Torque horsepower and being quick!!!

**Stav** · 18-02-2005, 05:50 PM

Hi all ...finally I have discovered how it all works after reading this article

http://vettenet.org/torquehp.html

Does anyone know where peak power occurs in rpm? Or peak torque? Does it change with a cam in the 4.0 engine?

It seems that to take advantage of power we must change gears at the top of peak torque or get more torque...

xdc351 · 18-02-2005, 06:07 PM

Peak torque is not produced at any given RPM, that depends entirely on your engine configuration with ONE major exception.... peak torque will always occur before 5252RPM.

Big HP is made by keeping the torque as close as possible to peak afterwards. Hope I'm making sense

18-02-2005, 06:22 PM

Woah, really? Before 5252RPM huh? Can you explain why please, xdc351?

Sox · 18-02-2005, 06:40 PM

Quote:

Originally Posted by xdc351

Peak torque is not produced at any given RPM, that depends entirely on your engine configuration with ONE major exception.... peak torque will always occur before 5252RPM.

Big HP is made by keeping the torque as close as possible to peak afterwards. Hope I'm making sense

You're not actually.

Many engines produce peak torque much higher than 5252rpm.

5252rpm is the point at which power and torque are the same, that is, if measuring in HP and ft/lbs.

Rick.

DanXR6T · 18-02-2005, 06:46 PM

I just wrote a long post but I hit the button and lost it so now I'll write a short one lol..

Useless
Basically going past peak torque allows the torque to increase as load is applied such as wind or a hill and revs drop.

Being at peak torque and hitting load will cause revs and torque to drop and make you car die in the ****.

Daniel..

rodderz · 18-02-2005, 07:02 PM

I could agree with that article...

Last year i was changing gears at redline (5850rpm or so), and after some advice from Rod in his pursuit, tried shifting lower at 5300-5400rpm, closer to where the peak torque point was. Next run took off a 10th, and I believe Rod got his 12.6 changing at the same point.

Maybe these Boss motors dont need an rpm limit increase after all

**Stav** · 18-02-2005, 07:34 PM

I just noticed that while peak torque at flywheel for AU standard

4.0 is 357 nm at 3000 rpm
4.0 is 366 at 3150 rpm xr6 hp
4.0 is 374 nm at 3500 rpm vct
5.0 IS 395 AT 3200 RPM
5.0 HO IS 412 AT 3500 RPM.

So in theory if peak torque occured at 5000 rpm when we thrash the car and gears changes take advantage of this then we will acclerate harder and have excellent times too.

On thinkng about this further in my mind then a stiffer diiff ratio combined with earlier gear changes will be awesome.

Therefore having a dev 5 or 4 (being a bigger cam than xr6) peak torque probably occurs at 4000 rpm.Theres some food for thought

champsky · 18-02-2005, 07:34 PM

hmmm so correct me if im wrong cause that article confused this simple mind, but its better to change gears @ peak torque not peak HP????

**Stav** · 18-02-2005, 07:39 PM

Quote:

Originally Posted by champsky

hmmm so correct me if im wrong cause that article confused this simple mind, but its better to change gears @ peak torque not peak HP????

Man Im no expert .But just thinking about it right...say our gearboxes are programmed to change at 4700 rpm under full throttle....and peak torque occurs at 4000 rpm say (for example )it is 450 nm.. at 4700 rpm you will be having a reduction in torque as peak has passed...so why the heck change when torque has died down and not top of the torque peak?? Change at 4100 rpm to take advantage and not slow down.At 4700 rpm you will be makng more noise and going slower!!!!

T3man · 18-02-2005, 08:22 PM

Quote:

Originally Posted by champsky

hmmm so correct me if im wrong cause that article confused this simple mind, but its better to change gears @ peak torque not peak HP????

No, not necessarily. You have to know the torque of your engine through the whole rev range.

Just assume max torque is at 4000rpm for simplicity. Even though torque may start dropping after 4000rpm, what is critical is the revs that the engine will fall to after your gearchange. Say you change up at 4000rpm and hit 3000 in the next gear. Now what you have to consider is the torque at 3000 rpm compared to the torque at say 4500 rpm. If the latter is greater then you should hold back your gearchange .. until you get to the point where torque in the lower gear at high revs (with torque falling) is equal to the torque in the higher gear at lower revs (with the torque rising).

Hope I've made that clear enough ...

T3man · 18-02-2005, 08:27 PM

Quote:

Originally Posted by useless

Man Im no expert .But just thinking about it right...say our gearboxes are programmed to change at 4700 rpm under full throttle....and peak torque occurs at 4000 rpm say (for example )it is 450 nm.. at 4700 rpm you will be having a reduction in torque as peak has passed...so why the heck change when torque has died down and not top of the torque peak?? Change at 4100 rpm to take advantage and not slow down.At 4700 rpm you will be makng more noise and going slower!!!!

See my explanation above as to why this isn't quite correct.

Think of torque as being the force that gives you accelleration. Now, as torque passes it's peak your rate of accelleration will decrease. However the mechanical advantage of the gears will help offset/overcome this, as gearing reduces load and therefore allows faster accelleration. So even though your rate of accelleration is falling it will still be greater than the rate of accelleration at lower revs in a higher gear ... UNTIL the criteria I mentioned above is met.

Hope this helps...

jonbays · 18-02-2005, 08:27 PM

power and torque are directly related to each other. plenty of discussions about which is better to have but this is a furphy as you can't get one without the other. power is what you really want.

Simple demo go out and drive a large diesel 4WD and then compare it to the petrol V8 version. Both engines deliver the same torque but you will understand the difference power makes.

Acceleration of a car is simply governed by the basic physics of the power divided by the weight modified by gearing and aerodynamics.

LuvinmyEB · 18-02-2005, 08:31 PM

I don't mean to sound rude, disrespectful or like a know it all, but I haven't read the posted article and I'm surprised that some of you guys didn't already know all this.

You push your car to Max RPM and change gears, you'll slow down, surely some of you have noticed this while you've been driving (this also depends on your engine and gear ratios).

If you listen and pay attention to your car, you'll very quickly learn when the optimum time is to shift and when your car is going to pick up speed instead of drop down.

Here's a trick, cover up your tachos, listen to yor car, feel what's it's doing, you'll soon stop depending on the tacho. You'll get to know your car so much better.

I suppose driving 1.6 and 2.0's without tachos that are little louder than new cars over a number of years helped me learn this.

Just my 2cents worth and probably over charging. :P

T3man · 18-02-2005, 08:34 PM

Quote:

Originally Posted by jonbays

power and torque are directly related to each other. plenty of discussions about which is better to have but this is a furphy as you can't get one without the other. power is what you really want.

Simple demo go out and drive a large diesel 4WD and then compare it to the petrol V8 version. Both engines deliver the same torque but you will understand the difference power makes.

Acceleration of a car is simply governed by the basic physics of the power divided by the weight modified by gearing and aerodynamics.

Hmmm .... you started out pretty good. Until you started comparing diesels to petrol engines. For the same capacity engine, diesels generally produce more torque. But, because they rev lower they don't produceas much power. For a diesel to produce the same power as a petrol engine it must, by definition have far greater torque, because, as you quite correctly stated power and torque are directly related.

**Stav** · 18-02-2005, 08:35 PM

Quote:

Originally Posted by jonbays

power and torque are directly related to each other. plenty of discussions about which is better to have but this is a furphy as you can't get one without the other. power is what you really want.

Simple demo go out and drive a large diesel 4WD and then compare it to the petrol V8 version. Both engines deliver the same torque but you will understand the difference power makes.

Acceleration of a car is simply governed by the basic physics of the power divided by the weight modified by gearing and aerodynamics.

Power is important JonBays. Peak power occurs well after peak torque. However by the time peak power is reached peak torque has died.They dont refer to power but the torque in the example between the 2 cars and their corresponding times and its availability at higher rpm

AUIII XR8 MAN · 18-02-2005, 08:39 PM

So that why i have a much stronger take off when the gear box is in economy mode.

**Stav** · 18-02-2005, 08:40 PM

What gets me about this is that shifts well into peak torque as opposed to peak horsepower will win the race.Am I wrong?

champsky · 18-02-2005, 08:41 PM

ahh so, you should try and keep the torque high so when you gear change you dont have a lag so to speak???

cause i know in me eski i dont redline it cause i think that i get better gear changes below redline (i dont read my tacho so i dont know what rpm it is)

**Stav** · 18-02-2005, 08:42 PM

Quote:

Originally Posted by champsky

ahh so, you should try and keep the torque high so when you gear change you dont have a lag so to speak???

cause i know in me eski i dont redline it cause i think that i get better gear changes below redline (i dont read my tacho so i dont know what rpm it is)

Thats what I am thinking.But generally when I am driving around I rev it the auto out and it seems to die then change gears.If I changed at the top of the torque acceleration curve and change gears quickly with the shift kit it flies.

LuvinmyEB · 18-02-2005, 09:09 PM

Quote:

Originally Posted by champsky

ahh so, you should try and keep the torque high so when you gear change you dont have a lag so to speak???

cause i know in me eski i dont redline it cause i think that i get better gear changes below redline (i dont read my tacho so i dont know what rpm it is)

In laymens terms for ya Andy, keeps your revs up but not until your car is screaming for you to change gears, if you change gears when the car is threatening to leave you without a gear box you are going to decrease in speed. Bummer dude... lol

With your car that's designed to go into a certain gear at a certain time/speed, if you don't get it spot on or close to it, yes you lose power. However if you hit that sweet spot, you'll be right in the engines power band and the car will accelerate and keep going until you reach the next gear change. :eclipsee_

That's about as simple as I can make it for ya. ;)

Catfish?

AUIII XR8 MAN · 18-02-2005, 09:14 PM

Are signs of a ture driver. Driving by the bumometre, not the what a silly tacho says. I found that the bumometre is better when to changs gears with manuals. You can feel a power declined as it get pass a certain rev.

LuvinmyEB · 18-02-2005, 09:29 PM

Quote:

Originally Posted by AUIII XR8 MAN

Are signs of a ture driver. Driving by the bumometre, not the what a silly tacho says. I found that the bumometre is better when to changs gears with manuals. You can feel a power declined as it get pass a certain rev.

Been trying to tell that to new drivers in their new cars for years, don't watch the gauges (except maybe the oil and temp. LOL!), listen, feel... be at one with your car.

py: :hihi:

**Stav** · 18-02-2005, 10:32 PM

You dont have to look at gauges unless you have run it on a dyno.I have to agree that you can feel when the time is right because you tend to know when it starts to die down.

If you can get more power and more torque higer in the rev range then wot acceleration will be better.

The MaDDeSTMaN · 18-02-2005, 10:50 PM

I could write an essay on this, but I won't, because I'm sure there are people on here who know more about all this then I do, and besides I'm sure no-one wants to read one of my essays, lol.

All I'll add is this, keep in mind that if you rev your engine to, lets say 6,000 RPM, then it only has a very small amount of time to get in the air/fuel mixture, compress it, ignite it, then get rid of the exhaust gases. If your engine is revving so fast that it can't get the air/fuel mix in efficiently, or get the spent exhaust gases out quickly enough, obviously that is going to have a negative effect on power.

I find that shifting my 2.0 Escort at about 4500 RPM gives me the best 0-100km/h runs, much higher then 4500 RPM is pretty much pointless, and shifting then (at about 4500 RPM) puts it right in the meat of the engines powerband in the next gear. I learnt this from changing when it felt right, then looking at the tacho when I did it, then trying a bit higher and a bit lower with the revs, but 4500 or so gave the best results, so that's where I shift if I'm in a hurry to get up to the speed limit for some reason.

*cough* Not that I ever race change, LOL *cough*

The MaDDeSTMaN · 18-02-2005, 11:02 PM

Quote:

Originally Posted by LuvinmyEB

Been trying to tell that to new drivers in their new cars for years, don't watch the gauges (except maybe the oil and temp. LOL!), listen, feel... be at one with your car.

py: :hihi:

Yes, those who are driving a V8 Commodore might well want to keep an eye on their oil, lol

I can say that, Fords 2.0 OHC "pinto" engine also apparently likes oil - I've known a few people who complain about endless oil leaks and oil being sprayed all through the engine bay by those engines. Not that mine does much, thankfully

LuvinmyEB · 19-02-2005, 12:20 AM

Quote:

Originally Posted by useless

You dont have to look at gauges unless you have run it on a dyno.I have to agree that you can feel when the time is right because you tend to know when it starts to die down.

If you can get more power and more torque higer in the rev range then wot acceleration will be better.

Sorry I have to disagree with your comment about running your car on a dyno. The readings that a dyno gives you tells you the maximum torque and horsepower, this is not when you change gears. You change gears after your car is at maximum torque or you will lose speed. Ideally you want the engine revs a little lower than max torque so that you your motor is about to produce peak torque therefore giving you more speed instead of dropping in power.

If you want to know what your max torque, RPMs etc are, you could also read a book or look it up on a website, however these are all theoretical. Only you know are able to tell when it feels fastest or the best time to change gears is. Or at least you should be able to, because if you're going to rely on websites, dyno's, books and tacho's your not paying any attention to the feedback your car is actually giving you, which any driver worth their salt is able to do.

Des · 19-02-2005, 12:35 AM

I agree with "luvinmyEB". I've got a BA mk I XR8 and when it hits the cam (1st and 2nd)the last 2000 rpm disappear real quick. If you try and watch the tacho you'll smack the limiter every time. I change up at approx. 5500 rpm (take a friend to call out readings so you can learn to listen to your motor) and land back on cam for the next gear. By the way, approx. 167 km/h is the limiter in 3rd, found that out on my first visit there....

svo347 · 19-02-2005, 12:56 AM

HorsePower is what sells engines...
Torque gets you over the line!!

LuvinmyEB · 19-02-2005, 09:34 AM

Quote:

Originally Posted by svo347

HorsePower is what sells engines...

Actually the guys name was John that sold me my engine, I don't think his surname is Power though. :hihi:

Casper · 19-02-2005, 09:40 AM

Quote:

Originally Posted by LuvinmyEB

Sorry I have to disagree with your comment about running your car on a dyno. The readings that a dyno gives you tells you the maximum torque and horsepower, this is not when you change gears. You change gears after your car is at maximum torque or you will lose speed. Ideally you want the engine revs a little lower than max torque so that you your motor is about to produce peak torque therefore giving you more speed instead of dropping in power.

If you want to know what your max torque, RPMs etc are, you could also read a book or look it up on a website, however these are all theoretical. Only you know are able to tell when it feels fastest or the best time to change gears is. Or at least you should be able to, because if you're going to rely on websites, dyno's, books and tacho's your not paying any attention to the feedback your car is actually giving you, which any driver worth their salt is able to do.

Except for every professional race driver in almost any motor racing catagory...all of which use a shift light that has been programmed to give the optimal rev point to change gears.

Feeling the car is good but, given that or cold hard facts off a dyno, along with an understanding of your cars gearing, I'll take the cold hard facts any day.