CL MAF CAL

[mituc]

Thanks a lot for that!
It looks like I'll have to do my own MAF cal and them compare to yours, as the values I have in the logs are too much off. I am probably going to do it tomorrow or next day after, there are going to be -3C outside but I'll just apply some corrections after the weather will warm up a bit in the spring.

[manselainen]

Yes, definitely make MAF cal as each car is different, I may have a leak somewhere etc. I have fine-tuned it (OL part) numerous times when analysing WOT logs. To my understanding, MAF cals should not depend on temperature, I guess it compensates for that automatically as it measures temp as well (IAT)?

[skiptownmcat]

I was thinking mass of air is the same regardless temperature, 260g/s is 260g/s whatever the weather?

[mituc]

well, theoretically no, but considering how our MAF sensors work (they are "hot-wire" MAF sensors) the measurements may be altered by various factors including air humidity, barometric pressure, and so on.
I did my own MAF cal earlier today, drove the car for about 15-20km and then went for a spin (another set of logging, this time I used the cruise control functions to keep the speed steady) and also did some WOT pulls in 3rd and 4th.
I didn't have time to analyse the logs yet, I also did some acceleration tests by logging with my dashdaq (did not have time to look at those either), but just at a first glance the FRP pressure went up to 1896PSI (that's freakin' huge considering that I have the stock internals) and the MAF measured 268g/s peak flow. With hypertech I never got more than 247g/s.
The load never reached 2 I think, but I need to load the logs into my database and take a look at them (the ones I have gathered with the versatuner do not show up any load spike above 2, which is good).

It was pretty cold outside, around +1C (so the IAT's were also around this figure, maybe +2C tops, as I have the CAI box), and I didn't give the ECU enough time to re-learn the trims. But the desired and actual AFR's matched pretty good even with my choppy MAF CAL (forgot mainselainen's at home on the desktop computer! ) and considering the peak g/s figures I can declare myself happy! Also, there's a lot more potential with this tune, but I may need to check with Steve and with other 2.3DISI T gurus and determine how should I change these tunes to make them usable for prolonged hard driving (track) as I don't want to spit pieces of the cat through the exhaust pipe or set the piston heads on fire.

[skiptownmcat]

What rpm did you make peak flow?

[laxplayermjd]

my understanding yes 260g/s is 260g/s however when its summer its much harder to hit that. Between summer and winter one can have 30g/s difference in their max. Colder air is more dense......

i copied this from the tuning guide steve made.....
First, a note about air mass and air volume. We need to flow more air molecules (oxygen molecules really) to make more power. Because of this, we measure air flow by Mass rather than Volume. A given mass of air will always have the same number of molecules, while its volume may change wildly with temperature. Mass Air Flow is typically measured in grams/second (g/s) or pounds/minute (lb/min). The goal is to increase Mass Air Flow, not Volume Air Flow. Keeping air temperatures low improves MAF. More MAF = more power.

I feel maf varies slighty in different temps and my viewing on the dashhawk seems to match. my ltft go further negative in the summer time. I also closely watched fuel trims on my trip last week. It changed up to 3% just by stopping at different gas stations.

[manselainen]

I also had with HT max. 250 g/s, measured mostly in summertime. Now, as temps drop and I have possibility to add load etc. myself, I have so far seen max. 290 g/s at 6000 rpm at 0 degrees centigrade. I have not revved much higher but flow curve pretty much settles at 5000 or 5500 rpm where I may see 282g/s or 287 g/s respectively. K04 maxed out I presume, or some other limitation.

Let's see what figures I see at -20C 300 g/s limit must be broken...

If desired and actual lambda match at those flow numbers, they should be pretty much correct, no? Too rich mixture would mean optimistic air flow g/s and too lean would mean too low g/s numbers.

edit: Merry Christmas to everyone and happy tuning in 2012

[skiptownmcat]

I'm yet to see over 265g/s.

[laxplayermjd]

i saw 260g/s in early spring here on the 91 octance tune. with cold temps you should be 280+ i think

[mituc]

I was just looking at my dashdaq logs and I've seen 270.77g/s from 5823 to 6297 during a 3rd gear pull. Also, during that pull the FRP dropped from 1660 down to 1450 as soon as I've got WOT, it was 1417 from 3968 to 5006 when it dropped to 1357 and stayed so until 5823rpm when it raised to 1795 up until 6297. I have NEVER seen this dangerous FRP drop before so I'd rather tend to believe that it has something to do with the tune and not with my pump. However, the KR was 0 all the time.

In a similar pull the load spiked up to 222 and the FRP was still 1441 or something (boost around 17PSI). I'm going to put hypertech back in tomorrow until someone will help me figure this out because now I'm obviously going to wreck my engine and my car is also slower. I'll review the MAF cal offline and a few other things (even though a slightly off MAF call would not cause this, the ltft's are: min: -7.81, max: 2.33, avg: 2.43.