RE: Rodin Cars introduces V10 as bonkers crate engine
Discussion
Caddyshack said:
Torque is a measure of work done as in lb ft and horse power is just torque multiplied by a set figure so I always thought that torque is the actual figure as in low torque you need very high revs to get the power and high torque often means lower revs - my lorry only revs to 3000 rpm but produces high torque to lug stuff…I suppose it doesn’t accelerate fast but that’s more to do with weighing 7 tons?
I don’t mean this as an argument, I just have an enquiring mind about this.
What accelerates a car is the force at the contact patch of the tyre divided by the mass of the car.I don’t mean this as an argument, I just have an enquiring mind about this.
The force at the contact patch is a function of the turning force at the drive shaft multiplied by the diameter of the wheel.
The turning force at the drive shaft is a function of the torque of the engine multiplied by the gearing
SO torque at the engine is the force that is developed at the tyre but significantly what is developed at that tyre depends on the gearing.
if you can rev the engine higher with the same torque you can gear to develop more force at that contact patch at the same wheel speed
The measure of torque and revs can be expressed as power.
Two cars, one with 100HP, one with 500HP both with flat torque of 200nM. Both travelling at 40 MPH geared to be at the start of the flat torque 'curve'. When they floor it, the higher power car will develop much more force at the tyre than the lower powered car and thus accellerate much quicker even though they both have exactly the same torque.
Problem is, developing torque becomes harder at higher revs, especially in normally aspirated engines as your attempting to get the same amount of fuel/air into the cylinder in a shorter and shorter time. Historically, dynamic effects in induction & exhaust would be used but they would resonate around certain designed rev ranges producing engines with very peaky torque curves meaning high BHP cars are often associated with engines with poor torque characteristics.
You can increase the cylinder capacity to create more torque but larger cylinders are even harder to fill at higher revs, you can go multiple smaller cylinders, or you could use a turbo to increase cylinder filling. At the end of the day, the force at the contact patch is only developed from the Brake Mean Effective Pressure on top of the piston.
So, in a nutshell, Torque is a fairly pointless figure to use to compare two engines without considering how its developed over the rev range, Power is almost as bad a comparison but at least it does consider the speed of the engine but as its a peak figure you again need to know how its developed over the rev range.
Given the lorry example, of course you could use a low torque engine to move the same load but it would just have to spin very fast and would probably be much more expensive, less efficient and less reliable.
EV performance of course is changing the field. These are motors that can develop high torque at very high RPMs but more significantly over a very large rev range giving high accelerative force at the tyre consistently as the vehicle accelerates.
Edited by Gary C on Saturday 20th April 08:44
Gary C said:
legalman58 said:
Very pretty- but in the real world unless you are as rich as Jeff Bezos will you really want to rev the engine as high as 8500 to get 391 ft pounds of torque - and we all know it is torque that produces acceleration where BHP is relevant for a high top speed?
Not another one who doesn't understand the relationship between power and torque.Starting at first principles, acceleration is the addition of kinetic energy, that being defined by the mass and the square of the car's speed.
The calculation of the power required to accelerate the car is therefore 6 bhp per ton per mph per g.
That is a universal formula that covers the acceleration of any vehicle on a flat road, ignoring any additional power required to overcome drag and rolling resistance.
It also says that the power required to accelerate a car of fixed mass at a fixed g value is directly proportional to road speed, starting from zero power at zero road speed.
The instantaneous rate of acceleration is therefore directly proportional to the instantaneous torque at the driven wheels.
The statement that 'torque that produces acceleration' is correct.
It needs to be caveated though, by saying that the power output is a measure of how well the car can sustain that torque as the road speed rises.
It's worth saying it again in different terms, the rate of acceleration is the instantaneous power divided by the road speed.
This engine will have a connection to the wheels via a gearbox and final drive (obviously).
This connection (assuming no clutch slip) forces the engine to be at a certain rpm at a certain road speed.
If that road speed corresponds to a dip in the engine's torque curve (and thus a dip in the ratio between instantaneous power and road speed) then at that point in time, the g value, i.e. the acceleration felt, will be lower.
For NA high-revving engines this has always been a talking point.
How to fix it?
Reduce the car's mass.
Add additional gears to keep in the torque rich, AKA power, band.
Add torque fill at lower engine rpms with electric assistance.
Legalman58 is right in that the engine will most likely not feel that fast unless its full rev range is used or it is installed in a very lightweight car where the instantaneous power to weight ratio is always high enough to result in a decent g value.
Problem is of course that that means way too much power at low road speeds...exciting or problematic, depending on your perspective...
At some point, the drag on the car will also start to become relevant in the discussion, as the power demand for that increases with the cube of speed. Ultimately it's the peak power power rating of the engine that will determine the top speed when there is insufficient power to overcome the drag.
The power demand to overcome rolling resistance is not relevant in this discussion because it remains about two orders of magnitude lower than 1g acceleration, regardless of road speed, and can be calculated using a rule of thumb of 6 bhp per ton per 100 mph.
I wonder what it weighs ? Very nice piece of work - looks to be a structual engine too so you'd need some kind of cradle to do a 'normal' install with it.
They need to post up a price and what you do about an ECU, calibration etc as I suspect that will be extra........
Also even in a kit car IVA type of build you still need to pass an MOT emissions test, does this engine do this ?
They need to post up a price and what you do about an ECU, calibration etc as I suspect that will be extra........
Also even in a kit car IVA type of build you still need to pass an MOT emissions test, does this engine do this ?
legalman58 said:
Very pretty- but in the real world unless you are as rich as Jeff Bezos will you really want to rev the engine as high as 8500 to get 391 ft pounds of torque - and we all know it is torque that produces acceleration where BHP is relevant for a high top speed?
I stopped buying Ferraris a long time ago as a matter of principle after I was charged £2,500 for 2 head gaskets for an admittedly old V12 I was having re built
My latest Sunday toy arrives in 2 weeks- and the engine is a lovely lazy Yank V8- producing 500 ft pounds of torque at only 1600 revs
I was speaking to the Bodyshop owner when he was spraying my car- and he showed me 2 Ferrari wing mirrors for a normal Ferrari ( as opposed to a very rare or very old classic Ferrari)
The cost of just buying the 2 wing mirrors was more than the cost to me of buying and having shipped from the USA to the UK my entire engine and gearbox!
Sorry but I cannot get excited about cars that will cost a fortune to run
Clarkson was so right when he once said words to the effect that when you drive a Ferrari part of you is always terrified that it may have a mechanical issue that will cost you one or two kidneys
Agreed to all, I was about to say the same. I stopped buying Ferraris a long time ago as a matter of principle after I was charged £2,500 for 2 head gaskets for an admittedly old V12 I was having re built
My latest Sunday toy arrives in 2 weeks- and the engine is a lovely lazy Yank V8- producing 500 ft pounds of torque at only 1600 revs
I was speaking to the Bodyshop owner when he was spraying my car- and he showed me 2 Ferrari wing mirrors for a normal Ferrari ( as opposed to a very rare or very old classic Ferrari)
The cost of just buying the 2 wing mirrors was more than the cost to me of buying and having shipped from the USA to the UK my entire engine and gearbox!
Sorry but I cannot get excited about cars that will cost a fortune to run
Clarkson was so right when he once said words to the effect that when you drive a Ferrari part of you is always terrified that it may have a mechanical issue that will cost you one or two kidneys
GT9 said:
Gary C said:
legalman58 said:
Very pretty- but in the real world unless you are as rich as Jeff Bezos will you really want to rev the engine as high as 8500 to get 391 ft pounds of torque - and we all know it is torque that produces acceleration where BHP is relevant for a high top speed?
Not another one who doesn't understand the relationship between power and torque.Starting at first principles, acceleration is the addition of kinetic energy, that being defined by the mass and the square of the car's speed.
The calculation of the power required to accelerate the car is therefore 6 bhp per ton per mph per g.
That is a universal formula that covers the acceleration of any vehicle on a flat road, ignoring any additional power required to overcome drag and rolling resistance.
It also says that the power required to accelerate a car of fixed mass at a fixed g value is directly proportional to road speed, starting from zero power at zero road speed.
The instantaneous rate of acceleration is therefore directly proportional to the instantaneous torque at the driven wheels.
The statement that 'torque that produces acceleration' is correct.
It needs to be caveated though, by saying that the power output is a measure of how well the car can sustain that torque as the road speed rises.
It's worth saying it again in different terms, the rate of acceleration is the instantaneous power divided by the road speed.
This engine will have a connection to the wheels via a gearbox and final drive (obviously).
This connection (assuming no clutch slip) forces the engine to be at a certain rpm at a certain road speed.
If that road speed corresponds to a dip in the engine's torque curve (and thus a dip in the ratio between instantaneous power and road speed) then at that point in time, the g value, i.e. the acceleration felt, will be lower.
For NA high-revving engines this has always been a talking point.
How to fix it?
Reduce the car's mass.
Add additional gears to keep in the torque rich, AKA power, band.
Add torque fill at lower engine rpms with electric assistance.
Legalman58 is right in that the engine will most likely not feel that fast unless its full rev range is used or it is installed in a very lightweight car where the instantaneous power to weight ratio is always high enough to result in a decent g value.
Problem is of course that that means way too much power at low road speeds...exciting or problematic, depending on your perspective...
At some point, the drag on the car will also start to become relevant in the discussion, as the power demand for that increases with the cube of speed. Ultimately it's the peak power power rating of the engine that will determine the top speed when there is insufficient power to overcome the drag.
The power demand to overcome rolling resistance is not relevant in this discussion because it remains about two orders of magnitude lower than 1g acceleration, regardless of road speed, and can be calculated using a rule of thumb of 6 bhp per ton per 100 mph.
swisstoni said:
I’m reminded of the piston engined fighters that arrived close to the end of WWII. State of the art. Magnificent.
But too late to have any real impact on the war and soon to be supplanted by jets.
Very true, and yet it's the piston engined ones that are highly prized by collectors and that still draw emotions from spectators who weren't even born when the switchover happened nearly eighty years ago. As impressive as the jets can be, I think most people would rather see a Spitfire in action.But too late to have any real impact on the war and soon to be supplanted by jets.
thegreenhell said:
swisstoni said:
I’m reminded of the piston engined fighters that arrived close to the end of WWII. State of the art. Magnificent.
But too late to have any real impact on the war and soon to be supplanted by jets.
Very true, and yet it's the piston engined ones that are highly prized by collectors and that still draw emotions from spectators who weren't even born when the switchover happened nearly eighty years ago. As impressive as the jets can be, I think most people would rather see a Spitfire in action.But too late to have any real impact on the war and soon to be supplanted by jets.
The torque / power misunderstandings are annoying.
You can’t tell anything about how a vehicle accelerates from the torque the engine produces, but you can from the power.
Or, to put it another way, the torque that the car exerts at the wheels at a given speed is a function of engine power, not a function of torque.
You can’t tell anything about how a vehicle accelerates from the torque the engine produces, but you can from the power.
Or, to put it another way, the torque that the car exerts at the wheels at a given speed is a function of engine power, not a function of torque.
Guybrush said:
GT9 said:
Gary C said:
legalman58 said:
Very pretty- but in the real world unless you are as rich as Jeff Bezos will you really want to rev the engine as high as 8500 to get 391 ft pounds of torque - and we all know it is torque that produces acceleration where BHP is relevant for a high top speed?
Not another one who doesn't understand the relationship between power and torque.Starting at first principles, acceleration is the addition of kinetic energy, that being defined by the mass and the square of the car's speed.
The calculation of the power required to accelerate the car is therefore 6 bhp per ton per mph per g.
That is a universal formula that covers the acceleration of any vehicle on a flat road, ignoring any additional power required to overcome drag and rolling resistance.
It also says that the power required to accelerate a car of fixed mass at a fixed g value is directly proportional to road speed, starting from zero power at zero road speed.
The instantaneous rate of acceleration is therefore directly proportional to the instantaneous torque at the driven wheels.
The statement that 'torque that produces acceleration' is correct.
It needs to be caveated though, by saying that the power output is a measure of how well the car can sustain that torque as the road speed rises.
It's worth saying it again in different terms, the rate of acceleration is the instantaneous power divided by the road speed.
This engine will have a connection to the wheels via a gearbox and final drive (obviously).
This connection (assuming no clutch slip) forces the engine to be at a certain rpm at a certain road speed.
If that road speed corresponds to a dip in the engine's torque curve (and thus a dip in the ratio between instantaneous power and road speed) then at that point in time, the g value, i.e. the acceleration felt, will be lower.
For NA high-revving engines this has always been a talking point.
How to fix it?
Reduce the car's mass.
Add additional gears to keep in the torque rich, AKA power, band.
Add torque fill at lower engine rpms with electric assistance.
Legalman58 is right in that the engine will most likely not feel that fast unless its full rev range is used or it is installed in a very lightweight car where the instantaneous power to weight ratio is always high enough to result in a decent g value.
Problem is of course that that means way too much power at low road speeds...exciting or problematic, depending on your perspective...
At some point, the drag on the car will also start to become relevant in the discussion, as the power demand for that increases with the cube of speed. Ultimately it's the peak power power rating of the engine that will determine the top speed when there is insufficient power to overcome the drag.
The power demand to overcome rolling resistance is not relevant in this discussion because it remains about two orders of magnitude lower than 1g acceleration, regardless of road speed, and can be calculated using a rule of thumb of 6 bhp per ton per 100 mph.
Big Thank You to the two posters who took time to type an easy to understand explanation, it has helped me a lot.
Guybrush said:
Yes, just to reinforce, in most situations (on the road particularly), low down torque is more important if you want to get a move on. An example comes to mind, I had a sports tourer bike whose torque was twice as much at 2000 rpm as a Yamaha R6 at 10,000 rpm, so in most instances I was off in the distance before the R6 rider had changed down two or three years to get the engine sufficiently stoked up to get moving. After a while of course, the R6 would catch up - if the road was long and straight enough.
Two or three years !Thats one slow change.
Of course the R6 rider should be riding with the engine spinning much faster all the time rather than languishing at low revs. An RX8 is a prime example of a car that should be kept at unusually high revs more of the time but the turbo which can fill cylinders at higher revs can also over fill them at lower revs and people just don't seem to want to rev an N/A engine these days.
Me, I love them. The 4AGE in the MR2 was perfect. Journalists complained (and sheep trotted out the line) that it was slow low down, the answer was, rev it. Similar thing with the 4U-GSE, its flat spot makes it feel underwhelming, so rev it !
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