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      01-04-2007, 08:36 PM   #67
teknochild
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what a gracefull way to run away from a debate when your proven wrong A+
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      01-04-2007, 08:55 PM   #68
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No I am not running away but I do have to run. Show some maturity and stop calling people you don't know names.

As for your 335i curve, YES the highest acceleration is at D and B. Just stop and think about it instead of selecting a new choice name to call me.

The caveat is that this acceleration occurs at the lowest speed on first gear as you go through that part of the RPM range only once (low RPM). After you run up first gear to redline and shift to second gear you will not see that low RPM range again. You will be running over the 4000-7000 RPM as you change gears from 2nd to 6th. In that area your engine has less TORQUE and therefore your car will have less ACCELERATION.

So the correct answer is D and B. That's where the highest ACCELERATION will occur!!!

Quote:
Originally Posted by teknochild


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      01-04-2007, 08:58 PM   #69
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its A an E but im aure thats what you meant, so how are you going to sit there and tell people that torque is what yields acceleration when those two points have the lowest amount of torque output by the engine?

keep dgging yourself deeper though please its more fun for me
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      01-04-2007, 09:01 PM   #70
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Quote:
Originally Posted by teknochild
its A an E but im aure thats what you meant, so how are you going to sit there and tell people that torque is what yields acceleration when those two points have the lowest amount of torque output by the engine?

keep dgging yourself deeper though please its more fun for me
FOR THE LAST TIME:

HIGHEST ACCELERATION IS IN "D"and "B" when you are in 1st gear.

Think :mad:
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      01-04-2007, 09:04 PM   #71
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Quote:
Originally Posted by Top_Gear
FOR THE LAST TIME:

HIGHEST ACCELERATION IS IN "D"and "B" when you are in 1st gear.

Think :mad:

OK, in that case, then why dont you rev your engine up to 4k and then shift? DUH

jesus your dumb
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      01-04-2007, 09:07 PM   #72
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Quote:
Originally Posted by teknochild
OK, in that case, then why dont you rev your engine up to 4k and then shift? DUH

jesus your dumb

Hey idiot,

When you shift gears your torque to the wheels will drop vertically by a factor equal to the gear ratio (could be as much as 50% of what you had in the lower gear).

Read the dam article I linked to a couple of posts back.
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      01-04-2007, 09:08 PM   #73
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yea, theres validitiy to that, but accoding to you even though the torque drops the HP stays the same right?

incase you forgot

Quote:
Originally Posted by Top_Gear

Different gearing changes the torque-rpm curve but NOT the power

edit: your taking to long to responde or dont want to because you know your wrong, torque cant drop without power dropping because horsepower IS torque just with respect to how often its applied to the wheels


and if you had half a brain you would realize this, and you would realize that if 200 pounds of torque is applied to the wheels 5 times as often at 300 pounds of torque that your going to go faster
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      01-05-2007, 09:38 PM   #74
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let's keep the war going here, i wanna see who wins this arguement....
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      01-06-2007, 06:30 AM   #75
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There's merit in a lot of what has been posted but i think that teknochild is correct.

The torque and power curves explain it all really. As an engine reaches is peak rpm, contrained by fueling, design, friction, fuel consumption regulations etc etc.... the torque figure drops faster and faster until the rate in increase in rpm is offset and at that point peak power is usually produced. Thereafter, torque drops very rapidly and power is lost.

Applying this to a car - lets compare it to a diesel BMW to a petrol BMW.

A 330d (my car) will accelerate faster in general than a 330i up to about 4000 rpm - thereafter the 330i will outaccelerate me but only when he reaches past 5000 rpm and at that point he will already be in my rear view mirror. He will then catch up as his engine starts to deliver more Power (HP) than I do at higher revs. Over a long race he will win by a (relatively) small margin.

Now consider this - we are both doing 70mph. I am doing around 1700 rpm and he is doing just over 2000 rpm (I guess). I am developing around 95KW of power against the petrol's 63 KW. If I accelerate, and we both stay in the same gear then I will just disappear. Thats what gives diesel their effortless power.

The Petrol 330i is quicker than the 330d but in the process, the driver has to really cane his car and he will use much much more fuel than I will. In Europe this is crucial and would be in the US if you had our environmental (or is it just general taxation ! ) taxation on fuel. Over 17k miles, I have averaged 38 mpg. And that is pretty amazing for a car with its level of performance.
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      01-06-2007, 11:36 AM   #76
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I think that most of the miscommunication on this thread stems people making different set of assumptions in the problem without giving enough qualifiers for the others to interpret. Let me try one:

Consider cars A & B, where both have ideal CVTs (i.e., have infinite, full range of gearing to maximize speed, no slip, no delay in shifting, etc.).

Cars have perfect traction, that is, don't slip regardless of their acceleration at time zero. There are no other parasitic complications (i.e., air resistance, etc.)

A and B have equal peak HP, but one car has higher or broader T range.

Q: Which will get to finish line faster or which one will reach higher top speed at the finish line?

A: Same. In this hypothetical, and UNrealistic example, both cars run at their peak HP the entire duration.

I believe it is this hypothetical scenario which has created the figurre of merit: Weight/HP ratio. I don't believe this is a perfect metric, and many have explained why we need to consider other parameters, but to the physicist, it's a clean FOM.
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      01-06-2007, 01:39 PM   #77
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yea poiney i already made that example id also like to point out that everytime someone says that two cars have "equal horsepower" but that one car has more low end torque, i point out that the two cars do NOT have equal horsepower

the other problem is a lot of people keep thinking were talking about peak numbers which were usually not
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      01-06-2007, 01:47 PM   #78
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Quote:
Originally Posted by Top_Gear
FOR THE LAST TIME:

HIGHEST ACCELERATION IS IN "D"and "B" when you are in 1st gear.

Think :mad:
something just occured to me, your still wrong, but i think i know where your confused, you probably didnt bother to actually read throgh what i posted so ill point it out again

d and B both have high jerkm meaning the acceleration at that point is increasing rapidly, compared to E the jerk is higher (Es jerk is actually negative) but the acceleratrtion is still higher at E than D and B, but thats why your but dyno made you think that way
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      01-06-2007, 03:22 PM   #79
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Quote:
Originally Posted by Top_Gear
No I am not running away but I do have to run. Show some maturity and stop calling people you don't know names.

As for your 335i curve, YES the highest acceleration is at D and B. Just stop and think about it instead of selecting a new choice name to call me.

The caveat is that this acceleration occurs at the lowest speed on first gear as you go through that part of the RPM range only once (low RPM). After you run up first gear to redline and shift to second gear you will not see that low RPM range again. You will be running over the 4000-7000 RPM as you change gears from 2nd to 6th. In that area your engine has less TORQUE and therefore your car will have less ACCELERATION.

So the correct answer is D and B. That's where the highest ACCELERATION will occur!!!
I believe this is correct as I read that maximum acceleration always occurs at peak torque. In my '02 M3 I can feel this. It pulls hard at 5,000 RPM (peak torque). At 8,000rpm (Near peak hp) it is definitely not pulling as hard.
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      01-06-2007, 03:40 PM   #80
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Quote:
Originally Posted by Insider
I believe this is correct as I read that maximum acceleration always occurs at peak torque. In my '02 M3 I can feel this. It pulls hard at 5,000 RPM (peak torque). At 8,000rpm (Near peak hp) it is definitely not pulling as hard.
if by pull you meen your butt dyno i think i have explained this three times now

you would have to be an idiot to actually think your car has a higher acceleration at 2k rpms then 6k rpms
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      01-07-2007, 01:39 AM   #81
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Quote:
Originally Posted by teknochild
if by pull you meen your butt dyno i think i have explained this three times now

you would have to be an idiot to actually think your car has a higher acceleration at 2k rpms then 6k rpms
I found the following on the net:

http://g-speed.com/pbh/torque-and-hp.html

- Maximum acceleration at any speed occurs at the HP peak.
- Maximum acceleration in any gear occurs at the torque peak

So yes, max acceleration in any gear does indeed occur at max torque.

At the same time, at 60MPH, max acceleration would be in 2nd gear since you would be at peak hp at that speed, as opposed to upshifting to 3rd where there would be more torque, but due to the gearing less acceleration.
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      01-07-2007, 02:50 AM   #82
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delete, im not even bothering anymore
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Last edited by teknochild; 01-07-2007 at 04:25 AM.
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      01-07-2007, 05:16 AM   #83
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Quote:
Originally Posted by teknochild
delete, im not even bothering anymore
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      01-07-2007, 05:55 AM   #84
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Why do F1 cars shift at 18500/19000 rpm and not at their max TQ?


I know the answer.ROFLOL.

If you want to be fastest, shift at max HP.(That would be at 5800 in my 335i, not 3000, 4 or 5000, or even 7000 but 5800.)
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      01-07-2007, 06:07 AM   #85
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Torque and Horsepower are simply different expressions of the same thing.

Torque vs. horsepower is a non question.

Neither is better or worse than the other.

'Peak' torque and HP figures offer only a very limited idea of a cars potential performance.

The key things which will indicate the cars performance are:

1. The torque curve of the engine. i.e the amount of torque generated at any given rpm.

2. Gearing

To understand how the engine torque is actually used you need to calculate what it will be at the wheels and in doing so you will need to bring the above 2 bits of information together.

You can also use this to work out the optimum shift points for maximum acceleration. Put simply the optimum shift point will be the rpm where the torque (at the wheels for the rpm relative to your wheelspeed for each gear) in the next gear up will be higher than the torque available in the current gear. Often this is the redline - but not always - especially in diesel engined cars.

A powerful car will have high torque.

If a car has high (peak) torque and relatively low (peak) horsepower it would suggest that the engine is low revving (eg a diesel).

If a car has lowish (peak) torque and high (peak) horsepower it would suggest that it is a screaming high revving sort of thing ... eg toyota celica, honda integra type-r.

Even this is only part of the story. The beauty of the latest turbo diesels is that the peak torque is derived very early and the torque curve is usually a flat peak almost until the redline. This means that they are pretty quick.

If you accelerate when the available torque is very high you are going to get a 'kick in the back' sensation. Since the torque is (almost) always high in a BMW diesel you get this a lot. But the petrol engines out rev them ... and at higher revs they can do more work and hence move faster. They also have a slight weight advantage.

The true debate is if it is better to design lower revving higher torque engines or higher revving lower torque engines.

The answer used to be high revving lower torque. This is still the case, but only just. Cars like the 335d and 535d clearly demonstrate that sustained torque at lowish revs can create very quick cars.
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      01-07-2007, 06:13 AM   #86
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Quote:
Originally Posted by teknochild
NO your an idiot, how are you going to tell people that acceleration is the same if the 335 exerts 300 pounds of torque on the wheels 1000 times a minute as 3000 times a minute

ive already explained in detail, and you are an idiot




your right, its proportional to torque and RPM, WHICH IS HORSEPOWER YOU SINGLE CELL IDIOT






your right 100%





just go back to that dyno i posted and rate the letters in order of acceleration, go on, (hint i already provided the answers)

by your reasoning it would be best for the 335 owners to shift between 2-4k rpms to go as fast as possible... and anyone that owns the 335 (or any car for that matter) knows thats not true

so again i say YOU KNOW NOTHING ABOUT CAR ENGINES STOP SPREADING YOUR HORRIBLE INFORMATION



here ill put it in here since i doubt your brain can handle drooling all over your keyboard and scrolling up at the same time

rank them in order of acceleration, go on, DB and C all have more torque than A and E so by your retarded reasoning your car is accelerating the fastest at those engine speeds

go on and actually try and tell me that acceleration is highest at D, B and C, this way everyone else can share in calling you a total idiot with me


Surely it depends on the gear ratios ?



But I'd shift between A and E.
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      01-07-2007, 08:14 AM   #87
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Nobody here is an idiot, but technokid is right. Shift at about A/E in a 335i.7000 sounds better but isn't faster. 2/3000 feels better but isn't faster irl. With the 330i I 'd shift at 6600 to be fastest. 258bhp@6600rpm.
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      01-07-2007, 08:22 AM   #88
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Quote:
Originally Posted by Robin Hood
Nobody here is an idiot, but technokid is right. Shift at about A/E in a 335i.7000 sounds better but isn't faster. 2/3000 feels better but isn't faster irl. With the 330i I 'd shift at 6600 to be fastest. 258bhp@6600rpm.
each gear shift at 6600?
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