2.0Tdi 170 auto revs when stationary

[Schmittster]

Amazingly i've not tried it before but today sitting in the drive after a short run out I revved the engine only to find that maximum revs was about 2500rpm.
I went for a quick spin around the block and engine revved normally (straight to the red line). Back in the drive and it only revs to 2500rpm (in N or P when trying this).

Is this normal??


Sorry...thread title may be a bit misleading but can't edit it.... The car is an Automatic (multitronic) it doesn't automatically rev when stationary. The question is about maximum revs when the car is stationary and gear selector is in Park of Neutral.

[MarkTM]

I just tried my tiptronic in both P & N and revs beyond 2.5k, perhaps a vagary of the multichronic?

[Schmittster]

Thanks Mark. Using google I have found one post that says it is a safety feature to prevent over revving when stationary but I'm not sure how that can be right.....After-all, how the hell would you fault find a noise/rattle/misfire/etc etc that only happens at >2500rpm if you can't rev the engine?

I'm sure someone will be along shortly with the same model as me and can confirm whether theirs does the same or not.

[MarkTM]

My revs sit at well below 2500 when cruising at the motorway legal limit.

[royclark]

This is normal.
It is a safety feature to prevent you from revving the nuts off it when stationary.

[Guest 2]

Again, normal.

[Schmittster]

Thanks chaps, all replies greatly appreciated

[royclark]

After-all, how the hell would you fault find a noise/rattle/misfire/etc etc that only happens at >2500rpm if you can't rev the engine?

With VCDS.

[Novica]

Even my, in idle , when car is stationary, the REV is not going beyond 2500rpm. My is manual, 2.0 TDIe 100kw, 2011 CY.

I notice few more things (I am thinking that they are also normal), when A/C is off, idle RPM are around 800, then if I A/C switch on, idle RPM are around 900.
When the car is stationary, with A/C switched off, idle rpm are 800, then if I engage clutch and start slowly releasing it (like I want to move the car), without any pressure on accelerator pedal, the RPM automatically increase from 800 to 900. As I am new to the car, I was surprised a little bit, but by the time passed I get used on it and convinced myself that this is normal :o

[MarkTM]

The AC higher revs thing has been common on every car I've owned with it for the last 20+ years. Hence why air con will use between 4-10% more fuel. As to power loss only really noticeable on sub 1.6 engines and virtually unnoticed on my 4l :)

[Novica]

It is strange, I suppose that will increase only if engine engage A/C compressor (during hot weather, high temperatures outside) but, now when heating (on this cold weather) is only used, engine is still increasing RPM. On my previous A4 (B6 1.9 TDI 96kw) I have never noticed this behavior that engine increase RPM (or the engine did not have valid reasons to do so).

[MarkTM]

An AC system does more than just reduce temperatures when hot, it also reduces humidity when either blowing hot or cold (hence the excellent demisting properties in colder months) so the condensor will still be running if you're heating with AC on.

Worthwhile reading this if you've the time:

Car Airconditioning - How It Works - Compressor, Condenser, Receiver Drier Hydrator, AirConditioningforCars.co.uk (http://www.airconditioningforcars.co.uk/ACpage03.htm)

Question does your current A6 have climate control and did your old B6 have straight.standard AC? That may be why there's a more noticeable affect.

Certainly here in the UK cars for the masses haven't been fitted with AC for much longer than 20yrs, indeed when I bought my 94 Mondeo AC was a chargeable option and only became a no cost option when Peugeot made it standard (as a USP) on the 405 that same year. Can anyone now imagine having to pay extra for AC:confused:

I remember at the time passengers thought it an indulgent luxury when I switched it on :)