Discussion
TB993tt said:
The power curve is just a mathematical interpretation of the torque curve so it is the torque curve of the 991 turbo S from 5500 to 7200rpm which shapes the power curve over these 1700rpm and on the turbo S this means over 510PS between 5500 and 7200rpm. In contrast the nat aspirated GT3 makes over 450hp between 7500 and 8500rpm.
People get confused with peak power numbers and it's one reason people say Porsche underquote their power figures, they don't under quote the peaks (by much) but they have bigger areas under the curves which make for better performance (than rival brands)
I know at times I can be the most boring ba$tard on this forum so I will say sorry to all in advance, however the first part of your post is all screwed up.People get confused with peak power numbers and it's one reason people say Porsche underquote their power figures, they don't under quote the peaks (by much) but they have bigger areas under the curves which make for better performance (than rival brands)
Torque, engine speed and Power are all fundamentally related and it is important if one is going to discuss them to understand what the relationships are.
Since Power is a rate; being either energy consumed over time or work done over time an engine in its most basic sense produces Power.
The Power it produces is actually quantified as the sum of the work done during one complete otto cycle (look up thermodynamics if you don't know what this is) multiplied by the number of work cycles done in a second.
Having this work expressed as a rate (ie as Power) is critical since without the time component you wouldn't know how long a cycle took, only the magnitude of the work done. Did it take an hour, a week, a year even to complete its cycle? If you had two engines, each able to do the same amount of work per cycle but one took a second and the other a minute to complete the cycle then the Power produced by the first engine would be 60 times greater compared to the second engine.
The Power produced by the engine as it completes its thermodynamic cycle enables it to then output this Power as Work done over time. At the output side the Work component consists of Torque (a rotational force) and an angular displacement (the distance over which the rotational force has acted and this is measured in radians). Since an engine is producing Power, this work component must be expressed over time. Doing so changes the angular displacement (radians) into angular velocity (radians per second ie engine speed). Radians per seconds equal 60/2*pi RPM since there are 2*pi radians in one revolution and 60 seconds in a minute.
The equation for a cars acceleration can be given as:
Acceleration = (Engine Torque x [Engine RPM/Wheel RPM] x Wheel radius)/ mass
Since Power output from an engine = Torque x angular velocity this equation is actually:
Acceleration = ([Engine Power/Wheel RPM] x wheel radius)/mass
Thus with all other things equal, the more Power the greater the acceleration. Torque itself is simply a component of Power in this case and without the other component of Power, angular velocity, it is not much use.
Now whether you like your Power as high RPM/low torque or low RPM/high torque. That's for a whole other time
Edited by fioran0 on Tuesday 31st March 03:44
fioran0 said:
Thus with all other things equal, the more Power the greater the acceleration. Torque itself is simply a component of Power in this case and without the other component of Power, angular velocity, it is not much use.
Now whether you like your Power as high RPM/low torque or low RPM/high torque. That's for a whole other time
Thanks - that's basically what I was trying to say.Now whether you like your Power as high RPM/low torque or low RPM/high torque. That's for a whole other time
hondansx said:
LOL... top trolling by Ronin. Surprised people didn't know who he was! He has a massive inferiority complex, hence the hostility and shameless self promotion.
Indeed, soon as I saw that name I knew what was to come. You can search for previous threads where Ronin in a loud oppinionated way tells you why his cars are best, why yours aren't and why you are wrong if you decide to point out deficiencies in his argument. He is a man who always believes he is right. The last time he was wrong Chuck Yeager was going supersonic. Apparently.Deficiences such as claiming the journalists like the GT3 so much only because they didn't use it as a daily driver. But neither did he, he only had it for 1 day and then drove it in the Canyons of Zog, not the normal USA drive of going to Walmart to buy a Gloch and some Oreo's and then to Mcdonalds and then to coffee and cars.
Now, as an MX5 driver this argument to me is like comparing one Faberge egg to another .. to me both are great but different.
I'm using non Porsche examples below not to offend anyone.
My mate likes his 330d but given same money I'd buy an Integra R as I prefer to rev cars rather than row along on the torque. The 330d would be best in some places, long roads with roundabouts for performance, but I prefer B roads anyway. Looking at the Canyon of Zog roads they don't have that many tight or jinky corners like our typical B road does in the UK, also they have good sighting and are hilly. Thats why Ronin, with his very odd way he uses his hands on the steering wheel (what's that about?), likes the Turbo S. Might prefer the GT3 in the UK? Or might not. The US have more of a weighting on acceleration than handling, you can tell this from how they test cars and they types of cars they like to build. The roads are just "bigger".
Getting away from brash bravado from the other side of the pond, a lot of good comments on this thread have talked about the speed v feel thing again. Once again it is down to personal preference. Some people would prefer to have more tactility or inter action than either the 991 turbo or GT3 and have something older. With Porsche that desire can go back 50 years if you want, which is cool. Real men prefer to hand crank their Tiger Tank of course.
Given that, all these threads seem to end up on speed or lap times. There is always someone faster than you or a car faster than you, I can safely tell you this as an MX5 driver
, so it's about enjoyment. Enjoy that Faberge egg whilst I enjoy my Cadbury's cream egg ....And to be blunt about it, modern day tyres are so good and so wide, that the speed becomes past the point of enjoying it on a good road and more "what if?" or " I am slightly terrified". You don't want to be arguing with the insurance agent that your GT3 actually is worth £150k
Hence why you can have fun in the Morgan 3 wheeler. Speed does not matter. Can I say that on PH?
has he gone back to Zog yet? Is it safe to come out?
Edited by Gandahar on Tuesday 31st March 07:40
fioran0 said:
however the first part of your post is all screwed up.
Torque, engine speed and Power are all fundamentally related and it is important if one is going to discuss them to understand what the relationships are.
I don't think it is screwed up,I think I said the same thing as you but in simpler terms Torque, engine speed and Power are all fundamentally related and it is important if one is going to discuss them to understand what the relationships are.
The power curve is just a mathematical interpretation of the torque curve
And this bit is effectively what you are getting at
510PS between 5500 and 7200rpm. In contrast the nat aspirated GT3 makes over 450hp between 7500 and 8500rpm.
As I understand it for a full load measurement the engine dyno software brakes the engine whilst it is at full throttle to match the torque output from the engine, this is done at rising rpm intervals. Torque curve is all these dots joined up and power curve is extrapolated from that this is what the curves we get from Porsche represent.
The way I like to think of it is the power curve represents the acceleration oomph (technical term
) of the torque as rpm rises and the more torque you have at higher rpm then the more power you will have.... BTW I know what engine dyno measured 840NM at 3500rpm feels like on my 7GT2 and I also know what engine dyno measured 840NM feels like at 7000rpm and the shove in the back/traction issues in third gear are pretty similar at 3500 and 7000 but as we know the power numbers at the respective rpms differs widely - I like torque
A technical answer on what is happening in that last para would be enjoyed and appreciated BTW
TB993tt said:
BTW I know what engine dyno measured 840NM at 3500rpm feels like on my 7GT2 and I also know what engine dyno measured 840NM feels like at 7000rpm and the shove in the back/traction issues in third gear are pretty similar at 3500 and 7000 but as we know the power numbers at the respective rpms differs widely - I like torque
A technical answer on what is happening in that last para would be enjoyed and appreciated BTW
Surely if you were generating the same torque at 3,500rpm and 7,000rpm then you'd automatically be generating twice as much power at 7,000rpm?A technical answer on what is happening in that last para would be enjoyed and appreciated BTW
the ronin said:
So three laps later he beats his own GT3 Cup time by over a second in a street legal Lotus...
As I said the GT3 was the benchmark....
Hold on a moment Mr it might well be street legal but its hardly standard is it , and that motor has to be a grenade in waiting As I said the GT3 was the benchmark....
ALso how many $$$ have you pumped into it
sidicks said:
Surely if you were generating the same torque at 3,500rpm and 7,000rpm then you'd automatically be generating twice as much power at 7,000rpm?
Correct but my point is the longitudinal G one feels at 3500 and at 7000 in a low gear (3rd since 2nd is severely traction limited and higher gears introduce too much drag into the mix) when the torque is the same and it is the G which gives the acceleration. For me Power and torque are just numbers to swap around in the rev band but I'd enjoy a technical insight if one is forthcoming Edited by TB993tt on Tuesday 31st March 14:27
TB993tt said:
sidicks said:
Surely if you were generating the same torque at 3,500rpm and 7,000rpm then you'd automatically be generating twice as much power at 7,000rpm?
Correct but my point is the longitudinal G one feels at 3500 and at 7000 in a low gear (3rd since 2nd is severely traction limited and higher gears introduce too much drag into the mix) when the torque is the same is pretty similar and it is the G which gives the acceleration. For me Power and torque are just numbers to swap around in the rev band but I'd enjoy a technical insight if one is forthcoming essentially power = torque x revs
torque is a moment, so is most often expressed in the force applied over a given distance, i.e. ft lbs, or newton metres, i.e. how much weight in pounds is needed to move a lever one foot long. It doesn't matter how far it moves, it's the effort required to move it at all.
Think we're going completely off course here. Mr Fergus I was just giving a real world example of how an engine which can develop same torque at low and high revs has same rate of acceleration (not the same but similar allowing for various drags) at low and high revs. I was just answering Mr Sid's correct assertion.
I was asking for Mr Foriano to give some more insight into his power giving acceleration speech in relation to the above example. It's all good stuff.
BTW I am in the GT3 is gutless camp not that anyone asked or is arsed !
I was asking for Mr Foriano to give some more insight into his power giving acceleration speech in relation to the above example. It's all good stuff.
BTW I am in the GT3 is gutless camp not that anyone asked or is arsed !
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