cars with variable power output
Discussion
I wondered if there were cars out there that allowed the user to choose the performance level?
The E60 M5 has the M button for 400 or 500 bhp and I have a feeling some American cars have a valet setting that restricts performance. However I have no idea whether this is designed for general use or just the trip to the car park.
I just struck me that most of the time an engine map or no of cylinders used that gave adequate power but decent mpg would be fine but that sometimes another chunk of performance would be great.
Suspension would need to adapt and brakes would have to be good for the full power mode.
Say a 250 to 400 jump?
Anything out there?
The E60 M5 has the M button for 400 or 500 bhp and I have a feeling some American cars have a valet setting that restricts performance. However I have no idea whether this is designed for general use or just the trip to the car park.
I just struck me that most of the time an engine map or no of cylinders used that gave adequate power but decent mpg would be fine but that sometimes another chunk of performance would be great.
Suspension would need to adapt and brakes would have to be good for the full power mode.
Say a 250 to 400 jump?
Anything out there?
Ignoring the obvious.
I think having an electronic power restrictor is a good idea, it means you could lend your wife / kids / mum a 400bhp car but restrict it to say 150bhp.
If you want to only pay for say 200bhp but have access to another say 100bhp for overtaking the obvious answer is Nitrous Oxide, technically illegal on the road but I know several who have used it for many years.
Similarly several turbo cars have a limited "overboost" facility designed to aid overtaking and there are multiple aftermarket boost controllers which will hold different boost levels allowing you a max of say 5psi in the rain and say 15psi in the dry.
I think having an electronic power restrictor is a good idea, it means you could lend your wife / kids / mum a 400bhp car but restrict it to say 150bhp.
If you want to only pay for say 200bhp but have access to another say 100bhp for overtaking the obvious answer is Nitrous Oxide, technically illegal on the road but I know several who have used it for many years.
Similarly several turbo cars have a limited "overboost" facility designed to aid overtaking and there are multiple aftermarket boost controllers which will hold different boost levels allowing you a max of say 5psi in the rain and say 15psi in the dry.
If a car has a switch/mechanisms to produce variable outputs I believe the NEDC test to obtain co2/mpg figures uses the default one it's in when started?
So, I'm surprised more cars don't have cylinder deactivation/variable engine(/throttle) maps (i.e. a soft eco one where the turbo doesn't kick in)/mild hybridization with a small battery etc etc) to gain good figures.
So, I'm surprised more cars don't have cylinder deactivation/variable engine(/throttle) maps (i.e. a soft eco one where the turbo doesn't kick in)/mild hybridization with a small battery etc etc) to gain good figures.
Renovation said:
I think having an electronic power restrictor is a good idea, it means you could lend your wife / kids / mum a 400bhp car but restrict it to say 150bhp.
Have you ever seen a non-car person accidentally get more than they bargained for when they poke the throttle in a car much more powerful than their own? It's hilarious, and let me tell you, you don't usually need to apply a restrictor to make them take it easy 
As to the OP's question, well.. I'm sure you understand that a "500bhp car" is not making 500bhp all the time, and therefore is not consuming fuel as if it's making 500bhp all the time. It's only doing what's demanded of it by the pedal on the right, and so having different maps that restrict the peak power is not going to have any influence whatsoever on fuel efficiency in normal driving. It's not commonly done because unless your car is seriously overpowered and has no good traction control, it doesn't really help in any way!
Cylinder deactivation (see Audi, Daimler and increasingly other engines) is probably the nearest practically useful application.
danp said:
If a car has a switch/mechanisms to produce variable outputs I believe the NEDC test to obtain co2/mpg figures uses the default one it's in when started?
Correct. Note the recent trend for an increase in "Sport" buttons and a decline in "Eco" buttons - the "Eco" mode is becoming the default setting so that it's in play for the all-important NEDC!Very funny to those who jumped in with the obvious.
However you are still using an engine/software set up for maximum performance whether you use it or not. Otherwise no one would complain about about 20mpg as you could just go slower and get 60. Sadly it doesn't work like that. Drive an 8 cylinder car like Miss Daisy you you aren't going to get more than say 25mpg.
But with fewer cylinders used or possibly a different, leaner map (just a theory I've no idea if its actually possible) you could.
However you are still using an engine/software set up for maximum performance whether you use it or not. Otherwise no one would complain about about 20mpg as you could just go slower and get 60. Sadly it doesn't work like that. Drive an 8 cylinder car like Miss Daisy you you aren't going to get more than say 25mpg.
But with fewer cylinders used or possibly a different, leaner map (just a theory I've no idea if its actually possible) you could.
Edited by DKL on Sunday 21st September 23:32
The engine management isn't just a fixed thing, it's a huge and very complex map of settings. The car considers its operating condition and your demand, and goes for the most efficient solution. No modern car, whatever its power output, is "set up" for peak power when you're cruising around at 1/8th throttle. The injection strategy, valve timing and ignition points all move around to achieve as efficient a delivery as they can, there's no need to "change maps" to do this, all these different areas are included in the one map the car has already.
The reason you can't get 60mpg out of some firebreathing V8 is not because it's mapped incorrectly, and it's not anything a switch on the dash is going to solve - it's the fundamental characteristics of the engine, the compromises made in its design. Its layout, inertia, pumping losses, friction, cam settings, manifold designs, everything.. but rest assured that the OEM has already taken a few steps to make it not firebreathing and as gentle as possible when you've not got it pinned open!
Unfortunately you can't just leave behind half your engine or change its fundamental design when you don't need it.. widely variable valve timing and inlet manifold tracts are about as far as we've come in that respect, and then cylinder deactivation goes a step further.
The reason you can't get 60mpg out of some firebreathing V8 is not because it's mapped incorrectly, and it's not anything a switch on the dash is going to solve - it's the fundamental characteristics of the engine, the compromises made in its design. Its layout, inertia, pumping losses, friction, cam settings, manifold designs, everything.. but rest assured that the OEM has already taken a few steps to make it not firebreathing and as gentle as possible when you've not got it pinned open!
Unfortunately you can't just leave behind half your engine or change its fundamental design when you don't need it.. widely variable valve timing and inlet manifold tracts are about as far as we've come in that respect, and then cylinder deactivation goes a step further.
McSam said:
The engine management isn't just a fixed thing, it's a huge and very complex map of settings. The car considers its operating condition and your demand, and goes for the most efficient solution. No modern car, whatever its power output, is "set up" for peak power when you're cruising around at 1/8th throttle. The injection strategy, valve timing and ignition points all move around to achieve as efficient a delivery as they can, there's no need to "change maps" to do this, all these different areas are included in the one map the car has already.
The reason you can't get 60mpg out of some firebreathing V8 is not because it's mapped incorrectly, and it's not anything a switch on the dash is going to solve - it's the fundamental characteristics of the engine, the compromises made in its design. Its layout, inertia, pumping losses, friction, cam settings, manifold designs, everything.. but rest assured that the OEM has already taken a few steps to make it not firebreathing and as gentle as possible when you've not got it pinned open!
Unfortunately you can't just leave behind half your engine or change its fundamental design when you don't need it.. widely variable valve timing and inlet manifold tracts are about as far as we've come in that respect, and then cylinder deactivation goes a step further.
Fair enough, that sounds a reasonable explanation. Out of interest which models have cylinder drop?The reason you can't get 60mpg out of some firebreathing V8 is not because it's mapped incorrectly, and it's not anything a switch on the dash is going to solve - it's the fundamental characteristics of the engine, the compromises made in its design. Its layout, inertia, pumping losses, friction, cam settings, manifold designs, everything.. but rest assured that the OEM has already taken a few steps to make it not firebreathing and as gentle as possible when you've not got it pinned open!
Unfortunately you can't just leave behind half your engine or change its fundamental design when you don't need it.. widely variable valve timing and inlet manifold tracts are about as far as we've come in that respect, and then cylinder deactivation goes a step further.
What is the US valet mode then? This sort of thing
http://www.post-gazette.com/auto/2014/06/26/Dodge-...
Edited by DKL on Sunday 21st September 23:43
Have a bit of a Google, as I mentioned above some Audi and Daimler engines have it now. I seem to remember Cadillac using it for a while.
The Northstar V8 sort of had cylinder deactivation way back in the 80s, though for a different purpose. It was designed to be able to run without coolant, which it did by alternating between cylinder banks, running one while the other was air-cooled then swapping.
Valet mode is, well, just that - presumably included so you can make an interesting car far less interesting and less likely to be subjected to burnouts and joyrides on the way to the car park!
The Northstar V8 sort of had cylinder deactivation way back in the 80s, though for a different purpose. It was designed to be able to run without coolant, which it did by alternating between cylinder banks, running one while the other was air-cooled then swapping.
Valet mode is, well, just that - presumably included so you can make an interesting car far less interesting and less likely to be subjected to burnouts and joyrides on the way to the car park!
DKL said:
Very funny to those who jumped in with the obvious.
However you are still using an engine/software set up for maximum performance whether you use it or not. Otherwise no one would complain about about 20mpg as you could just go slower and get 60. Sadly it doesn't work like that. Drive an 8 cylinder car like Miss Daisy you you aren't going to get more than say 25mpg.
But with fewer cylinders used or possibly a different, leaner map (just a theory I've no idea if its actually possible) you could.
It takes the same amount of power do do what ever you want a car to do. So for a particular car to do say 60mph, it needs x bhp regardless of what the peak power available is. The extra losses an 8 cylinder engine (over say a 4) are what accounts for the lower mpg. Thats why shutting down banks of cylinders raises mpg.However you are still using an engine/software set up for maximum performance whether you use it or not. Otherwise no one would complain about about 20mpg as you could just go slower and get 60. Sadly it doesn't work like that. Drive an 8 cylinder car like Miss Daisy you you aren't going to get more than say 25mpg.
But with fewer cylinders used or possibly a different, leaner map (just a theory I've no idea if its actually possible) you could.
Edited by DKL on Sunday 21st September 23:32
Acceleration is a little different as the extra power can be used to accelerate more quickly (which uses more fuel). As others have said though, you can modulate your foot rather then pressing a button.
I'll probably get flamed for this, but thats one of the advantages of EV's. An electric motor doesn't anything like the same same losses when you have a high opeak powervs a low peak power motor. Thats why the Tesla Model S can have a 400+ bhp motor, yet also have decent economy.
The Honda Insight ( a really PH car if ever there...) has, in 'Econ' mode reduced power and torque (a third less I think) and also, strangely, reduced battery power and capacity - it only uses a percentage of the full charge.
It feels okay to drive in normal or sport modes, but is seriously gutless in econ.
Does that count?
It feels okay to drive in normal or sport modes, but is seriously gutless in econ.
Does that count?
98elise said:
It takes the same amount of power do do what ever you want a car to do. So for a particular car to do say 60mph, it needs x bhp regardless of what the peak power available is. The extra losses an 8 cylinder engine (over say a 4) are what accounts for the lower mpg. Thats why shutting down banks of cylinders raises mpg.
Acceleration is a little different as the extra power can be used to accelerate more quickly (which uses more fuel). As others have said though, you can modulate your foot rather then pressing a button.
I'll probably get flamed for this, but thats one of the advantages of EV's. An electric motor doesn't anything like the same same losses when you have a high opeak powervs a low peak power motor. Thats why the Tesla Model S can have a 400+ bhp motor, yet also have decent economy.
'I'll probably get flamed for this,' No, essentially that's all spot-on Acceleration is a little different as the extra power can be used to accelerate more quickly (which uses more fuel). As others have said though, you can modulate your foot rather then pressing a button.
I'll probably get flamed for this, but thats one of the advantages of EV's. An electric motor doesn't anything like the same same losses when you have a high opeak powervs a low peak power motor. Thats why the Tesla Model S can have a 400+ bhp motor, yet also have decent economy.
DKL said:
Very funny to those who jumped in with the obvious.
Ask a stupid question...DKL said:
However you are still using an engine/software set up for maximum performance whether you use it or not. Otherwise no one would complain about about 20mpg as you could just go slower and get 60. Sadly it doesn't work like that.
Very true, it doesn't. If you drive, say, a Ferrari gently you can bimble through town traffic like anybody else, or hold everybody else up at 35mph in an NSL. If you remap it deliberately badly, you can get it to do that at wide throttle openings, too. But, no matter how you do that, you are never going to get it to deliver 60mpg.Gassing Station | General Gassing | Top of Page | What's New | My Stuff