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-   -   Do all Turbos require idling before shut-off? (https://www.team-bhp.com/forum/technical-stuff/17463-do-all-turbos-require-idling-before-shut-off-8.html)

Palio MJD's manual says no need to idle while starting the day, but recommends idling before switching-off.

BTW, what do we do when we stop at traffic signals?
Say, a 2-minute signal - switch off after 30 seconds and crank 30 seconds before green ??

- it would drain the battery faster
- why would you want to unnecesarily cool the turbo when it's already hot and charged, and you would be needing it when the signal turns green?

How many such signals do you encounter? Here in Chennai on the roads I commute daily, there are two traffic prone stretches where such 2 minute stops are APLENTY. I wouldn't want to do this often. The only time I might do this is when the road is blocked for more than 15 minutes to allow VIPs to pass :D

No, the air is injected onto turbine side. This is to achieve higher turbo rpm inspite of transient lower exhaust energy. Higher revving turbo means better air supply through higher rpm of compressor wheel.

This thread is just the opposite of this one: http://www.team-bhp.com/forum/techni...pollution.html

As a First Diesel Car Experience, i started idling 30seconds religiously, if i have to goto ATM, i used to idle for 30seconds, switch off the engine, goto ATM, come back, then again idle for 30seconds and then move, this had become nuisance and i never switched off the engine in any signals, all these returned me only 11.8 kmpl mileage on my indica.

Now this is what i do, Morning when i start the car, i idle for 30seconds, then drive slowly for 3-4km until the temperature gauge reaches in the center, then if i had to switch-off the engine in middle, i slow down 1-2km before (dont hit above 2k RPM), then i just idle for 10seconds and switch-off the engine, Again when starting the engine (when hot), i only idle for 10seconds, now i want to know what i am doing, is it technically correct ?
Because now i get a mileage of 13.5 in bangalore traffic with 70% AC ON.

I never really follow the idling before starting/stopping deal on either petrol (although I don't believe the petrol vehicles I've driven had a turbo) or diesel vehicles (all of the diesel vehicles I've used regularly had turbos) and I haven't had a problem yet. 7 years without a problem on the Maruti Suzuki Esteem Di 2004 and 8 years without a problem on the 2002 Maruti Suzuki Zen are testimonies to that. One could say that slowing down while entering a residential area despite having the air conditioner running reduces the engine load enough and the rpm is quite low at up to 2,000 rpm (even these residential areas have uphill travel!). Idling wastes fuel and, unless you have to go uphill, you might as well get started as there's almost no hard driving that one can do when leaving a residential area during most of the day.

Sindabad, I maintain air is injected at the compressor wheel!
Could you point me to some reference material that supports what you say?

Yes Anup you are right, it is indeed injected onto the compressor wheel.

Esteem Di and Zen both do not have a turbo in their diesel avatars!

Surprising that GTO pointed to this thread in his review of the Quanto. I did not find a conclusive anwer to the question, is it requried to idle the turbo vehicles.

Here is my take and something which I have followed religiously for over 6 years in my Indica DLG. When I start the car, I idle it till the time I put my set belt on, then the googles and then adjust the radio and then wait to see the surroundings. Does this take the whole minute? I am sure it does as I ensure I do all of these slowly. My commute to office takes me anywhere between 30-45mins and in moderate to heavy traffic and there is only one signal which lasts a little longer than two mins, I ensure to switch the engine off only when I am close to the signal and not far from it, coz the further I am from the signal, the sooner it is to turn green and the exact opposite if I am closer to the signal. After reaching office, the car is again idle for a minute while i pick up my laptop bag, remove googles, seat belt adjust shirt etc etc... (not necessarily in the same order).

Now, the Indica DLG does have a sticker which states to idle the car while starting and before stopping.. so I see no reason not to follow it.

Sorry for the long post and in an old thread....just my few cents

I follow the 1 min idling rule when shutting off the engine in my Rapid, drive very low throttle for about 5 mins after first turning the car on.

The reason for this is that the exhaust manifold after going through the turbo is still very hot, hotter than the turbo infact, coming to idle after high throttle the exhaust gas temperature drops by 400 deg C or so.

The added thermal mass of the exhaust manifold and pipe maintains the higher temperature longer than the turbocharger which is oil cooled. When you turn of the engine instantly after a drive at more than idle, the heat from the exhaust pipe flows back into the turbo charger which is cooler. This isn't a problem when the engine is running as the oil cooling removes the heat effectively, but if the engine is stopped the oil cooling is also stopped leading to very high temperature of the turbo (thermal mass of turbo is negligible compared to that of entire exhaust system), this isn't a problem for the metal parts but for the seals which can only take low temperature (150 deg C typically).

You all know what happens once the oil seals fail in a turbo. This is the most common cause of turbo charger failure. Please don't turn of your engines without idling for atleast 30 seconds.

Cheers,

P.S Have looked into this in detail thanks to some project at work. :)

I spoke with a TBHP member recently who works with automobile turbos and asked him this exact same question.

He said to me that turbo and engine technology has advanced so much that manufacturers are confident enough to put the stop-start technology into turbo engines. They have tested it and he says the average engine life was shortened by a span of maybe 20,000 km over a testing life of 500,000 km. Ok, even assuming 25k over 500k is a 5 percent decrease in engine life.

Obviously this applies to the more modern engines and not something that is ancient. Therefore, if the manufacturer asks you to follow idling, then do so religiously.

In the event you are not asked to do so, follow a sensible procedure. At the start and end of the day let it idle for 30 seconds to one minute. If you have done a long hard high speed drive let it idle. The whole reason for this is to let the engine have identical temperatures all over. Otherwise you tend to have localized hot and cold spots, which is a long term problem.

Idling before shut-off is largely if not all a thing of the past.
If your manual doesn't mention it, you don't have to it. You can, but I doubt it is really useful or does anything to the life of the turbo.

I've had several turbo charged car, never idled before shutting down.

On many large marine diesels the standard operating procedures might still call for idling of several minutes before shutting down, especially after running at full power at long duration. The main issue is temperature, or rather to get a relatively even temperature throughout the turbo housing, bearing assembly etc. As turbo's on these very large diesels are very big, they have a lot of material, ie it takes a little longer for the temperature to come down evenly.

On car diesel/petrol engines the turbo's are much, much smaller and design and materials have made a tremendous improvement over the last two decades. Thus doing away with the need for idling before shut-off. I've never come across it in a manual of any of my cars. All my company cars, Audi, Mercedes, Ford, Volkswagen, Volvo had turbo's.

Jeroen

Completely agree with what you say.

Just wanted to add that petrol exhaust temperatures are much higher than diesel and those engines always require idling.

The fiat mjd´s require idling for sure as the number of cases with oil in the intercooler is massive.

Cheers,