[Coopin05]

Just installed aftermarket exhaust and my active exhaust worked immediately after install but now it won't properly change modes without reverting back to normal.

I know I need to take it back to get it fixed but is there anything I need to know or can do to help my problem?

Also bonus question, just installed a JLT intake without getting a tune, engine is now giving me check engine light, is it safe to drive until my tune comes in through the cloud?

 

[JBert]

I don't know about the active exhaust thing, don't know why it would have changed its behavior a little while after the install, assuming it was working normal after the install

regarding the tune -- it is probably running a bit lean, should be OK as long as you go easy, no heavy throttle and no lugging the engine until the tune is installed

 

[Braindead]

Agree with JB on lean condition regarding CAI. If so it appears those really work- more air? Try changing modes with exhaust and immediately disconnect power, see if setting will revert back. Might be in default and reboot needed.

 

[JBert]

... lean condition regarding CAI. If so it appears those really work- more air? ...

Minor tangent: the reason it is likely running a bit lean, is not because it is flowing more air. It is because the MAF (Mass Air Flow) readings going to the computer are wrong. Most aftermarket intakes have a bigger tube than stock, and this throws off the math that the computer does with the signals coming from the MAF sensor. The MAF sensor basically measures velocity (of the air) and then (oversimplifying) multiplies velocity by area of the tube to get volume (and mass) of air coming in; then it commands the right amount of fuel for that amount of air. If the tube is bigger than the computer thinks it is, then it is calculating less air than is really coming in, so it commands less fuel than is needed, and it runs lean. The "tune" corrects this math.

 

[Braindead]

^^^ Isn’t that the same thing? Less velocity due to 4” tube increase I could see… would that cause less or more fuel compensation. I would think “less then“ as flow demands are met with lesser flow and less velocity with 4” intake meaning lower speed Is falsely sensed by TB? It still only has a 3.5” manifold entry and even there the matching TB throttle plate is going to be restrictive open and closing within those 3.5” confines of entry orifices?

I still never found out why some ‘13 Bosses had OEM TB spacers and others didn’t. Mine didn’t of coarse… no answers on this ever.

 

[JBert]

yep, if you go to a bigger tube but have the exact same air coming in, the velocity will be lower, the computer will think there is less air coming in, it will command fuel for that lesser amount of air, and it will run lean .... then I think the O2 sensors will detect the lean condition, and attempt to compensate (not sure if that is what you mean by "compensation") ... but it can only compensate so much, plus I think it detects that something is off in the math, and that's what triggers the CEL

about the TB spacer -- my guess is they realized it didn't do anything at some point, and decided not to bother putting them in ... or they ran short of inventory

 

[Braindead]

Think where I wrote “compensation” meant if intake detected more or less air flow would adjust fuel delivery pulse duration lean or generous. But still, looking at any aspect of larger CAI or even TB has effect of engine performance. Not saying enough to notice now but overall smoothness- running a bit better. Not worth the $$$.

Always was for more power you’d go with a tunnel ram (today’s TB spacer?) and more gas and air, within reason. Now nothing ever noted with dyno 🦕 (dino came up) tests if ram air (speed) would change air flow delivery? I say absolutely like going to “high” with a cooling fan from low speed… dynoed the car is strapped down, no wind tunnel even, what’s next…

Always go back to this idea with the masses?