why EL 4-2-1 headers rule for power everywhere, it's simple fluid dynamics.

The thing is at low power levels, this matching pulses isn't so critical, and other UEL characteristics can show their hand, to a point, this is what I want to look at.

I was willing to "risk it for the biscuit", and, after the tune, if I end up making less power overall I will just throw the decated OEM header back on, go back to the old tune and sell the UEL header.

I will be grabbing some more data this week to see if it has lost anything pre-retune.

As I stated before though, the only reason I went UEL was all the UEL hype, I had to see for myself.

Was it a waste of money? Maybe, but it has been a fun little trip with alot of first hand lessons learnt, which is the way I like it and what playing with cars is all about.

Next adventure may be to see how a Harrop supercharger goes, that won't be for a while though, my car fund has been accosted by my holiday fund.

Opinions may vary

[new2subaru]

Originally Posted by 86MLR

From a quick look:

Exhaust gas will create a boundary layer inside the exhaust, in effect lowering the ID.

The longer the exhaust, the greater the effect, the other effect, apart from reduced flow is noise cancellation.

The UEL header has about 1/5 (rough guess) the pipe length on 1 and 3 to the collector at the overpipe.

The thing is you need to try and keep the exhaust port and primary faily typical, until the collector, the primary length should be so the exhaust pulses follow each other through the collector into the secondary or collector, and finally to promote and increase scavenging.

Hence why EL 4-2-1 headers rule for power everywhere, it's simple fluid dynamics.

The thing is at low power levels, this matching pulses isn't so critical, and other UEL characteristics can show their hand, to a point, this is what I want to look at.

I was willing to "risk it for the biscuit", and, after the tune, if I end up making less power overall I will just throw the decated OEM header back on, go back to the old tune and sell the UEL header.

I will be grabbing some more data this week to see if it has lost anything pre-retune.

As I stated before though, the only reason I went UEL was all the UEL hype, I had to see for myself.

Was it a waste of money? Maybe, but it has been a fun little trip with alot of first hand lessons learnt, which is the way I like it and what playing with cars is all about.

Next adventure may be to see how a Harrop supercharger goes, that won't be for a while though, my car fund has been accosted by my holiday fund.

Opinions may vary

Thanks for the detail. I don't understand it and that bothers me. I'll do some more research eventually. I too will be doing a header at some point or maybe just gutting the cat

Nothing is a waste if you learn something from it. Me, I read a lot of hype about losing weight so I did some basic weight reduction, maybe 80lbs or so. I was like

I left it out because I didn't really need it anyways but it certainly didn't make me want to do more. Last year I needed to get rid of my headliner as I needed more room for a helmet. I gutted the entire interior to remove it including the passenger seat. While out I took it for a drive. Bam! Now I know what all the hype is about. I'm currently at 2489lbs and going lighter. It's made a massive difference on how the car feels and behaves.

[86MLR]

Punched out cat in front pipe.

Had a play.

Tomei UEL header showed no gains over the punched out OEM header.

Hell, the punched out OEM cats with the 2.25" OEM stuff showed typical gains to the Tomei UEL with 2.5" catless exhaust.

I will be reinstalling the punched out header and selling the Tomei.

Making more noise for no extra performance is pointless.

I'm thinking of keeping it NA and a cheap daily, maybe building something else for fun, I've crunched some numbers and to get any worthwhile power gains, with reliability, I could buy and build a different chassis for half the cost.

Maybe another motorbike?

Time to start looking in the classifieds again, more, still.....

[86MLR]

LOL

So......

Boredom and interwebs shopping happened.....again.....autosalon style...LOL

Nothing special, just a bracket that replaces the black chunky bracket/cover that, umm, cover the rail and injectors.

The black box is the control unit for the fuel injection, or.....the flux capacitor.....

Pointless, yeah, but a quick little mod that removes the chunky horrible unbelievably heavy steel covers.

Check out the cool sticker, GAS GAS GAS, at least 11ty extra hypnopowers....

[86MLR]

More boredom, more eBay

[86MLR]

Got bored

There is a SME 2.5" resonated front pipe now, replacing the punched out OEM front pipe.

The exhaust was a little "tinny" at high RPM, the resonator has fixed that.

[RToyo86]

How much louder was the decatted OE header vs with the cat?

Looking at options for my Corsa and this may be worth an experiment if it's reasonable.

[86MLR]

Originally Posted by RToyo86

How much louder was the decatted OE header vs with the cat?

Looking at options for my Corsa and this may be worth an experiment if it's reasonable.

Cold start had alot of bark, apart from that it was good.

The resonated front pipe knocked out some of the bark at cold start, I ended up with a single resonator, positioned where the cat was.

The car is a pleasant place to be on the hwy now, cabin noise is well down, and cold start isn't obnoxious.

If I was going to do it again I would get the duel resonated front pipe, all of the advantages of a straight pipe, but none of the noise.

Pity you are in the US, you could have my old decatted front pipe to test with.

Have fun with your project