madfish

fitted. The manual states you should idle for 2 mins after hard driving. A stop is a stop, during / after spirited drivin you turbo is spinnig v v fast and v v hot. give it chance to slow down and cool off even if coolant is being pumped to it. It's just not worth the risk

MichaelTT

if so why does the 225TT have a 'turbo cooler' cycle. Turbo cooking is a real issue and please do not down play as a 'stone age' issue

13377

Me too, I am glad I am not the only one!

Rawhide Rosenwad

and experience. In this case, I feel, however, that the current body of knowledge favors my view.

Do you have a copy of Maximum Boost by Corky Bell handy?

MichaelTT

Chapter 16 Developments in Turbochargers...interesting read but where we disagree is most manufacturers (including Audi...it is stated in the service manual) note the need to idle engine after hard running and obviously Audi had enough of a concern on the issue of turbo heat to add the turbo timer system on the K04. Yes there are exceptions, rare but there, to the turbo timer requirement...reference Subaru:

The use of turbo timers to shut the engine off some preset time after the ignition key is removed was needed in the old days. Early turbocharger bearing housings were only cooled by the lubrication oil of a running engine passing by the turbine bearing. If the engine was shut of when the turbine was still very hot excessive heat wick into the turbo bearing and seal area, cooking the oil to black carbon, causing bearing/shaft failure and heavy oil consumption. The newer (for over 15 years now) style turbo housings are water cooled as well as oil cooled. The original EJ20 Subaru turbo motor took advantage of water cooled bearings from the start and have never had this problem due to a unique design feature we will now explain. It is the reason you do not need to purchase a turbo timer.

The Subaru WRX engines have their water catch tank high on the engine above the turbocharger. It is that little can where you check the water level. When the engine is shut off the water continues to circulate via a physical property of water called a thermal siphon. Simply put, hot water rises up to the catch tank, being drawn from the relatively cool cylinder head water jacket up through the turbo housing. This nifty little idea works every time you turn off your engine.

One still needs to take a cool down lap at the track and perhaps should not stop at the top of a mountain pass to enjoy the view if you have been on the boost all the way up, but for the other 99% of the time there is no need to let the engine idle for a minute before shutting off ignition. Even when the engine is off, the cooling water will circulate past the turbine bearing housing.

Tongpo~Dr. Evil

have you ever seen your turbo after a hard run? i know i've seen mine....and glowing orange-red color on the turbo housing to me is normal after hard runs....don't know about you, but when metal is that hot, i wouldn't want to just shut it down....

Rawhide Rosenwad

Thanks for being "informatively disagreeable!" :- )

Rawhide Rosenwad

Either way, fail-safe engineering has taken care of it in our case, 225s.

At any rate, Living in "armpit" NJ, I'll never have the opportunity to not experience a significant "cool down" period. Our congestion problem makes sure of that!

I wish you many years of coke-free turbocharging!

MichaelTT

lol... I like that terminology