[a4anurag]

Originally Posted by amit_purohit20

The fuel saved in this period should he high enough to justify the early replacement of batteries which have a limited number of engine start cycles.

Also the engine idle time before switch off should also be optimized to avoid damage to the turbocharger. I wonder how Mahindra designed Micro Hybrid for a turbo charger engine. I mean how much time it takes in idle, neutral gear before the engine switches off using the Micro Hybrid technology.

I personally follow a minimum 30 to 45 second rule before switching off the diesel engine even though my vehicle has been driving slow in heavy traffic.

What M&M have done is jointly developed this with Bosch that was used in the Bolero first, later on the improved version was in Scorpio that gained attention. The Scorpio equipped with this feature get a better starter motor, better alternator and Battery for counteracting this frequent start and stop.

The Mahindra's start-stop system is linked to the crankshaft sensor sends information to the ECU which in-turn decided when to use the 'start-stop' system.

When the car is stationary and idling (No clutch pedal input with the gear in neutral), the engine waits for 5-10 seconds and then activates this feature and switches off the engine. The moment the drives depresses the clutch pedal and shifts the lever from N to 1st, the engine fires itself. Now the idling issue I feel is in question and I think there is a secondary method of cooling the Turbo in these start-stop equipped ones. AFAIK, water is circulated to keep the cooling happening when the engine is off or else oil itself is circulated. Shall check and see if I can get any information on this.

Originally Posted by rajneeesh

One question that comes to my mind is : what is the minimum duration before which one should wait before turning off the engine at red lights ? This will be different for Normally Aspirated petrol engines and the turbo charged diesels that are becoming increasing popular on Indian roads.

Originally Posted by arunphilip

The other aspect around 'different rules for NA and TC' is to also separately make allowances for turbocharged petrols that are gradually gaining popularity - this is because the temperature of exhaust gases in a petrol engine are higher, which will lead to higher heat soak in a petrol engine that is at standstill.

I'd say 50+seconds on the timer and it is good to switch off the engine at signals be it an NA or TC engine.

Originally Posted by wildsdi5530

Doesn't starting a car esp. naturally aspirated ones require a lot of fuel? Also I've noticed that if you switch off the A/C, when you restart it takes a while to cool again. Meaning more fuel again. Plus in Bangalore at least signals don't have a stop. It's always Go-Get ready-Creep. Never stop.

Starting any engine uses up lot more fuel than the amount used in idling. It also puts unruly load on the starter motor and battery.

Once the engine is switched off with everything OFF, the time taken to get everything up again will need some fuel + time.

Bangalore traffic is special

Originally Posted by rajeev k

Generally, turning off the engine is advisable, if the wait period is more than two minutes.

2 minutes is a long time in traffic to keep the car idling. If the timer is 50+ seconds then it is good to switch off the engine. Anything above 50 seconds is a waste of fuel IMO.

Anurag.

[rajeev k]

Originally Posted by a4anurag

2 minutes is a long time in traffic to keep the car idling. If the timer is 50+ seconds then it is good to switch off the engine. Anything above 50 seconds is a waste of fuel IMO.

The One minute rule for Turbochargers, needs consideration.

[amit_purohit20]

Originally Posted by a4anurag

When the car is stationary and idling (No clutch pedal input with the gear in neutral), the engine waits for 5-10 seconds and then activates this feature and switches off the engine.

Thanks for the information. 5-10 seconds seems a killer for the Turbo.

AFAIK, water is circulated to keep the cooling happening when the engine is off or else oil itself is circulated. Shall check and see if I can get any information on this.

Water circulation cannot happen because the waterpump is belt driven through the engine crankshaft pulley.

Engine lubrication pump should be again driven through the engine crankshaft. So if the crankshaft is not rotating when the engine is off then both water and Oil lubrication by force feed cannot happen.

Cooling the turbo by oil can be made possible through gravity feed. If they have a small cavity which can retain oil and gravity feed the turbo bearings then its possible.

[D C]

Originally Posted by a4anurag

2 minutes is a long time in traffic to keep the car idling. If the timer is 50+ seconds then it is good to switch off the engine. Anything above 50 seconds is a waste of fuel IMO.

Anurag.

If I keep idling with AC for a minute on a trip of 100 kms (approx), my fuel efficiency dips by 0.1. That means, if my fuel efficiency was at 15 kmpl (calculated for a 100 kms ride by resetting) and I keep the engine running with AC for a minute after the 100 kms, my fuel efficiency drops to 14.9 kmpl.
Source: Tried and tested successfully many times

However, I would let experts comment on the technical aspects of frequent switch off and switch on.

[Mr.ASG]

Originally Posted by a4anurag

The Mahindra's start-stop system is linked to the crankshaft sensor sends information to the ECU which in-turn decided when to use the 'start-stop' system.

The ECU also relies on data from the engine temperature sensor, Various environmental sensors, Clutch & Break pedal position sensors too.

In many start stop systems Integrated starter generators are used which combines starter & alternator into one unit. So power from the battery is used for starting & during running the battery can be recharged.

Originally Posted by D C

If I keep idling with AC for a minute on a trip of 100 kms (approx), my fuel efficiency dips by 0.1.

Engine will be least efficient at the time of idling & this is particularly true for petrol engines.

[extreme_torque]

I always switch off my car if the time is 45+ seconds which eventually becomes more than minute to account for the time when the traffic ahead starts to move and then you, after the light turns green.

[mi2n]

I have almost completely stopped shutting down my car at signals, unless it's an absolute traffic snarl. What I do though is turn off the A.C. while the car is idling to minimize load and fuel consumption at standstill. This being my first turbo diesel, I'm very weary about the turbo unit and want to keep it in good health. I also religiously follow the 1 minute idling rule while starting my vehicle and before shutting it off. Doing the opposite in traffic would make the entire exercise redundant in my opinion. Moreover, those 8 beeps before every start (Figo TDCi) takes more than 5 seconds during which the car behind me honks to glory. Keeping the Turbo and the battery healthy at the cost of a bit of fuel seems a fair bargain to me.

[sheldon4888]

Its a very tricky situation about shutting the engine at signals. My personal opinion is not to do the same it will only strain the major components like battery and starter motor. Overall if you see over a period of time the cost saving of keeping the engine running wont be much but if any of the other components fail be ready to shell out a huge sum to fix the same.
Also in diesel cars with turbo its not a good idea to experiment with the same though new generation cars dont necessary need this process to be followed but its always good to be on the safe side.
Regarding environment conservation if any one is gonna point out to than i will say there are many other ways to conserve the same.

[sumeshmani]

I came across this Autocar India video made with the support of Shell.
This video has an expert from Shell clarifying facts of improving efficiency.
He says, we should switch off the engine if the wait time is greater than 10 seconds. Yes, only 10 seconds.

I have shared this on another thread:
http://www.team-bhp.com/forum/owning...ml#post3685433

[ashwin.terminat]

This has been conclusively answered by Jason from Engineering Explained.

The gist: If your car is going to stay stationary for more than 7 seconds, you're better off turning off the engine.

https://www.youtube.com/watch?v=dFImHhNwbJo