Hello,

 

I have a 1.2TSi engine with Start-stop system.

 

As I know an engine needs a little more fuel at start-up so I was wondering if start-stop system really is more fuel efficient since it

shuts down engine at every red light even just for a few seconds?

 

Is fuel economy really better if the engine shuts down just for lets say 10 seconds?

 

 

 

As I know an engine needs a little more fuel at start-up so I was wondering if start-stop system really is more fuel efficient since it

shuts down engine at every red light even just for a few seconds?

 

The engine will only shut down if the the driver lets, stopping the engine for just a few seconds is daft.

 

Is fuel economy really better if the engine shuts down just for lets say 10 seconds?

 

No, as stated in owners manual you need at least 20 seconds with the engine stopped to make a fuel saving.

OK, thanks for reply. Now I found it in manual - it says that if the engine shuts down the fuel economy is better after 30 - 40 seconds comparing to engine re-start.

 

So on average not much use of it at traffic lights I guess.

That all depends on the traffic lights - you know your local ones the best.  I have a set near me where I used to turn the engine off in my car-before-last (before I had experienced Stop-Start) because I knew that if I missed the change, I would be sitting there for 2 minutes.

I dont think it does much if anything to improve consumption as such. Its there as a means to drop a cars official CO2 rating as I gues they can somehow wrangle the fact that when a car is sat stationary without the engine on its not emitting any CO2 so helps reduce its average g/km output.

I dont think it does much if anything to improve consumption as such. Its there as a means to drop a cars official CO2 rating as I gues they can somehow wrangle the fact that when a car is sat stationary without the engine on its not emitting any CO2 so helps reduce its average g/km output.

I'd guess it's also to reduce emissions in congested areas therefore attempting to improve air quality in towns and cities.

I'd guess it's also to reduce emissions in congested areas therefore attempting to improve air quality in towns and cities.

 

Exactly.

All manfacturers have to run the same city & urban cycle (defined by european law) for quoting emissions figures (CO2 and mpg).

Most countries have tax incidentives for cars with <100 and <120g/km CO2.

During the cycle it is benefitial for the manufacturers to have a stop/start system as stopping the engine during the city cycle reduces the CO2.

This is the only reason why they include this function & other after treatment functions like DPF or SCR & energy recovery.

 

If you dont spend a lot of time in stationary traffic or driving in the city, you wont see much benefit from Stop/Start systems.

 

 

They could use the Intgegrated Starter Generator system (like the PSA group) which are fuel neutral afer stopping only for a few seconds but I guess there are lots of trade-off between this kind of system & traditional starting.

Edited 30 July, 201411 yr by Gabbo