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Old 5th February 2006, 22:39   #16
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Quote:
Originally Posted by abhibh
Hi,

I have a simple question regarding Performance of a CAR:

If there are 2 cars like Ford ikon 1.6. Now out of these 2 cars 1 is 100PS@6000RPM and other is 100PS@5000 RPM. Now i want to know which car will out perform?? I mean the one with 6000 RPM will be better in terms of pickup, top speed etc. or the one with 5000 RPM is better ??.

Thanks.
The Power@Rpm figure indictes the engine RPM at which maximum power occurs. For car that produce their peak power at a lower RPM, have a good low end response. So more suitable for city, where you are not likely to revv the car much/drive at high speeds. The car producing more power at an higher RPM, will have a better Top end. Meaning, it will be outperform the former at higher speeds. Hope it clarifies your point. There are many posts regarding this, i suggest you use the search feature.


P.S. Whats that song in your signature.. 50 cent?..

Last edited by DCEite : 5th February 2006 at 22:42.
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Old 5th February 2006, 22:52   #17
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hi,

Thanks for the info. Though can u tell me which car will have better pickup?

Also the song is Rollin' on 20's by Lil' Flip (Its a 2 fast 2 furious soundtrack).
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Old 5th February 2006, 22:54   #18
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Quote:
Originally Posted by abhibh
hi,

Thanks for the info. Though can u tell me which car will have better pickup?

Also the song is Rollin' on 20's by Lil' Flip (Its a 2 fast 2 furious soundtrack).

The lower the RPM at which peak power occurs, the better the pickup (i am assuming by pickup you mean stop-go driving acceleration)
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Old 6th February 2006, 00:57   #19
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Hmmm
This sounds so easy...
Well Lets complicate things here a bit....
Lets say, wat about the gear ratio.
Ideally engines with different power output at different RPM will have different gearbox or the gear ratios would be altered to suit the engine.

Wanna make this look more complicated. What about the weight of the whole car which will redefine the power output.

I know ur questions was regarding Ideal cars.. I am talkin about realistic ideal situations....

Hehehe!!!
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Old 6th February 2006, 01:39   #20
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you cant judge a performance of a car solely by the horsepower ..you need to consider the torque aswell and most important of all Power to weight ratio...

gearing and transmission loss plays a huge role too ..along with suspension (at the time of launch)...
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Old 6th February 2006, 08:44   #21
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Quote:
Originally Posted by general_neo
Well Lets complicate things here a bit....
Lets say, wat about the gear ratio.
Ideally engines with different power output at different RPM will have different gearbox or the gear ratios would be altered to suit the engine.
bingo!...
But say gear ratios are same!....
then.. the 0-100.. of the car with 6000rpm is expected to be better..
though 0-top speed .... of the car with 5500rpm is expected to be better (bcoz you don't normally go 5500+rpm for top speed)

You have a very good real life example here.... Xing & WagonR.... almost same power different rpm. But unfortunately it doesn't always work with hyundai cars...
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Old 6th February 2006, 11:02   #22
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OKAY. Both the cars have same gear ratio, same weight, same power but RPM is different.

Also if there is Car which TDi and other is MPFi. Both have everything same like ford ikon diesel and ford ikon petrol (this is just an example). The diesel is 100PS@4000RPM where as Petrol is 100PS@6000RPM.

Out of the above 2 which will yeild better results in tersm of pickup.

Thanks.
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Old 6th February 2006, 12:02   #23
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As I said earlier.... 0-100 is expected to be better for a car with higher revlimit.... b'coz it would require less up shifting.
The other one... with 4000rpm limit... would maybe require to be shifted into 4th before it touches 100. (gear ratios are same - remember)... so it'll lose time there.

In top speed .. the 4000rpm car would be quicker.... and maybe even faster (if we are talking about the overdrive gear - BUT lets not get into that)

Basically in pure theory the 4000rpm car will be quicker.

In a real life scenario ... the cars those have a 4000rpm (rather lowish limit) don't have free revving engines as the 6000rpm ones..... i.e. in a given gear a 6000rpm car might be able to reach its limit before the 4000rpm one reaches its (making 6000rpm faster)

This problem in real life has too many variables to be dealt with ... this discussion won't get you anywhere.

p.s. .. plz.. don't compare Petrol Vs Diesel... .. its another war altogether.
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Old 6th February 2006, 14:51   #24
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The car with higher RPM will have higher top speed (assuming it can develop enough power to pull the car at that speed).

However, the car which develops same power at lower RPM, will be more efficient and fuel economical.

The max acceleration will occur at torque peak. So, to compare that you need power-torque curve of the engine.

This is the reason why formula one cars have engines which have 10,000+ RPM. It helps them to go over 300+ km/h. Remember, if you rev engine too much at high RPM, its life gets shorten.
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Old 6th February 2006, 15:08   #25
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100PS is 100PS, whether it happens at 5000 rpm or 6000 rpm.
PS which stands for Pferdestärke which means horse strength, in German, is a measure of power.

It's defined as follows:
1 PS = 735.49875 Watts = 0.986 hp(SAE)
So 100 PS = 0.735 kiloWatts = 98.6 bhp

Post-1992, the Germans use the kiloWatt as their official power measuring unit, not PS.

But Pickup is related to torque, not power.

A gearbox with suitably picked ratios will get the best out of the engine, by utilizing its band of high-torque rpms.

A case in point is Peugeot's 2112 cc diesel engine. That engine in a Peugeot 404 would propel it to 150 km/hr. However the same engine in a Mahindra MM540 would be badly strained above 90 km/hr. The difference is in factors like gearbox, differential, overall body weight, aerodynamics, etc.
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Old 6th February 2006, 15:47   #26
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Quote:
Originally Posted by sbasak
This is the reason why formula one cars have engines which have 10,000+ RPM. It helps them to go over 300+ km/h.
I think its b'coz an engine can not produce that kind of 'bhp' at any lower rpm - and not b'coz it needs to go above 300km/h.


Quote:
Originally Posted by ram
But Pickup is related to torque, not power
but torque is nothing other than distribution of power over the revv range. So if you say the engine is more torquee at a paticular rpm... that just means its producing more power at that rpm.

Here both engines have absolutely similar torque curves... its just that one has an elongated/hence lower curve.... .. (its getting tricky, isn't it?)
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Old 6th February 2006, 16:27   #27
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Quote:
I think its b'coz an engine can not produce that kind of 'bhp' at any lower rpm
Truck engines can produce 500 hp @ 2000 RPM!
http://auto.howstuffworks.com/question381.htm says that engine naturally produce torque! Power is basically an infestation of torque.
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Old 6th February 2006, 16:28   #28
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Quote:
Originally Posted by SLK
Here both engines have absolutely similar torque curves... its just that one has an elongated/hence lower curve.... .. (its getting tricky, isn't it?)
Yes it is ! Actually without knowing the torque curve, isn't it impossible to tell which one would accelerate quicker ?

The 100PS@5000 rpm car, may be having peak torque lower rpms say < 3000, in which case initial acceleration would be quick (can't say upto what value of X when we say 0 to X kmph).
The same car, i.e. 100PS@5000 may have peak torque at higher rpms > 4000 in which case it would lose out on initial acceleration but would win later.
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Old 6th February 2006, 16:58   #29
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Quote:
Originally Posted by sbasak
Truck engines can produce 500 hp @ 2000 RPM!
http://auto.howstuffworks.com/question381.htm says that engine naturally produce torque! Power is basically an infestation of torque.
But they are not 1.5 litter engines....
Power and torque are related....
The way I see it... torque is a better indicator of drivability at city speeds.
Power is the ultimate capability of the engine.

One funny scenario...
You have 2 engines --- truck and F1.. both same power (but obviously different torque.)
You put the F1 engine in a truck ... and change gear ratio's to compensate for the higher rpm. (Assume weight remains same).... I think it'll pull the same amount of load.

The thing is torque is always adjusted through the gearbox... but power remains same (except for little losses).

So when we refer torque the rpm is very important… but power is already adjusted for rpm.
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Old 6th February 2006, 17:24   #30
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I think what Abhibh meant was both the cars are EXACTLY equivalent EXCEPT power@rpm figure. For one its 100PS@5000 rpm, for other its 100PS@6000RPM.
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