180+140=220 Bhp - Thoughts!

[darrude]

I was saying to a friend that the car has a 180BHP petrol engine and a 140BHP electric engine but that equals 220bhp which got me thinking of why that might be.

I have a theory, but know nothing about electric engines, and not that much about petrol engines, but here goes....

Petrol Engine outputs 180BHP at say 5,500 RPM.

Electric Motor produces 140BHP at 15,000 RPM (completely plucked this figure out of thin air).

Engine and Electric motor both drive into the gear box on the same shaft (complete assumption of how hybrids work), so when both are running there is no slip between them (assuming a clutch disengages engine when engine switches off).

So Max output of car is:

Peak Engine power 180BHP + Power output of electric at 5,500rpm (40bhp maybe), and hence we only 220bhp.

Or am I completely wrong and it is due to Battery discharge rate protection or something else.

Does it go Engine -> Electric motor -> Gearbox -> Wheels?

Or is it Engine -> Gearbox -> Electric motor -> Wheels? in which case the the power output of the electric motor could only be calculated by the input speed into the rear diff.....

So confusing, but the Geeky side of me wants to know though!

[ganzoom]

The micro-hybrid system in the IS300H is set up for economy first and fore most. The electric motor is there to compensate for the weakness of running the ICE unit using the Atkins cycle. The Battery pack in the IS300H is far too small to really allow the electric motor to deploy its full potential.

The Golf GTE is rated at only 200bhp but has a quicker 0-60 time than the IS and is a full Plug In Hybrid Vehicle (PHEV). The downside is many GTE owners report mpg figures of low 40's once the Battery pack on the GTE is drained, and the GTE becomes like a micro-hybrid like the IS300H.

On the BMW i8 PEHV uses all the potential offered by its electric motors...till the batteries die, and than it becomes essentially a mini-copper S, with the fuel economy to match.

The fundamental weakness of hybrid setups is the what happens to energy management when the Battery runs out. The IS300H only has a 1.5kWh of usable Battery charge, the i8 5 kWh. For comparisons my all electric Nissan Leaf has 20 kWh of usable Battery, a P85D Tesla has nearly 80kWh of usable Battery.

Of course the bigger the Battery the more initial charge but you have to carry a bigger weight penalty....So it's a balancing act for manufactures.

You can use brake a regen for recharging the Battery on the go, but the current setups on roads cars are very inefficient. However this season F1 cars have been using very complex energy recovery systems like the MGU-H units. These allow energy recovery from the exhaust system and therefore batteries in F1 car are very small (25kg compared to 50kg in the IS300H), and simply are buffers to allow the MGU-H unit to generate a continues supply of electricity to power the electric motors. In addition there is a separate MGU-K systems that recovers energy from brakes and can supple another lug of power for 33 seconds of a lap..Its all very clever stuff!!

So actually F1 cars these season are using electric motors nearly 100% of the time via the MGU-H setup, and using the MGU-K system to boost additional power. The power output of the ICE unit is around 600bhp, but the total output is around 750bhp... The electric motor in the IS300H is nearly as powerful as the motors used in F1 engines, it's just there isn't enough power generation in the IS300H to use the electric motor to its full potential :)

You can see just how much F1 engines this year depend on the electric motor by how uncompetitive Kimi's Ferrari become at the last race when his MGU-K unit failed and he was forced to retire. A few races prior Vettel's MGU-H system failed during qualifying and he qualified nearly at the back of the grid.

Toyota is running similar technology in its hybrid LeMans cars, so one day we might just see some of these highly efficient energy recovery system on road cars.....

The alternative ofcourse is to ditch the ICE units and instead just fit a massive Battery to power the electric motors, simple but practical solution. Or you could try to develop a crazily complex onboard electricity generator like a hydrogen fuel cell system ;)

[Tel]

My IS is best described as swift, particularly in Sport-mode when both on-board motors are in sync producing 231bhp from the

320 bhp available.The car certainly is "faster" my previous IS 300 & IS 250's & its smooth delivery surprises all non-hybrid peeps on most occasions & can give good economy if driven in Hybrid Mode.

Like Darren I need to understand why it feels more than the stated bhp!

Tel

[ToreOe]

The explanation to 180+140=220 that I find simple to understand, is that the NiMH Battery in the IS300h is capable of delivering up to 30kW of power. This equals to approx 40hp.

If you are using all the power from the engine to drive the car, the electric motor needs to get all it's power from the Battery. Thus, you end up with 180hp + 40hp = 220hp.

In reality, some of the power from the engine will be converted to electric power by the generator and used to drive the electric motor to alter the gear ratio. That is why the electric motor can use more power than the batteri alone can provide.

The sum of the power *sources* is 220hp, even though the sum of the maximum engine and motor output is more. And you cannot use more power than your power sources can provide.

-Tore