Just a question here. I drive Swift Diesel. It has a turbo lag and the turbo kicks in at around 2000 rpm. So does that means that before 2000 rpm turbo isn't working at all or is it not rotating hard enough.
If my the last part of my drive say the last 2 kms have been slow in traffic and the turbo didn't get a chance to come into play, then in such cases can i turn off the enfine sooner than what i normally do i.e. gap of 30 secs.
This is not the real reason why you to idle for 30 secs before switching off. The turbo gets really hot because of high RPM at which it runs.
The engine should be running for the oil pump to work. To over come this problem, turbo timers are available which keep the engine running for specified amount of time even if you lock and leave.. the turbo timer runs the engine and switches the engine OFF after the specified time. thus keeping the turbo bearings lubricated and cool.
more so in a petrol as comp to a diesel. but principle is the same. easy on starting till warm and coast before shutdown especially if you ve been driving hard
where are such turbo timers available?
can you recommend where I can buy one in Bangalore?
Originally Posted by shazikon
This is not the real reason why you to idle for 30 secs before switching off. The turbo gets really hot because of high RPM at which it runs. Because of the high RPMS ( ~200,000 RPM) the bearing which holds the turbine gets superhot and even the lubrication gets very hot. The only wat the ball bearings ( ceramic or steel) can cool down is from the oil it feeds directly from the oil sump of the crank. while the engine is running the oil is circulating through the inlet to the ball bearings fed by the oil pump. when you suddenly stop the engine after a hard run, the bearings are still super hot and not yet cooled down and the oil supply is cut off - no cooling. Prolonged abuse of the bearings will burn the bearings and cause turbo failure. This is the reason why it is advised to keep the engine running so that the turbo bearings are fed with oil from the oil pump. The engine should be running for the oil pump to work. To over come this problem, turbo timers are available which keep the engine running for specified amount of time even if you lock and leave.. the turbo timer runs the engine and switches the engine OFF after the specified time. thus keeping the turbo bearings lubricated and cool.
when you start a turbo vehicle like your DI Bolero or the Scorpio you are supposed to idle for 30 sec and then move. While stopping, you are supposed to go a bit easy for a bit, just before coming to a dead halt, then idle for another 30 sec and then switch off.
I ve also been in doubt about this and have checked with several TBHP members who own Turbo vehicles and this is what I ve learned from them.
Originally Posted by Rough Square
But the trouble is - there is a sticker on my dash board which says idle for 1 minute before switching on and before switching off. Thats about 120 seconds.
Turbo starts spinning once you start the engine. As engine rpm rises, your turbo spins faster.
So when you do a cold start there is still a period where the turbo spins dry, but due to low speed there is no damage.
However if you start engine and then rev the engine, you are looking at turbo damage.
Sadly when you give your cars for service, none of the mechanics at any workshop(I have seen Tata Mahindra and Hyundai) idle the vehicle.
For them its full throttle from word go.
My understanding is like this:
On a cold engine I agree with what tsk is saying and hence religiously follow the 1 min idling before rolling off. I also follow the 30 second idling before engine shut-off when I know that the car is not going to be in use for at least one hour.
On signals, what green horn has said is what makes sense (about staying at low RPM's) and I follow the same procedure. On a warmed up engine - the engine oil is hot and at the viscosity it's supposed to be at (Hence coming into effect quicker). I see no harm in killing the engine at signals. I just ensure i start about 10 seconds before it goes green.
Last edited by viper_711 : 19th August 2008 at 15:14.
viper its nothing to do with viscosity.
when engine is shut off, the oil pump stops and no oil is sent to turbo.
So if you were at revs where turbo was spinning fast, when you switch off your turbo will run dry for more time.
If you idle you allow turbo to come to a slower speed. So when you shut off engine, oil supply stops and slowly turbo comes back to 0.
At full boost I am told turbo's can touch 20,000rpm
The following BHPian Thanks tsk1979 for this useful post: