Do the drop-in filters make their power by messing with the MAF signal or by decreased air restriction? If both, is it more the former or latter.

It seems like the gains are large enough that it has to be attributable in large part to altering the MAF readings, which raises the question to me as to whether they could mess up the efficiency of part throttle closed loop operation by skewing the fuel trims.

Thanks.

 

my guess would be its due to the fact they flow more air, and the maf reads the increase and matches it with more fuel...but i duno.

 

Good question. I would like to know this as well.

 

it allows better flow... it can't theoretically reduce airflow and give more power since fuel is calculated based on airflow (mass)

 

The car runs leaner at full throttle (open loop) with the aftermarket filter, which means that the car thinks its getting less air than it actually it is. If the filter increased flow and the MAF simply added more fuel, then it would run just as rich as stock. If you took the stock filter and retuned the car to run the same AFR as the car runs with the aftermarket filter, then it would likely pick up just as much power.

I think the aftermarket filters do allow better flow, but that doesn't explain the change in AFR which is probably helping the power more than the actual airflow. I think these things trick the ECU into misreading the air flow (falsely low), which leans out the car and makes power.

Has anyone datalogged fuel trims with a drop-in? I guess that's really my question. If the long and short fuel trims stay close to zero even with the filter, then I wouldn't be concerned. But if they are moving around constantly because there is a tug of war between the MAF signal and the O2 feedback, then that would be bad and I'd stay away. The fact that some people have reported a hesitation developing with the drop-ins makes me think that perhaps they do mess up part throttle -- at least unless the tune is adjusted for them.

 

You are 100% correct about most of the gain coming from leaning out the afr. If the filter was just allowing more flow then the maf would register that and add more fuel accordingly as you also stated.

As for the fuel trims, I don't think you need to worry with regard to a drop in filter, as the change in afrs at wot is minimal and you will be well withing the range of the fuel trims for closed loop (+/- 25%).

 

^



he nailed it

 

i am not sure i am following, how can air filter trick MAF to thinking its getting less air than it actually is?

i think that the maf sensor

 

Hrm...now that you guys started in on this...how does this make sense? (This coming from someone with a drop-in. LOL.) The MAF is there for the express purpose of determining how much air is coming through, (mass air flow sensor), which then in part dictates the amount of fuel to be injected so that a target Air:Fuel ratio is reached. If you put a drop in, you get more flow which *should* signal to the ECU that a larger amount of fuel needs to be injected, bringing the AFR back to target.

Only thing that might affect it is if its hitting different cells...But how/why would it do that? I'll have to think about this/stare at some ECUFlash maps for a bit...LOL.

verkion

 

If you're in closed loop, sure. I'm pretty sure in open loop you end up running fuel trims based on load cells, throttle position, and what-not. So if the drop-in flows better, the extra air isn't accounted for by the MAF at WOT. Someone please correct me if I'm wrong

 

When you're in open loop, the ECU continues to read the MAF but the readings of the O2 sensor don't make a difference. The load cells in which the car is operating are largely a function of the MAF reading in fact.

Fuel trims are the learning adjustments that the ECU makes in closed loop based on the feedback from the O2 sensor.

These filters work by altering the path of the air through the MAF sensor such that the MAF reads falsely low -- in other words, more air is getting by than it thinks. That makes the car run leaner and adds power, not from the increased air flow but from the decreased fueling relative to the air flow.

The concern that I voiced in my initial post was whether this inaccuracy that is introduced in the MAF readings would have any more than a neglible effect on closed loop fueling such that the fuel trims wouldn't be able to adequately learn to adjust (to make the stock O2 sensor happy) and/or the adjustments would be great enough to create drivability problems at part throttle. Sounds like my concern isn't perceived to be a practical one in the real world given the range of the fuel trims.

 

That 1st paragraph is wrong ..

The MAF doesn't read falsely low .. this is a hotwire .. this is not the karman vortex of the previous generations ..

A dropin filter reads approx. 3-5% higher load than the standard filter load % with a corresponding increase of about 7-10g/s across the rpm band ..

If you have a fuelmap of the X, you'll see that 3-5% change in load is ****all change in fuelling ..

An aftermarket filter OTOH, has a 5-8% drop in load compared to standard, but an increase of around 14-18g/s across the rpm band (G/s difference is much higher at higher speeds) (GruppeM intake) .. this is because of the extras that come with the intake (those with GruppeM will know what I'm talking about)

So the answer to the OP is .. LESS RESTRICTION .. unless you're using aftermarket JDM intakes.. then you're are partially correct ..there's some trickery involved ..

Looking at the g/s airflow sorts of answer the other question that most people are asking .. drop in or after market ..

Lastly .. the intake piping is stock .. and I've not tested an aftermarket intake piping ..

 

Ok, thanks. I was a bit fuzzy on open versus closed loop.

 

The sensor is calibrated with the rest of the intake by mitsubishi. When you change a component that can change the calibration of the sensor due to differences in flow paterns around the sensor element.

If the maf "see's" less air the ecu will calculate a lower load cell and thus a shorter injector pulse width and more timing than you would have at higher load so in effect you lean the car out a tad and add a bit of timing.

 

The sensor is calibrated based on the amount of sample volume that passes thru it.
Increase or decrease the sample area and the sensor will read "false positives".
It has nothing to do with flow patterns nor does the MAF sensor read "falsely low" when changing filters. I know you did not bring up the filter idea, I am just agreeing with Gunzo and his theory behind the induction readings.