Has anyone that dislikes this feature disconnected the small battery in the trunk yet? If so, have you notice any change in the reported MPG on the trip computer. Jaguar claims an average fuel savings of 5% with the Eco Start/Stop feature.

 

The amount of fuel saved by this feature certainly varies enormously...depending on driving conditions. Stuck in NYC or LA freeway traffic is not the same as less congested rural situations. How much does it cost to replace the starter and starter battery? How much energy is required to produce and recycle the same? How much fuel will be consumed when you need to drive the car to and from the dealer to have such repairs conducted? Worse yet, a tow truck? I don't believe anyone (including the EPA) has conducted an all inclusive, comprehensive analysis on this matter.

This conversation brings to mind the days in the 1970's when interlocks were used to prevent cars from being started unless the seat belt were buckled. Yes, that actually took place....and people developed defeat techniques.

This is just the manufacturers and EPA playing "feel good" fuel economy games. BTW, emissions at idle are essentially zero. The exhaust flow rate is very low which means the mass of the emissions is also very low and the exhaust residence time in the catalyst is much longer resulting with very high catalyst efficiency. I'd venture a WAG (wild *** guess) that the emissions reduced in one year by the start-stop feature are less than those produced in 100 feet of driving at 70 mph (yes, this may be a bit hyperbole).

But, hearing this discussion and facing the 3.0 S/C will encourage me to hold onto my 2012 5.0 NA XF longer than I had anticipated. Many of these fuel economy initiatives may not be as productive as the EPA and manufactures believe. Again.....probably just "feel good" stuff. The 8 speed provides real fuel economy gains with no sacrifice in performance or drivability. The next elegant step probably should be weight reduction.

 

Good Post and well said...

 

This arises from a misunderstanding about how AC works. No, the AC compressor doesn't need to run continuously to deliver cooling. It rarely does so. The cycling if the compressor is controlled by a hi/lo switch (and an anti frost switch). The expansion valve determines the rate of pressure drop which affects how often and for how long the compressor runs.

The automatic climate control blends cooled air and heated air to deliver the required air temperature to maintain cabin air temperature at the selected level. The engine only needs to run when the cool air temperature rises to that temperature. Unless you select LO the air entering the cabin is mixed cooled and heated air.

Unless you have actually measured the temperature of the air coming out of the vents with the engine on and then off you likely have not experienced any actual temperature change. The human brain is not very good at judging temperature. The fan runs more slowly during engine off events due the slight voltage drop when the alternator isn't running. You likely sense this as a slight rise in temperature. If you were a sailor (as in sailboats) you would immediately recognize this as the cause. If there really is a noticeable increase in temperature of the air leaving the vents as measured by an AC test thermometer you should have your AC serviced.

The stop start system receives inputs from the climate control and restarts the engine as required.

 

Jaguar is moving to an aluminum line up as is Land Rover. This doesn't save as much weight as one might think but it does save some. For example the XJ weighs about the same as the smaller XF.

Fuel saving from stop start depends on traffic volume. It saves a lot in rush hour and almost none at 2AM.

When the new generation of smart hybrids arrives all of them will have stop start. Better get used to it.

 

Having now experienced BMW 's stop start in a manual transmission 116d I am even more impressed with the Jaguar system.

 

As the battery is not noted for strength, are there any issues with it going dead in a long stop in a traffic jam?

 

True, plug-in cars use mostly power plant generated electricity. Some of it may be using hydro or wind, but most of it is coal or gas.

But it takes a lot of electricity to make a gallon of gasoline. So much electricity, that you could have just driven the same distance as a gallon of gasoline with that electricity used to make a gallon of gasoline.

So you still come out ahead with plug ins.

 

Say whut? Just where do you consume electricity making gasoline?

 

Two batteries. If the stop start drains a battery it stops operating. No worries.

 

I've had a few BMW 3 series loaners that have this and I can't stand it. Is this on all XFRs or just 13 and newer? Disabling this would be my first mod.

 

Just to let you all know my dealership disabled the ECO mode on my 2014 XF. If I want to have the option again I'll have to take it back in. Don't forsee doing that in the near future though .... I absolutely hate it.

 

First I've heard of this. How did they do it? I'm still operating under the idea that it cannot be disabled!

 

Go to Ftype forum... post... eco mode default to off..
This is a recent post and on page 3 the answer is given.
Lawrence.

 

I had a '14 when I took my '12 in for service. The issue I ran into was when running the AC if I didn't have the brake pressed down good, when the AC came on, the car lurched forward when the AC compressor came on, re-starting the engine. Very disconcerting!

 

Must have missed something. All I see is another reference to the battery disconnect method. The problem with this is that it is a permanent disable (until you manually reconnect the cable). BMW can reprogram their system so that the default is off, but you can still enable the system by pressing the button. Basically making the button work the opposite way from how it was delivered from the factory.

I was hoping that Jaguar had come up with a software reprogram. Can tapau confirm what was actually done?

 

Sorry, only way I know of.
Lawrence.

 

So you think gasoline just magically appears in your gas tank?

Check google for more detailed information on how the world works. It will explain to you how gasoline is made from oil that first has to be located and then has to be removed from miles under the ground and then refined and then transported to your friendly gas station until it is pumped into your tank. Electricity is used throughout the process. Lots and lots of it.

You disappoint me.

 

Ahhhhhh……but in California, most of this "electricity" is generated by Hydro and wind …not so much solar…..definitely not coal.

 

Sorry, it was permanently disabled. Don't know what the dealership did, probably the disconnect from battery solution.