E67 MAF vs MAFLess and what makes a good tune?

[benno25]

Hi all,

In Australia I've noticed a MAF tune appears to be cheaper than a MAFLess tune, however this seems to contradict my understanding in that the VE table or coefficients are still used under some conditions.
Can any of you tuners out there confirm when the VE calculations are used and when airflow calculations are purely based on the MAF reading?
Is there such a thing as a "MAF" only tune? Or is this simply bad practise and poor tuning?

As an example, I've had a MAF tune carried out on my supercharged car with E67 pcm where the tuner hasn't modified the VE coefficients at all.
Basically the MAF calibration has been updated and the Dynamic Airflow Hi RPM Disable and Re-Enable values lowered to 1,500 and 1,400rpm respectively.
Does this mean my cars airflow calculations are purely MAF based, and if so, is the MAF suitable for handling fast changes in throttle position, etc?

Interested to hear peoples thoughts.

Cheers
Benno

[07GTS]

when MAF is used it will always revert to blended VE/VVE for transients as the MAF isnt fast enough to react at lower air speeds, with a MAF only tune and thats it the VE or VVE really should be done at the same time its like only correcting half the job, alot of AUS tuners just do the MAF only cos it so easy it and out and there done, to get a proper job tune SD get it dialed in then tune MAF and then use both and blend where u want and throttle response/ behavior should be good in all areas

[benno25]

Thanks 07GTS, your comments plus another useful thread I found reinforce what I thought.
Based on this I seem to think my tuner has likely butchered my cars fueling during sudden jumps on the throttle and other transients?
I'm wondering if I'll be able to see any lean spikes during this sort of driving with the stock narrowband O2 sensors? Will do some logging and find out.

[07GTS]

VVE could still be reasonable but if u have more mods which change the airflow then it would be worth looking at, the narrows act very quick so if it spiking lean u should see it, if u can fail the MAF and disconnect the signal but so u still keep the IAT sensor then just go for a drive in SD and dial in all part throttle using trims as far as u can without triggering PE see what its like if it is way out then prob best to use a WB and go over the VVE properly then re enable MAF and it should be good

[benno25]

Mods are a blower pulley change, Harrop CAI and blower lid spacer.
I'll get some logs over the weekend.

Cheers

[APS Luis]

when MAF is used it will always revert to blended VE/VVE for transients as the MAF isnt fast enough to react at lower air speeds

I would have argued that the MAF is the first port of call ? as the measurement to the airflow is instantaneous , the VVE would be the 2nd point and is the look up table when the MAF fails ?
But yes , a good correlation between both can help , specially if you have drivability issues .
I wouldn't look at it as butchered ,IMHO you'd have a much better chance of getting through an emission test with a modified MAF transfer and untouched VVE than the other way around .

[benno25]

Thanks Luis,
I tend to agree with you saying the MAF is the first port of call during steady state conditions, however this forum would seem to suggest this isn't the case during transient conditions (sudden throttle changes) at low rpm or airspeeds.
Have you found relying solely on the MAF during sudden these conditions is ok, or is there some merit to people saying the MAF is too slow to react?

As a customer, I guess this raises a couple of questions in my mind:
1. Why would the stock tune bring VE into the equation in some instances if it isn't needed? And should a tuner be disabling this?
2. What happens to my car if my MAF was to fail? Shouldn't it run nearly identically if it was tuned correctly?

Anyway, interested to hear from those who know more than me and have real world experience. I'm only going on what I've read on forums like this and could be completely misunderstanding it all.

Cheers

[07GTS]

if u give the throttle a quick stab u can see even before rpm barely changes to ingest more air the MAP is instantly changing to suit, as the MAF only sees airflow not pressure it can be slower as to why the VVE (coefficients ) are used even when MAF is set to be used all the time