i want to avoid coking/shearing in a turbo car

[peterr]

Originally Posted By: BuickGN
I'm not a big fan of water cooled turbos except in the Porsche 951. They do it the right way with a small electric water pump that continues to run after the engine is shut down.


Me too, thats why I have a Porsche 951.

But yes for turbos a decent synthetic oil changed on a not too aggressive schedule will prevent coking. A lot of the euro cars spec a thicker oil. I run 0w40 Esso XD-3 (available in Canada) but German Castrol 0w30 or M1 0w40 or 5w40 or many other oils would be fine.

I am happy with Dino oil in my NA cars but the only time i ran dino in a turbo was doing a short Auto-RX interval of 15w40 HDEO in the summer

 

[gtx510]

I still think water cooled is better but oil cooled is simpler to install. Either one should be cooled down regardless whether coolant circulates after shutdown b/c the oil is definately going to drain out. If the turbine shaft is still super hot the oil coating it will coke. I'm kinda on the fence whether or not oil cooling is a street or (drag)race app. The link below says most of Garrett's small turbos (GT15-22) are oil cooled and I think those are mostly used on small diesels (and in FSAE). That's definately a street app, but then there's no oil cooled turbos until you get to a GT32.
http://www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/turbo_comparison_sheet.htm

That Precision Turbo could be a Garrett GT CHRA in older style housings or GT wheels in a older style turbo. They make cool stuff, I just hate how all of it it too big for my dinky 1.6L

Turbonetics, Innovative, Tial? and a bunch of others make custom Garretts like that.

bb GT CHRA's for older Garretts
http://www.tialsport.com/prod_tc_gt_t3t4r.htm

the Saab quote is from Garrett
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech101.html
Oil & Water Plumbing
The intake and exhaust plumbing often receives the focus leaving the oil and water plumbing neglected.
Garrett ball bearing turbochargers require less oil than journal bearing turbos. Therefore an oil inlet restrictor is recommended if you have oil pressure over about 60 psig. The oil outlet should be plumbed to the oil pan above the oil level (for wet sump systems). Since the oil drain is gravity fed, it is important that the oil outlet points downward, and that the drain tube does not become horizontal or go “uphill” at any point.
Following a hot shutdown of a turbocharger, heat soak begins. This means that the heat in the head, exhaust manifold, and turbine housing finds it way to the turbo’s center housing, raising its temperature. These extreme temperatures in the center housing can result in oil coking.
To minimize the effects of heat soak-back, water-cooled center housings were introduced. These use coolant from the engine to act as a heat sink after engine shutdown, preventing the oil from coking. The water lines utilize a thermal siphon effect to reduce the peak heat soak-back temperature after key-off. The layout of the pipes should minimize peaks and troughs with the (cool) water inlet on the low side. To help this along, it is advantageous to tilt the turbocharger about 25° about the axis of shaft rotation.
Many Garrett turbos are water-cooled for enhanced durability.