mark kibort

ah yes, the aero drag / HP ratio.... maybe that should be a factor too!

mark kibort

I was planing on running more Porsche club , NASA GTS this season, so i checked out the rules and it seems that Part of my work with NASA GTS committee helped out when at first they were averaging HP with numerical torque values. After months of discussion, they finally changed it to exclude it, but left it in for higher torque (numerical value in lb-ft) to hp, where it still is averaged. Now, because , at the time, my HP and Lb-ft torque levels were equal, i quit while i was ahead with the success and went along with the lingering, incorrect technique of using torque as an equalization factor . Now, however,i do have a car with more torque than HP and i dont want to be penalized, so i guess i need to finish what i started many years ago.

HP is the direct value of a car's ability to accelerate at any speed. engine torque has no bearing on this at all. its all about rear wheel forces and any two cars at any same speed with the same power, will have to accelerate the same (off any corner, down a straight, etc etc because - power = force x velocity. it's a Newtonian identity)

the irony, is i understand the concern of the rule makers and those that have high strung, low torque engines. they think that higher torque cars have an advantage. generally, this is not true. especially if the lower torque cars have closer ratio gear boxes , which most do to keep the engine RPM in the max HP range. most all cars, tend to use about 91% of the peak torque ,as an average. Interestingly, NASA GTS has a new calculator and this calculator actually has the drivers input HP levels from a dyno sheet at all the usable HP levels. 3000rpm to redline.......so , with that, you have a perfect tool for classing vehicles HP to weight ratios. what is the use of torque? unfortunately, there are those that still put importance on torque and have some misconceived notions of its importance.
I would hope with some of these discussions, that could be fixed.

so, in the sport of leaarnig and talking about the issue, I've attached 3 comparisons.

1. a porsche V8 vs a porsche Spec Boxster dyno both with equal hp, but greatly disparate torque values
2. a porsche GT3 vs my porsche with a V8 also equal HP, but greatly disparate torque values
3. a porsche GT3RSR and a Viper both with 430rwhp. also equal HP , but greatly disparate torque values

see if you can find any reason to think that the higher torque engine has any advantage at any point around the track. i particularly like the viper vs porsche comparison, because i actualy shows the porsche GT3, with more average HP over any operational range. this means the high torque values is a meaningless factor and should be removed from the GTS challenge rules.
if you do the mat with the respective gear boxes or even use any gear box you want, you can see the answer is clear. torque is meaningless as far as using it as a factor for an advantage or not. its a number with specific relationship numerically to HP, depending on the units used.. that in itself should be the answer!! (e.g. Kg-cm, Nm, etc etc are example of torque values where torque would always be higher.. shoot, what would you for european rules? )

thoughts?

MK

ace37

In general I'm in full agreement, but there is one caveat.

To take extremes, assume one engine produces constant torque and the other constant horsepower over the useful rev range. Obviously the average power in the gears used on the track (weighted by their utilization) will dictate performance, and if those two are equal the two engines will essentially offer the same performance in a race setting. And even though this uses more extreme assumptions, it seems to be a very similar idea and result to the point you're illustrating.

I think there is a common and real case where the theoretical high torque / constant horsepower power engine has a small advantage though. Assume you're a new driver and in the wrong gear or your perfect shift point is right at the middle of a tricky corner. In either case with the torquey lump it doesn't hurt your time as much so your brain can relax more and you gain a razor's edge of speed both at once. You can almost shift when you like as the engine is always giving you full power.

Now with pro level drivers the 'wrong gear' and shifting in the corner cases essentially disappear. So this is more likely a problem if you aren't a great driver. And a better transmission would make more difference than this subtle effect anyway. But whining doesn't care about facts so what does that matter.

So all that said, I agree with you, it doesn't matter enough that it should be a factor. Average power at high RPMs representative of the typical gear on track should be the gold standard.

mark kibort

Great post Ace.... i agree, that there are cases where a "mistake" in driving, can cost equality.........However we cant make rules to cover mistakes and driver errors. . the elephant in the room is really provisions for heavier cars vs light cars with same Hp/weight ratios. but thats another discussion.

However, you have to realize that even with a higher numerical torque value (i keep on saying that, because the units are so unrelated and have no basis for one being used in reference with each other... ft-lbs and Hp... what if we had Nm and Kw then what would the pseudo science use then?) so, with the higher numerical torque value, (lb-ft) you can still have identical HP curves, which means, EVEN if you make a gear selection error or are left in the wrong gear, the rear wheel forces are IDENTICAL............just look at the real word example below. Porsche GT3 vs viper V10 . thats 500lb-ft vs 270lb-ft. ironically, its the GT3 that has more forgiveness for being in the wrong gear, slightly......

so , the net net here is that torque should never be looked at as a factor.
its all about averaging the HP over the operational speed range and though the car's gears. again... as you seem to know.. power at any same speed will yield the same force at the wheels (acceleration force) PERIOD

POC made the most blatant error here that has gone undetected due to a irrational bias (as you explain a hint of it in your note), but they ignore HP all together if you have higher numerical torque than HP........ this means, if you have more numerical torque vs HP, they use a torque to weight.
ratio..............NOW, are there any engineers that find an issue with that? They use PEAK TORQUE TO WEIGHT RATION ????? really............... so, I'm working with them now to get that changed. The good news for the POC, is that there are probably a handful of cars that are effected , but in a very bad and irrational way.... otherwise, their classing system is Very simple and very good. these guys are smart and will figure it out.

A CHALLENGE : find one spot on this porche's HP /torque curve where it would be at a disadvantage to the viper , any gear, any speed, anywhere on the track!

yet, according to POC rules, the viper would have been given 30-40hp unfairly to calculate the weight. NASA, not so much.. they have almost figured it out. in fact torque is not that much of a factor at all in their calculator... And i worked with them initially about averaging torque and hp and they removed it back in the early 2000s.... rightfully so.... I suspect POC will do the same.

Mark

ace37

Whoa!!! Yeah, that's just indefensibly wrong.

Let's just poke a bit of fun at this....
>>The Cayenne S Diesel has 385 hp and 627 ft-lbs of torque (850 N-m). Claimed 0-62 of 5.4s.
>>The Cayenne Turbo S has 570 hp and 590 ft-lbf of torque (800 N-m). Claimed 0-62 of 4.1s.

So with their rules, we'd need to add some ballast to the Cayenne S Diesel so it doesn't outrun all of those poor disadvantaged Cayenne Turbos.....


I also have to say I was surprised by your result on the Viper vs. the GT3, and I was surprised when I also noticed the GT3's "torque" advantage! They make nice motors...
Are the Corvette's pushrod motors different? The LS motors and the Viper are the only ones I ever think of these days as really high torque motors (as opposed to motors with a reasonably flat torque curve) that are suitable for road racing. Apparently that Viper isn't as torquey as I'd have thought... or the Flat 6 is just even better than I give it credit for...

Cupracer

Mark,

What is the point of your argument. Are you trying to race your personal race car in the group and you are not competitive. Are you planning on running with NASA.

Do you have specific data showing that a car that is normally run in NASA GTS is not competitive, and therefore the rules need to be changed.

I understand the theoretical math behind what you are saying, but there is more to it. You need to also look at the in car data. You need to realize that a car does not get to stay in the optimum RPM range for very long. A car that accelerates out of a corner well is going to do better than a car that has great top end on a race track. This is because there are typically around 12 corners and 2 or 3 actual straights.

The rules were not made to, exactly, provide a theoretical parity between every car. They were made to create an actual parity between actual cars that run on the actual race track in NASA GTS events. Does that mean that there are race cars out there that are not competitive because the rules did not consider them ? no. Do I really expect that a bunch of Vipers are going to run in GTS and be upset because they are not competitive. well, no. It is GTS, not ST.

We now see cars that were tumed to have flat line tunes being competitive against cars that have a peaky Hp curve.

I hope I have helped explain why the rules are the way they are. Now, if you could please explain to the group why you are looking to change them.

Thanks

mark kibort

My car is perfectly classed and have raced with many of those cars in prior races. now that ive gone up a group class based on HP increases, i noticed the error and urged it should be corrected. (Yes, i want to do a few races this year in GTS4) in NASA case, its a fine tune, in POC's case its complete removal ... (because they are doing something that is not scientifically sound or mathematically correct) using a HP/weight ratio is correct. averging like nasa does is even better, but using a toruqe to weight ratio, even under certain circumstances ,is not.

the point is the rules should reflect sound physics and in nasa, it does for the most part. they actually have a calculator that ignores the "torque" factor even if it is MORE than hp in some cases. This is due to averaging HP . (they get it... almost.... still if a car did come out with a LOT of torque, it would be penalized ) Did you see the dyno graphs? try and find one instance on the track where the higher than HP torque car would have an advantage? i understand your point , but if the average HP is the same between the two cars.. (time spent at the lower and higher RPM areas of the HP curve) their performances will be the same.... especially out of turns . its not about higher or lower speeds ,its about time spent in the associated HP range for those speeds (HP-seconds)

You say, you cannot keep the car in the RPM range.... what does that even mean? all cars have gear spacing and keep the car in the RPM range that the gears allow... the engine torque level doesnt determine that. the HP curve determines that. WE have a TON of video that shows where the car has its RPM range over a lap of the track.. Take the cayman GT4 videos we all saw... you keep the car in the 5500rpm 7800rpm over a lap and NEVER below. out of a turn , down a straight, it doesnt matter. the car is kept in a very high HP range due to a flat HP curve, and IF you ever have the same HP coming out of turn as another car, you have the same rear wheel forces.............doest that make sense? do you agree?

to your point about flat lined HP... there are very few.. however, to your point a GT4 cayman is one of those. for equal HP , it''s flat line for an equal HP peak is a big advantage, yet a higher than torque car like mine would be at a distinct disadvantage because , ironically and contrary to the perception as it has a arcing HP curve) if you look at HP averaging, even though it has LESS torque (numerically) torque is not a performance factor.. it cant be .. it makes no sense to have it as a factor, thats why i and others want it removed. just use HP, and HP averaging, that makes the most sense...... If you really want to get it right, start using gear ratio closeness. so, to your point, if anyone cared about HP averaging, like NASA does, you would just do that and problem solved. (using a numerical value of a unrelated factor is not the way to do it, as i can easily prove)

Now, if you can look at real Life situations above for the dynos Ive shown and tell me an advantage , at any point around a track, then we have an argument. BUT, because there isnt and because not many people have a problem, doesn't make the rule correct. I understand the goal and the rare instances where that might indicate a equalization factor, but its just coincidence. again, look at this comparison of two porsche below and tell me how one has an advantage over the other.

as a note: i address your concern and point specifically by showing the shift points of the two porches below, AND their average HP. both cars come off the slowest turns at the lowest RPM range, at the exact same Power level... this means that the torque at the rear wheels (actual rear wheel forces ) are the same. make sense???

mark kibort

Thats a GREAT comparison.. never thought of grabbing those cars! so, just think , you have 385 hp, but now you get judged as if you have 627HP (because that is the POC rule to use the torque value) now, you go 0-62 in 5.4, before, but now you have to add 500lbs to the car to make the same power to weight ratio with 627hp (unfairly adjusted value) vs the 570hp cayenne turbo.

you are one of the few that absolutely GETS IT! thanks for the post. Yes, it is suprising about he GT3 holding on to its hp and actually producing it down low. its why even though it has very low over all torque, its 430rwhp matches up eqvenly to the viper 430hp and its V10. however its long stroke and lots of cylinders make a lot of engine torque as the RPM is much lower...so , in the end the cars are almost perfectly matched, anywhere on the track in any gear and at any speed. this is the BEST example i can find. (but the 928 vs the boxster is a pretty good one, and so is my car vs the GT3 cup car)

i hope this discussion can just create awareness and make changes for even more fair racing!

ace37

I think part of the problem is the rules are written to interchange torque in ft-lbf with english wheel horsepower, and that doesn't make any sense - it's completely arbitrary. Taken alone, torque or peak torque has *nothing* to do with acceleration, so it should not be treated as though it does by the rules. With cars, torque @ RPM is what relates to acceleration, and when you include RPM it's not torque anymore, it's power. That's why NASA's rules are written the way they are - they use power to capture the actual difference in performance.

The result of the rule may have been ok for the cars that have shown up in recent years, but the only thing the rule would actually do is overclass any cars with high torque engines. VW TDIs for instance.

If the rules were made that way because it was easy, seemed to make sense at the time, and solved the problem of the day that's a reasonable history, but the rules should be rewritten the next time it's convenient. The purpose of the rewrite would be so that the rules reflect the actual relative performance of the cars that are being classed. Currently it's about the same as if there was a yellow car that was a cheater three years ago, and since that was the only yellow car the rule was made that all yellow cars are moved up a class so it would be fair again. While that would work for the problem of the day, it would still be a bit silly to penalize a car for being yellow and it shouldn't be a permanent solution for a racing organization. That example might sounds trite at first, but genuinely, torque alone has nothing to do with acceleration - the units don't even match - so it's not as trite of an example as it sounds.

The Cayenne Diesel vs. Cayenne Turbo S example should mean something. Yeah, I know, they aren't racing at your track, but if they did that's what the rules would actually say, and it's clearly unfair and wrong. You can see something is funny with the rule. VW TDIs won't be as ridiculous but they'll still be overrated inappropriately. Those are just off the cuff examples.

NASA's rules would be a good reference. They're not perfect but they're easy enough to use, to understand, and they work about like they're supposed to.

mark kibort

More good points Ace. Yes, again, its one of those things that just seemed like a good idea because by chance, it worked ........... a little........and it didnt effect the majority of the cars . interesting you reiterate what i was saying about the units being used... HP and Torque.. as i always say, we are using numerical values, because there is no relationship between the two. In fact, as you mention, what would (they) do if power and torque were in other units??? that is the acid test. below is a car with HP vs Nm of torque. .... first of all, torque (numerically) will always be higher, so how do you deal with those two values ? it would be impossible.... threshold averaging or exchange?

Great discussion and good information. This is why i always jump into the HP/torque discussions, as it just raises awareness for the concepts and the correct way to interpret them in most any circumstance. (shift points, classing, tuning, gearing, etc)

Below is a common car dyno graph and the only change is the torque units are in Nm (Newton-meters).... so, what would the rules makers do with torque if hey never heard of a Lb-ft unit before to accomplish the parity goal?

(as a note and referencing to you mentioning the VW TDi..........don't forget about a real car that runs with a BMW tag on it... the 325e... it was a long stoke 120hp car with 170lb-ft of torque. it would be KILLED in the averaging or using torque/weight ratio technique. something to think about.

EDIT: I added a BMW 325e dyno run.. you can see by averaging HP and toque, you unfairly class this car.. using torque alone.... oh boy, you use 155lb-ft instead of 122HP..... a 27% increase in HP for no other reason than not understanding math! UGGGGG! just hthink , POC rules say that bmw would have to add 600lbs to compete against a comparable 122hp porsche or BMW who's weight would start out at 2500lbs.. the 325e now would have to weigh, 3100 lbs to make class weigiht. 600lbs!!! to make 20:1 HP/weight class restrictions. (and by the way, the BMW still would an average HP of 91% of peak, which is the norm for most cars racing today based on gear/shift spacing)