Is a remap possible?

[ColinBarber]

6 hours ago, cachaciero said:

Now my 400 decelerating from 70 will often require a touch of brake to get the speed down to an acceptable level in the distance available under these circumstances I will often put it into B mode thus increasing  the deceleration and getting a little extra into the battery, as the stream speeds up back into D and touch the throttle, now I don't require much energy to get back to 70, the battery is well up and there is more than adequate electrical energy available to restore speed but the moment you touch the pedal the IC engine springs into life, burning petrol which does not need to be burnt,

Keeping it in D and applying a little braking would achieve the same thing provided the energy meter doesn't go off the regen scale. In fact in B, the fuel to the engine is cut so some energy is wasted overcoming the compression in the engine as it is turned over. 

The 400h has an older hybrid design. It cannot go that fast without the IC running otherwise the transmission would be damaged. Current gen systems allow running at 70 mph in EV - IC shut down.

[cachaciero]

6 hours ago, Herbie said:

There's a knack to driving a hybrid.

Indeed there is after six years with a Prius and the RX I am still learning.

Accelerate briskly to the desired speed and then very slightly back off. You should be able to run on battery for a while but remember, these are not electric cars and you'll only get a couple of miles by relying on the traction battery alone.

All the 'B' mode does is to increase engine braking

Which is technically a regen function and no different to normal braking.

and it's not a very efficient use of the system, which really relies on the use of regenerative braking for maximum efficiency. You get much more charge by braking and it's easy to prove. Next time you're on a long descent put the selector in B and watch the power meter, then put it in D and use the brakes - the power meter will move a lot further down the scale (indicating more charge going into the traction battery) when in D and braking, than in B.

You are correct but you don't appear to have tried the final test which is to brake in D and while still braking select B, you will see the power meter indicate even more negative energy and increased deceleration.I say negative energy because the energy may not all flow into the battery, if it is well up some energy, maybe all will be dumped into a dump resistor and the energy dissipated as heat. To use B is more efficient if the battery charge state is low enough to benefit from the extra energy other wise the only thing you are doing is to save the pads a little more.

The vast majority of braking is, or should, be done regeneratively by the hybrid system. The idea is to read the road ahead and brake gently. The regen brakes operate until the car is almost stopped (3mph if I remember correctly) and then the traditional hydraulic brakes take over. The only exceptions to this as far as I'm aware is when you have to anchor on in an emergency and the hydraulic brakes come on immediately, or when the traction battery is fully charged and can accept no more, then again, the hydraulic system takes over.

I suspect that it is more complicated than that,

Now here I am guessing because as i said before the required technical documentation is not available.

The braking system will be modelled in the Brake part of the ECU it will monitor pedal position and car speed amongst other things. Pedal position and speed will be equated to a demanded  total brake force . Available brake force will be the sum of regen force available plus braking force available from the pads. If regen force available is higher than the demanded force then regen will provide all the braking force otherwise the hydraulics will progressively take up the difference. Thats just for straight line braking AntiSkid and Stability Controls, individual wheels hence hydraulic control of individual mechanical brakes will add a whole new set of variables into this.

 

This is the reason why brake pads and discs last thousands of miles longer on a hybrid.

 

[Alan64]

My gs450h is a hell of a lot better on a long motorway spin than around town, the rx450h seems to give me a similar return either around town or on a country run

[flookyk]

My 2011 RX450h has averaged 29 mpg since getting around two and half years ago in mixed driving (the power is too tempting at times)

On the motorway it depends on the traffic and my driving, I have had it regularly up to around 38 average when travelling long journeys for holidays and taking it steady and once got a 15 mile trip to work at 47mpg following a lorry up the motorway to work at around 55mph.