........or from my point of view, the declining part of the torque curve.

Good job Grunt......see, that was easy!

Yes, this is a typical result for a GT500 5.4l motor with a 2.3 TVS uprade, a tune and a boost-a-pump mod, otherwise bone stock. With a Kenne-Bell 2.8 or Whipple 3.4 the results are even more impressive 700hp+ with absolutety stock driveability, until the throttle is depressed. DOT approved racing tires do help somewhat, but one must be very careful whilst messin about.........and I not even a ford guy!

John

All this torque reminds me of what Dick Johnson (Famous Oz V8 Supercar driver) said once.

Reporter "How was practice in the rain Dick?"

DJ " scary when you got 500 foot pounds of torque from idle".

This was when it was still called Touring Cars and DJ was the number one Ford Guy with 351 cubes then.

Yes sir......


Candy Store for GT500

John

So nothing, other than the fact that a function that returns multiple values is not a constant function. I'm not re-inventing any mathematical definitions here, I'm merely pointing out your own appalling lack of awareness of the existing ones.

McGuire, stick to gray areas, bullshit works much better in those. You're not going to slip this kind of gibberish past someone with a math degree and near-infinite patience like myself.

That was his choice, but it was still irrelevant.

Do we have any professors of mechanical engineering participating here? And in any way, you are pointing fingers the wrong way, I'm the one backing up my statements with mathematical support, you're the one who doesn't address them and instead returns profanity. The torque guys are the ones insisting that everything they state be accepted as facts, simply because their handwaving statements are unsupported by sound math. They're only supported by abusive language.

Debateable, and entirely irrelevant. We're discussing theory here.

NTSOS has some sound arguements, and pretty pictures that back up quite conclusively what he is saying. I've seen you coming aross using the word 'math' about a million times. The calcualtions check out both ways. Its more convenient to use power sometimes, but going back to very first principles then torque is the key.

NTSOS posts nice dyno graphs, that both he and grunt agree on. NT from the torque perspective and GG from the power perspective.

you are simply resorting to whining like a little girl.

I suggest then that you pay closer attention to the arguments he's making. Claiming that flat torque curve is preferable to flat power curve for acceleration is an indication that at the very least his analysis of calculations does not check out. Just because it is possible to correctly analyze the situation from either power or torque perspective doesn't mean that anyone analyzing it from the torque perspective is automatically correct (and in fact the majority of torque people in this thread are not correct). I stress the word "math" a lot to stress the fact that a lot of what torque guys say doesn't agree with it (and I actually point out how it doesn't agree with it).

I'm not resorting to anything. I don't need to resort to anything, I'm correct and my opponents are not. The good thing about being a math guy is that sometimes you can be justifiably 100% sure that other people are full of it. I do not deny that their refusal to reason does annoy me somewhat, however.

...ah, well.
Let us all agree that torque and horsepower are inter-related....and by that I mean HP is always torque X Rpm...
...as far as I am concerned, at the track, I will say that when doing gear-ratios, I use torque or HP to do my calcs, depending which programme I'm using....if I am doing aero calcs HP at the wheel is easier, as it takes away all the conversions....these things have worked for me, and given coherent results, backed up by data in several assorted formulas, from FFord through F3 to F2, to F3000 to F1, Group C to WSC to LMP, GT1 to GT3,Champcars, IRL, Touring cars, ice-racing, Paris-Dakar Rallye-Raid cars, normally-aspirated, turbo, with and without restrictors, and all stations in between....and I still come back to the fact that I personally like a nice, fat, flat torque band....peaky engines are dyno operators wet dreams, and the main argument between the people who build engines, and those who have to run them...

..this is what you need, calcs for Lemans, with the torque input and given aero data=

[/URL]
On the other hand, maybe we can discuss the number of angels that can dance on the head of a pin? We might get a bit further...

Click here for full size graph

Let me ask you a follow up question. Let's say you do have an engine with a fat, flat torque band. When you're on track and driving at the limit, how often do you actually operate in the band where the torque is flat, as opposed to the band where the torque finally starts dropping off?

Arghhhh.....don't get me started...
The point where your torque starts dropping off is at the top range, where you are at the limit of of its breathing capacity...in the graph I just posted, is one of the few examples of tracks where you reach terminal speed for an appreciable amount of the lap-time, Le Mans.

On the previous layouts, where you didn't have the two chicanes on the straight this argument might have been more relevant, but on the following histograph you will see the amount of time you spend at terminal speed, or RPM, and it is @ 6% of lap time on most of the tracks I have been on.

Can you please explain the reasoning behind your question? It seems to be evading the issue...
..or are you a Bonneville specialist?....( By the way, I am working on a land-speed project at the moment, so if you can clue me in I will be most thankful)

Actually, my intention is to get to the heart of the issue.

People associate flat torque curves with drivability, and drivability is usually synonymous with how well the vehicle accelerates. There is certainly a grain of truth in that notion, an engine with a fat, flat torque curve will be more drivable than the engine with a torque curve that's still rising almost all the way to the RPM of the power peak.

However, what really makes the "flat torque curve" engines drivable is the wide band where the torque is dropping off, which makes for a flattish power peak. In those engines power peak is not just a number you achieve in a very narrow range that takes forever to get to and requires seven gears to stay in, but rather a wide plateau that you can't easily fall out of. When you drive a car with a "flat torque curve" IC engine in anger and are feeling that awesome drivability, you're not actually operating in the flat torque curve band most of the time, you're operating beyond it.

Let's step aside from IC engines for a moment, and think about electric motors. Electric motors are considered to be very drivable, often to the point that they don't require gearboxes (in some cases they are used precisely because they don't require gearboxes, like the traction motors in diesel-electrics). Do electric motors have a flat torque curve?

That is exactly wrong.

At the point you feel the greatest acceleration from the vehicle, the engine is at the rpm of greatest torque in the operating range. That would be max torque rpm if it is available with the chosen gearing; if not, simply the rpm of greatest engine torque available. The broader the torque curve, the greater the sensation is spread over the operating range.

But in the area you refer to, the top of the rpm range where the torque curve has nosed over, acceleration is minimal. It's about time to shift to the next gear, or if in top gear the car is now done accelerating. When the engine is at the max rpm it can pull, the driver feels nothing at all.

I think you need to refine your term "awesome driveability," which seems deliberately vague and evasive.

.

I'm not referring to the top of the RPM range, I'm referring to the range where the torque is simply decreasing. In "flat torque curve" engines torque tends to decrease for a long time before hitting the top of the RPM range.

As for your other statements about torque and feelings, we've been there plenty of times before, I'm not going to repeat my standard counter-argument yet again. I've laid out the equations in the last few pages that support my statements, get back to me when you can disprove them without assuming a gearbox stuck in a gear.

Doesn't matter. If engine torque is decreasing the vehicle's acceleration rate is decreasing, and so is the sense of acceleration for the driver.

.

That's true, but irrelevant. The objective is to maximize the actual acceleration, not the driver's sense of acceleration in any one gear. You know what my equations have to say about how you achieve that.

Actual acceleration and the driver's sensation of acceleration are exactly the same thing. Acceleration is rate change of velocity. I believe you are still failing to fully distinguish speed from acceleration. One g of acceleration is one g of acceleration, regardless of speed.

I suggest examining the proposition that the sole objective is to maximize acceleration. That seems to be where you are jumping the tracks.


.

Signatures are all the rage these days, so I'll have one as well. Hopefully this will stop baseless criticism about me making unsupported statements in this thread.

I fixed the quote 15 minutes before your reply.

Then I guess it would be easy to disprove my equation, wouldn't it be? It would have to be speed on the left hand side, and not acceleration.

My point was (you obviously didn't read the post carefully) we only need the shape and the CF will not affect the shape - unless you are varying the CF during the pull and I only noticed one value of CF on each of the graphs you presented.

Yeah but the torque curve does start declining at 4,500 but peak power happens at 6,500. In an F1 I would try to operate this engine between 6,000 and 7,000 - a long way from 4,500. You need to look at the power curve to work out where to operate the engine.

The torque peak - where you feel the maximum acceleration - is not even used when accelerating throgh the gears because once you are out of first gear, the best acceleration at all times occurs when the engine is closest to its power peak.

Torque in the tailshaft is equal to engine power divided by tailshaft speed and is maximised when engine power is maximised.

No I don't, and no you wouldn't....it is a GT500 street engine and the operating range is from off idle to engine cutoff at *6600* rpm.....don't start!

But I already did start - in post 943 when I said...

"Here is my answer. For a street engine its fine - leave it like it is. Its going to be difficult to use the HP its already got (very often) and the torque means we can go pretty hard without wearing out the shifter.

If we needed to put this power curve in an open wheeler, I would do whatever this engine needs to get another reliable 500 rpm. Then it could spend more time in the flat part of the power curve."

And the flat part of the power curve - the operating range in an open wheeler going flat out - would be 6,000 to 7,000.

Ok pal.........nope wrong again, irrelevant and redundant information, the torque curve dictates exactly what the power curve will look like.

I am right and you are wrong!

Sorry, it is as simple as this.....I am right and you are wrong!

That is correct, one dictates the other but the torque curve does not tell you where to operate the engine for max acceleration unles you go to a lot of trouble computing thrust curves or similar. With a power curve you can tell at a glance where to change gears. If I am wrong, give me an example of an engine (with power curve) that shouldn't be operated at the power peak.

Good executive summary of your arguments.

Nope, that's nonsense......no trouble at all..........I disagree!

I knew you would like that.........here is another one for you, I ran a memory dump!

Acceleration is caused by torque and not by horsepower. Of course, an engine with higher horsepower at a given RPM automtically has more torque at that given RPM because horsepower = (RPM * Torque) / 5252.

But acceleration time is calculated using the following formula:

t = ((WK^2)*(delta N)) / (308 * T)

where
(t) = acceleration time in seconds
(WK^2) = inertia
(delta N) = change in RPM
(T) = acceleration torque in ft-lbs

As a result, more torque at any given RPM will result in a higher acceleration rate.

[QUOTE]Originally posted by NTSOS
But acceleration time is calculated using the following formula:

t = ((WK^2)*(delta N)) / (308 * T)

where
(t) = acceleration time in seconds
(WK^2) = inertia
(delta N) = change in RPM
(T) = acceleration torque in ft-lbs

As a result, more torque at any given RPM will result in a higher acceleration rate. [/QUOTE]Yes but the relevent torque to use in your formula is driveshaft or axle torque - after the gearbox and this can be expressed as either engine torque x reduction or power/driveshaft speed. The first of these formulae is not useful because the terms are not independant eg to move the engine speed to the peak torque rpm in order to maximise the torque term, you must change the gearing. Fortunately the equation can be rearranged to the second expression which is independant of gearing. This equation tells us that torque in the driveshaft is greatest when engine power is maximised.

In a nutshell - although "more torque at any given RPM will result in a higher acceleration rate." is true, if you need to run lower revs to get to the "more torque" range of the engine, you will need taller gearing which loses you more driveshaft torque than you gained in crankshaft torque.

Look at these thrust curves. Can you not see that the shift points need to be way up in the rpm range from the torque peak - in fact up above the power peak?


By gruntguru at 2009-04-04 [/B][/QUOTE]

Darn, that just threw any reasonable chance for me to debate you out the window

Only 17 to go......

Have to disagree with you, you troll and troublemaker you, different cars most certainly give different sensations of acceleration mostly through changes of pitch all the way to a simulator that can do it without actually going anywhere.

Now only 16....

Now YOU are just being argumentative. You know McGuire meant "for a given car" and "in a given gear"!!!

15 to go.

Nah, I didn't actually, I don't have the inclination to fully include myself in this thread, I was just trolling and being a troublemaker

All the while blatantly manouvering to get the post count up into 4 digit territory.

Well guys I finally have some real data that I am happy with and is reportable regarding acceleration rates (via G force) versus RPM and KPH in a couple of gears.

Getting the data was a much greater pain in the bum than I ever thought it would be but perseverance pays off. As previously reported I used my GTech 2 by Escort. I used it because it reads G forces directly whereas my other choices don’t have G input sensors so I would have had to back calculate G from speed/distance downloads. Plus I would have had to install the sensors and rewire my daily driver to get the data. Seemed to be too great an effort just to try to put some information into the various camps that seem to have developed on this thread.

The GT2 has two problems to overcome. Both took time to overcome. First is that the GT2 does not store data; one has to grab data on the fly. The second is that it provides G forces to two decimal places where three would have been better. Except the Gs change too fast in 2nd gear to discern the third decimal if it had it. Third was OK. Fourth, the gear used by most rear wheel dynos would have been better yet except that puts one up to some truly anti-social speeds.

Had the help of my secret weapon daughter to gather data. She ways 45 Kg and has an outstanding record as a rally navigator. Her navigation apogee was being in a class-winning car in a round of the WRC. She is ultra experienced in heads down looking at instruments while moving a great rates of knots. I read revs, she read and recorded Gs.

Anyway I now have lots of data that checks backwards and forwards and seems sound. I can present it in any number of forms of G rates, m/sec^2 etc versus revs or specs in KPH or MPH. Can also convert to metric torque and power outputs.

I don’t know how to post charts and after this much time spent not too interest in learning how. Plus I think that it requires joining a recipient group that doesn’t excite me too much.

In the meantime I will post raw data that really does tell the story by itself. By the way my engine provides max T at about 3500 and max power at about 5200 revs.

In second gear:
Revs KPH G
1800 33 .37
2300 42 .45
2800 51 .48
3300 60 .50
3800 69 .49
4300 78 .47
5100 92 .41
5500 100 .30

Same info for third gear:
Revs KPH G
1800 47 .25
2300 60 .30
2800 73 .32
3300 87 .33
4000 105 .32
4500 118 .30
5000 131 .27
5300 139 .24
5500 144 .18

I also gathered coast down data. Plotting against 5th gear power indicates that rear wheel power and combination of rolling and aero loads come together at about 253 kph or just past the max power revs. I possibly have the aero plus rolling loads a trifle low but that is just a gut feel and I am not going to prove if it really will go that fast which is the final proof of that data set.

I offer the information without comment. Make of it what you will.

Regards and will watch for your analysis

Theory is a whole lot different from practice. As a mathematician, I'm sure if you tried, you could submit an acceleration equation that does not include 'power' as one of the factors. Submit the chapters of your resume' that pertain toward your motorsport experiences and successes, why don't you? This may be from an engineering, a builder or a driver perspective. RDV is the most respected member on this forum as regards race car engineering. The other members with whom you differ, are all involved with professional motorsport and in particular, from an engine perspective.
Since acceleration is your thing, how many different types of cars have you driven down your local drag strip?
If you had, you would have discovered that most of the cars will require different shift points than you would have thought, particularly the ones with the highest and flattest torque curves.

Thanks for the effort. You could have used a cam-corder. Torque wins again. Like I said, I shift my Z06 long before max power rpm for the fastest 1/4.

As far as I'm concerned Joe Bosworth's data on post 988 confirms my belief maximum acceleration occurs at maximum engine torque rpm.Not only that,the acceleration falls away such that acceleration at the "peak power" RPM, much vaunted by grunt guru,Guller and the rest, is signifigantly less.

That plume of smoke over there is where the power guys crashed and burned. VIVA TORQUE.HASTA LA VISTA.

I took the liberty of plotting the G force data. I suppose it also shows the heart of the discussion:


Yes, the graph shows max acceleration in a single gear close to max torque RPM, no you don't run the engine there for best vehicle performance (while engine torque at 87 km/h is lower in second gear, torque at the wheels is actually higher due to the gear ratio difference).
Funny thing is that the optimum trade off between engine speed (and gear ratio) and torque is where the area under the power curve is greatest, nice huh?

I believe the calculations are valid, I totally reject your "unbiased" analysis....torque determines the rate of accerlation, power is derived from torque, power = (RPM * Torque) / 5252, the torque curve defines the exact parameters of the power curve and if you are shifting at the power peak or over, your are in fact shifting at the exact same point in the declining torque curve!

The power curve is redundant information!

A flat torque *CURVE* is not a perfectly straight line!

A flat power curve in not magically created by devine
intervention, its parameters are defined by the torque curve.

I am right and you are wrong!

Acceleration is a moving feast.A driver cannot select the torque peak or the power peak and simply use one in preference to the other.Even a non-technically minded novice driver will instinctively feel their vehicle accelerate at it's best as the torque area arrives,hold that gear until the engine becomes uninterested and torque drops well away,then shift to a higher gear.No amount of scatological debate will tell me the novice is wrong.Power figures are only measuring work done,like a detective coming in after a murder.

If an F1 driver is using 13000rpm to 17000 rpm lapping fast,it will be an engine with torque peak around 13000 and power peak around 17000rpm.

That is THE key. If you're going to stick with the torque method, then you have to a realize that when you're maximizing output torque, you have to maximize the product of two terms that are dependent on each other. Most of the common fallacies in the torque camp in one way or another involve setting one of the two terms of the product constant by some sleight of hand, when in fact you can't change one without changing the other.

As a "mathematician", I concern myself with making rigorous arguments rather than waving my resume (although I did make an exception recently with McGuire, just to get him to stop trying to convince me that I don't know what constant functions are). The point of math is to make arguments stand on their own, and not on some other foundation succeptible to extreme bullshit.

Practice may differ from idealized theory, but that's no excuse to get the idealized theory inconsistent or wrong. And let me be clear, McGuire and NTSOS are getting the idealized theory wrong, they're not merely stating the same thing we do with a different-but-equivalent logic.

In any case, it's not like I'm taking on all motorsports engineers, Fat Boy is one example that you don't need to have a confused understanding of acceleration dynamics to work in motorsports. He was also way too sensible to let himself get involved in this debate again.

You're actually making a wrong conclusion from a good data. Let's look at 92 kph, for example. In 2nd gear, when we're near the power peak, we get .41 G acceleration. In third gear, when we're near the torque peak, we get either .32 or .33 G acceleration. Which number is bigger, 41 or .33? When do we get a bigger number, when we're at the power peak, or when we're at the torque peak?

Will I be??

Really, will I be??????

YES!!!

1000!!!

you are sad. (if i could have got there i probably would have done so i guess im sad too)

edit


1001.... means im one better!!!

This exchange immediately below, I agree with and my torque at the drive shaft post is how I select ratios. So why the roundy round?

Originally posted by gruntguru:
In a nutshell - although "more torque at any given RPM will result in a higher acceleration rate." is true, if you need to run lower revs to get to the "more torque" range of the engine, you will need taller gearing which loses you more driveshaft torque than you gained in crankshaft torque.
Response:
Originally posted by Guller:That is THE key. If you're going to stick with the torque method, then you have to a realize that when you're maximizing output torque, you have to maximize the product of two terms that are dependent on each other. Most of the common fallacies in the torque camp in one way or another involve setting one of the two terms of the product constant by some sleight of hand, when in fact you can't change one without changing the other.[B]

The max power of the engine is 5500rpm. Plot the power curve, why don't you? This particular engine is so inefficient at this rpm, that this rpm can not be obtained in top gear and anything over 5 gs is a waist of time. Torque at max power in second is .3 as you state but you gotto shift some time. With this engine and tranny combo, I'd shift at 4900rpm in 1st, 2nd and 3rd for max acceleration. The power aint gonna help me. What is your point? The gear box has almost the right ratios for maintaining the min torque shift after a gear change which is the objective. An S 2000 would be designed differnty. This combo, you stay with torque, the Honda with power. The S2000 has lost 1000rpm to accelerate faster, don't you know?