Revisiting Torque

K

Knestis

Moderator
The ITAC continues to noodle over how to equitably consider what we all seem to think of as "torque" in our specification math, and I have a question: Without getting bogged down in math, can I sample your first principles on the issue...?

Some questions for consideration...

** When you say "a Mustang has a lot of torque" or "Hondas don't have any torque," what do you mean? Drill into your own language and try to be as explicit as possible about what you are thinking when you say that.

** How would you compare these four cars, in terms of their "torque" relative to one another, AND how would you expect them to compete against one another (there no "right" answers, so far as I know)...

Car 1 - 150 hp, 150 lb-ft of torque

Car 2 - 110 hp, 190 lb-ft of torque

Car 3 - 190 hp, 110 lb-ft of torque

Car 4 - 170 hp, 170 lb-ft of torque

** If they were all otherwise the same, which of those cars would you choose to race against the others? Why?

** (The first hard one) - How is it that you think "torque" makes a difference in competitiveness? If we all have different conceptions of the mechanism by which it matters, we'll probably never get anything like a consensus answer re: how to manage this variable - or variables.

** (The second hard one) - The ITAC can really only control a very few factors, in terms of specifications we can set, the key one of course being weight. How do the factors that we MIGHT control bear on torque, to your way of thinking? Is it safe to say for example that more weight mitigates against a "torque" advantage?

** Finally (and this is kind of an easy one, since it's about philosophies) - Do you even think we should try to accommodate torque in the processes we use? One philosophy says, "We don't try to control a lot of the variables that make a difference to competitiveness, and since we don't have a very good grasp on torque, we should ignore it." Another would suggest that "mathematical models are good enough that a digital car on a digital track can reasonably approximate the real thing, so we should try to take any and all variables that we can into consideration, to make the cars as equal as possible." Where are you on these issues?

THANKS!

K

PS to ITAC members. I'd be interested to hear from the membership before we dive into the conversation ourselves.
 
I'd choose car # 4, because it's numbers are almost the same as my "C" car!:rolleyes:
Seriously, it has the best of both worlds, should come out of the corners hard and wind tighter than the low hp high torque example.

Question 1, sure take torque into consideration, but it's going to make the "napkin" math more "interesting". Add weight, but then take it off for bad brakes? Where does it stop?

Maybe it wasn't politically correct back in the beginning when we raced at our manufacturers "curb" weight, but it did let those that could read specs pick the right car. The old "we'll give you a place to race, but your car may not be competitive" has been replaced by "no car left behind".

Just my opinion, yours may be wrong!:D
 
I would prefer a similar hp/tq because the curves will be flatter making a wider power band and easier to drive fast. However, you left the most important variable out of the equation....RPM. Torque only works at the wheels. Applied torque is what moves the car. The 190/110 example, if it turns 9k, will easily out run the 170/170 that turns 7k beacuse it can run a much shorter gear.

I don't think tq is a consideration above what is currently given based on the parity of the top running cars in SEDIV. (clevat: that would be a most biased comment although I am researching the rpm route rather than torque.) Of more concern to me is the ability to generate grip, and the fully independent cars seem to have a better handle on that than the strut cars. As more of the fully independent cars are classified/built, consideration should be given to the older strut cars. Jes Sayn Chuck
 
Assume that the minimum weights are the same for the purposes of this discussion. Since we're talking about figuring out how to consider torque (or if we should), don't presume that given whatever the final process might be, the result would be that they are different.

We have WAY too many of these conversations that get all tangled up because we're all talking about different things. All I want to understand from this is how people understand this torque thing, and generally how (or if) we should tackle it.

K
 
Looking at torque w/o rpm is senseless.
Engines that develop torque at much lower rpm than their peak horsepower peak are potent because they neccessarily develop good torque across a relatively large (rpm) band. This implies good airflow design and somewhat agressive cam timing or variable cam timing. The allowed IT prep and their pre-existing advantages will make them competetive.
Engines that develop torque at low speeds and rpm at conservative speeds, (often more torque than hp), imply airflow restricted engines. Often they are on the large end of the displacement spectrum for their #of cyls. Their response to IT tunes will depend on how much that restriction responds to IT prep. If the airflow restriction is due to conservative cam timing/lift and/or restricitve cylinder head design, then they likely won't respond as well to IT prep-and they will be toads.
V8s that have well seperated torque and hp peaks-look out! phil
 
Kirk,

Have you considered running the cars through a simulator? Bosch LapSim has a free version that you can do this on.

http://www.bosch-motorsport.de/content/language2/html/3589.htm#a_D9200D2E6B014D0792809A16EA4A4C14

This is a good way to compare the cars.

I assume for this comparison all other aspects of the car stays the same, i.e. same car with different engines. In that case the gearing options are eliminated.

I think it's track dependent and more specifically turn dependent. I prefer an engine with more torque if there are elevation changes (VIR). On a flat (Roebling Road) track I'd settle for less torque.
 
K, I applaud your thought process relative to being a ITAC member. :023: As stated all else being EQUAL including were road racing, torque gets you there & HP keeps you there. Overall car number 4 please.:eclipsee_steering:

With all that ^ aside is this IT class slipping towards, well you know where................
 
ddewhurst said:
... With all that ^ aside is this IT class slipping towards, well you know where................
Click to expand...

Actually, I don't...

We already consider "torque" when cars are specified - and have for ages, formally or otherwise.

We're just trying to work through some "should we and if so, how?" questions.

K
 
if all the weights are the same, and we take RPM out of the equation.....

car #1 isn't even in the running.
car #2 is quickly dismissed because that sounds like something that will only do well at very specific tracks....if anywhere
car #3 is only slightly favorable to car #2. but everytime i ask myself "why?" i end up with an answer that is directly related to RPM.
car #4 is the obvious choice to me. it's the only one that you KNOW will have a solid powerplant for racing.

to me there is no consistent way that torque "matters." climbing up the hill at Road America it matters a lot. but a fast, flowing track with high speed corners it matters very little. i think it matters less in lighter cars than it does in heavy cars (which kind of answers the third question). the more rubber you can put to the pavement via advantage in drive-wheel suspension layout, wheel size, and drive layout, the bigger of an advantage it is.

i don't think there is a consistent, repeatable way to treat ALL cars in the ITCS equally for torque. peak HP can be used because it's always measured within the usable RPM range. this is not true for torque. i don't know if i think it should be 100% ignored, as some cars are so far "out there" one way or another that they warrant some sort of consideration, but the means in which that is done doesn't seem to be the goal here.
 
I've never owned a muscle car, and only ever raced a rotary, so I probably know squat, but... I'm pretty sure that the only thing that matters is the size and shape of the HP curve in the RPM band of interest - in simple terms "the area under the curve". On my rotary, the torque keeps climbing all the way up to 6200 RPM, so the HP curve is very steep. Drop your RPMs and you lose much of your HP - the peak is good, but the area under the curve sucks. On engines where torque exceeds HP the torque curve is falling with RPM, leading to a more flat HP curve. This maximizes the area under the HP curve. So if you class based on peak HP, the flat HP curve engine has an advantage.

BTW, if someone has some dyno plots confirming or refuting my premise I'd love to see them.
 
Some have said that because final drives are free, torque is a factor we should not try and manage because you can make up for less torque with shorter gearing and take advantage of torque with taller gearing. It's about building around your platform.

So the question for me is simple: does the open final drive rule mitigate these strengths and weaknesses enough to not want to monkey with it?
 
Andy, while the final drive helps I really think the low torque cars are hurt more by lousy tranny ratios. I was looking at the gear spacing on the newly classed mustangs and comparing them to my Rx7 and thinking it is a good thing the stang has high torque and probably a wide power band.
Final drive would make up for a lack of torque if we had 6 speed hewlans.
 
The way to look at torque properly is to graph wheel torque vs miles per hour for all gears, then take the area under the combined curve from say 25mph to 125mph...(appropriate race speeds for car and tracks)
This is how one chooses the correct gear shift points, tire sizes, and final drive ratio. Once you have a torque curve, it is realatively easy to do in Excel. Even easier if you have the data output from a Dyno. Anything else is just guessing!
 
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.
 
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.
 
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?
 
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.
 
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
 
JeffYoung said:
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.
Click to expand...

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.
 
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