Revisiting Torque

[Knestis]

I kicked this off without benefit of any real world context but there ARE some things to be considered.

Such as, we are stuck with limited data so are trying to find some proxy or estimate for actual measures of "useful torque," that would require the kinds of data Tak describes. We know that "anything else is just guessing" but don't have any choice but to do so.

Ultimately, the questions are DO WE guess and, if so, HOW...? **

K

** By "guess" I mean "informed guess," not POOMA. We're trying to get away from the latter. EDIT - and we're talking about informed guesses to establish repeatable practices/processes for all cars, rather than informed guesses in isolation for each car we look at.

[GKR_17]

First off, for all who have forgotten, horsepower is just torque multiplied by RPM (with a linear factor to make the units work). A single torque number has very little value. As several others have pointed out, the area under the power curve is actually what matters. In general, a higher torque motor will have a flatter power curve, but that is far from the whole story. Higher reving motors get the same power to the ground from less torque. The transmission ratios are just as important as the power curve.

The important factor here is how much power does the engine have after shifting gears? Any math that doesn't account for the power curve and the transmission ratios is never going to get the job done. Since it is unrealistic to get the power curve for every car, I think it should be ignored. Sure that's not perfect, but using one torque number is no better than what we have now, and is more complicated. I would rather have the rules more stable so we know what to expect year after year - something that makes IT far better than prod, most of us would agree right?

I was glad to see the V-8's added to ITR, but I think the torque adder was excessive.

[dickita15]

So the information that is available to the ITAC is: peak hp at a specific rpm, peak torque at a specific rpm and tranny ratios. Can any constructive formula be made with this data?

[JeffYoung]

To me only peak hp at a specific rpm means anything.

I've personally reached the conclusion, barring a stroke of lightning, that we can't do anything formulaic with torque.

[Tak]

A crude rule of thumb has always been to run the engine between the torque peak and the HP peak.
Since you have HP peak @ rpm, you have the torque at that rpm (torque = HP*5250/rpm).
I suspect a linear interpoloation between the two points on the torque curve will be reasonable.
You have the gear ratios, pick a popular tire size, and reasonable final drive (e.g. 4.10 for a torqy motor, 4.60 for a medium torque motor, 5.10 for a low torque high revving motor). I think that is enough information to draw the torque vs mph curve for all the gears.
That is better than guessing in my opinion.
The more I think about it, I like it.
Use excel to calculate the wheel torque value for each mph from 25 to 125. Summing the torque value at each mph is simple way to get the area under the curve. A conditional function (if/then) will be needed to pick the higher of the two numbers when curves overlap. Another conditional could linearly extend the torque curve past the HP peak when curves do not overlap.
Such a model might even help balance gearing differences between cars...

Tak

[dickita15]

A crude rule of thumb has always been to run the engine between the torque peak and the HP peak.
Since you have HP peak @ rpm, you have the torque at that rpm (torque = HP*5250/rpm).
I suspect a linear interpoloation between the two points on the torque curve will be reasonable.
You have the gear ratios, pick a popular tire size, and reasonable final drive (e.g. 4.10 for a torqy motor, 4.60 for a medium torque motor, 5.10 for a low torque high revving motor). I think that is enough information to draw the torque vs mph curve for all the gears.
That is better than guessing in my opinion.
The more I think about it, I like it.
Use excel to calculate the wheel torque value for each mph from 25 to 125. Summing the torque value at each mph is simple way to get the area under the curve. A conditional function (if/then) will be needed to pick the higher of the two numbers when curves overlap. Another conditional could linearly extend the torque curve past the HP peak when curves do not overlap.
Such a model might even help balance gearing differences between cars...

Tak

Tak, that is the way I think it works as well but I admit limited real world knowledge.

[Knestis]

I've been playing with something that tries to get to that same place but yet another challenge looms. We'd have to figure out what weights to associate with the resulting "torque number." Knowing something is only half the battle: The ITAC has to turn that into a factor it can specify that will adjust for the differences we're trying to control for - weight.

I've gotten dinged by some who've seen it because we have to make assumptions to set how the torque input variable influences the weight adder/subtractor. I KNOW that's necessary, and am willing to trade a couple of assumptions right up front that we then stick with, for a new set of assumptions with every car classified.

Any ideas on this piece of the puzzle, from a theoretical perspective?

K

[Gary L]

A crude rule of thumb has always been to run the engine between the torque peak and the HP peak.
Since you have HP peak @ rpm, you have the torque at that rpm (torque = HP*5250/rpm).

Hold on a minute. We do not have the HP peak @ rpm, nor the torque at that rpm, for the engines actually being raced... we have the data for stock engines. I submit there is enough difference between the two (using headers, ECU tuning, etc.), to make this just another WAG. Without the as-raced data for every engine out there, we've simply replaced a guess with another, slightly more sophisticated, guess.

I tend to agree with those who think the way to handle this is to look more closely at gearbox ratios, specifically the split percentages between the reasonably useable gears. At least that's something for which we have hard data, and unlike HP/torque numbers, it's not a moving target.

[ddewhurst]

****We'd have to figure out what weights to associate with the resulting "torque number." Knowing something is only half the battle:

Any ideas on this piece of the puzzle, from a theoretical perspective?***

Use the model our production car big brothers use.

[Andy Bettencourt]

Without the as-raced data for every engine out there, we've simply replaced a guess with another, slightly more sophisticated, guess.

This is the main question. If you think 'sophisticated' is also 'a little more accurate', then it deserves consideration. If not, then no.

3 choices in my mind. Eliminate torque from the equaion all together, keep using subjective chunks or create a formula that removes subjectivity and applies weight in small amounts OR chunks once thresh-holds have been met.

[dickita15]

To me only peak hp at a specific rpm means anything.

I've personally reached the conclusion, barring a stroke of lightning, that we can't do anything formulaic with torque.

Jeff I understand you do not think this is workable but I applaud Kirk’s effort to explore in this conversation whether it is possible both technically and with political consensus to account for torque in a les subjective manner. It is very possible that in the end your position that this is too hard will be proven right but we will not know unless we fully vet the options.