wouldnt it set a cel code if i was?

 

Not sure? However, any intake that is going to add power, is going to lean out the engine. You will need tuning to correct this. I had the old model S&B, which didn't flow as well as the new model, but still enough to lean out the motor. I took it off and now patiently awaiting a Troyer tuned xcal 2 and 3.5" AF1.

 

just subscribing to the great info in this thread...trying to learn all I can.

 

The 3" AF1 is the only CAI that Troyer recommends without needing tunes. Never had a CEL with mine and there is a noticeable gain in performance.

 

Just briefly.........

No, you can't depend on a check engine light to tell if you are running lean or rich - and no, the PCM CANNOT magically make up for a lean or rich condition just because it is mass air and has O2 sensors - but it's easy to understand why a lot of people are under that impression, and I'll try to explain very briefly.

The PCM can make a certain amount of adjustment ONLY when running in CLOSED LOOP (basically idle & light throttle - light load conditions) to correct the A/F's back to stoich - 14.64:1 - you are always running at stoch A/F in closed loop. But that is ONLY under light load conditions, only in closed loop, which is the ONLY time the PCM is "listening" to the upstream O2 sensors - you will NOT get any kind of MIL for a lean or a rich condition in open loop (any time you are under any real load), nor can the PCM make correct changes to alter the A/F's properly in open loop (meaning when you are under any real load) - yes, some strategies allow C/L corrections to be written into the fuel table all the way up to WOT, but that is usually bad, as it's taking the corrections needed at light load and applying them to heavy load conditions, rarely good, and not consistent, either - only some strategies do this. In many cases, what is needed at light load is the opposite of what is needed at heavy load (there are some exceptions - intake kits for 5.4 3V's usually need more fuel everywhere, but still, the PCM cannot do that on it's own no matter how the factory strategy is set up it cannot make proper correction in open loop).

So remember, only under LIGHT LOAD conditions can the PCM properly "correct" for a lean or rich condition, and even then it is only by a limited amount. And proper tuning means the fuel trims need to be within a very narrow range in C/L (closed loop), and the A/F's within a very narrow range of variance in O/L (open loop) anyway.

Also - the issue of intake kits on the 5.4 3V's also applies to the 4.6 3V in the 2005 & up Mustangs, and the 3V V10's in the newer SuperDuty's - see, intake kits that actually increase power have ALWAYS leaned out ANY engine - but in the F-150, it wasn't until the redesign in 2004 MY with the new MAF setup and the way the factory intake worked that gave us an end result that any intake kit that actually increases peak power (well, aside from the 3.0" AF1 so far) leans out the engine enough to require custom tuning to correct it, instead of how it used to be, which was usually just throwing it a few tenths of a point off.

All that having a mass air system means is that, IF PROPERLY TUNED it is far more tolerate of modifications - mass air does NOT eliminate the need for custom tuning. For example, speed density systems do not generally like camshaft changes - well, with a mass air system they will tolerate that much better, but you still must have custom tuning done to correct for any significant differences in valve timing events caused by a change in camshaft(s) - or to correct A/F's that go lean due to a low restriction intake system - etc., etc. Mass air is a better system, but it still requires tuning to make it work right - from the factory, it is tuned for the *factory* parts - not for aftermarket parts.

You can do a cat-back exhaust system, or shorty headers, or electric fans, and some other mods without absolutely needing custom tuning in some cases with mass air systems, that is certainly true - but alter the air intake tract's cross sectional area by very much, or change fuel injectors, camshafts, heads, and many other types of mods and you WILL need custom tuning.

Also, there are intake kits like the K&N FIPK and the S&B for the 5.4 3V F-150 that do not cause a check engine light because they don't cause a lean enough condition in closed loop, but they still DO cause a lean condition in open loop (at higher loads) that requires correction via custom tuning - in fact, that is what most intake kit manufacturers are doing for these engines, is making intake kits that don't lean the engine out badly enough to cause a code in C/L, but still lean the engine out at heavier loads - once it is no longer "listening" to the O2 sensors - which is any time you are in open loop (under any real load). Just because an intake kit does not cause a check engine light means absolutely NOTHING with regards to the effect on A/F ratios in open loop (under load), so don't forget that.

That's the best I can tell you about the topics discussed in much of this thread specifically just in a brief post - if anyone has any specific questions about their modifications and whether they actually need custom tuning, give us a call & we'll be happy to let you know, OK?

I hope that helps a bit,

 

The ECU uses the MAF and O2 readings to "trim" F/A mixture and in some fuel injections timing as well. However there are limits on what it can do. In many cases the MAF sensor saturates, goes to max reading and stops not allowing the ECU to properly adjust the mixture for the amount of air coming in and causing a lean condition. Because of this the ECU sees that the motor is lean(via O2 readings), but doesn't know how to fix it because it can only adjust mixture BY the MAF output voltage and throws a code to save itself.

I haven't dug to deep into the 3 valve's ECU programming to see the exact process but generally that is the sort of cause and effect I noticed shoe-horning a pizzabox intake on a chevy 383 and custom tuning the stock ECU to work with the motor on a 92 z28. Eventually I gave up and got an aftermarket DFI that had no issue with the setup on that car.

Edit...nevermind Mr. Troyer beat me to it...so yeah what he said.