Peak MAF

[Dippy]

I've got to sort out my peak MAF 'issue'.

I once logged a peak of 280g/s, but recently the peak has been 255g/s.
I've had the car serviced and back on the RR. The graphs are roughly the same as they were 18 months ago (8 hp & 10 lbft lower which I guess is nothing to worry about and could be accounted for by my different wheel & tyres).

I did some more logging today and got a 250g/s peak. It was very hot so that seems the same as it was a few weeks ago.

What I really want to know is what should be considered normal. Can everyone with chipped K03 cars let me know their peak MAFs?

[Nige_RS4]

I have never seen much above 255g/s on mine (stage 2 ) so I would say you're in the right ball park. Have you tried cleaning your MAF?

My MAF readings were a bit low last time I did a FATS run, but since cleaning it I can feel the difference - haven't had the chance to re-log it, but I am expecting it to be back in the 250's.

280g/s seems quite high for a stage 2+ car?

Nige.

[Wak]

Group A: '002
Engine speed Engine load Injection time Mass air flow
TIME 2-5/1.6-5ms 2.8-5.6/10-15g/s
STAMP /min % ms g/s

3305.54 4160 37.6 5.44 61.31
3306.5 4760 167.7 21.08 240.19
3307.54 5800 156.4 21.08 263.42
3308.67 6680 139.8 18.7 272.5


272 for a AmD remap and Milltek

[Nige_RS4]

Wak, you've got the full Milltek system right? i.e stage 2+

[Wak]

Milltek Cat back - Stage 2
as far as I can tell, is there a Stage 2+ ? whats that then?

I have the single pipe Milltek , nice looks but a bit subtle on the noise front IMO, I didnt realise there is a dual race version at the time of purchase but is that a Stage 2+ ?

be careful about comparing cars, Audi engines can gain 10-15% more bhp from age alone if well maintained and oil changed regularly and we are on 121k miles.

Ross-techs, website quote approx "0.8x power" is roughly what you should get on your MAF output.

As a ballpark figure I have found this to be reasonably accurate in comparing power to maf outputs on cars, taken with a pinch of salt of course.

this may be silly, but we have removed the fog lights, I thought they were a bit pointless and took up a large amount of frontal area. the mouldings seem to make a nice scoop and flow design for airflow and maybe is helping efficiency of the intercooler.

[Nige_RS4]

AFAIK stage 2 is chip + cat-back, stage 2+ is the full Milltek system, incl. sports cats & downpipes - stage 3 is RS4 turbos.

If you are to rely on the x0.8 rule, your output would be 350bhp, which seems a tad high for just a cat-back?

[tartan_rob]

I consistantly get 260g/s, on test recently I got 267g/s. Prio to Maf chnage it was 220 ish.

[Dippy]

Thanks guys.

I haven't cleaned the MAF, primarily because it's a Hitachi one and I was under the impression that only the Bosch ones caused problems.

I actually think that about 255 g/s is about right. My peak power on the RR has at best been about 325 hp. That's been fine for me because my peak torque, which is more important to me, has been 415 lbft, and my power curve is flat to the redline (the advantages of the Miltek cats). I know that my engine is quite rare for an S4, being the later ones which meet updated EC regulations. This could mean that its power potential is actually less than previous engines? Also as Wak notes, in Audi terms my engine is still youngish at 54K miles.

What I do find very interesting is that Wak used group 002 to measure his 272 g/s. All my recent measurements used group 003. Any guess which group I was reading when I logged 280 g/s. Yes it was 002.

I did do a group 002/003 log recently to compare the readings, and they were similar, but I didn't get to check the much above 200 g/s. So maybe I need to do some FATS runs using group 002.

[Wak]

AFAIK stage 2 is chip + cat-back, stage 2+ is the full Milltek system, incl. sports cats & downpipes - stage 3 is RS4 turbos.

If you are to rely on the x0.8 rule, your output would be 350bhp, which seems a tad high for just a cat-back?

Just divide the maf output by 0.8
272/0.8 = 340bhp.

It was at 6800 revs if you take the previous figure... at 5800 revs
263/0.8 = 330bhp.

So how good a result is this...
my 315 was stage 1,
Milltek added gives me AmD's claimed 5bhp so 320bhp
Add to it the RR will never give the airflow that the real road will give then it shouldnt be far off 320-330bhp

this may be silly but we have removed the fog lamps as I thought they were a waste of space and quite a large frontal area blocked. the mouldings look nice as little scoops and maybe makes the coolers a little more efficient.

I have yet to find the 0.8 rule of thumb wildly off and like I said take it with a pich of salt, but if you know your typical power output it is a good way of doing a basic check on your maf condition.

[Wak]

I did do a group 002/003 log recently to compare the readings, and they were similar, but I didn't get to check the much above 200 g/s. So maybe I need to do some FATS runs using group 002.

you'll find the differences are because of timing.

When you log 2-3 blocks in vagcom e.g,
002 003 004

Vagcom can only look at each block of 4 values individually, it cant read all 12 at the same time
So you get snapshot 002 then 003 then 004 and hence they can be different even though they are presented on the same line of the spreadsheet.

p.s if you want to get a 2nd opinion then have a look at my website www.wak-tt.com

[buzzard]

does the MAF sensor work on the hot wire theory (I'm new here!!) cos in bosch early days they worked on amount of air rushing passed cooled the wire and electric current measured to keep it hot was how it worked out the reading but air temp was taken into account as well. these used to be self claening due to nature of operation.how do you know if MAF wants cleaning and how is it done?
although these engines are high tech they still go off the boil and can vary from tank full to tank full .still keeping with optimax each time.

[KayGee]

I get around 150G/s on mine but I think thats cause its RS4 MAF and g/s is scaled figure to work with the S4 ECU.

[cpufreak]

I consistantly get 260g/s, on test recently I got 267g/s. Prio to Maf chnage it was 220 ish.

thats good news (for me).

currently getting 220-230ish...just bought a new S4 maf sensor, so once thats arrived + fitted, will report back.

andy

[KayGee]

S4 MAF is hot wire type, cleaning MAF has been known to extend life however not significantly. Not so bad now can get exchange MAF sensors.

[smurfbus]

I get around 150G/s on mine but I think thats cause its RS4 MAF and g/s is scaled figure to work with the S4 ECU.

it might be dying also? My rs4 maf reads 270, but that is with stg1 chip so no other scaleing than the size and sensor. You might be scaled also by the chip?

have you done the FATS test to see if you are in the ballpark. STG3 should be at around 4 sec give or take .5 sec