bhp v torque

[xtrailman]

Just to put some figures to the Lexus RX400h performance data: -
The petrol engine develops 211bhp at 5600rpm and 212ftlb torque at 4400rpm -
The electric motor at the front axle develops 167bhp at 4500rpm and 246ftlb torque at 0 to 1500rpm -
The rear electric motor develops 68bhp at 4610 to 5120rpm and 96ftlb torque at 0 to 610rpm -
However, because the respective values are achieved at different rpm, one cannot add all three sets of figures together to calculate the net overall performance. The actual maximum is 272bhp.

Lutz
I realise a petrol engine is more refined, but wouldn't a diesel engine be a better choice on paper.
I know there are merks and volvo engines that provide max torque at 1400 rpm or 1500 rpm, so they would give a very nice amount of torque upto and over 2K revs.
Do you know the reason for the petrol choice, and would you think a diesel would be a better choice, and finally out of a score of ten how do you rate the car at towing?

 

[otherclive]

So please correct me if im reading this wrong,by your reckoning Clive if you took the two stage turbocharging of your D5 it would still produce the same torque?Is this what your saying?The formula Berties using is correct but nowadays it doesnt really stand up.Even going back to the late seventys Cummins were offereing engines called custom torque, were HP was kept low (225) but the torque output was very high to the level were it matched the offering of the same engine but with a lot higher HP.With the addition of EDC the game has completly changed.

Seth you are correct, but as I said all that the turbo or supercharger does is put more air into the cylinder where the torque,power is generated. Fuelling maps are modified to accept the extra air. JohhnyG seems to be confusing turbo fitments with basic engine combustion characteristics.
I will be going back to petrol soon when we sell our caravan as for solo ownership diesels are getting too complex and costs of ownership are above those of a petrol if doing less than 20k miles. We will keep our small Note diesel that doesnt have a DPF and gives 60mpg without trying. But the main car will be petrol and the Lexus is on the list.

 

[Lutz]

Lutz
I realise a petrol engine is more refined, but wouldn't a diesel engine be a better choice on paper.
I know there are merks and volvo engines that provide max torque at 1400 rpm or 1500 rpm, so they would give a very nice amount of torque upto and over 2K revs.
Do you know the reason for the petrol choice, and would you think a diesel would be a better choice, and finally out of a score of ten how do you rate the car at towing?

The argument put forward by Toyota for choosing a petrol engine rather than a diesel was that the electric motors already provide ample low end torque. Any further increase would require a beefier transmission to cope with even more torque. Also, diesel engines do not lend themselves to constantly being switched on and off. A frequent stop-start function is easier to accomplish with a petrol engine.
I seem to recall that it is also easier to ensure that the ambient temperature of the traction batteries is easier to control with the running temperature of a petrol engine.
Having said that I believe since Toyota were the first to market a hybrid car Peugeot have, in the meantime, overcome the above issues and do offer a hybrid drive coupled with a diesel engine.
Hybrid has little or no advantage while towing as both the electric motors and the internal combustion engine, whether petrol or diesel, are working at near maximum load much of the time. Its big advantage is solo in a city traffic mode, where it achieves truly impressive fuel consumption figures.

 

[Gafferbill]

Lutz.......a genuine question. You have given the output of the electric motors fitted to your Lexus.The supply of electric current comes from the batteries via a charging system. How does that charging system work? Does it gather energy that otherwise would be wasted when braking the vehicle as in F1?

 

[Lutz]

Lutz.......a genuine question. You have given the output of the electric motors fitted to your Lexus.The supply of electric current comes from the batteries via a charging system. How does that charging system work? Does it gather energy that otherwise would be wasted when braking the vehicle as in F1?

I'm not too familiar with the charging system in detail, but I do know that the traction batteries are charged by the petrol engine in the same way as the starter battery, and, in addition, there is also a braking energy recovery system, as in F1.

ps: One indirect advantage of the RX400h when towing is its 300kg higher kerbweight compared with the non-hybrid RX350 variant.

 

[Surfer]

As this is mainly a caravan forum, the questions remains on whether hybrid or lectric cars would be suitable to towing a twin axle caravan through mountainous areas like Wales? Would a hybrid make it up Fish Hill without coming to a virtual stand still?

 

[Lutz]

As this is mainly a caravan forum, the questions remains on whether hybrid or lectric cars would be suitable to towing a twin axle caravan through mountainous areas like Wales? Would a hybrid make it up Fish Hill without coming to a virtual stand still?

Why shouldn't it? The maximum gradient of Fish Hill is 9.6% which is less than the 12% standard for which Lexus quote 2000kg max. towload for the RX400h.

 

[otherclive]

An electric car is years away if ever from towing a caravan unless fitted with additional energy sources such as fuel cells or a prime mover. But I have no doubt that the large Lexus hybrid would take a weighty van any where that you cared to go. Just look at its power output supplemented by the torque from the electric motors when required. These are highly engineered vehicles from the same company that bought us the land cruiser. The Lexus being petrol may rev higher than a diesel but that's not an issue given the silky smoothness of the engines.

 

[JonnyG]

So please correct me if im reading this wrong,by your reckoning Clive if you took the two stage turbocharging of your D5 it would still produce the same torque?Is this what your saying?The formula Berties using is correct but nowadays it doesnt really stand up.Even going back to the late seventys Cummins were offereing engines called custom torque, were HP was kept low (225) but the torque output was very high to the level were it matched the offering of the same engine but with a lot higher HP.With the addition of EDC the game has completly changed.

Seth you are correct, but as I said all that the turbo or supercharger does is put more air into the cylinder where the torque,power is generated. Fuelling maps are modified to accept the extra air. JohhnyG seems to be confusing turbo fitments with basic engine combustion characteristics.
I will be going back to petrol soon when we sell our caravan as for solo ownership diesels are getting too complex and costs of ownership are above those of a petrol if doing less than 20k miles. We will keep our small Note diesel that doesnt have a DPF and gives 60mpg without trying. But the main car will be petrol and the Lexus is on the list.

hi clive i am not at alll sure where you are coming from but alas somewhere you are drastically missing the piont.. the "all it doe is add air" you come out with is laughable. you need to knock " the all " off that statement. more air means more fuel can be adding more air more fuel more torque power BHP call it what you like. and my point i made is on the nail. they manipulate the max torque figures by giving max boost at below 2000 rpm. then the boost is dropped a few psi, dependant on what the manufacturer wants as its max BHP..so you can have,has an example 4 different makes all developing 250 ft/lb of torque at 1800 rpm all developing max power at 4000 rpm and all having differing max BHP..which the formula says shouldnt be the case,but the turbo psi changes all that...
Anyway dustydog, thanks to lutz's input on the electric motors torque,it would seem the lexus has an abundance of torque lowdown to make it a very decent tug,

 

[otherclive]

So please correct me if im reading this wrong,by your reckoning Clive if you took the two stage turbocharging of your D5 it would still produce the same torque?Is this what your saying?The formula Berties using is correct but nowadays it doesnt really stand up.Even going back to the late seventys Cummins were offereing engines called custom torque, were HP was kept low (225) but the torque output was very high to the level were it matched the offering of the same engine but with a lot higher HP.With the addition of EDC the game has completly changed.

Seth you are correct, but as I said all that the turbo or supercharger does is put more air into the cylinder where the torque,power is generated. Fuelling maps are modified to accept the extra air. JohhnyG seems to be confusing turbo fitments with basic engine combustion characteristics.
I will be going back to petrol soon when we sell our caravan as for solo ownership diesels are getting too complex and costs of ownership are above those of a petrol if doing less than 20k miles. We will keep our small Note diesel that doesnt have a DPF and gives 60mpg without trying. But the main car will be petrol and the Lexus is on the list.

hi clive i am not at alll sure where you are coming from but alas somewhere you are drastically missing the piont.. the "all it doe is add air" you come out with is laughable. you need to knock " the all " off that statement. more air means more fuel can be adding more air more fuel more torque power BHP call it what you like. and my point i made is on the nail. they manipulate the max torque figures by giving max boost at below 2000 rpm. then the boost is dropped a few psi, dependant on what the manufacturer wants as its max BHP..so you can have,has an example 4 different makes all developing 250 ft/lb of torque at 1800 rpm all developing max power at 4000 rpm and all having differing max BHP..which the formula says shouldnt be the case,but the turbo psi changes all that...
Anyway dustydog, thanks to lutz's input on the electric motors torque,it would seem the lexus has an abundance of torque lowdown to make it a very decent tug,

johnny
i don't deny that the turbo increases torque. I even mentioned the fuelling maps. But at the end of the day the engines ability to produce power is carried out within the cylinders and is governed by the laws of thermodynamics and physical engineering constraints. All the turbo does is add a greater air mass which allows a greater fuel mass to be burned. The equation is correct. Other things such as valve timings etc only go to modify the thermodynamic cycle and engine output parameters such as power and emissions and economy. Hence Lexus run to an amended Atkinson cycle which gives less power density but greater econmomy.

 

[xtrailman]

Lutz
I realise a petrol engine is more refined, but wouldn't a diesel engine be a better choice on paper.
I know there are merks and volvo engines that provide max torque at 1400 rpm or 1500 rpm, so they would give a very nice amount of torque upto and over 2K revs.
Do you know the reason for the petrol choice, and would you think a diesel would be a better choice, and finally out of a score of ten how do you rate the car at towing?

The argument put forward by Toyota for choosing a petrol engine rather than a diesel was that the electric motors already provide ample low end torque. Any further increase would require a beefier transmission to cope with even more torque. Also, diesel engines do not lend themselves to constantly being switched on and off. A frequent stop-start function is easier to accomplish with a petrol engine.
I seem to recall that it is also easier to ensure that the ambient temperature of the traction batteries is easier to control with the running temperature of a petrol engine.
Having said that I believe since Toyota were the first to market a hybrid car Peugeot have, in the meantime, overcome the above issues and do offer a hybrid drive coupled with a diesel engine.
Hybrid has little or no advantage while towing as both the electric motors and the internal combustion engine, whether petrol or diesel, are working at near maximum load much of the time. Its big advantage is solo in a city traffic mode, where it achieves truly impressive fuel consumption figures.

Thanks Lutz. Yes it makes sense now, stop start and city driving is more suited to petrol, and i suppose the car was designed with solo city driving in mind. Hybrids i find very interesting, along with the new F1 cars, which hopfully will push hybrid technology forwards at a faster rate.

 

[Dustydog]

May I thank everyone for all their words of wisdom. I now fully understand the Atkinson cycle and how a hybrid petrol electric match works so well.
Whilst I like the X5 it is expensive and higher mileages used than the Lexus and Toureg. Whatever I buy will have to last us 5 years or so.New cars every 3 years disappeared when I retired.
SWMBO drives to family in Birmingham every week. A round trip of 190 miles. Solo economy is important as indeed is towing the Wyoming. I need to examine the Toureg in more detail but at the moment believe the Lexus ticks all the boxes with lower mileages and price when compared to the X5.
If Kia had refined the mark 1 Sorento with better engines and mpg I'd buy one.

 

[Sproket]

DD .... How about a Isuzu ? The Isuzu D-Max engine is one of the cleanest powertrains available in the pick-up segment, with CO2 emissions of 194 g/km and class-leading fuel economy of 38.2 mpg*. This means the new engine meets stringent Euro5 emissions standards. This is a significantly re-engineered 2.5-litre twin-turbo common-rail diesel engine. Producing 163 ps (120 kW) at 3,600 rpm and 400 Nm of torque between 1,400 and 2,000 rpm. This engine delivers a 20% increase in power and 43% rise in torque, compared with the previous engine. & it has a 3.5 ton towing capacity I get 24mpg out of my 3.0 auto towing the van with over 100k on the clock ( but mine is nearly 10 years old now )

 

[xtrailman]

1400 to 2000 rpm ideal for towing. I would like that.
D5 Volvo is simular.

 

[seth1]

And to top it all of,i expect its got normal gearing to.

 

[otherclive]

1400 to 2000 rpm ideal for towing. I would like that.
D5 Volvo is simular.

2.4 litre D5 puts out 215ps with a really nice growl!

 

[Dustydog]

Lutz

If the Lexus gets stuck in the mud does the rear drive automatically kick in?
Will it get me out of a boggy field like Stowford!!

Thanks

 

[Lutz]

The short answer is yes. The rear wheel drive kicks in as soon as the front looses traction. Although the rear wheels are only driven electrically they should have adequate power to get out of a boggy field. I've never got stuck (yet).

 

[Dustydog]

Thanks Lutz

I wasn't sure how the rear electric motor interfaced with the front drive. Thanks for that.

 

[Humphrey]

Regarding the difference between Bhp and torque, in laymans terms, as explained to me many years ago, was that you think of 2 horses, one being a racehorse (Bhp), the other a dray (torque), line them up for a race (say quarter of a mile) naturally the winner will be the racehorse (Bhp),.Now line them both up again, now attach a one ton load behind each, the winner will be the dray (torque)