Fuel Management Question
 

My question concerns the effect of aftermarket CA/SR air intakes on fuel management. My rudimentary understanding of a modern FI ECU is that they process input from various sensors such as engine and air temp, MAF, O2 sensors, etc. and control the injectors to provide the optimum air/fuel ratio under varying conditions. I understand that the compensation parameters of a stock ECU have a limited range but I'd like to assume that even the stock ECU can adequately compensate for simple intake and exhaust mods. The question I'm getting to is this; can the diameter/length/MAF placement of an aftermarket air intake cause an undesireable air/fuel ratio even though the ECU has O2 sensors giving it real-time A/F ratio information or is the ECU smart enough to compensate for small deviations in MAF readings caused by aftermarket intakes with varying lengths/diameters and MAF locations? I'm more concerned with overly rich/lean AF ratios than small HP differences which no doubt exist.

My thought is that the ECU should be capable of learning from real-time O2 readings that the MAF reads a little high with 2.75" dia/26" long intake 'A' and a little low with 3" dia/22" long intake 'B'. What are your thoughts?

My reason for asking is that I am running a modded 05/06 TC CAI on my box which has been shortened by a few inches. The engine runs great without any problems or CEL but I wonder if there is any validity to intake manufacturer claims of having designed the "optimum tuned length/diameter" with their intake.

:eyebrow:
Huh?

LOL :rofl:

im running the trd inake...and am wondering the same things...i havent ran it fron full tank to e yet to figure out if there is any real significant change in mpg's other than the result of me gassing it :p

My mpg dropped when I first installed the CAI but it was due to a change in driving habits. The engine sounded so much better that I was running it harder to enjoy the new sound and power. It's back to normal now and I get 22-25 city and 28-30 hwy.

I was more interested in whether the shortened intake might be mismatched to the engine resonance and causing it to run lean or rich under certain conditions. It's probably a moot issue since the ECU should be able to compensate for small changes in MAF readings. If it was bad enough to worry about I'd probably get a CEL.

i'm not 100% sure what the difference in the lengths have to do with cold air intakes, something like longer intakes decrease low end torque but increase high end horsepower or whatever.

but yeah, with any kind of performance intake isn't one of the procedures to disconnect the battery to reset the ecu and then connect it back and start the car, let it idle so the ecu relearns the air intake.

but yeah, the increase in air flow is recoznized by the ecu through the maf sensor. and as more air comes into the engine, it adds more fuel, so you will not see an increase in mpg no matter what, but the decrease shouldn't be very noticible.

According to some manufacturers, the intake diameter/length can be tuned to match the resonance caused by the intake cycle pulses created by multiple cylinders. Also, according to an intake dyno comparision in the TC folder, the A/F ratios measured were affected by different intakes. Personally I think that they didn't give the ECU enough time to adapt to the different intakes but it did make me wonder if different diameters/lengths/MAF placements could potentially cause the MAF to read inconsistently enough throughout the rpm range that the ECU can't compensate completely. Thereby causing the engine to run slightly lean at ~2000rpm and slightly rich at ~5000rpm.

I'm probably splitting hairs here. If it runs good, mpg remains good and no CEL is triggered, it's probably good enough, even if it ain't perfect. It is just a tube with a filter on the end and the stock airbox doesn't appear to be especially well tuned to the engine.

it seems that way