MHEV - mild hybrid - does it really improve MPG

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pcheaven
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MHEV - mild hybrid - does it really improve MPG

Post by pcheaven » Mon Aug 12, 2019 10:43 pm

Curious.

From what I have read landrover are very vague on the assistance / power that the 48v electric motor provides during acceleration to the ICE.

Does it help ?
How much does MHEV improve the MPG ?

Anyone know ?
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Re: MHEV - mild hybrid - does it really improve MPG

Post by Ian_S » Tue Aug 13, 2019 6:42 am

I would expect the gains are small as the battery is very small too. As far as I can see you get two benefits:

Faster engine restart, as the 48V system is more powerful than the traditional stop/start, which in turn allows them to turn off the engine and coast below 11mph as they can now restart whilst moving and apply electric torque.

Smoother initial pull away using some electric assistance.

I suspect both the above are more to do with reducing CO2 to keep the right side of tightening emissions levels rather than any significant increase in MPG. If the latter improves I doubt it will be by more than a few MPG. It will be interesting to see how well it works in stop/start traffic as in that scenario the 48v system battery won't get easily recharged.

Given that just about all manufacturers seem to be adopting MHEV, you can only assume it has enough CO2 benefit to keep them from paying the huge EU fines for missing CO2 targets., which I'm sure is the main driver for its adoption.
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Re: MHEV - mild hybrid - does it really improve MPG

Post by roadster » Tue Aug 13, 2019 9:56 am

Its only when you get full access to all the design aspects of an engine that you realize just where the savings in fuel are accumulated. Because of my commitment to buying a Rav4 hybrid I have studied their 2.5 litre petrol engine in some depth, this is all published and open design information from Toyota and probably much more accurate than anything that JLR will ever put out. Here is a listing of all the specialized features ( quite apart from the electrical drive and energy recovery).

1) Long stroke under square engine with high nominal compression ratio.
2) Included valve angle which has been reduced to increase intake swirl in combustion chamber.
3) Laser deposited inlet valve seat material to optimize flow over valve head.
4) Dual fuel injectors, low pressure into manifold, high pressure direct into combustion chamber, controlled to optimize complete combustion under different conditions.
5) Variable speed oil pump to avoid unnecessary pumping losses.
6) Electric water pump ditto.
7) Variable valve timing on both camshafts allowing engine to be operated on what Toyota refer to as the Miller cycle.
8) Full electronic control of coolant system ( thermostat and water pump) for more efficient warm up.

This all demands huge complexity both in manufacture and in control electronics and if it was any other company you might be very worried about reliability even before considering transmission and battery management controls. Toyota have decades of experience so I just hope they have got it right! Can JLR match this challenge …?
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Re: MHEV - mild hybrid - does it really improve MPG

Post by PedroT » Wed Aug 14, 2019 8:12 am

I agree that mild hybrid is simply a mechanism to sneakily comply (just) with latest emissions rules. I also believe this additional engineering makes for a far too complicated vehicle. I am probably going Petrol next month and in a few years time I’ll be going full electric ( once electric vehicles are proper) and charging infrastructure is fully in place.
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Re: MHEV - mild hybrid - does it really improve MPG

Post by pcheaven » Sun Aug 18, 2019 8:53 am

Hymn. When comparing manufactures mpg for my19 againts the MHEV variants. Seems there is a 10-20% increase and an expected much reduced co2
Not too shabby.

May wait for a phev variant though.
Orange DS HSE +toys
Gone : 2019 I Pace first edition
Gone : Velar D300 r dynamic HSE plus toys
Gone : D5 HSE Lux + a few toys
Gone : MY17 DS HSE Dynamic Lux with all the toys
Gone : Orange MY15 HSE


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