Gregs

whats more important?
what would be faster on the track? a car with say 200 bhp and 250 lb of torque or
a car with 250 bhp and 200 lb of torque?
just interested in what differance it would make.

Graceland

track car - torque lowdown for powering you out of the corners etc

bhp is important for the top speeds


thats just a very very general summery tho

Mr S1

iTrader: (2)

Personally I'd rather have more torgque than horsepower. Makes the car more driveable and quicker on the road.

Anonymous

correctly geared and assuming it doesnt have a very narrow spread of power over only a tiny rev range, the car with the higher BHP will always win.

the thing that determines the rate a car accelerates at (ignoring aerodynamics etc which isnt relevent to this discussion as is the same for both) is the torque @ wheels divided by the weight.

torque @ wheels, is a product of BHP @ flywheel and the gearing.



So short answer, the 250bhp car.

GARETH T

BHP is work done
torque is turning power

Tony Ryan

Chip , also depends on the track , no point having a lot of horse power if you can t stretch the cars legs, on a short circuit i'd rather have more torque to drag out of corners , and a short spread of power coupled with a close ratio box .

markk

iTrader: (2)

torque is waaay more important , especially for me , but even so, i would never build an engine with a massive hp figure and fook all torque figure, but there are soooo many variables like tony has said

AlexF

Is the only on correct.

Torque is how HARD your engine turns the wheels... the more is manages to do this in a set time the more power it has.

So as such BHP is meaning less, its simply a formular:


max torque x rpm that it happens at
---------------------------------------
5252



This is why a rolling road or dyno measures torque as BHP is a function of torque!

Alex

Anonymous

Tony Ryan, thats why i was so clear about stipulating the importance of gearing.

a car with half the torque @ twice the rpm and half the gearing will accelerate at the same rate basically.

so more bhp is always going to win IF you can gear the car to take advantage of it, as more BHP without more torque means it MUST be revving higher, so you then need to gear it lower for any given speed to take advantage of the extra rpm, and that lower gearing is a torque multiplier on the way to the wheels.

how can anything other than the amount of torque at the wheels possibly be relevant as its the turning force applied to the car which ultimately accelerates the car.

JohnnyB

bhp is torque over time.

Eg the amount of work over a given time.

Gregs

laymans terms anyone?!

AlexF

So you can see... if you have very low torque such as a motorbike engine then at "normal" revs say up to 5000 rpm it would have very very little BHP. BUT and its a bit but, if you move the revs upto 12000 and produce the same torque you have much more BHP!

As to whats fastest on track it depends on many other factors, but mainly it comes down to gearing!

Gears are torque multiplies, hence you use a low gear to pull away as at low revs all engines produce less torque then they do at full chat.

Some good reading :

http://www.seight.com/torque.html

Anonymous

Depsite peoples love affair with torque and how it feels to drive, BHP is what counts most in reality, hence you dont see formula one cars tuned for midrange torque!

Tony Ryan

think i was agreeing with that bit of the statement !

Gregs

that link was very good thanks for clearing that up!

YBP

I agree with you on your opinions regarding this subject. But I think you are wrong here on the F1 bit.

I have often seen F1 cars go out of the corners @ 11k and revved beyond 19k before changing gear. I think that´s a very impressive rev range.
When I look at rr/dyno papers I look at max torque and then see how big the rev range is within 80% of the max torque.
That is what I think is important. Obiously a very nice and long rev range doesn´t do any good with 20bhp, but you get my point.

morto

hi all, i think the worst car for torque has to be the vtec thay have shocking figuers , but sopposed to be brilliant engines? can some one explain?

andy

Anonymous

YBP, the fact they rev to 19k in the first place shows how desperate they are to make peak BHP


Morto, vtec engines dont have low torque figures, thats a myth, they have torque figures roughly equivalent to other N/A engines of that size (there is a slight compromise on mid rnage due to the size of the ports/valves), they just have more BHP due to revving so high.

morto

thanks chip

andy

morto

torque is more important to me as i like the fact i can pull very strong from any gear what amazes me is how fast your going with not alot of revs on a turbo car, unlike n/a were u need loads of revs

andy

GARETH T

buy a golf gti150 then,, you will love it

LEE-RS

torques good if you cant drive

Jim Galbally

i think you need a healthy helping of both frankly...

i'd rather have a car with a graph that goes ---/ than ___/

GARETH T

love the graphs jim

AlexF

Chip, BHP is torque

sunny

iTrader: (1)

In most cases people are forgetting that a well spec'ed engine with serious HP particulary with peak power around or past 7000rpm is going to have a healthy dosage of torque considering what happens to them both just after 5k. Therefore I would go with Chip on this one.

I think it all comes down to what the car is going to be used for. WRC cars have mental torque and not so much HP (this is not just to do with the resitrictors) where as a straight line top speed car would benifit more from the raw horse power.

choppa

BASICALLY if you want to race on short straights or with lots of corners, you want lots of torque (or grunt) to pull you out of a bend, or from off the line. BUT if you've got lots of long straights, few corners and top speed work to be done, then horses would be better. this is assuming that the same gearbox is being used.
as for F1 cars... the only reason they make em rev to 20k is because they are n/a (not turbo'd). how else would you expect to get 7 or 800hp from a 3litre. these are highly developed engines that none of us could afford. i think some of their engines have electronically operated valves, which gives you the ultimate timing control over the head. they are also "under-square" engines which means that the pistons dont throw up and down as far as the size of the bore they sit in. so the throw of the crank is quite small. this makes them idle fast, like 3000rpm, but to make up for the lack of torque from such an engine lots of pistons are used, like a V10 or something, to get a continuous flow of power on the crank. also, generally speaking, a "V" engine will deliver power smoother than an in-line engine. so an F1 car has torque, horse power, smooth power delivery and revs in a fairly compact unit.
but more revs are more destructive to your bearings and other moving parts.
hope it helps

Mark V8

iTrader: (2)

No one has mentioned capacity
Given a choice of a 2 litre making 250 bhp (for arguments sake ) and a 5 litre making 250 bhp which one would you choose , area under the curve is the best way of knowing what will give the best drive and bigger tends to be better

Mark

choppa

i would expect the 5litre engine to make a lot more torque than the 2litre with the same hp. making the 5litre, effectively, a more powerful choice. but its heavier, by quite a lot, so that has to be put into the power to weight calculation.

Mark V8

iTrader: (2)

Not really
A wildcat 6 litre Rover V8 probably weighs less than a YB 2 litre but can and has made 747 bhp and 525 lbsft Nat Asp on high octane unleaded fuel.

A turbo charged big engine will obviously have even more advantage, why cripple yourself with a small engine when a bigger one can do it on less boost with more torque at low rpm.

Mark

choppa

i like your style, bigger is better! i got an xr2, my mates were sayin turbo it turbo it, but i said NO. i got a modded n/a cvh1.8 now and its pukka. no waitin for a turbo, just torque when you want it.

LEE-RS

mate a na 1.8 is gonna be shite compared to a turbo

choppa

well, i can keep up with most rst's. so its fast enough for me. i estimate 130hp as most rst's have had something done to the engine but the engine's pulling a slightly heavier car. but my engine is more torquey than it is horse power so it pulls well. lacks a bit of top end though... only 125mph. but its an over square engine. designed for torque not revs. pukka round town. what can i say?

Anonymous

No its not, its torque AND multiplied by revs.

Keep peak torque the same and shift it up the rev range and your car gets MUCH quicker because it means you are a gear lower all the time, so your same torque figure@flywheel results in a greater torque @ wheels

Moose 130

Torque gets you moving

Horse power makes top end speed.

My 5.0 mustang has 225hp/300Ft-lb torque and gets moving quite nicely. Planing on adding to the HP without harming the torque though!

AlexF

aye... so its a multiple of the two. BHP is just a number that sounds great in the bar but has little meaning else where.

As for torque getting you starred and bhp giving you top end.... thats not right.... what gets you going is GEARING and its the same thing that gives you top end.

You need lots of toque to pull away, hence 1st gear in your gear box. Gears simply mutiple the torque, you have to turn the gear round and round more times inorder to get an increase of the torque you have, but thats no real problem if you have a choise of gears.

A typical set of gears would be:

3.52:1 1st Gear
2.22:1 2nd Gear
1.43:1 3rd Gear
1:1 4th Gear

All running through a final drive of say 3:1.

1st gear is needed to get you moving as when the car stationary it takes lots of torque to get going. The other problem is that the wheels start off not turning and the engine (to which you are connecting the wheels is!).

Once your up and running you work your way through the gears into top (4th), which is usually a direct drive. This effectivly bypasses the gearbox and connects the engine to the wheels via the diff.

The engine does not change the max torque it can produce (well most don't). The only thing that changes is gearing. The lower the ratio the faster you will go IF the engine has the torque to turn the wheel.

So where does BHP fit into this? No where really its just a measurement used to express torque in different units.

Alex

Jay,

iTrader: (4)

i dont care wat u say chip cos the best racer of all time Sir Sterling Moss said bhp sells cars torque wins races


cheers jay

YBP

Bhp is how MUCH labour beeing done, not saying anything about how it is done.

Torque is how HEAVY labour beeing done, not saying anything about the pace it is beeing done in.

jaycos:
Most racecar drivers doesn´t know sh*t about the car they´re driving.

gearboxman

Chip, I don't agree with you I'm afraid
Power is king.
I agree that whatever the amount of reduction through gearing gives a multiplication of torque, but, the reason you have gearing, is to have your engine revving in its POWER BAND.
Rate of acceleration is governed by power to weight ratio (assuming traction achieved).
If it was all about torque, when you came to a steep hill, you wouldn't change down to make the engine rev (in its power band), you'd happily allow the revs to be dragged down to where maximum torque is and that would pull you up the hill.... which doesn't happen.
Power obviously wouldn't occur without torque, and how much power you make relies on how much torque you have available, coupled with the work rate (rpm) that your engine will provide.

Jay,

iTrader: (4)

man i was just pissin about


jay