Borla UEL Headers sent car into a low power mode
 

I installed the borla unequal length headers on my 2015 automatic brz and the car would not accelerate in 5th or 6th gear. I'm not getting a CEL nor are the O2 sensors affected. I ended up changing the headers back to stock and the car is running almost the way it used to. I reset the ecu by disconnecting the battery terminals with no change. Does anyone have any ideas of how I can run the headers without have to get a tune?


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You can't lol it's no wonder it drives that way. You'll need a tune for the headers for sure

I thought this car came in that mode from factory? Ok im out :bonk:

If you change the intake or output of air you have to change the tune to deal with it. Just slapping parts on will not work. The ECU has the ability to change things within the OEM specs and equipment but does not adjust for things beyond the scope of the original tune.

This issue is significant to me as well. Is he getting this low power issue due to the header not having a cat? I plan on getting catted headers this month. I will not have a tune.

2017 WRB BRZ

I have a Perrin cai and a catted ark exhaust. I made sure the cats are clear and flowing. I think the issue is that it's much less restricted than what it used to be with the headers and it's throughly the ecu off.


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The issue is that you removed the cat in the header. The ECU measures the air before and after that cat and adjusts itself accordingly. Now with no cat, the resulting values are beyond its ability to compensate for. You need a tune. The easiest/cheapest way would be to get an OFT and flash stage 2. Or get an ECUtek and have the car tuned.

I repeat^^^^^^^^^
There is no magic bullet that you can just bolt on the car and have work miracles without a tune to accommodate it. None. The car can only adjust to the OEM perimeters and any changes beyond them will mess with you.

Basically the stock Tune is limited to the flow of stock headers but now the flow is greater the Ecu doesn't know what to do with the larger amount of air taken in and expelled so it tends to try to correct the air by throwing some away since it doesn't know what to do with it. So now you need a tune to teach the ecu to use that extra air for something instead of throwing it out somewhere random this is why you have that low power spot

In no way am I saying not to get a tune if you do headers. Of course the way to the most out of a new set of headers is to get a tune. Just throwing that out there before I say this.

I feel there is something else going on here besides not having a tune, possible install error. You should be able to drive the car just as it was before you got the header. It will feel different of course, especially at first as the car learns. With out a tune you may notice a power drop down low and a slight increase up top, this will be more pronounced in the upper gears since the ratios dont make for a good acceleration in the first place. Of course you may get a CEL from no cat, but this does not put the car in limp mode.

My suggestion is to install it nice and secure, especially making sure there is no exhaust leaks. Then reset the ECU, makes learning a little faster, and drive around for about 40 to 50 miles at the least. This drive will be nice and relaxing, no more then 3/4 throttle and 4500 rpm. Just like if you were driving your grandma to store, basically cruising speeds and relaxed acceleration. The car has got learn what is going on before you start smashing on stuff.

Still going to have problems without a tune, the autos are more sensitive to aftermarket headers.

The headers were installed perfectly fine. They are catted and I drove the car for 100 miles under 4K rpms. I disconnected the battery during the install to reset the ecu as well.


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To my understanding Borla does not sell catted headers.

2017 WRB BRZ

ffs, please tell me you knew about the cat removal...

I ain't mad about the lack of knowledge but you basically wasted $800 from not researching beforehand. I was an idiot when I joined here (and I still am), but I at least asked questions before making decisions like this.

And no, you cannot use a catless header without getting a tune. There have been other methods reported on here but none of them are 100% reliable.