Also depends on how you are measuring performance - a modern Mazda 6 is a much quieter and more refined car than your Astra so is going to feel slower even if it isn't necessarily.
smac,
Jul 10, 7:38pm
Care to clarify/quantify!
timmo1,
Jul 10, 7:51pm
Not only that, the comparison is somewhat meaningless without considering what the engine is pulling (i.e. heavy car vs light car), what the job is (sports car vs family car vs tow vehicle), what transmission is sitting behind that engine (ie gear ratios) and what environment the vehicle is being used in (city/stop start vs crusing etc)
There is no 'right' answer without other info.
smac,
Jul 10, 7:58pm
Agree completely. Which is why I wasn't comparing hp to torque, and why weight was in the discussion.
clanky,
Jul 11, 6:52am
Simple engineering, chaps.Power (W) = 2 x Pi x N x T, where N is working cycles per second and T is torque in Nm (Newton-metres). Also, Power can be calculated from Pmean x Length of stroke x area of piston x number of working cycles per second, where Pmean is the mean effective pressure in the cylinder. There is also a formula for power using the mean piston speed, but I can't remember it just at the moment. So, for 2-cycle engines, N = number of revolutions per second and for 4-cycle engines N = number of revolutions per second/2. This is always assuming thet the engine is single acting or not runningat 6-cycles. So, with a reasonabe sized engine, torque is measure in Tonne-metres and power output in MW!
sr2,
Jul 11, 8:57am
To Quote Alexander Pope, "A little knowledge is a dangerous thing".
smac,
Jul 12, 5:37pm
What bollocks.
This makes no consideration what so ever for combustion efficiency (among other things).
But apart from that, what was your point!
mrfxit,
Jul 12, 6:47pm
LOL fight ya buggers
Classic case is my 2.4T Surf (5sp manual) It's almost as quick getting through 1st & 2nd gear as it is 3rd & 4th gear almost regardless of what weight is in or attached to the truck, BUT, The usable torque power band is only between 2K & 3K Under that it's gutless & over that it's just revving & gutless (if gearing allows) ***** Oh & the add to that, the surf is a tad over 2T of flying brick wall
clark20,
Jul 12, 8:01pm
I found that while the turbo diesels have plenty of torque, they do not have the KW however if you add about 20% you get about right amount to compare to petrol, so a 100kw diesel with lots of torque is about the same as a 120kw petrol motor (in the same car, comparing Audi and BMWs 0-100 etc petrol vs diesel)
tonyrockyhorror,
Jul 12, 11:27pm
You might think that but it's not the case. It's only possible if the engine power increases at the same rpm as the gears climb. which you'd be doing with your right foot without knowing it.
morrisman1,
Jul 13, 5:19am
the only way I can see it being remotely possible is that the flywheel is that large that it becomes the major energy sapper than actually moving the vehicle, then the differences between the gears would become less must as you have said must still exist
mrfxit,
Jul 13, 7:45am
LOL, & you can happily use that explanation regardless of "my right foot" being firmly flat on the floor between gear changes.
Ha ha he he ha ha. yea whatever ;-) Had this truck for nearly 4 years now & been all over most of NZ, With trailers of assorted loads & sizes With 5 ppl in it & assorted camping gear Just me in a hurry
The average mechanically minded logical person thats noticed my comments on this message board in the past . would probably already understand that I Learn to drive & understand my vehicles & not simply OPERATE them
I understand where you are coming from but YOU need to understand what a 1988 2.4L turbo indirect injection vehicle is like to drive.
She's a lot of fun & pretty damn solid. Nearly wrote off a car a few months ago that DID under cut my front bumper off a roundabout, I got a few more scratches on the bumper & he got the whole side flattened on his car
mrfxit,
Jul 13, 8:04am
Close but no cigar. KW / HP is in reality an OVER ALL measurement of usable power & revs Torque is PULLING power at specific rev ranges
Someone mentioned above that his rotary has a lot of torque for it's size. Mmmmm theres part of the crunch " for it's size" + body weight
ANY rotary vehicle will leave my Surf far behind if both vehicles are empty Add a 300kg trailer + a 1 tonload (1.3T) & lets see who's left behind
I Don't know the weight of that rotary but would be around 1.2T at best The Surf is 2.24T Surf + trailer + load (3.54T) Rotary + trailer + load (2.5T)
Torque = towing & maintaining speed abilitys Total kw/hp = overall figure Wide rev range = long leg gears/
You can't have both without very high tech engines / high fuel costs & high maintenance costs
BUT Getting the balance without costing a lot depends on what you NEED either spec for & a combination of how it's intended to be used & really IS used.
clark20,
Jul 13, 5:21pm
Plenty of cigars here! I am talking about same type comparisons, like midsize range cars and compare diesal with petrol, not a 4WD vs rotary
mrfxit,
Jul 13, 5:23pm
LOL yea but you know how rota fan boyz go on about how fast they are
smac,
Jul 13, 7:43pm
That's really, REALLY wrong.
flashgordon_nz,
Jul 14, 10:24am
horsepower sells motors, Torque wins races.
tonyrockyhorror,
Jul 14, 10:25am
'Pulling power' (hint in the word you used, 'power') is the power at the specific speed. Torque is as a result of power, not the other way around. It's just easier to calculate power (the rate at which work can be done) from torque than it is to measure it directly.
tonyrockyhorror,
Jul 14, 10:25am
Another falsehood as the result of oversimplification.
clark20,
Jul 14, 10:45am
No its not,as its only a rough guide,check out BMW or Audi (A4s for examples) and as they perform the same if you add 20% to the diesel KW output compared to petrol. hey, its only my opinion.
And only Turbos not NA
smac,
Jul 14, 11:05am
It's not opinion.saying you like black cars or red cars is an opinion. Saying a cars actual power output is different dependant on it's fuel type is just, well, wrong.
A diesel car with 100kW at 4000rpm will perform exactly the same as a petrol car with 100kW at 4000rpm. Actually that's wrong, in that example the diesel will probably have a better torque curve so would probably be the better drive.
The difference is though that in reality a petrol and diesel develop their peak power at difference places in the rev range, so will have different characteristics. As a result the manufacturers SHOULD match them with different gear sets, but don't always.
This is touching on what was supposed to be the whole point of this thread - that in my opinion(!) comparing torque values makes more sense for road cars, than comparing max power.
vtecintegra,
Jul 14, 11:11am
Modern petrol turbos generally have much more pleasant power delivery than modern turbo diesels - with the petrol you still get low down torque but you also get a far broader usable power band.
tonyrockyhorror,
Jul 14, 11:13am
Exactly.
mrfxit,
Jul 14, 11:21am
Turbo or not Thats always been the case The confusion is comparing petrol HP with diesel torque Both delivered in very different ways at very different rev ranges
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