I have a P400 HSE. I most often drive in the city with the start/stop feature turned off, but there are definitely times when it's a helpful feature (e.g. we have drawbridges in Seattle that go up for boat traffic). While the system seems smoother than some others I have driven, this is a large, heavy vehicle and with city driving, I'm most often trying to make a quick left turn in a break in oncoming traffic, so any lag is too much.

 

Are you saying that when this extra torque is required, the super charger starts spinning or spins faster, forcing more air into the engine? More air would require more fuel. You said "under the impression." What gave you this impression, did you read about it someplace?

My impression, which is really just a guess, is that there is a electric generator/motor sitting between the engine and transmission. When you hit the brakes, the computer tells it to generate electricity. This causes drag, almost like engine braking. The electricity is stored in the battery. When the computer thinks you need extra torque, it draws energy from the battery and the motor generates torque.

But like I said, this is just a guess, I don't have any information one way or the other.

 

I have a D250 Defender 90

not only is there no start up lag from the (very much working - and always has) stop/start feature, I am getting >26mpg driving in London and managed 38mpg on a journey back from Wales to central London - including ‘useful’ speeds on the M4. Great engine, great vehicle - all round excellent experience.

 

I'm going have to assume you have the PHEV and not the MHEV.

 

It’s an MHEV

 

I also have a D250 90 (that's the 6 cylinder 3 litre diesel) and it is definitely a MHEV. I would concur with the no lag and high 20's mpg and some excitement at achieving mid 30's with a following wind.

 

I was only halfway being facetious. 38mpg is impressive.

 

Don't forget the British gallon is 25% bigger! Inflates their MPGs...

 

Side question to you all - does anyone know if you can run pure biodiesel in the modern JLR Ingenium Diesel engines?