Turbo Timers

Submitted: Tuesday, May 06, 2008 at 11:46
ThreadID: 57323 Views:2981 Replies:10 FollowUps:1
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Hi All,

I'm new to turbo diesel 4WDs and towing caravans. My (new) 2006 L/C 100 manual says I should idle the engine for 1 or 2 minutes after stopping depending on how far you have driven to allow the turbo to cool down.

My experience so far is that I (and particularly my wife) often forget and turn off the engine as soon as we stop. Is an after market turbo timer "standard" fare for most people, do you all have better memories than me or is Toyota too paranoid about its turbos?

Is one brand head and shoulders over the others? Thanks Barry
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Reply By: TrickGU - Tuesday, May 06, 2008 at 12:50

Tuesday, May 06, 2008 at 12:50
I have a Bogard timer in my Nissan GU diesel and am very happy with it, you can set times from 30 seconds to 5 minutes.
AnswerID: 302306

Reply By: robak (QLD) - Tuesday, May 06, 2008 at 12:56

Tuesday, May 06, 2008 at 12:56
If you've been driving hard just before you stop then I would idle it for 1 to 2 minutes. Otherwise I wouldn't bother.

So if you have stopped immediately after driving in soft sand or turned off the freeway into a servo then let it idle. In city traffic you shouldn't need to idle more then 5 to 10 seconds.

I have an automatic turbo timer and after being on the freeway for an hour it needs to idle for about a minute and a half.

AnswerID: 302307

Reply By: Member - Stephen L (SA) - Tuesday, May 06, 2008 at 13:09

Tuesday, May 06, 2008 at 13:09
Hi Barry
I have had Turbo timers before, but have not had them for the last 2 diesel vehicles. The expects on this site will give you the correct details, but from past replies, most turbo should have cooled down enough after idling for a few minutes. You will find that after a while, it will become second nature to let your vehicle idle over before turning it off.
The most important thing is you must cool down the turbo before turning your vehicle off.


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AnswerID: 302308

Reply By: Member - Roachie (SA) - Tuesday, May 06, 2008 at 13:11

Tuesday, May 06, 2008 at 13:11
IMHO you'd be better off fitting an EGT gauge, to tell you what the actual temperature is "down there". You'd be surprised how quickly the turbo's temp drops once you button-off on the LOUD pedal. Around town there is no way you'd ever get it hot enough to require idle down time.

If you've just come off the highway at 110k/h and pull into a servo etc, then by the time you've backed off (a kilometer or so before you turn in?), again, you'll barely need to idle down.

The time you really need to watch the temp is, for example, having just climbed a steep hill on a highway, trying to maintain a decent speed and if you get to the top of the hill and brake to pull over for any reason (eg: copper pulls you over), then that is when your engine temp is going to be at it's highest point and you'd want to avoid switching off immediately.

Likewise, as stated above, prolonged driving in soft sand will make everything hotter than normal, so you'd want to exercise caution then too.

The disadvantage of a turbo timer is that (technically) you aren't supposed to leave the vehicle running and unattended anyway, so why not just sit in the thing and idle it down, watching the EGT gauge until it has reduced to your self-imposed cut-off temp (say about 250oC to 300oC)? If you do walk away from the vehicle while it is idling down, then you need to be on dead flat ground OR have a very effective hand-brake (something Toyotas are not renowned for.....)


AnswerID: 302309

Reply By: Member - Serg (VIC) - Tuesday, May 06, 2008 at 14:03

Tuesday, May 06, 2008 at 14:03
As other suggest – if you did it hard (not long, but hard) immediately before stopping then idle a bit before shutdown. I do have timer, bur use it rarely – I just get it easy before shut down. Why Toyota does not fit them? I think because leaving car working and go way actually illegal in some places – not sure about Australia.

AnswerID: 302319

Reply By: Martyn (WA) - Tuesday, May 06, 2008 at 15:54

Tuesday, May 06, 2008 at 15:54
Timid trekker,
The reason for letting the turbo cool down is to take the heat out of the turbo unit, the bearing/s and the seals. If you use a mineral based oil you are more likely to get coking in the lubrication system around the turbo, in some cases the coking has blocked the oil drain line which then leads to oil leaking into the turbo past the seals, lots of smoke and eventually failure of the bearing. End of turbo..........
If you use synthetic oils they are less prone to coking, and have better heat transfer properties so they take the heat away quicker to a place hopefully where things get cooled by the cooling system or "in air flow" cooling.
Hope this helps understand a bit more, I think I'm pretty well on the mark. And yes I do have a turbo timer and I have synthetic oil, bit of overkill but things seem to work as they are supposed to.
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AnswerID: 302337

Reply By: Member - Mfewster(SA) - Tuesday, May 06, 2008 at 16:17

Tuesday, May 06, 2008 at 16:17
My understanding of the issue agrees with both Martyn and Roachie, but combines the two. Turbos have engine oil pumped through them, Once the engine is turned off, a small volume of oil just sits in the turbo. If the turbo iis very hot. the oil in the turbo carbonizes. This is particularly likely to happen if you have been running hard on cold nights. ie the turbo is very hot and it is cooled very fast.I have a turbo and EGA. If the exhaust gas is showing 200 or greater when I stop, I let it run until the temp drops below 200, or I just let the timer do it for me. I cooked the turbo in my previous vehicle (no timer or EGA). The mechanic showed me the dismantled old turbo, and gave me the explanation above. No trouble since using both timer and EGA, but agree with Roachie that if you are happy to sit in the car for a bit and monitor the EGA, a timer is not really necessary. Some contributors to the forum have prviously disputed this. I don't know, but this seems to have worked for me..
AnswerID: 302342

Reply By: Member - barry F (NSW) - Tuesday, May 06, 2008 at 17:44

Tuesday, May 06, 2008 at 17:44
Howdy Baz, Like you we are fairly new to diesels & caravanning, so the responses above are of interest to us as well.
Our vehicle is not fitted with a timer, but we are now in the habit of letting it idle for a while before switching off, although I have probably never let it idle for a minute & a half. The practise quickly becomes a habit. SWMBI drives a petrol vehicle & when I drive it & come to a stop I let it idle for a while out of habit.
Much to her annoyance, but it is just a habit now for me. I love the diesel, wished I had of got one centuries ago. Cheers.
AnswerID: 302369

Reply By: macbushy - Tuesday, May 06, 2008 at 20:35

Tuesday, May 06, 2008 at 20:35
I travel 90% of my kms at max state speed limit (but officer, i was close to it ....lol) .

My turbo timer (i assume) is invaluable.

Just going flat out, then decide for a quick pit stop..... ........... c r a c k ........ mmmmmmm ..... whoops I must of turned it off when red hot mmmmm

Weigh up cost of timer vs broken car

Never had one "go" but at least i dont have to worry about it.

Always wondered why they are not std on all turbos.
Are tubo timers one of those items that are 99% gimmicky and 1% usefull?
Are we being had?
Like pushing hand up against window to prevent stones cracking window
AnswerID: 302397

Follow Up By: Member - Roachie (SA) - Tuesday, May 06, 2008 at 21:03

Tuesday, May 06, 2008 at 21:03
Mate, as I stated above, you'd be surprised how quickly the exhaust gas temps drop once you take your foot off the accelerator. So, when you say you do a lot of highway driving at the speed limit, that is not necessarily a huge reason to worry about switching off when you pull up.

In fact you may also be surprised how "cool" a turbo will operate, even at highway speeds.....if you are just going along a flat section, not into a head wind etc.

Another thing that a lot of people don't realise is that a turbo does NOT produce heat.....Quite the opposite; it is a USER of heat. I only worked this out when I had my last Patrol (a 4.2TD) and I had 2 thermocouples fitted into a digital EGT gauge. One was fitted in the exhaust manifold immediately above the turbo, whilst the other one was in the usual position of the dump pipe...a couple of inches below the turbo. Typically, the temp in the manifold was about 150 to 250oC ABOVE the dump pipe's temp, proving that the turbo was soaking up a lot of the engine's heat.

I personally would never bother with a turbo timer again, but I am the sort of bloke who drives my rig with a passion and watch the gauges all the time...... I like to know what is happening under the bonnet (within reason). If it were viable to fit temp sensors to each of my 8 cylinders etc, I probably would do so...hahaha


FollowupID: 568446

Reply By: Timid Trekker - Wednesday, May 07, 2008 at 13:40

Wednesday, May 07, 2008 at 13:40
Hi guys,

Your collective wisdom is AWESOME! Thanks heaps for all the replies. A turbo timer sounds like cheap insurance and cheap compared to the suspension upgrade I think I need for a 350kg ball weight van.
AnswerID: 302485

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