best O2 spacer for ACE 350 header?
 

Curious if anyone has info on effectiveness of an O2 sensor spacer on the ACE 350 header, and if a particular spacer fits better. Did a search and found nuttin... I'm going to initially run without a tune (I *know*!) and would like to avoid CEL. Speaking of which, if I *do* get a CEL, will it affect how the engine runs? I.e. will it limit revs or cut timing or anything that would prevent me tracking it?

TIA!

are you not tuning your car after installing the headers? i'm confused as to why youd need one

do not ever put spacers
they trick the secondary o2 in a bad way and it WILL someday trigger extra CELs even if you disable the AF#3 compensation

I also think the idea of tracking a car with uncatted aftermarket headers and not getting a tune is a very dumb idea

See original post:

So the secondary 02 is only for emissions. Yes, there will be a CEL until you're tuned but it will not affect performance or put you into a limp mode.

Thanks for feedback! I had thought that for '17+ the AF is strictly dictated by the 1st O2 sensor, is that not true?

Duly noted! Doing this 'cuz I want to know how much of any gains are due to the header itself, and how much due to the tune. I'm curious. '17+ ECU is closed-loop all the way up, so no worries about the AF part of it being "off", which is what would concern me most for reliability reasons...

TBH I think every modern car is this way. The primary 02 is the more accurate location for reading lambda, technically. I have no doubts that's the case in our platform too.

Awright, good to know...

Cool, cool...

Plan now is to skip the O2 sensor spacer, one less thing to worry about.
Would like to avoid CEL but if it's only for one track event and 1000ish miles (most likely), so be it, I'll just check and clear throughout the day (assuming it keeps coming back).

i see a lot of disinformation in this thread, not going to insist cause you can do wha you want, i gave you my opinion

you 'll run leanish , with unefficient cam timing, maf scaling etc etc
it will run closed loop until a certain (VERY VERY UNPRECISE) EGT threshold then it will switch to open loop pretty soon if you track it


Again, do what you want !

You won't probably damage anything, anyway.

Yeah, that's a terrible idea and you will probably do engine damage. It's going to run open loop and you'll be flowing a lot more air with the ACE header and cat delete. Dangerously lean. Do not do that.

So much misinformation here it's crazy. Hundreds of people have run headers without a tune here. Should he get a tune before he goes WOT? Of course. But claiming you can't run and drive safely it simply false. The ECU does WAY more closed loop than you think everywhere except for WOT.

OP are you planning on tracking it without a tune? If so why? My initial impressions were that you are wondering if you can drive the car around without a tune but not track it.

here's a thought you are spending that kind of money for a header what's another 300 to 500 for a great tune trust me its well worth it

For DD it should be safe enough (i wouldn't track until tuned though). And it's probably what many international Ace's buyers may have done (even if later used remote tuner services of DT/CSG).
If CEL will be thrown, probable biggest impact - no cruise control (not limp mode).
O2 spacer .. i wouldn't get it for various reasons, like it's not certain to eliminate CEL, on some cars it may affect fueling in bad way (don't know if ours is such).

I would just leave stock headers till your ready for a tune. IMO the car can learn but the Ace 350 headers are a much different breed. Its gonna affect throttle response and the car is really going to need to constantly adjust fuel trims.