Power/Speed vs Weight
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Have some questions here. For simplicity sake, i will use simple round values.
Car A has 100 bhp and weighs 1000kg.
Car B has 200 bhp and weighs 2000kg.
i duno if i am right in using bhp or should i use torque?
Which car would be more power? is there a formula between the power and weight values? -
been wondering abt that tooOriginally posted by l0st-s0ul:Have some questions here. For simplicity sake, i will use simple round values.
Car A has 100 bhp and weighs 1000kg.
Car B has 200 bhp and weighs 2000kg.
i duno if i am right in using bhp or should i use torque?
Which car would be more power? is there a formula between the power and weight values? -
yeah also do i have to consider the weight vs traction on the road at higher speeds? maybe HENG or some gurus can enlighten us on these issues.
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both cars have 100 bhp/tonne.
Car B is still more "POWER" cuz it does have 200 bhp. But speed wise, THEORETICALLY and without counting in other factors, the 2 cars are similar.
But yes, gotta see torque and wat rpm it come in for each car (the bhp rpm oso impt). Car B's braking might be worse cuz heavier and take a longer distance. But then again, with more weight pressing down on the tyres, it could be shorter too.
Gotta see gearing, gotta see race how long, straight line or sharp bends or long sweeping bends etc...
the long and short of it, the 1000 kg car will probably be reduced to shrapnel if it bangs on a wall and the 2000 kg car prob won't...haha -
hmmm.. yes, and since we're at that, what's the difference between BHP and torque in determining the acceleration? And how does the gearing affect the acceleration?
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BHP is more of TOP SPEED.Originally posted by cornyfish2000:hmmm.. yes, and since we're at that, what's the difference between BHP and torque in determining the acceleration? And how does the gearing affect the acceleration?
TORQUE is more of HOW FAST YOU CAN REACH THAT SPEED
To determin the acceration is more of torque.which is also called raw power in ah-beng terms or Twisting power of the crank thru the drivetrain in the vehicle.
For exp: Both car hv to reach 100km/h
Car A is 200BHP but only 100Nm(a measurment for torque)
Car B is 100BHP but hv 200Nm.
Car B should reach the 100km/h make faster.
Torque is also define as "stick to the seat feeling" "G-Force" "something that push you down to the seat" when acceralating.
Gearing plays a part too..
Have tall gear is "faster" to reach the speed u want at a certain gear.
Normal gearing> 1st can reach 40km/h max,2nd can reach 80km/h max..etc
So if u change rear ratio to a taller one,or fix a final gear >1st gear mayb can reach 60km/h max, 2nd can reach 110km/h max...etc -
hmmm.. ok.. then i wonder why people are blaming the Nissan Sunny's lethargic performance to too tall gearing?
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I personelly feel is that..cos that vehicle may be under powered, so it take ages to reach that speed lor..Originally posted by cornyfish2000:hmmm.. ok.. then i wonder why people are blaming the Nissan Sunny's lethargic performance to too tall gearing?
If same gear ratio on a powerful car may take 6 sec to reach 100, but on a under powered car, yet the same gear can also reach 100 but take longer time lor... -
answering directly to this question, b4 all other factors r taken into account, i would choose car A.Originally posted by l0st-s0ul:Have some questions here. For simplicity sake, i will use simple round values.
Car A has 100 bhp and weighs 1000kg.
Car B has 200 bhp and weighs 2000kg.
i duno if i am right in using bhp or should i use torque?
Which car would be more power? is there a formula between the power and weight values?
because its lighter, its inertia and momentum would be smaller. these r what kills performance. stopping distances and handling would be better.
sure both cars have the same bhp:weight ratio, but any bhp gains from modifying would have more significance in car A than car B.
of course i won't say both cars accelerate at the same rate because of the difference in torque figures and gearing. also since we can't be sure what the difference in engine capacity here is, we cannot comment on likely torque figures or fuel consumption, as well as the more intricate details of weight distribution and how that affects handling.
so based on the given info on power and weight alone, i would choose car A.
most people compare the bhp: weight ratio by taking the power of a car, dividing it by the weight of the car in kg and then multiplying it by 1000. this gives the number of bhp available to the car for every 1000kg, and makes comparism easier.
btw any car that weighs 1000 kg is very light. -
Most are these days due to the light alloys used.
Vios i know stands at around 950k. the older hondas hatches are about that weight too.
83' corolla is at 970kg but with solid steel parts..old cars can withstand accidents better. -
yeah..old cars can withstand accidents...but theyre not necessarily safer...newer cars are built to crumple to a point as to absorb the collision........Originally posted by jiayong:Most are these days due to the light alloys used.
Vios i know stands at around 950k. the older hondas hatches are about that weight too.
83' corolla is at 970kg but with solid steel parts..old cars can withstand accidents better.
so anywaes.....wat do u guys look at in a car anywaes?...
good torque or horsepower? -
good torque
it improves drivability in a way u wouldn't imagine! -
so its ok to say that BHP is useless unless there is a fast way of reaching it pronto huh?Originally posted by HENG@:good torque
it improves drivability in a way u wouldn't imagine! -
not exactly. most lorries have high torque but low bhp. so u can see bhp is also impt. bhp is still impt, but bhp is secondary to torque for me.Originally posted by Rockhound:so its ok to say that BHP is useless unless there is a fast way of reaching it pronto huh? -
You forgot to mention the rpm vs power/torque curves.
If you factor how the curve runs, as well as the drivetrain... generally all these will matter even more.
An S2000 or Ferrari F360 have high HP, low NM, and compared to a WRX, Skyline or some other car with a forced induction engine, that have comparable HP but much higher NM, they will lose out (unless in the hands of a skilled driver).
The layout of a race circuit or road will also determine how the driver uses the powerband (usually between peak NM and peak HP). If the driver is in a car which requires high RPM (like most NA cars), or if the turbo kicks in slower (single large turbo 4WD), and the course is full of tight corners and slow speed bends, a more responsive car (like a BMW 330d) may actually be even better despite having relatively lower HP/weight ratios.
There are so many physical factors to consider besides mere power, speed and weight... and once you factor the human element, that's when you have a good race.
cheers -
thanks for the input guys. really boarden my knowledge.
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there always balance betn. e 2,
if u compromise the speed with weight(like more fuel needed) -
err, catch no ball.......Originally posted by ha8n:there always balance betn. e 2,
if u compromise the speed with weight(like more fuel needed)
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Ai-ya..best is can hv a vehicle that is 1.3 ton, got 400Nm, 400 Bhp..best liao..hahaha