which header to go with and why?

[Apoc]

Originally Posted by bur****jp

I would caution to avoid an unequal length manifold, as large differences in volumetric efficiency between cylinders require different fueling and ignition. If this isn't accounted for then you aren't maximizing power, or worse, running quite a risk, as cylinder mixtures and temps will vary.
If you feel like paying for tuning with individual cylinder exhaust gas temperature probes and individual O2 logging, then you'll get broader torque delivery.

I think you are making tuning UEL headers sound much more complicated and risky than it really is. I don't think the VE difference between cylinders is significant enough to worry about tuning individual cylinders on a N/A FA20.

[Mr_YUzU_FRS]

Yes, he made it seem like engine is going to blow up. Lol

[EAGLE5]

I'm 100% happy with my gen 1 Borla EL. It sounds great. Seems put together poorly, but hey, it was cheap as hell used. More power? No idea.

[burdickjp]

Originally Posted by Apoc

I think you are making tuning UEL headers sound much more complicated and risky than it really is. I don't think the VE difference between cylinders is significant enough to worry about tuning individual cylinders on a N/A FA20.

Originally Posted by Mr_YUzU_FRS

Yes, he made it seem like engine is going to blow up. Lol

If your fuelling or ignition timing is out of whack then yes, you can pop your engine. This is true no matter what. The trouble with a UEL is that it is intentionally creating a difference in VE between cylinders so that they peak at different places, smoothing out torque delivery.
This is a good thing, but in practice is hard to account for. Here's why:
When you're looking at O2 and torque production, the two things most commonly used to tune, you're looking at an average of all four cylinders. You could have a cylinder running dangerously lean and would not know it as long as another was running rich. You tune for this average, and are at best leaving power on the table because you are tuning only as far as the worst cylinder will allow at any given point along the rev range. You could have a cylinder well past its torque plateau while the other three are still making more torque as you add advance. This is one of the cases which would cause knock when adding timing still makes more torque. That's the best case, because you could recognize the knock and pull timing and be left where there's still power on the table to be had, but you can't have it because you have one cylinder acting a fool.
Worst case, you don't catch it because you happen to have a good tank of gas and a cool day with decent humidity the day you're tuning so you keep adding timing because it keeps making power and you don't recognize how close you are on the one cylinder. Then a dry, hot hay comes along and you get a bad tank of gas and the variance between cylinders is great enough to pop it.
Would you likely pop considering modern knock control? No. Probably not, but it won't be happy, that's for sure, and it will behave like it's not happy.

It actually gets worse, though. Some manifolds stick the O2 in a place where you're only getting O2 readings from one or a few cylinders. Now you're doing all of this based not on the average fuelling of all four, but one or two, and you don't know how that one or those two compares to the rest of the engine at any given point. Is this the leanest cylinder at 6000 RPM, or the richest?

4 O2 sensors lets you see exactly what's going on and tune your individual fuel trims to compensate for each cylinder's specific VE requirements. After that you can use individual EGT sensors to tune each cylinders specific ignition requirements. Now you can push that unequal length manifold much further than you could before because you're not limited to the weakest cylinder at any given time. You can push the other three which are still capable of making more power. How awesome is that?!

Those individual cylinder tables are there for a reason. If you aren't going to use them then you should opt for hardware which is most similar across the cylinders, minimizing the VE differences between the cylinders, making it easier to tune.

So, for the sake of ease of tuning to maximum benefit, I'd suggest an equal length manifold.

[Koa]

Originally Posted by bur****jp

If your fuelling or ignition timing is out of whack then yes, you can pop your engine. This is true no matter what. The trouble with a UEL is that it is intentionally creating a difference in VE between cylinders so that they peak at different places, smoothing out torque delivery.
This is a good thing, but in practice is hard to account for. Here's why:
When you're looking at O2 and torque production, the two things most commonly used to tune, you're looking at an average of all four cylinders. You could have a cylinder running dangerously lean and would not know it as long as another was running rich. You tune for this average, and are at best leaving power on the table because you are tuning only as far as the worst cylinder will allow at any given point along the rev range. You could have a cylinder well past its torque plateau while the other three are still making more torque as you add advance. This is one of the cases which would cause knock when adding timing still makes more torque. That's the best case, because you could recognize the knock and pull timing and be left where there's still power on the table to be had, but you can't have it because you have one cylinder acting a fool.
Worst case, you don't catch it because you happen to have a good tank of gas and a cool day with decent humidity the day you're tuning so you keep adding timing because it keeps making power and you don't recognize how close you are on the one cylinder. Then a dry, hot hay comes along and you get a bad tank of gas and the variance between cylinders is great enough to pop it.
Would you likely pop considering modern knock control? No. Probably not, but it won't be happy, that's for sure, and it will behave like it's not happy.

It actually gets worse, though. Some manifolds stick the O2 in a place where you're only getting O2 readings from one or a few cylinders. Now you're doing all of this based not on the average fuelling of all four, but one or two, and you don't know how that one or those two compares to the rest of the engine at any given point. Is this the leanest cylinder at 6000 RPM, or the richest?

4 O2 sensors lets you see exactly what's going on and tune your individual fuel trims to compensate for each cylinder's specific VE requirements. After that you can use individual EGT sensors to tune each cylinders specific ignition requirements. Now you can push that unequal length manifold much further than you could before because you're not limited to the weakest cylinder at any given time. You can push the other three which are still capable of making more power. How awesome is that?!

Those individual cylinder tables are there for a reason. If you aren't going to use them then you should opt for hardware which is most similar across the cylinders, minimizing the VE differences between the cylinders, making it easier to tune.

So, for the sake of ease of tuning to maximum benefit, I'd suggest an equal length manifold.

tl;dr UEL people like to live dangerously. I'm ok with that

[burdickjp]

Originally Posted by Koa

tl;dr UEL people like to live dangerously. I'm ok with that

OR are ok with not making as much power as they could, possibly at the detriment of engine longevity.

[Yoda]

What about the PTuning header? Didn't they get to 200whp with just a tune?

[steve99]

Originally Posted by Yoda

What about the PTuning header? Didn't they get to 200whp with just a tune?

you need to know the delta ie what did a stock car make on the same dyno ??

also from memory it had a complete exhaust and possibly intake not just header.

also whats it like in the 3000-5000 area where you spend most of your time ?

[steve99]

Originally Posted by bur****jp

OR are ok with not making as much power as they could, possibly at the detriment of engine longevity.

Many subaru including wrx/sti running UEL stock for years, their not all blown up yet

Your Theory is correct but i think your just scaring people unnecessarily

[burdickjp]

Originally Posted by steve99

Many subaru including wrx/sti running UEL stock for years, their not all blown up yet

Your Theory is correct but i think your just scaring people unnecessarily

The stock ECUs have individual cylinder trim. They're also tuned conservatively, and turbo engines have very different VE behavior with concerning exhaust manifolds.

[steve99]

Originally Posted by bur****jp

The stock ECUs have individual cylinder trim. They're also tuned conservatively, and turbo engines have very different VE behavior with concerning exhaust manifolds.

I doubt their are many tuners that tap in bungs for 4 02 sensors and also monitor individual cylinder temps when tuning an NA car for street

Their are thousands of tuned cars on uel headers. Yes EL generally produce more top end power but some people like the midrange torque you get with UEL and their all not on the side of the road in pieces.

[Mr_YUzU_FRS]

Has anyone done this on their FRS/brz? 4 o2 sensors?

[burdickjp]

Originally Posted by steve99

I doubt their are many tuners that tap in bungs for 4 02 sensors and also monitor individual cylinder temps when tuning an NA car for street

Their are thousands of tuned cars on uel headers. Yes EL generally produce more top end power but some people like the midrange torque you get with UEL and their all not on the side of the road in pieces.

The entire concept of where power falls has little to do with if a manifold is equal or not, and more to do with how long primaries and secondaries are. As an example, both Nameless and Ace make equal length manifolds which work well in the midrange.

My conjecture is that most equal length manifolds sacrifice length for packaging purposes. Ace and Nameless both have novel solutions to this.

There's really not that many people running unequal length naturally aspirated manifolds.

[burdickjp]

Originally Posted by Mr_YUzU_FRS

Has anyone done this on their FRS/brz? 4 o2 sensors?

This person deserves a cookie.
I'll be doing 4 EGT and 4 O2 as soon as funds allow.