LTFT High after Tomei Header install
 

Good evening!

I have been searching around FT86 Forum for possible solution of my problem. It has been bugging me for almost a week now and trust me I couldn't even sleep thinking about it.

So, This is my first twin, Got it December of last year and I absolutely love the new BRZ, I already have BC Racing Coilovers Installed, Enkei TFR Wheels and MXP Comp RS exhaust installed on 4 months of owning it.

Fast forward to when I installed Tomei UEL Headers
Disclaimer: Yes I know, There is no available tuning solution yet for the 2nd Gen So I hope you be easy on me.

I bought a used Tomei Header a couple of weeks ago and it was still on wrap when I got it, however I check the flange and the collector for possible cracks and possible red flags however I found none, I did not bother to check behind the wrap because it wasn't accessible.

Upon installing the header, I accidentally, switched the o2 sensors (Upstream went to Downstream Slot w/ Defouler & Upstream went to the Downstream Slow) BTW, I installed new Grimmspeed Header Gasket on the header but Used OEM Gasket from Header - Overpipe

It thew a P0420 code and as soon as I troubleshoot it, I noticed that the two O2 sensors are on the wrong spots ( I switched them back). The next day, the CEL from P0420 did not went off so I decided to reset the ECU by pulling of the battery (Negative).

Everything was fine until one day the CEL came on and my buddy scanned it with the OBDII sensor and came P0171, P0170 Sensor on Bank 1 running Rich. In the mean time we erased the code on that spot and until now CEL havent came up yet.

THIS IS WHERE IT GETS INTERESTING
I was being nosy on the OBD2 Parameters and looking at fuel trims
STFT was normal, it fluctuates -4 to +5.\
AFR was normal (Stoichiometry) hovers on .950 ~ 1v (on idle)
it goes to 1.517v when decelerating
LTFT goes +18 when the engine is not even started yet. But on cold start it goes close to 0, however when the RPM goes down on idle it shoots up slowly to +20.

I have searched and looked possible causes but maybe I have not looked enough:
1. Checking MAF Sensor if its clogged, Did not clean (Car is around 5000 Miles)
2. Checking for Vacuum leak, Hoses and under the intake manifold as well, most of the hoses are clamped
3. Soap test on the header, to the overpipe
4. Went to use a Leaf Blower from the Exhaust tip and use paper to see if it moves around the header to detect any possible leak.

So far, I am losing my mind and I will appreciate any input on this.

You're running lean due to the header likely affecting AFR's so the ECU is dumping fuel in thereby affecting your LTFT

If your AFRs are good that means the ECU is compensating sufficiently to maintain a good afr by dumping fuel in.

afr and stft are likely fine because the ECU has learned the ltft values

cold start doesn't use ltft values afaik

decelerating/engine braking the afr will get maxed because no fuel is being injected

I wouldn't run a header without a tune TBH, switch back to OEM header and wait for a tuning solution.

Yes I understand it's not advisable and/or recommend to run a header without tune.

However I have talked to some people on the 22 BRZ/86 group on Facebook who already have installed headers and overpipe. However their LTFT are normal compare to mine.

How long does it take for LTFTs to stabilize? I was always under the impression it takes many drive cycles for this.

The reason why some people on Facebook have already installed and some have not reported any issues is because results vary from vehicle to vehicle. They'll eventually run into some code. It is the same as 1st gen. Some folks haven't reported a CEL after installing headers without a tune.

I would take Facebook recommendations with a grain of salt as a majority of folks that tune and work with these cars hang in here. Not discrediting the Facebook groups, but there's tons of info in here that is nicely compiled and easily accessible.

I would recommend switching back to stock, see if that clears out, and wait for ECUTek to post results. I would hate for you, and the sake of your twin, to run into a bigger issue being so new.

Different cars are different, ltfts take time to learn (and it sounds like you started having issues after multiple cycles).

What are you trying to gain via header? Based on dynos from stratified tuning results seem MIXED at best and you appear to lose power in parts of the band and gain in others. If you're just chasing sound just put on a CBE for the time being which should have minimal effect on your fuelling.

I'd be concerned about longevity if your ltfts are that high, I would imagine there are still lean spots and if you get a bad tank of gas it could be no bueno for your engine.

My question exactly. Why in the world would you put on new headers without a tune - it makes zero sense in my opinion. As for sound, maybe you get a little something but from at least first gen, it didn't make much difference because it was the exhaust choice that made all the difference.

As soon as the rpm goes above 2000 it goes to 0. Then goes back up as long as take my foot off the gas

Just for the rumble alone. I'm putting back my stocker header this Friday and see if this goes back to normal. However we gonna try to diagnose leaks and faulty O2 sensor as well before switch

For the rumble sound. I'll be putting back my stock header this Friday and see if it make changes

Might be waiting forever for that one unfortunately (at least in terms of US). Given Cobb is pulling support for a ton of stuff and ECUtek is owned by the same parent company... Was talking to the shop working on my Supra, primarily a Subaru centric shop, and they told me all kinds of things going on right now that are super unfortunate.

(article for anyone not already aware: https://www.thedrive.com/news/cobb-l...rs-are-furious)

Not sure about this gen BRZ, but many cars use the secondary O2 sensor (post-cat) to tune LTFTs. Running a defouler is going to affect that.

You are correct, this refers to the flexfuel kits and the uncatted components. Which already has been a thing in some states, like CT. No cat? Fail. CEL on? Fail.

There is always a loophole and a guy who likes to tinker with OBD ports, so wouldn't completely lose hope.



Not that your engine would blow up if you live with an eternal CEL on, but I would think you'd be compromising some other components by leaving a header that this platform is not used to, yet, just for the sake of a rumble sound.

I never got a much different rumble (or anything that I could hear that well) from my decatted JDL UEL headers on stock exhaust on Gen1. You want a rumble? Pick an exhaust you like. If/when tunes come out for the Gen 2, THEN change your headers.