I have a friend who owns an Audi RS4 turbo. He told me to let my 535i stand idle for 2 minutes after driving before i switch off the engine. Is this right?

BTW he loved the way the 535i drove. He thought tat it felt like an M3.

 

This is a good practice to let the turbos cool down, but I don't think this is needed anymore. Perhaps the more technical and knowledgeable about the 335i's engine members could comment on this.

 

in generaly i would always recommend it to any turbo car driver. its more good practise and may keep the turbos better for longer .

 

As a previous owner of a biturbo audi, I would recommend the same cool down especially after spirited driving or long freeway hauls at high speed. Just as important is to get the oil temp up before stepping on the go pedal too hard.

 

Not the total expert, but I've doing that to my stage1-2 A4 with bigger turbo mod so far no boost lost and car still pulls strong even @100000 miles. (about 40000 mile with bigger turbo).
So, I'll do the same to my 535i. I've not confirmed on my 535i but on A4, the turbo glows red after 20-min freeway cruise at 65-70 mph. After hard run, I swear I can see the turbine spining since the turbo glows so red almost translucent

If you can't just go easy on the last mile or two before reaching destination.
Also change the oil around 7500 mile (not the 15000 interval ).

 

The second "Myth" my friend told me was that the air conditioner, when on, eats up about 40 horse power units. Is this true?

 

The days when this was needed are over, allthough it doesn't hurt still doing it.

Let the engine run a bit idle after highway driving, break-in your engine... Oh yes, the A/C does eat up ressources, but your headlights among other things too...

 

When I used to drag race my Mustang at the track I would put on a short belt to bypass the AC but I never had the car dyno'd to verify how much HP was lost. The AC causes para static drag on the engine which does reduce the HP but by how much I do not know. I can say you may be talking .1 to .2 differents in your Quarter mile traps.

 

Specifically the idling lets oil run over the turbo bearings, which gets heated up by both normal friction and by conductance of heat from the exhaust side of the turbo. Non-synthetic oils would fry much more easily than synthetics at these elevated heat levels (the term is coking) and go into thermal breakdown.
If you drive normally its not needed. If you just beat the piss out of the car and are stopping immediately thereafter (like running the cops and ditching into a garage), then let it idle for a minute or two.

 

You be the judge. Here's some math:

40 hp = 29.8 kw.

Let assume the air conditioner has an efficiency equivalent to SEER 8, which is very low by housing standards (SEER 13 minimum in the US).

With that level of efficiency, 29.8 kw of power would be capable of generating 238,600 Btu/h. This is equivalent to 20 tons (in the refrigeration sense: 1 ton = 12,000 Btu/h).

You could cool 5 2,500 sq.ft. homes with that amount of power. If the unit has efficiency equivalent to SEER 13, you get 32 tons, enough for 8 homes.

I'm not a refrigeration expert, but I think your friend's number is off by a factor of 5 to 10.