GS 450h Sustained Performance ?

WSandME · October 29, 2017

I've had mine just over a week now and am very happy.

However, I've been thinking about the characteristics of this hybrid system. For 99% of driving, I can't see a problem, but...

Let's imagine I'm on the Autobahn. Start off with a full tank and hybrid Battery full.

Foot down and KEEP IT DOWN. Fantastic performance until the hybrid Battery is exhausted. So, will I find my top speed is limited below 155mph??? After all, I'll only have the ICE, and that will presumably be diverting some power to recharging the Hybrid stack?

How long between setting off at maximum performance before the hybrid stack is exhausted?

Before people get their dander up - I'm not being serious - just wondering

NemesisUK · October 29, 2017

My perhaps naive assumption is that the traction Battery power is there to reduce fuel consumption and provide low down torque, stop-start driving comfort. Once one drives at WOT all the power will be from the ICE and you'll not notice any significant reduction in Vmax

If my RC300h is anything to go by the traction Battery will last, perhaps 1.5 miles on electric alone and if in combination with the ICE it never depletes completely.

Britprius · October 29, 2017

Peter above is correct. Basically at high motorway speeds there will be little or no electric assist. The Battery display will remain at or about 5 blue bars.

On a slight downhill run the electric drive "may" kick in, but will turn off as soon as more power to the wheels is needed at that point the engine will power the wheels, and recharge the Battery. All this is done without any difference in the feel of the car as far as the drivers concerned.

John.

stevet · October 29, 2017

I’ve always wondered that if you do a 0-60 test then turn round and do the same will each run be slower as the Battery depletes?

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rayaans · October 29, 2017

57 minutes ago, Britprius said:

Peter above is correct. Basically at high motorway speeds there will be little or no electric assist. The battery display will remain at or about 5 blue bars.

On a slight downhill run the electric drive "may" kick in, but will turn off as soon as more power to the wheels is needed at that point the engine will power the wheels, and recharge the battery. All this is done without any difference in the feel of the car as far as the drivers concerned.

John.

Im not entirely sure if that is true.

The hybrid Battery is there is aid performance as well so will certainly be activated when flooring it at higher speeds. It won't just sit there doing nothing.

The total system output of the 4GS is 345ps at 6400rpm. It doesn't change with speed which would suggest its 345ps at 6400rpm at 70mph and at 20mph.

Otherwise it'd only be 296ps over a certain speed.

Britprius · October 29, 2017

1 hour ago, rayaans said:

Im not entirely sure if that is true.

The hybrid battery is there is aid performance as well so will certainly be activated when flooring it at higher speeds. It won't just sit there doing nothing.

The total system output of the 4GS is 345ps at 6400rpm. It doesn't change with speed which would suggest its 345ps at 6400rpm at 70mph and at 20mph.

Otherwise it'd only be 296ps over a certain speed.

Under acceleration things change, but at a constant high speed very little electrical power is used. The scenario that Sandro envisaged. In real terms the Battery has very little capacity.

The theoretical full capacity of the Battery is 1872 watt hours (a little over 1.75 kwh) 6.5 ah at 288 volts nominal. However the the usable capacity from 40% to 80% charge is only 748 watt hours (close to .75 kwh) 3 ah (amp hours) at 288 volts nominal. The electric drive motor "MG2 is rated at 186 hp or in electrical terms approximately 140 kw (746 watts = 1 HP). This can be driven by the Battery alone, but as the maths show the Battery would last a matter of seconds in this mode.

I do not know the rating of MG1 in generator mode, but I do know it is nowhere near 140 kw, but the power split device is around 72% to the wheels, and 28% to MG1 as a generator. The power produced can be fed directly into MG2 to assist the engine in driving the wheels. Or it can also be used to do this, and charge the Battery. If the power is used to drive MG2 the full power from the engine minus some conversion losses is available to the wheels.

Further electric motors in use are the virtual opposite to the petrol engine. The torque from MG2 falls off as it's revs rise. It has full torque at zero revs. Again I do not know what that figure is, but it is not unusual for the type of motor used to have 140% of design torque at zero revs.

John.

Hangie · October 30, 2017

I can add some personal experience.

When you are maxing car out (155mph) there is no usage from the Battery and you can drive it at that speed as long as you got petrol in tank :)

Some energy will be taken from the batteries during the acceleration but car will accelerate without it too - just a little bit slower I assume. Additionally at that speed any braking is charging batteries really quick. In my case driving at 155mph in normal DE traffic keep batteries topped up for whole time.

Mike Hartland · October 30, 2017

On a similar note, the top speed, as we know, is electronically limited to 155mph. Does anyone know what it would be if it were not limited?

stevet · October 30, 2017

7 minutes ago, Mike Hartland said:

On a similar note, the top speed, as we know, is electronically limited to 155mph. Does anyone know what it would be if it were not limited?

Whats the bhp without the electric assistance? The 245 bhp GS300 will do 148mph so I can't see the 450 doing much more than 155mph.

Britprius · October 30, 2017

The BHP figure for the engine on the GS450H is 296 or 298 BHP depending on where you get the figures from. It is electrically limited to 155mph.

The electric motor is rated at 186 HP, but this cannot be directly added to the engine output because of the transmission configuration, and the path the engine power takes to drive the wheels.

John.

mrfunex · October 30, 2017

Having touched the limiter a few times abroad in my old mk3 GS450h, which appeared to be set just below 160mph indicated, the acceleration was certainly trailing off by then! I’d imagine the top speed to be 170, given a long enough road.

For day to day driving, I’m pretty sure the GS450h was marginally quicker than my ISF, although certainly not once the IS has been wound up. Is the mk4 GS any quicker?

Hangie · October 30, 2017

My estimate would also be in 170mph (indicated) area. But then we need to remember max speed is not going to be sustainable as when (very quick) Battery will get depleted we will lose 50bph. For my needs 155mph is enough but I got one stubborn A8 (also limited I guess) on my tail and this few extra mph would be nice :)

royoftherovers · October 30, 2017

4 minutes ago, Hangie said:

My estimate would also be in 170mph (indicated) area. But then we need to remember max speed is not going to be sustainable as when (very quick) battery will get depleted we will lose 50bph. For my needs 155mph is enough but I got one stubborn A8 (also limited I guess) on my tail and this few extra mph would be nice :)

Krzysztof, in Surrey, the stubborn A8 will be a Police Car !! :):):)

Hangie · October 30, 2017

Do 155mph in Surrey and you will finish on the first page next morning as bloody maniac :)

In my case it was between Leipzig and Dresden which was perfectly fine with everyone and acceptable.

WSandME · October 30, 2017

In comparison, my '96 LS400, when I gave it a chance in Germany a few years back, managed an easy 150mph from its 290 ? hp, and that's a bigger older car.

Funny how quickly your exit comes up at that speed! Cost me a 40 km round trip to the next exit and back!

Linas.P · October 30, 2017

What I gather from US forums is that GS350/IS350 (same 2gr-fse) is just barely makes past 160MPH without limiter, same goes for Toyota Camry on custom ECU map (plus other mods). I struggle to find any info re: electric motor either working or not working after certain speeds, so it is hard to tell if electric motor assists the car on such top speed run at all (the only official statement is that "MG1 and MG2 will come on as needed depending on road conditions and other factors"). The only caveat is that GS450h has CVT, which if I am right has lower final gear ratio than 6 Speed Auto on GS350/IS350 (I believe something 3.27 vs. 3.9). Ballpark figure of ~160MPH seems to be it, though it would be very impressive anyway ... and you limiting factor would not be engine, but it seems CVT.

Britprius · October 30, 2017

Below is a link to a video of the GS450H against a BMW 350i. The interesting thing is if you keep your eye on the Battery condition, and use gauge at the bottom of the speedo the Battery gives assist all the way up to top speed, but is virtually fully depleted in the 30 seconds taken to achieve 260 kmh (161.6 MPH)

https://www.youtube.com/watch?v=7mEJAGw_nNU

John

WSandME · October 30, 2017

I had seen that video, but I hadn't noticed the Battery status. Pity it didn't show how much charge was recouped on deceleration, or whether that speed could have been maintained without Battery assistance.

My (imaginary) trip to the 'ring is enticing me :~)

Linas.P · October 30, 2017

Good video, though 260km/h on speedometer is NOT equal 161mhp, nor 260km/h for that matter. Don't know how on GS450h, but by speedo on IS250 is just not accurate (it meant to be not accurate). Real speed is 2 miles less at 30, 4 miles at 50, 6 miles at 70, 7 miles at 90... and when it showed 140MPH GPS speed was only 129MPH. If the same thing would be true for GS, at 161MPH, the real speed would be maybe ~148MPH.

This is because speedometer cannot show less speed by law, but can show more... so that is what they do on all cars.

Glover · October 30, 2017

Linas you're right. 260 kph is not 161; it's 161.551:-) Rough calc is 8km = 5miles.

Real speed varies from speedo to speedo; by law they are allowed to read up to 10% lower but never higher so at 30 the real speed could be anywhere between 27 and 30. My RX450 is doing a real 28mph at 30, my Yaris does a real 27 at 30. So using that equation an indicated 161 could be anywhere between 145 and 161.5

Glover · October 30, 2017

Sorry should have said an indicated 260kph could be anywhere between 145 and 161.5 in mph!

Linas.P · October 31, 2017

22 hours ago, Glover said:

Sorry should have said an indicated 260kph could be anywhere between 145 and 161.5 in mph!

Is that now what I have said?

23 hours ago, Linas.P said:

[...]real speed would be maybe ~148MPH.

This is because speedometer cannot show less speed by law, but can show more...

Britprius · October 31, 2017

I suppose this now brings up the question of "is the car limited to 155 mph?" or "Is the car limited to an indicated 155 mph?" and if so how does does the limiter system know the speed of the car?

John.

Glover · October 31, 2017

Not wishing to labour the point but a speedo can be accurate or read up to 10% less. The real speed could be 148 but it could be anywhere between 145.5 ( i.e. 10% less than 161.5) to 161.5. In practice because it is costly to calibarate speedos exactly most are inaccurate within the permitted tolerances and the accuracy can vary across the speed range e.g. a speedo might be 10% out at 30 e.g. it's reading 33mph but only 5% out at 60 e.g.reading 63mph (out being reading more than the actual speed). Either way it's legal providing it doesn't read less than the actual speed i.e. you can't be doing 30 and your speedo read 27.

Linas.P · November 1, 2017

That is correct... mostly. First of all I know that by the law speedometer cannot show less, but I don't know where 10% comes from. It might be right, I am just not aware of such thing - my point, I believe it can show more than 10% more. Second, there is quite good reason why car manufacturers would set speedometer to show as much exaggerated speed as legally possible. Why? Because on sportier cars it gives impression of faster acceleration and in case of top speed it can be deceptive as well i.e. "wow my car does 161 when it is limited at 155, my example must be lucky". Third, in all cars I had it was almost consistently off by 10% at 30MPH, but it varied at different MPH - kind of most accurate around 60-70MPH, but then way off after 90MPH... sometimes more than 10%.

@Britprius - that is good question. My assumption would be that ECU would read engine/gearbox revs. vs. calibrated wheel size and calculate it from there. But if that is the case, then there is no reason why speedometer is wrong, because modern cars (GS450h including) have electronic speedo and not mechanical ones, so the speeds comes from same ECU.

It is known that you can go faster than limiter if you have larger diameter wheels, because it would fool ECU to think you doing less speed than you are actually doing, opposite for smaller wheels. As such when having larger wheels you speedometer can actually show less MPH than what you are actually doing.

So my assumption is - Lexus knows that they speedometer is of by some margin and they set the limiter with that certain margin e.g. if car reaches 155MPH "real", when speedometer indicates 162MPH, then they will set limiter at 162MPH speedometer speed, which in turn would be equal 155MPH real. That is pure speculation - I guess the only way to find out is to get good GPS tracker and go to Germany. That is exactly how I got my 140MPH=129MPH "real" on IS250.