Why not use MAF for entire RPM range?

[redhardsupra]

MAF and SD are equivalent but not equal. They do the same job, but they don't do it equally well at the same set of conditions. So pick whatever works best for you. Personally, I like the hybrid model because of the double safety, but once I've came across a car that despite my best effort I could not make idle with MAF, so it's obviously not perfect. However, and this is very important point, once you pick a method, tune it right.

Here's my last take on MAF vs SD, I like it because it quantifies where MAF and SD shine and where they fall apart.
http://redhardsupra.blogspot.com/201...omparison.html

[LS1_Dragster]

redhardsupra - great info, thanks.

Now on to another question. Why couldn't you incorporate the MAF wires an circuitry right into the throttle body? Mentioned above, it was said there's reversion and turbulence at low RPM. If that's the case then so what, the stock settings use MAP under 4000RPM and MAF above. Now you have the best of both in a smaller and more responsive package. It seems that you could also lower the RPM when MAF takes over to sweeten the pot even more and to help tune large cams.

[redhardsupra]

_I_ couldn't incorporate wires into anything, because I'm a mechanical moron. I just mangle the equations and fondle the data

On a more serious note, I think I can figure out a method to determine the optimal 'switchover' point over between MAF/SD mix. I feel a blog comin' on... thank you for the idea.

[swingtan]

As said, one of the biggest issues with retaining the MAF and modifying the engine is reverberation. In this case, the MAF works "too well" and can cause fueling issues. Big cams with lots of overlap can cause pressure waves in the intake that travel back up the intake to the MAF. These "waves" can be read by the MAF as the intake air slowing, stalling and even reversing direction ( not that the MAF actually indicates the reversal ). One method of reducing reverberation in the stock intakes was the use of "resonance chambers" in the MAF pipe. These would absorb pressure pulses and even them out to give the MAF a more steady signal. They also help overall airflow by reducing turbulence caused by the pulses. In a back to back test by one of the workshops over at www.ls1.com.au, it was found that the 2006 VZ SS intake gained 5kw at the rear wheels over the Holden GTS MAFless pipe. Overall intake size was very similar, but the stock VZ intake had the resonance chamber.

Hymey and I played with MAF activation a while ago and it did work to some degree. The idea at the time was to disable the MAF when airflow dropped into the idle area of the MAF. So if the MAF reported 3000HZ when idling, you would set the min fail frequency to around 3200HZ. The MAF would then fail and you would drop into SD mode for idle. I think there may be other ways to do this now though.

Simon.

[5.7ute]

_I_ couldn't incorporate wires into anything, because I'm a mechanical moron. I just mangle the equations and fondle the data

On a more serious note, I think I can figure out a method to determine the optimal 'switchover' point over between MAF/SD mix. I feel a blog comin' on... thank you for the idea.

You have been a bit quiet lately.(JK)
Simon, once the maf fails using the frequency method, did it reenable once the maf frequency increased? Or did it stay disabled until the next key on?

[swingtan]

It re-enabled as soon as the test parameters allowed. Joel ( Hymey ) did most of the testing on his car and said that he may have felt the cut over between MAF and SD, but I can't remember now.

[DrX]

I have observed effects that seem to indicate the shift times not following the tables while the MAF is failed...

[ I worded it vaguely because I don't have the data at my finger tips... but yes, I seem to vaguely remember this... my $0.02. ]

But, yes, various functions seem to disable while MAF is failed.

To find a way of running SD without failing the MAF would be advantageous.

If that is the case, then running a SD tune could kill an auto transmission!

[Mr. P.]

If that is the case, then running a SD tune could kill an auto transmission!

It all depends on how the trans is setup; the way that we build our 4L60s we want these adaptive timing tables zero'd out anyways. With the factory 4L60 setup in trucks, I agree with you it would probably not last long!

[joecar]

If that is the case, then running a SD tune could kill an auto transmission!

Yes, this is why it is very important to get the VE table correct (and avoid any portion of it being lower than actual)... i.e. if the VE table correctly allows the correct torque to be calculated, then the transmission will survive...

but it would be nice to have a non-failed SD mode.

[swingtan]

What would be "really nice" is to have a section of the COS that "reverse populates" the MAF data from the VE table. In this way, the PCM/ECM is fed a value that it thinks is coming from the MAF and continues to run normally. It might be that the existing gm/Cyl value, which is calculated from the VE, is converted to gm/Sec on the fly using the MAF calibration table as a correction. Or maybe the existing "speed density air flow per second" values can be used directly and the MAF signal just ignored.

Simon.