Torque vs. HP

[titanic]

Re: Torque vs. HP

For a street car, people prefer higher torque at lower RPM so you don't have to rev the nuts off the engine just to overtake. Meaning longer engine life and "quicker" perceived response, ceteris paribus.

I believe where you want torque depends on what speed you want to overtake. Low RPM means low speed. The ideal is to have flat peak torque for as broad a RPM range as possible. That's my conclusion after reading the whole thread. Please correct me if I am wrong.

 

[Shaun]

Re: Torque vs. HP

OK agree redline and optimum very close perhaps few hundred or even tens of rpm from redline, so shift at redline

Often the ideal is not just tens or hundreds from redline, but tens or hundreds past redline. Former allows free choice both sides of ideal, latter constrained by redline on the far side. This is an important difference.

Glad you brought up Visual and aural cues - both human senses, contribute towards "feel". Are you recognising the importance of sensory input now?

No, because even combined with other nerve and muscle input, they are inaccurate in terms of sensing longitudinal accelaration. The senses sometimes even conflict.

Did I say take the tacho out of the car or avoid looking at it? Point (1) in my previous post; agree - shift at redline (use tacho).

You said you had many other things to do while driving.

Difference between optimum and redline small by your arguments, so shift at redline, especially on sporty or racing engine.

No, what I said was, difference might be small, but difference almost always lies between redline and a point past redline (in which case we are still constrained by redline) - so shift at redline. There is a significant difference between what you say I say, and what I actually say.

No I did not, I have agreed with all your statements above - which is to shift at redline. I suggested that trying to shift at the optimum which is close to but not actually at the redline and which is at different rpm for each gear ratio is anal.

The idea that optimum is going to fall 2, 10, or 20 RPM short of redline is a figment of your imagination. Do the math and see what the exceptions are, and when the exceptions occur, how far they are from redline, and whether this number can be differentiated and shifted on.

Did I say no time to glance at the tacho? I meant to sufficiently accurately read the tacho to get close to the optimum points you will need to more than just glance at your perfectly accurate tacho.

You keep making the assumption that RPM is changing too rapidly to follow and shift to and that tachos are horribly damped and inaccurate. They're there for a reason, and the quicker a car is built, the less damped and more accurate they are.

To know an optimal point, and to target it, is something a lot of people do. Just because you don't want to, or because you can't, doesn't mean others shouldn't. What you call anal, others call precise and efficient.

2 separate points,
1. I'm convinced, shift at redline so not much point in using optimum shift points (see above)

See above my reply.

[quote2. Your sweeping statement about human feel. Don't underestimate humans. If Schummi (sorry got to use him again) loses his rev counter in the middle of a race, is he still going to be quick or is he going to slow down drastically (which he should be if going by your arguments he may shift thousands of revs off optimum).[/quote]

There's no logic to this because he has already been told the optimum, and has spent prior laps shifting at the optimum, he now has markers in his head, and is not sensing acceleration to pick shift points.

Without knowledge of what the engine power delivery characteristic are, what gear ratios are, he isn't going to find the shift points and get round the track quicker than another driver of roughly equal driving capability who has been given the information. It will take him hours to figure close to optimum out. He may never get to optimum. He may feel he is there, but he won't be.

You say poor, bad inaccurate, how much accuracy is actually required??

Required to do what? Pick optimal shift points? A lot of accuracy is needed.. You can't even detect a hundredth of a G. Even if you somehow could, now you need to try out different shift patterns... huge number of permutations.. and select one that has best accel by feel. It isn't going to happen.

Any names or numbers from the study, or a reference?

Nope, no study. Just 7 out of 7 good people in a range of industries that require this knowledge. 7 out of 7 who vocally agree on these things, and 20 or so other excellent ones who hear it and do not disagree and who are also involved in industries that apply these things (including F1, LMP, GT insiders). All 30 or so of them are people who are hugely anti-error and will call anyone out on anything that is found to be false, or can be argued logically to be false.

Disagree, yaw acceleration at the limit can change quickly or not so quickly depending on the vehicle, tyres suspension design, conditions etc.

Have you ever performance driven? Your statements really convince me you have never driven hard. When you're cornering and you reach the limits, you are made very aware by yaw acceleration changing quickly. Again you raise the possibility of extreme exceptions just for the sake of doing so. The vehicle you describe would be the worst car on earth because it would push all over the place at the lowest of speeds, on the hardest of tires, as if it was on ice. You could go out and buy or rent the cheapest car on the market right now and if you drove it to its cornering limit, there will be obvious signs when you reach it.

I don't want to argue this point. This is totally different from straight forward long. accel. which gives no clear sign if you're non-optimal or optimal.

By the same token, if longitudinal acceleration changes this is also jerk. If you insist that humans can only sense quick and obvious changes in acceleration, you will have to quantify quick and obvious, and define poor, bad, inaccurate. If a proper study has been done, then there will be some quantifiable conclusions eg. the average human can sense jerk of x magnitude. You cannot just say it is known to be poor, and apply it to your specific situation, just because these engineers and pilots and whoever said it. This is not doing justice to the people who actually did the study and who no doubt put numbers to their findings.

Humans do not sense well enough to pick optimal shift points by feel... plain and simple.

I'm sure such a study exists, I just don't want to spend the time to dig it up because it is outside of my main interests, and because I am firmly convinced that I already have the truth on the issue, from all these good people. Also because I can prove it with some very quick and simple experiments. I could put you in a car and shift switch patterns arounds on you to yield total difference in 0-200km/h times of a second or more, and you wouldn't be able to rank the runs in terms of acceleration. I could do the same and keep shift patterns similar and switch maps around to vary acceleration, and out of 4 or so runs with no run closer than 0.4 seconds to the next closest run, and you wouldn't be able to rank them correctly. I could even cruise up to top gear and have different maps that yield different low accel across long periods of time, different by 0.05 G, but also different degrees of open exhaust or aero config and you wouldn't be able to rank the runs.

Next you're going to ask me to do it, but first I'll ask you to put money down for my time, and also as insurance for the car that is being abused.

Your primary school math syllabus is way ahead of mine.

You didn't learn multiplication and division in primary school?

Now if we don't see peak torque RPM peak torque must occur above
redline revs.

Contradiction?

No contradiction. Look at engines driven for max accel. They'll never see peak torque because they're operated in a range above peak torque.

I'm not sure why you double space your text?

 

[TripleM]

Re: Torque vs. HP

The ideal is to have flat peak torque for as broad a RPM range as possible

Sure thing, that is very nice and healthy torque

 

[Shaun]

Re: Torque vs. HP

hmm, ok, may i ask, if torque is mathematically linked to HP, why do some engines have high peak torque and lower peak HP whereas others have high HP but low torque?

Because engine speed (RPM) is the other factor.

Equation is..
(Torque X RPM) / 5252 = HP

So power constant, torque and RPM are inversely related, but still linked mathematically. Torque, power, engine speed, are all linked.

 

[TripleM]

Re: Torque vs. HP

Increasingly, high perf cars hv built-in shiftlights to indicate gear changes.
Eg. BMW M cars
so naturally, the drivers don't need to do much of thinking nor memoring the points of optimal shifting but being electronically aided in this instance for alert purposes.
It's wonderful.

 

[Shaun]

Re: Torque vs. HP

I believe where you want torque depends on what speed you want to overtake. Low RPM means low speed. The ideal is to have flat peak torque for as broad a RPM range as possible. That's my conclusion after reading the whole thread. Please correct me if I am wrong.

High power at crank allows you to gear down and create wheel torque which is what accelerates. Crank torque means little.

Broad torque is for ease of driving, not for best acceleration.

Many street engines have more torque then the previous generation V10 F1 engines (~250 ft-lb) Few street engines have more power than the previous generation V10 F1 engines (900+ hp)
F1 engine torque curves have never been broad or plateau like.
Racing engines that do not have longevity priorities or driver control issues have never had plateau like torque curves.

 

[Shaun]

Re: Torque vs. HP

Increasingly, high perf cars hv built-in shiftlights to indicate gear changes.
Eg. BMW M cars
so naturally, the drivers don't need to do much of thinking nor memoring the points of optimal shifting but being electronically aided in this instance for alert purposes.
It's wonderful.

Here's a photo of one of the systems I program at work... top row of lights are shift lights and can individually be any colour, light at any engine speed, and are matched to individual gears. Was messing around with displays and alarms the other day, so ignore the rhetoric

 

[TripleM]

Re: Torque vs. HP

nice ones..................now what current production road going car has got something closest to this?

 

[axl]

Re: Torque vs. HP

Mountain-fish: What the heck does "So Fu" means??

When you come back, I shall commission you to do one for my car... redline starting at 9k rpm pls!

 

[goggomobil]

Re: Torque vs. HP

Nice, now if I had these

progressive shift lights which come on at different rates depending on gear, which max out at the calculated optimum shift point (dependent on gear ratio)

and probably even take into account my reaction time between the shift light and my action to shift, then of course I would use these to shift at the optimum point if I wanted to have maximum acceleration or do some "performance driving".

Using a traditional rev counter I wouldn't have a snowballs chance in consistently getting close to the optimum points, especially when they are as you say at different revs depending on gear. I would just shift at redline even though it may not be exactly optimum.

Presumably this is why racing drivers get these lights and not a traditional rev counter like the rest of us.

I would be a bit worried if my dash told me So FU though.

 

[axl]

Re: Torque vs. HP

OH... I dint notice the "U" in "So FU" was a capital "U"!

 

[Shaun]

Re: Torque vs. HP

nice ones..................now what current production road going car has got something closest to this?

I recall the Enzo having something similar. Though at the supercar level, as long as you are specific enough with what you want and communicate in a simple but correct terms, any of them should be able to do it for you, or install a system like that for you at additional cost.

Anyone with access to the stock ECU code should be able to control the sequence. DMS might be able to customize the sequence for any of the stock BMWs that have the progressive shift light feature, but there is little need to because the acceleration rates aren't going to be much different unless gearing is changed or lots of power added.

======

Axl, FU stands for Four Umbrellas.

=====

and probably even take into account my reaction time between the shift light and my action to shift, then of course I would use these to shift at the optimum point if I wanted to have maximum acceleration or do some "performance driving".

Using a traditional rev counter I wouldn't have a snowballs chance in consistently getting close to the optimum points, especially when they are as you say at different revs depending on gear.

Your car, my car, street cars, supercars, don't have RPM sweep speeds like big power open wheeler or LMP type cars do with their large engine speed range, big power, low mass, good traction. 99.99999+% of the population will never drive car like that. Don't forget that a race driver has to deal a lot more than we do on the street, at trackdays, or in low level competition. Lights are the most compact and adaptable method of letting the driver know what to do through peripheral vision. Also good for doubling up as visual alarms when required, saving even more space. Numerical readouts are bad for fast changing numbers. Traditional gauges are actually very good provided they are large enough and close to the vision center (lights can be a lot further out and still be noticed esp when varied in colour and intensitiy). Space constraints almost always lead to progressive shift lights in formula cars if they can be afforded.

I would just shift at redline even though it may not be exactly optimum.

Though it almost certainly is, and if you would take the time to find out once, you'd know for sure.

 

[titanic]

Re: Torque vs. HP

Broad torque is for ease of driving, not for best acceleration.

But given that the power of a car is fixed, say 300bhp, or 400bhp whatever, and peak torque is fixed at a level that corresponds to its bhp, what shape of the torque curve will give the best acceleration over a broad range of speed?

If I am just cruising at say 90kmh or whatever, I have the option to do this with low gear at higher RPM, or higher gear at lower RPM. Which is the better one?

 

[Shaun]

Re: Torque vs. HP

But given that the power of a car is fixed, say 300bhp, or 400bhp whatever, and peak torque is fixed at a level that corresponds to its bhp, what shape of the torque curve will give the best acceleration over a broad range of speed?

If peak power is fixed, then broad torque will give best acceleration. Don't forget that broad torque is also known as power width. They are exactly the same.

The problem is that the broader your torque curve, or the greater your power width, the more you sacrifice peak power. This is a rule and although there are some forms of technology that allow less of a compromise, or even none at all, they are very limited in effect.

There's a balance to be struck between how broad you want a torque curve, and how much power you want. The limit to broad power is low power realized (compared to power potential) from a fixed specification engine. The limit to peak power is driver ability, course requirements, and engine life.

In real life driving outside of certain restrictive racing classes, peak power is not fixed, so best accel really comes down to power and gearing. Traction in the lower gears at some point becomes an issue, but for you it is still a long way off.

It may get confusing sometimes to with subjective terms like "broad", "wide", etc. If you go by % of peak power at different points in the RPM range, it makes things clearer.

If I am just cruising at say 90kmh or whatever, I have the option to do this with low gear at higher RPM, or higher gear at lower RPM. Which is the better one?

If you're cruising, then you want to be at lower RPM in the upper (taller) gears. This is to extend engine life and reduce friction. Friction rises exponentially with engine speed so you shouldn't cruise at high RPM unless it is a high speed cruise, or if you're anticipating the soon arrival of the need to accelerate hard

Cruise in the upper gears at low RPM, and when you need to accelerate from a cruise, drop down the gears as necessary and throttle up.

 

[YAS-M-Sport]

Re: Torque vs. HP

i install the sprint booster , i feel the power when aceler. but lag when initial start from 0 to 100km/h. are this normal?