Fuel Consumption went up after the header+tune?

[JIM THEO]

Regarding O2 sensor position, heat wrap well the headers as to keep their high temp and kinetic energy (that helps scavenging exhaust from cylinders) and place the primary O2 at the end of where secondaries mate close to the overpipe.
According to the wideband I had in previous Subarus w/aftermarket headers this place gives the most accurate measurements!

[steve99]

I think everyone has good points and there is no perfect solution, unless you had one o2 sensor in each runner for each cylinder.

Its best to put it close to exhaust ports
You probably get a more accurate reading by measuring jist one cylimder, but then your ignoring tge other three.

If you measure a mix of all four your likely getting an average reading, or depending on the placement near collector you may srill get a bias toward one or two cylimders as the sensor tip looks very close to collector so gasses likeY not mixed from all cylinders.

If one cylinder was rich\lean you woulnt know which one anyway and if it all moxed in it would need to be way rich or lean before you would notice. Think thier good and bad in each and its not perfect either way, but stock header its after the secong megge collectpr

[Wayno]

I would be more concerned with trying to extend the sensor wiring. If it reaches with the factory wiring and you aren't pinching the wiring anywhere, then put it wherever you want.

[tomm.brz]

I think i have problem understanding your answers Wayno
If I put the front sensor on the collector near the overpipe the plug doesnt reach the other plug and that s why hks gave me an extension
What do you mean by "put wherever I want'?

[churchx]

He wrote "If it reaches". It doesn't, so move on

[Kodename47]

Originally Posted by steve99

There is no perfect solution, unless you had one o2 sensor in each runner for each cylinder.

Correct

Originally Posted by steve99

You probably get a more accurate reading by measuring just one cylinder

Definitely not!!! What if that one cylinder is way richer than every other cylinder, injector goes faulty. Sir, my logs look good but 3 pistons are melted.... Alternatively if that's the lean cylinder then you're running too rich in the rest. Measuring one cylinder alone and using as primary fueling enrichment is a no no and bad advice.

Originally Posted by steve99

If you measure a mix of all four your likely getting an average reading, or depending on the placement near collector you may srill get a bias toward one or two cylinders as the sensor tip looks very close to collector so gasses likely not mixed from all cylinders.

And that average still helps give an overall picture. You may still have one lean and one rich but it's a better average than doubling up that issue. Think about the math.... 2 cylinders one at 14.0 and one at 15.0 and target at 14.5. At the merge you get 14.5 average reading assuming both reach the sensor at similar times and no correction. However if read on a single cylinder you would get +4.5% fueling correction, causing the rich cylinder to now hit 13.5 or -3.5% meaning you get an AFR 15.5 in the lean cylinder. Rule of thumb, you want as many cylinders merged together for a better picture. Reduce those combined if you add sensors. Really one sensor per pair of cylinders would have been the right balance IMO as we know that there are variances in cylinder fueling from factory.

Originally Posted by steve99

stock header its after the secong megge collectpr

Yes for the above reason. Measuring all 4 is preferable, 2 is OK but a single runner alone is stupid.

[tomm.brz]

So Those header one guy posted a picture of some post ago, with an integrated spacer in the hole Near the collector.. And i guess the other hole is on a single runner.. Are just bad design header? It forces you to measure only one cilynder

[tomm.brz]

But actually also the Open Flash Header forces you to put the front sensor in the single runner. Is Shiv giving people bad design header that could potentially break cars?

[Kodename47]

Originally Posted by tomm.brz

But actually also the Open Flash Header forces you to put the front sensor in the single runner. Is Shiv giving people bad design header that could potentially break cars?

I personally wouldn't. Each to their own. It's interesting that after having a look about that many UELs are this design, but HKS go out of their way to make you move the sensor. It's not the cheap or simple option.....

[tomm.brz]

Yes i paid my hks uel More than 1050 euro, almost 1200 dollars I guess. But as far as i know they are the only one doing that.. A bit too bad they arent so great for performance and i think the runners are a bit smaller compared to other aftermarket headers

Do you think I could drill out totally the little cat inside them to hope. For. More performance? This cat is useless anyway, i smell super toxic fumes also when car is totally warmed up

[killy]

Originally Posted by Kodename47

I personally wouldn't. Each to their own. It's interesting that after having a look about that many UELs are this design, but HKS go out of their way to make you move the sensor. It's not the cheap or simple option.....

Do you or anyone else here think that a possible solution to this problem is to use the secondary hole with the primary sensor (in THE UEL like the one posted in the photo or OFH)?

To do so you will have to:

1 - grind the height of the spacer in the secondary to match the height of the primary
2 - tapping
3 - make sure that the sensor reaches the hole

not talking about IF it is possible to do the 3 points above, let's assume it is possible.

Would it work? Would the sensor read the flow of all the 4 cylinders merged correctly? does the inclination of the secondary spacer impact on the reading?

[steve99]

Originally Posted by killy

Do you or anyone else here think that a possible solution to this problem is to use the secondary hole with the primary sensor (in THE UEL like the one posted in the photo or OFH)?

To do so you will have to:

1 - grind the height of the spacer in the secondary to match the height of the primary
2 - tapping
3 - make sure that the sensor reaches the hole

not talking about IF it is possible to do the 3 points above, let's assume it is possible.

Would it work? Would the sensor read the flow of all the 4 cylinders merged correctly? does the inclination of the secondary spacer impact on the reading?

In theory you could do that, you would need extension to the front 02 sensor wiring


you would also want to remove the inclination.


Id also suggest that even if you did all that because the merge collector is so close to 02 bung in most header no matter where you put the sensor its not going to read the average of all cylinders its likely going to sit in the flow of one or two cylinders predominately. might be a bit different if you moved it further downstream of merge like the ft86 speed factory photo

[tomm.brz]

So actually even in my hks uel the front sensor doesn t sense all 4 cylinders



It looks like only senses one on a shorter runner, did they make me move it with an extension to sense it on a shorter one instead on the longer?


At least in the OFH if one shortens out the spacer, it could possibly move the tip of the sensor more in the middle To try sense all 4 together

[Kodename47]

Originally Posted by tomm.brz

So actually even in my hks uel the front sensor doesn't sense all 4 cylinders

It does, the exhaust gasses from the other 2 cylinders won't bypass it and remember the sensor is picking up the oxygen content in the system. It might weight it towards those cylinders, but it's going to be better than just monitoring after the primary collector in a 4-2-1 for example.

[ame=https://www.youtube.com/watch?v=lyv0wh3fsLM]Youtube[/ame]