williamr91

I would never shut off mine after a hard run, including a few redline shifts and .8bar boost (tuned)...I had a b5 S4 (2.7 bi-turbo) Audi for those that don't know, these turbos blowing up where quite common, with that said I let her run for about 30 sec after driving, if I get on her hard, I drive about a mile or two before shutting off at normal operation. My problem could stem from Audi's overly hot turbos.

Some disagree but its cheap to go an extra mile normally and only takes a few mins.

user 83838290

I know the heat transfer in the bearing is way higher than radiant heat it's getting while the engine is running - the oil is circulating. When you shut the engine off, oil stops circulating and there will always be a little oil in that almost horizontal feed line right next to the most heated parts of the engine. What happens is the oil is slowly being carbonized in that little pipe. It's diameter isn't that big so just a little burnt oil is enough to get you into serious trouble.

snzuloz

Good quality synthetic oil doesn't "coke" like conventional oils once did. I still agree it's not a bad idea to let it idle for 1/2 minute or more, it can't hurt anything lol

wrinkledpants

That's why a lot of B5 S4 guys, myself included, got the low-temp switch for the after run system so it would trip on at a lower temp. Many of those turbos blew up because of boost leaks causing an over speed condition. Combine that with the fact that the K03 and K04 are both journal bearings instead of the ball bearing turbo in the 955, and the B5 S4 was ripe for turbo failures.

cwazyeurodrivr

Think I'm just going to let it idle for 90 seconds or so after getting to my destination, and do oil changes every 5K.

hahnmgh63

BTW, the IHI RHF5 Turbos in the Cayenne are Journal bearings and not Ball bearings. They would have a B suffix if they were Ball bearing.
http://turboparts.ecrater.com/p/1549...-kit-ihi-rhf5h
http://www.turbomaster.info/eng/cata...hi&pagina=RHF5
Typical Rebuild Kit: http://www.ebay.com.au/itm/Turbo-Reb...-/271531508260

cwazyeurodrivr

hence why turbo owners, should let it idle for 60-90 seconds after driving, keep the oil flowing & it lubed up while the turbos spin down, then let the water keep cooling it after shutdown.

wrinkledpants

Interesting. The dealer that replaced my turbo said they were ball bearing.

wrinkledpants

Porsche wouldn't build a turbo car that needed to be idled for any amount of time after daily driving. You're turbos don't get that hot unless you're ripping through gears at WOT, and even then, they cool off pretty fast with cool oil and coolant.

Seriously - do you really think all those wifes and soccer moms are idling their cars? It's been a long time since i've seen a post about a failed turbo. The only reason my turbo was replaced was because there was oil leaking from the charge pipe, and they thought it was a failed turbo. Nope - just a bad o-ring, LOL. Glad that wasn't on my dime.

I will idle the car for a minute after a hard, hot climb, but never during daily driving. If the Cayenne was that delicate, I would have sold it a long time ago.

cwazyeurodrivr

Piece of mind for me esp when I'm putting 175-300 miles a day on my rig.

5k oil changes , idling , and proper maintenance is how I've gotten 175-200k on my vehicles in 4 yrs

J'sWorld

FWIW, I drove my cayenne hard and only would tame my drive the last few miles before shutting it off. I never let it idle first. I got ~180k out of it before an exhaust valve broke. The rfh5 IS a journal bearing turbo, not bb. Upon dissasembly I see no coking of oil in the bushings. However, both of my turbine housings were cracked internally in the same spot on each side. To me it is amazing that guys can get 520 hp out of two turbo's that are rated at 210hp each.









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user 83838290

The housings were cracked on mine when I replaced them as well. It's very common on cayennes as I've heard from a guy that does regurbishments.

danagaul

This is slightly off model subject since I have 993tt and have been searching on and off to figure out why the secondary "key off" fan that blows onto the turbo housing is not coming on (it used too) after driving car. This is an interesting 993tt feature to help cool turbos with the key off. I replaced temp sensor (looks like a 2" coiled piece of steel) on left side of engine bay and checked fuses in same area which seem to be fine. However, there are several relays in the same area inside sealed box and I have no way of id'ing if they play a role in the cooling. I have Bentley manuals but don't see discussion their either.
Any 993tt folks "been-there-fixed-that"? Please refer me to prior threads if discussed ... I can not find!