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Guys - I've got a little problem brewing - I think...

My fuel economy has dropped off quite a bit and the performance is up and down - even the wife noticed it the other day. She drives a new 325i and said the S4 was not very fast...cheeky cow.

It is not slow but does not always give me the wow factor. I had this before and it turned out to be an exhaust gas temp sensor on the right bank was starting to play up. I checked with VAG COM and there are no errors. Have checked the "normal" flow checks (airflow, boost etc, see below) and nothing seems to be awry, but there is definately something brewing. I thought it may be my MAF but that seems to be fine and no significant drop off in air volume. Got any idea's?

Engine speed, Engine load, Injection time, Mass air flow,Spec'd Boost, Actual Boost, Current torque
960 36.1 4.42 11.89 990 990 132.3
1080 55.6 5.78 17.86 1450 990 214.6
1360 88.7 9.52 37 1520 1100 264.6
1640 105.3 10.54 58.69 1770 1240 317.5
2000 121.8 12.24 90.58 1770 1440 358.7
2400 148.1 14.96 120.14 1730 1690 388.1
2880 157.9 15.64 144.39 1720 1770 402.8
3360 151.1 14.96 156.14 1700 1710 382.2
3800 143.6 14.62 164.22 1680 1700 367.5
4200 138.3 14.28 173.41 1630 1630 346.9
4640 134.6 13.94 184.11 1600 1610 329.3
5080 128.6 13.94 192.44 1580 1580 311.6
5480 124.8 13.26 200.47 1560 1540 299.9
5880 119.5 12.58 204 1530 1530 285.2
6240 113.5 12.24 205.86 1490 1510 291.1
6560 109 11.56 206.92 1480 1480 291
6720 102.3 11.2 208.52 1470 1470 290

Try checking your BPV's - I suspect it might also be due to the hot weather, as the std IC's seem to heat soak quite quickly.

Shouldn't your MAF figures be higher? would expect 215-225 std, 260+ chipped?

I'd agree. The peak boost and torque seem OK at 2880 rpm, but at the top end it looks like it's struggling. Why less than .5 bar above 6000 rpm? Unless I've forgotten what a stock S4 is like!

Thanks guys, the BPV's (by-pass/dump valves??) were done about 1 year ago. But I did a run the other day and noticed that the car was boosting more than requested off load (anything from 0.01 -0.1bar) I know from experience that this is normally damage in one of the dump valve diaphrams but surely not after one year. Are the std jobs any good, is it worthwhile putting in better uprated ones. Also what do you think about MAF or ambient air pressure switch?

Bypass valve and Mass sensors are non too special!
I have two black stratmosphere piston valves going spare.
Rare to get problems with the boost sensor, certainly never changed one myself.
Altitude sensor built into ECU again no common probs.

Morpheous - please drop me a mail on robbie_beaton@dell.com so as we can discuss your "spare" DVP's?

Thanks Rob.