[SS-Traveller]

Originally Posted by nilanjanray

The Toyota Fortuner manual has some conflicting advise:
1. Don't idle before driving off
2. Normal city driving: no cooling off period required
But why # 1 and #2? In fact it says that excessive idling can damage the engine.
...would like to get the 'no need to idle for normal/city driving' confusion sorted out for peace of mind :-)

Most auto manufacturers don't recommend prolonged idling at cold start. There are a number of reasons why:

1. Cold engines idling = very rich fuelling. Exhaust valves and turbo waste gates don't like being coated with half-burnt fuel. Look up "wet stacking".

2. Cold pistons and rings tend to flutter without load - can cause terminal damage. Also applicable to prolonged idling for hours even on a warmed engine.

3. Driving off warms the engine quicker than just standing there and idling away.

4. Time taken to circulate oil into the system is 30 seconds or less, which is the logic for idling for a short time before driving off on a cold engine. Newer oils have friction modifiers which coat metal parts well enough to minimise damage for the first 30 seconds before the oil starts to flow.

5. Diesels will pull away at idling rpm in 1st gear, no need to rev hard, so doing it isn't going to hurt. If you have to climb a 25* slope soon after cold start, waiting for a 30-60 seconds makes sure the engine is well lubricated before being loaded that heavily.

Cooling off after coming to a stop - well, if you habitually shift to neutral and turn the ignition switch off when doing 4000 rpm, you'll certainly get a busted turbo soon. OTOH, as you slow down, engine rpm falls, the turbo also spins down, and by the time you are ready to switch off, you've idled already for 30 seconds - enough for the turbine to have slowed down, so that it stops almost simultaneously when exhaust gases stop flowing. When moderately hot, a turbo that is not turning over (when oil isn't flowing) won't incur damage. For a really hot turbo (such as if you've been running full-throttle laps on the BIC), sudden switching off can also crack the vanes due to rapid cooling. Applies especially in very cold regions.

In "normal/city driving", neither is your engine running at more than 50% of its rated rpm, nor is the turbo spinning over beyond 30-40% of its rated rpm. Switching the engine off 10-15 seconds after coming to a full stop under such conditions doesn't cause damage due to loss of lubrication and/or heat soak followed by rapid cooling.

[Vid6639]

Originally Posted by karan561

But what after a high revving run if i approach the signal & the engine shuts down to save fuel would'nt it harm the turbo ?

Have you tried to see after a spirited run if the start/stop works and switches off the engine immediately. I would think that the start/stop would not work when the engine has been worked hard.

Originally Posted by nilanjanray

Great thread.

The Toyota Fortuner manual has some conflicting advise:
1. Don't idle before driving off
2. Normal city driving: no cooling off period required

I follow the 'slow down before reaching destination', 'don't rev/push a cold car' and 'idle for 2 minutes after high speed driving' diligently, but would like to get the 'no need to idle for normal/city driving' confusion sorted out for peace of mind :-)

Don't idle applies for prolonged idling, not the 1-2 minutes that is needed for the engine to warm up a bit. With no airflow prolonged idle increases the temperature a lot.

Normal city driving doesn't require cooling off since you never have the turbo at boost continuously. The rpm's in city are much lower and turbo usually goes from boost to no boost. This doesn't heat up as much as a spirited highway drive where the turbo maybe at boost for a long time.

In city infact there is all chance that the turbo maybe on boost only for 20-30% of the drive.

[karan561]

Originally Posted by Vid6639

Have you tried to see after a spirited run if the start/stop works and switches off the engine immediately. I would think that the start/stop would not work when the engine has been worked hard.

Frankly not sure about this. Because most of the times the start/stop is kept off

Will try it out in the next run & report back

[Tassem]

A very helpful article GTO! It's good to have info collated in such threads!

Here's what I do (Verna 1.6 D) -

1- Never accelerate in a parking lot. Idle is more than sufficient for driving around in the lot. Its safe for the car (engine, dents etc) and for others who may be present in the lot.

3- While setting off, I get into the car, start it, wear the seatbelt, choose a playlist and move out in idle. This takes about 30 secs. Once I get out of the lot (Another 30 secs) and out onto the road (Another 30 secs), I turn on the AC and drive normally. So I get about 1:30 of warm up before the AC is on. I stay below 2k RPM till I reach the main road and then continue as usual. The 2K limit is not really a deal breaker in diesel cars as they can clip at quite high speeds even at that RPM.

2- When returning, about three to four minutes away from home, I play one of my favorite songs. Once I reach the lot and park, I turn off the AC, lights etc and let this song complete before getting out. Usually its about a minute. Not only does this help me unwind, it also cools the car down.

Important - [b]Never loiter around the car after getting out. While idling, the parking area will invariably be filled with noxious exhaust fumes. [b] If you have things in the boot etc. to unpack, either come back later and do it or while the car is idling, making sure you dont waste time standing around and inhaling the fumes.

3- Never leave any of the doors/windows open while idling.

4- If I have company, I always have them get out at the entrance, rather than accompany me to the parking. The main reason for this is that I've noticed a lot of people jump out of the car immediately on reaching the destination and then wait for you to get out of the car. During this time, they will be breathing in fumes.

Hope this helps.

Tassem.

[F50]

White Mischief is my first diesel which is equipped with a small turbo, a turbo nonetheless. After chatting with our in-house DDiS guru - Jaggu, an idling of 2 mins both ways is enough.

Well, I have been following religiously,

1) City runs - Idle for 3+ mins on cold starts. After 14 odd kms run, cooling down for 2 mins. I would prefer to idle for more time rather be a slow moe in peak hour traffic.

2) Highway run - Idle for 7+ mins on cold starts and cooling down for 5 mins.

[SDP]

Originally Posted by Mudhalaipatti

XUV comes with the start/stop option, where the engine switches itself off at thse signal. Does this mean, we should disable this function, to extend the longevity of the turbo? Or is there some fuzzy logic on the electronics, that takes care of this idling time ?

The start-stop in the XUV does not stop the engine if the engine hasn't reached a certain temperature. I believe there are other conditions as well under which the engine does not stop. They are listed in the manual, but I am unable to recall them now. BUT, is the start-stop in the XUV smart enough to keep the engine running for 30 seconds to let the turbo cool down? I don't think so.

So in my opinion, one should either keep the start-stop disabled OR take care of idling yourself (i.e. lift the foot off the clutch only after 30-60 seconds of idling) before the start-stop switches off the engine.

I switched off the start-stop today. My turbo is much more precious than the small convenience offered by the start-stop.

[fundagenie]

Originally Posted by GTO

The start / stop function kicks in only after a couple of seconds, right? That should allow the turbo to cool down a bit. I believe you can set the start-stop timer too? Take it to 30 - 45 seconds.

But of course, there isn't a doubt that the start-stop system puts additional stress on the turbo, starter & battery. In my 4 days with the XUV500, I put the start/off system off.

The XUV does not have any option to set a timer for the start/stop interval. For start/stop the default time is 2secs meaning the engine would stop after 2secs.

Also the manual says the following about idling "After the engine has started, allow the engine to run for few seconds prior to placing the vehicle in gear". It does not mention anything about idling when stopping the engine.

FundaG

[gandalf]

I am a bit confused now.

What everyone is saying here in a nutshell is that the Turbo needs to be cooled/Warmed up initially or before stopping the vehicle.

So wouldnt driving the car for the initial 2 minutes and the final 2 minutes @ lower RPMs (below the turbo spooling levels) do? why do we need to idle the engine on start and stop for the turbo to cool or the oil to reach operating levels?

[bigron]

A great time to come up with such a thread. With everyone from average joe to millionaires buying diesel cars and most of them first time diesel owners , this will go a long way in appraising the people how to ensure long lasting reliability and performance from their diesel engines. Good Job.

[Macfreak7]

Originally Posted by SS-Traveller

Most auto manufacturers don't recommend prolonged idling at cold start. There are a number of reasons why:

All great points. To that I would also add another reason for not idling and instead driving off immediately is to help warm up and lubricate all other parts of the car as well. Idling only helps warm up the engine, but other components such as transmission, tyres, brake pads etc. also require a warm up period to reach optimum temperatures. What also helps is to keep an eye on the idle RPM needle, which should come down after about 30 to 60 seconds of idle time. For example on my car with a 1.8T petrol engine the idle RPM on a cold start is about 10.2 (x100), but settles at about 8 (x100) after idling for about 60 seconds.

My ideal rule of thumb is to idle for about 45 seconds before driving off, then drive in a relaxed mode for 10 minutes (enough time for engine oil to warm up). After that you can drive like a bat out of hell (if your car begs for it, and if traffic/roads will allow it of course).

BTW, a related question, anyone know how does having the A/C on or off affect the temperature of the engine oil?
What I've noticed on my car is if I push hard with the A/C off and the engine oil temp goes up by a few degrees (to about 103-105), then turning the A/C on brings the temperature back down to about 99-100 pretty quickly. What gives?

[audioholic]

What a good initiative to spread awareness on the turbo. I have heard two cases of owners in my native who had packed turbos as early as around 60k kms. That time they were blaming the manufacturer about heavy costs. However, little did they know about anything called as idling the car. While one guy got his manzas turbo replaced under warranty somehow, the other person whom I met paid up for his car, which is a Verna, as it was out of warranty.

Just as I saw this article, maybe coincidence or as usual, my neighbour entered the parking lot, seeing me revved the car like mad. This person is someone who never listens to people. He already had a failed turbo, which was cleaned and repaired. Even after that, same practice.

[noopster]

Must confess that I wasn't aware that idling a turbocharged car was this essential. Most of my friends drive turbo diesels (and soe drive turbo petrols) so when I borrow their cars, they usually warn me to idle the car before starting and after stopping. Since I am a "petrol" head (literally) this hasn't been a natural driving habit for me.

But since my basement parking now has a steep incline that needs to be scaled, have got into the habit of idling about 30-45 seconds before starting off. I guess this habit will serve me well if and when I move to a turbocharged engine-powered vehicle.

[vnabhi]

Another article par excellence--rated 5 stars!

I was not aware of this precaution till I bought my Fiesta (petrol) 6 years back. There is a mention in the manual for cooling off the turbo for 30 seconds before switching off. I wasn't sure if that applied to the petrol Fiesta too, and hence posted a query on this forum. Based on the instantaneous responses, I came to know that it applies to the diesel model only, as the petrol Fiesta is not turbo-charged.

Nevertheless, I've made it a point to idle my petrol cars for around 15 seconds before logging off. And on the new Figo tdci in my garage, I've religiously inculcated the 30-second habit among my kids for both switching on and off.

While on this topic, I was surprised that the salesman from the dealer did not know about this entry in the manual, and thanked me profusely for educating him.

[SPIKE ARRESTOR]

Originally Posted by SS-Traveller

Most auto manufacturers don't recommend prolonged idling at cold start. There are a number of reasons why:

To add on to your point, an engine when cold has the maximum amount of friction losses. That makes idling when cold much more important.

Spike

[Rehaan]

Originally Posted by amolpol

..would basement parking allow for suitable time to cool down the turbo and keep it lubricated? Typically one has to stop and reverse their car in the tight spots which is done at idling rpms.

If you spend about a minute or more at <2,000 RPM at low loads, this should be fine.

Originally Posted by Mudhalaipatti

XUV comes with the start/stop option, where the engine switches itself off at thse signal. Does this mean, we should disable this function, to extend the longevity of the turbo?

When you're in traffic, chances are you are driving at <3,000 RPM. And if you every go above that its for a short burst. This in itself doesn't let the turbo heat up too much, so the start stop turning off the car in traffic is almost like you turning off the car after idling.

Originally Posted by ghodlur

I am surprised as to why the car manufacturers havent thought about automating this simple technique - Have some kind of a timer to allow the clutch/gear/accelerator to be used only after a minute of starting and dont allow the engine to shutoff unless idled for a minute.

See the link in the article to "Turbo Timer". Why they don't enforce this at start-up - probably because its not required, and it can be a huge inconvenience.

Originally Posted by ghodlur

Does the coking have an effect on turbo charged petrol engines too?

Yes. The turbocharger is essentially the same basic design, using the same lubrication, etc.

Originally Posted by SDP

Hayek sir, I believe the point is about having enough lubrication for the turbo rather than cooling down the turbo. The lubrication is dependent on whether the engine is running.

Actually the other way around! (Though they are closely linked).

If your turbo was relatively cool and the lubrication stopped (which is what happens when you turn off your engine) that wouldn't be too much of an issue.

If the turbo is hot and you turn off your engine (even if its spinning slowly by this time), the heat damages the now stagnant oil. Kind of a catch-22, as if the oil was flowing, it wouldn't get damaged -- but you can see that its essentially the HEAT thats the problem.

Originally Posted by Hayek

What is the definition of high loads - is it only high RPM, or would Bombay style stop and go traffic also be a high load?

Bombay style stop-go wouldn't really be high load, except perhaps the first 1 second when you release the clutch and move your car from a standstill.

High load is : climbing a hill, heavy acceleration, car full of people, etc.

Originally Posted by Vid6639

It's now embedded. Manson and Rehaan will agree with me

Secret confession: I idle my car for 1 full extra minute whenever you're around

Originally Posted by Jomz

How do cars equipped with start/stop technology .. like the latest BMW 3 series , deal with the one minute idling requirement for the turbos?

Answered above, but i'll add:

In cars with water-cooled turbos, the average temperature of the turbo is lower from the start, so its even safer than what i've mentioned in my reply above.

Originally Posted by karan561

But what after a high revving run if i approach the signal & the engine shuts down to save fuel would'nt it harm the turbo ?

Would be interesting to see if a higher limit temperature is also specified, after which the start-stop disables itself. Will wait to hear back from you, but i wonder if you'll be able to hit that limit!

Originally Posted by SS-Traveller

Most auto manufacturers don't recommend prolonged idling at cold start. There are a number of reasons why:

Excellent post. Add to that: environmental reasons (not like they really care at this point), but a warmed up engine will be a lot nicer to the environment to one thats just been started up. So the sooner you get up to operating temperature, the better it is for the environment.

Originally Posted by gandalf

So wouldnt driving the car for the initial 2 minutes and the final 2 minutes @ lower RPMs (below the turbo spooling levels) do?

Yes, thats a perfectly fine way to cool the turbo down!

cya
R