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Noticed over the past 6-8 wks the surge in power that used to happen at 2000 revs doesn't now occur until about 3000-3500 revs. The oil temperature also seems to be a little higher than what I remember.

I checked for fault codes with VAGCOM and the following turned up:
16502-Engine Coolant Temp Sensor (G62): Signal too High
P0118-35-10----intermittent

I then logged block 003 to redline:
Time stamp, Eng speed, MAF, Throttle Angle and Ignition Timing:

495.49 3600 066.81 22.0 27.80
496.40 4000 109.44 34.1 22.50
497.34 4520 107.14 27.1 17.30
498.31 4840 084.33 21.2 17.30
499.31 5040 077.44 20.0 30.80
500.32 5160 056.97 16.9 35.30
501.34 5200 048.83 14.9 37.50
502.37 5240 037.89 12.9 41.30
503.39 5320 082.11 20.8 31.50
504.44 5560 069.33 18.8 33.80
505.51 5880 117.92 27.1 27.80
506.63 6440 149.81 38.4 28.50
507.76 6840 115.75 25.5 07.50

The mass air flow readings appear to be very low. I note from other posts that ideally I should log from 2000 revs right up to redline with wide-open throttle. Does WOT mean completely flooring it from 2k revs rather than doing a controlled, gradual acceleration?

Zen

A search for the above fault code revealed this:

16502 - Engine Coolant Temp. Sensor (G62): Signal too High
P0118 - 35-00 --
Readiiness 0010 0101
The symptoms of this small device are varied and wide:-
It can cause the ecu to cut back on boost,
It can cause soft limp mode and poor running.
It can make you feel you have a boost leak and
It can provide false reading that could cause lean or rich running.
It could cause strange dash temperature readings.
It is quite surprising how varied and dramatic an effect this sensor can have.
http://www.waheedkhan.com/tempsensor/tempsensor.htm

Looks like I'll need to book in for a replacement sensor.

Zen, your MAF log isn't right as you weren't wide open throttle, and without WOT you can't gauge if the sensor is bad or not...

You have to press the throttle all the way at 2k and keep it there to 7k....

HTH,

Mihnea

Thanks Mihnea... just preparing to go out for another couple of runs....

OK. WOT in 3rd:

Columns are time stamp, revs, mass airflow, throttle angle% and ign timing.

654.32 1840 058.58 074.9 13.5
655.24 2200 081.81 087.1 13.5
656.14 2600 112.28 100.0 09.8
657.05 3040 130.67 100.0 12.8
657.95 3480 147.25 100.0 13.5
658.86 3920 157.33 100.0 12.8
659.78 4280 166.42 100.0 14.3
660.73 4680 178.42 100.0 14.3
661.73 5040 185.00 100.0 18.0
662.75 5400 193.36 100.0 18.8
663.81 5680 194.67 100.0 18.0
664.90 6000 194.75 100.0 23.3
666.01 6280 201.25 100.0 23.3
667.14 6560 202.86 100.0 24.0
668.26 6800 206.31 100.0 29.3
669.40 6800 075.28 019.6 27.0

Block 003 presented above but I also logged blocks 001 and 002 at the same time. Did three different runs and all registered max airflow of 206.

Zen

your MAF looks ok-ish to me... a little bit on the low side, a new one would do around 212g/s peak but it's not too bad still... Try disconnecting it and see if it makes any difference...

Coolant temp sensors fail for a past time on loads of VAG engines. I would just buy a new one for 19 quid plus a new seal. They often give that error code. Like what was posted earlier. They can make the ECU pull back the boost.

Fit new sensor, top up lost coolant, clear DTC's,and try again.

Address 01: Engine
Controller: 8D0 907 551 D
Component: 2.7l V6/5VT G 0002
Coding: 05711
Shop #: WSC 01972
1 Fault Found:
16502 - Engine Coolant Temp. Sensor (G62): Signal too High
P0118 - 35-10 - - - Intermittent
Readiness: 0000 0000

I have the same fault. Although I shall change the sensor, does anyone know what the peak boost should be on a standard s4?

0.7 to 0.8 peak