Torque or HP ????

[Mel4fun]

OK.....something that bugs me.

 

Imagine this, if a particular car has its max torque @ 3800rpm, whereas its max BHP @ 6200 rpm.

 

If I'm coming out from a corner to a straight with a gentle uphill, do I hold on to the rev up till the redline and shift or do I shift after 1000 rpm after the max torque ??

 

What should I do :-

1) I rely on the BHP to pull the car all the way (rev till near redline then shift)?

 

2) I shift near the max torque rpm ??? (so as to maintain max torque throughout the power band)

 

Any pointers from forum gurus ????

TIA

[Turtlekar]

okay....i'm actually more keen on the torque.....which most ppl do....

 

the torque is the amount of power that push your car upfront.....and the ponies are the one that carry u as far as it could.......

 

taking your example, coming out from a corner to a straight with a gentle uphill....assuming u are on 5th gear, at the speed of say 100kmh....u will be using the momentum to bring yourself up to the hill......

 

however, if u are on 4th gear and needs to brake hard for the corner due to centrifugal force, u will need to downshift to 2nd or 3rd gear so that the amount of torque delivered from the car are able to push the car uphill......

 

normally, on the road when we are overtaking...if u notice, we always like to downshift our gears to create more torque so that we are able to overtake a car easily....or we will floor the accelerator....that's the amount of torque delivered from the engine.......

 

but, i got a question as well....how is it possible to create more torque other than changing the gear ratio???? that's the tricky part.....hope somebody can help me out as well......

[Wrxblue]

Bigger engine capacity or turbocharging lor...heheheee

[Turbobrick]

Ok, here's a quick and vague explaination:

 

Torque gives acceleration, power helps maintain speed and determines top speed.

 

bhp = torque x rpm (it's all relative )

 

http://www.technofile.com/cars/horsepower_torque.html

[Turtlekar]

aiyo yo, cannot lah.....i prefer na car lah......anymore suggestions...

 

in fact, i did tot of doing the manifold.....say instead of 4-2-1, put it 4-1....but don't know what's the result to be like leh.....other than that, is either doing the remapping of ECU loh...but really no ideas lah...

[Turbobrick]

4-1 will give better high rpm performance but low end may suffer due to increased flow (or too high flow )

[Turtlekar]

i understand that it's relative to each other, but how to increase torque? to gain hp is easy, but what abt torque???

[Assassin]

To me...as I understand it in simple terms..for me anyway..

 

Torque = Pulling power

Bhp = Top Speed

 

Anyone pls correct me if I'm wrong, for going uphill and overtaking...torque is more impt...hence follow the torque band rather than the bhp redline.

[Turtlekar]

would u care to elaborate on this high flow???

[Turbobrick]

Firstly, increasing torque is tough

 

The few methods I can think of are elaborate and expensive:

 

1) forced induction

2) shorten gearing

3) use smaller diameter wheels/tires (cheating )

4) NOS at WOT

 

As for the flow of the 4-1 over 4-2-1, imagine the exhaust backpressure being "restricted" by the 4-2 portion compared to the 4-1 direct. However the backpressure generated helps restrict some exhaust gases in the combustion chamber to aid the next powerstroke (that's all chemistry which I'm also blur). However at high rpms the exhaust pulse has shorter frequency thus "needs" to escape faster with much lesser backpressure so a 4-1 is ideal.

 

Lemme know if any part of the above makes you I'll try to explain in more detail without myself

Edited December 17, 2002 by Turbobrick

[Madarmour]

I think the torque curve is important. The flatter the better.

[Assassin]

Yup...

[Turtlekar]

thanks alot pal, but i'm still abit confused ....regarding abt the backpressure required to aid the next powerstroke kind of thing......perhaps u can provide me with some details abt the chemistry stuff, and i'll try to work it out.....however, i do understand abit more abt the 4-1 compared to 4-2-1....but will need to find out more for better understanding.....once again, thanks

[Presea]

Hi.... this has always been a fav topic of mine...

 

The powerband around the Peak torque is the point of greatest acceleration.

If a car has a 4000rpm peak torque (most are around there), most likely between 3800 to 5000rpm or more is a generally flat torque curve.

When overtaking, one should be downshifting to a point within this powerband to get maximum pulling power.

 

But the point at which one changes gear should maximise the next gearchange's torque. this is often at the redline or just above maximum power. Not below! Any gearchange below the point of max power would most likely result in a poorer acceleration after that gearchange.

 

I should explain:

Lets say a car is travelling at 80kmh in 5th gear (2500rpm)...and wants to overtake effectively.

The gearchange should go down to the gear that corresponds to the speed for maximum torque. For me, at 80km, I'll drop to 3rd gear and accelerate to 120-125, going from 4000rpm to 6500rpm. If I had gone to 4th gear only (3000rpm), I'd take at least 2 to 3 seconds longer to get to 120-125. (this can be timed....it would be rather obvious in reality)

 

If I was travelling at 50kmh, I would drop to 2nd gear to accelerate to 80+kmh and change to 3rd gear after reaching 6000rpm.

 

BUT...when taking bends/tight corners....rpm should be below maximum torque....3000-3500 so that the car is more controlled, and in the case of oversteer, there is less likelihood of "losing it". Unless you are already past the apex of the curve (midpoint between entry and exit), then you can "whack" it to the redline

 

Of course I am talking about most cars with a max horsepower around 6000-7000rpm.

(If a car has a V12 engine, and peaks below 5000rpm for power, in any gear, it would have loads of torque)

 

....cheers

Edited December 17, 2002 by Presea

[Turbobrick]

Here's a document for you to digest

Exhaust Facts.doc

[Turtlekar]

thanks alot pal, deeply appreciated .....now will have to go back to my text and evaluate the situation on my car..... i guess it's abt mass balance stuff...will update u guys abt my findings, let's hope that i can succeed.......

Edited December 17, 2002 by Mazdie

[Turbobrick]

Anytime

[Super7]

hang on a moment:- you said " .........when taking bends/tight corners....rpm should be below maximum torque....3000-3500 so that the car is more controlled..... "

 

why is it that the car is more 'controlled' below peak torque rpm band??..... i tot the control has more to do with the driving skills????.... stay within peak torque rpm band will give us max acceleration out of the corner, won't it??........ juz curious leh

 

cheers

Edited December 18, 2002 by Super7