simonds1

I'm just reading a book that a mate lent to me so I could learn a bit more about turbos & forced induction etc. It's called "Forced Induction Performance Tuning" and it's by "A. Graham Bell". Really cool book actually, and I thought I'd share something that I thought was interesting, seeing as most of us on here probably do this!.......

"....After a hard run which has put a huge amount of heat into the turbo it must be allowed time to cool for a period of about 3 minutes. Actually I don't advocate allowing the engine to idle for that period. I would rather see it run about 1500rpm or a little higher to promote a good flow of oil through the turbo bearings. At idle the oil flow will not be sufficient, which could allow the heat in the turbine to carbonise the oil. If the oil becomes carbonised it blocks the minute clearance between the shaft & bearings. When the engine is next operated, oil flow through the bearings is reduced and without adequate lubrication the bearings soon fail. However, this may not be the limit of the problem as the shaft may also be wrecked; the turbine & impeller wheels may touch their respective housings, damaging the turbo beyond economical repair."

I dunno does that apply to all turbos or what, but thought that was interesting seeing as most of us on here probably let our cars idle after we've used em....and there it basically says not to, and to run em a bit higher than idle! Never heard that before tho, so not sure how true or not it is

Jay m A

iTrader: (2)

Yes it makes sense, but even better drive the last mile off boost

simonds1

Aye I normally try and do that if I can

The rookie

iTrader: (1)

That book was written before water cooled cores were used, or synthetic oil for that matter, while it won't harm your car to let it idle or to fast idle it, unless you cane it right up to when you stop its not necesary nowadays.

Simon

scoobynutta555

I never sit there idling away, certainly not for 3 minutes. I drive the last bit of my journey off boost and switch off as soon as the disklok is on.

Shark Man

Exactly, no need to idle at all. Just need to drive like a granny for the last five minutes of your journey

Save fuel, save the environment, and save your turbo

The only single exception is after comming off the motorway after a sustained 80mph+ cruise on to a service station.

And even if one does inadvertantly forget there is safeguards to help minimise the problem; Water still flows through the turbo bearing housing when the engine is off via thermal gravity, allbeit at a much lower flow rate.


Mind, how many Imprezas has anyone seen with a knackered turbo? Certainly plenty exist, but there are more that have knackered the big ends bearing before the turbo (ignoring the turbo failures caused by the contamination from a big end bearing failure).

andythejock01wrx

Sharkie has this thread sewn up.

simonds1

Funny you should mention that.....because it wasn't. lol. This comes before the bit in my first post......

"Today, most turbos have a water-cooled bearing arangement to increase the reliability and life of the bearings. Unfortunately, this has lulled many into a false sense of security as they feel the turbo no longer needs to 'idle down' before the engine is stopped. This just isn't true."

Then it carries on where the extract in my first post starts. The book is from 2002 by the way