What is: history of, and reason behind, '(HP + torque)/2' ?

[rabbit_diesel]

Is there anyone around that knows the history of the '(HP + torque) / 2' section in the GTS rules? Things such as: when was it implemented; and what was the reasoning? If so, please tell me.

 

Will

Edited September 6, 2009 by Guest

[mikew968]

Mark ain't talking!!!!! LOL

[B.Watts]

I don't know, but I suspect it was to somehow "equalize" the playing field between NA and FI cars. You can make a nice fat torque curvewhile turning low overall RPM's on a turbo motor without having big wheel hp numbers from what I've seen.

 

Just like the penalty for running slicks over DOT's, I'm not sure it makes sense in a class that attempts to have an open rule set where "anything goes".

[RSCoupe]

It's to equalize a car such as a TDI, that has monster TQ, but relatively low HP.

 

Hmm, an Audi A4 with the new TDI V8. Interesting...

[2thAche]

That just made me think of how fast the TDI Audi LMP's in American Le Mans pull away from the porsches on straights. It's kind of ridiculous.

[ianacole]

It's to equalize a car such as a TDI, that has monster TQ, but relatively low HP.

 

Hmm, an Audi A4 with the new TDI V8. Interesting...

 

Thinking small ... how about the new TDI V12?

 

http://union1609.com/forums/showthread.php?t=3418

[911.racer]

Well, what it does is equalize the relitive max power of a car that make power below 5300 rpm vs a car that makes power above 5300.

 

It is similar to what I have been saying about the area under the curve.

 

If you build a motor that makes 500 ft/lbs of torque at 2800 rpm, but it falls off by 4000 rpm, then you will want to make sure that your shift points take full advantage of all of that torque and ignore what happens when your motor gets above 4000 rpm. Lets say your Hp in that motor gets up to 350 Hp. That said, if your car makes no power (torque) below 5353 and has great Hp up high around 7000, then that is where you want to shift. Lets say that motor makes 425 Hp, but only 375 Ft/lbs of torque

 

That said, all things being equal, I would rather have the 500 ft/lb stump puller than the 425 Hp screamer. The stump puller will get you out of the corners a lot faster and stronger.

 

It is almost unfair for the higher Hp guy because all of his Hp is concentrated in a very tight band. The rules should always consider torque based on what I just showed here. always be Hp+tq/2. except that the 7000 PRM guy never lets the car drop below 6000 rpm, so he is never at his max torque.

 

Who will win a drag race ? I do not know, but I would rather have the high torque to get out of the corner.

 

It is all about the motor you build. If you build a motor to make all of the power below 5353, then you have high torque, if you build a motor to make all the power above 6k, then you have high Hp.

 

All of this written by a guy with two race cars. Both of which have the tq and hp within 5 points of each other.

 

If you take the tq gotcha out of the rules, then you will end up having a bunch of guys going out and building toque monsters and rule the class. Me being one of them.

[RSCoupe]

It's to equalize a car such as a TDI, that has monster TQ, but relatively low HP.

 

Hmm, an Audi A4 with the new TDI V8. Interesting...

 

Thinking small ... how about the new TDI V12?

 

http://union1609.com/forums/showthread.php?t=3418

 

Yeah, saw a bunch of those in Germany back in May, very cool. Would make a sweet tow vehicle, to bad they're not bringing it here.

[ianacole]

Yah, VAG sure makes some interesting choice when deciding which cars to bring to the US I'd sure like a new Scirocco...

[cwbaader]

As y'all know, I have lobbied long and hard against this requirement. By averaging hp and tq, you end up using the torque number twice. Now, horsepower is not a real thing...it is an engineering number designed to manufacturers a basis of comparison. When you classify cars with the second torque figure, you skew the whole number in favor of high rpm cars. This has been hashed to death on the SCCA site, and the final consensus was that high torque cars do not have an advantage. CB

[ianacole]

It finally came to me what it is about the math argument that I struggle with, and I read through that document you posted awhile ago, and while I couldn't put my finger on it, it bugged me then, too.

 

In it's simplest terms, the equation for 3 includes the number 2 (1+2). What you're effectively saying is that since this equation already has the term 2 in it we should never divide that equation by two. Yet doing so results in two different numbers, clearly (3 versus 1.5). Just because a calculation is used in both the numerator and denominator does not mean that you can just negate the denominator (look at the quadratic formula).

 

In a practical scenario, a car with 225HP and 190TQ is going to get outrun by a car with 225HP and 261TQ. This, in my opinion since I wasn't part of the original decision, is an effort to mitigate this performance difference potential.

 

At a philosophical level, at the end of the day it doesn't really matter what we do with the rule as it will always give one type of build an advantage over another. The function of any car builder is to maximize the potential of his car given the ruleset in which he is operating. As someone pointed out earlier, if we do away with the TQ portion of the calculation, people will start building high TQ applications, and in a few years someone will be arguing that we should be including TQ as part of the classing (as, I presume, it was argued to include in the first place).

 

Regardless, though, once the rule change has been submitted, the community can weigh in and we'll see where it goes from there.

[rabbit_diesel]

In a practical scenario, a car with 225HP and 190TQ is going to get outrun by a car with 225HP and 261TQ.

In some cases this is true, but it is not necessarily true in all cases. This is because the RPM at which the peaks occur is not being taken into account.

 

It is true, for instance, if we have two identical cars and drivers, except one car has 225 HP @ 7000 RPM and 190 FTLB @ 3500 RPM, and the other car has 225 HP @ 7000 RPM and 261 FTLB @ 3500 RPM. (Both cars have the same final drive ratio with the engine turning 7000 RPM at maximum speed.) In this case, the car with 261 FTLB @ 3500 RPM will outrun the other.

 

However, consider the situation of: two identical cars and drivers, except one car has 225 HP @ 7000 RPM and 190 FTLB @ 3500 RPM, and the other car has 225 HP @ 4600 RPM and 261 FTLB @ 2300 RPM; and except both cars have the appropriate final drive ratio such that at maximum speed the engines are turning 7000 RPM and 4600 RPM respectively. In this case, the car with 190 FTLB @ 3500 RPM will outrun the car with 261 FTLB @ 2300 RPM. (*1)

 

For those who are wondering why the situation described above is the case: it is because the engine with 225 HP @ 7000 RPM and 190 FTLB @ 3500 RPM has a 'torque rise' of 12.5%, while the engine with 225 HP @ 4600 RPM and 261 FTLB @ 2300 RPM has a 'torque rise' of only 1.6%.

 

Will

 

Footnote:

(*1) The current rules in this case would tend to penalize this slower car, because if the weight divided by 225 HP is near the class limit, then the slower car will be bumped up a class.

[rabbit_diesel]

1) The engine with 225 HP @ 7000 RPM and 261 FTLB @ 3500 RPM has a 'torque rise' of 54.6% --- and at 3500 RPM is making 174 HP.

 

2) The engine with 225 HP @ 7000 RPM and 190 FTLB @ 3500 RPM has a 'torque rise' of 12.5% --- and at 3500 RPM is making 127 HP.

 

3) The engine with 225 HP @ 4600 RPM and 261 FTLB @ 2300 RPM has a 'torque rise' of 1.6% --- and at 2300 RPM is making 114 HP.

 

It is not possible for any engine that makes 225 HP @ 4600 RPM to have a peak torque less than 257 FTLB.

 

(Note: all numbers are rounded, and have only three significant digits.)

 

Will

[JSG1901]

1) The engine with 225 HP @ 7000 RPM and 261 FTLB @ 3500 RPM has a 'torque rise' of 54.6% --- and at 3500 RPM is making 174 HP.

 

2) The engine with 225 HP @ 7000 RPM and 190 FTLB @ 3500 RPM has a 'torque rise' of 12.5% --- and at 3500 RPM is making 127 HP.

 

3) The engine with 225 HP @ 4600 RPM and 261 FTLB @ 2300 RPM has a 'torque rise' of 1.6% --- and at 2300 RPM is making 114 HP.

 

It is not possible for any engine that makes 225 HP @ 4600 RPM to have a peak torque less than 257 FTLB.

 

(Note: all numbers are rounded, and have only three significant digits.)

 

Will

OK, so just to be clear, are you nit-picking the specific numbers thrown out by Ian or are you saying that given two real-world engines, one with a great deal more torque than the other, you would expect the low-torque motor to be faster? I would have thought the Audi R15 pretty much answered the latter.

[rabbit_diesel]

OK, so just to be clear, are you nit-picking the specific numbers thrown out by Ian or are you saying that given two real-world engines, one with a great deal more torque than the other, you would expect the low-torque motor to be faster? I would have thought the Audi R15 pretty much answered the latter.

Not nit-picking -- I think that Ian's numbers are fine. In fact, I had been contemplating coming up with some numbers; so when Ian put those out, I just used them as the basis for discussion.

 

I am saying that in my opinion, given three similar cars, one each with the three engines described above and appropriate final drive ratios, that I would expect the car with engine #1 to blow the doors off the other two cars, and to easily win a race between the three.

 

And saying that I would expect the cars with engines #2 and #3 to be fairly close in performance.

 

And pointing out that the current GTS rules would class together the cars with engines #1 and #3, while the car with engine #2 would likely be down one class.

 

Does GTS have any real-world data on cars with engines that have a peak horsepower below 5000 RPM? If so, may I see it?

 

Will

[cwbaader]

140hp@5000, [email protected]

[rabbit_diesel]

140hp@5000, [email protected]

Thanks. What is the weight of your car? How does its straight-line acceleration compare to other cars in your GTS class?

 

Will

[cwbaader]

You have run against the car...you are faster in a straight line. My car accelerates well off the corners, but dies half way down the straights to the higher hp cars. Note, I am classified at GTS2 because of the torque. The cars that are optimized for "2" I cannot run with on the straights...period. That means off the corner, down the straight, etc. Even if I upped my hp to 170 to optimize for the class, I still could not run with the e36 cars. Just my opinions. CB

[cwbaader]

Almost forgot...came off track yesterday at 2586# CB

[gimpstang]

He has run with you before Chuck but that is with his old engine combo. Will is planning a new engine combo and is wondering about the ruleset to which he will build the engine.

[B.Watts]

The cars that are optimized for "2" I cannot run with on the straights...period.

 

I can't run with cars that are optimized for GTS5 on the straights either. The rules don't prevent me from optimizing my car.

 

You're running a car optimized for SCCA IT in a series with a power/weight classing system and an otherwise wide open ruleset. There's a lot of things you could do to your car to further optimize it for GTS2 without even touching the motor. Throw a 6-speed sequential transmission and the optimum rear gear into your car and your torque monster might dominate the straights.

[cwbaader]

Until the rule about hp/tq was implemented, my car happened to be optimized for GTS1. How would you like to be legislated to non competitiveness or be required to spend a fair amount of money developing another motor to use in only one venue. Seems to me, with entries down everywhere, organizations should court cross over racers. My .03 CB

[rabbit_diesel]

In the June event at Road Atlanta, my Yellow Rabbit was about 1950 pounds with about 104 hp @ around 7000 rpm, and about 90 lbft @ around 6000 rpm. (I turned in my only copy of the dyno sheet; should have kept a copy!) It was running on old Yokohama Advans. A definite GTS-1 car. But that engine is now out of commission...

 

Will

[rabbit_diesel]

I am told:

That before the 2007 version of the GTS rules, that the previous classing rule was W/HP, only.

That in fall/winter of 2006 the (2*W)/(HP+T) addition was put into the 2007 ruleset.

That there was a huge objection in the forums.

 

(Not having been around at the time, I do not know personally; and the threads from that period are no longer on-line.)

 

Will

[944-Spec#94]

Guys,

GTS is a very open class. So open you can drive a truck right through it. Their are only 3 factors

1) Engine performance

2) Weight

3) Slicks or DOT.

 

 

So engine performance is limed by hp and torque. Now why HP & torque? Peak HP is just a number an shows potential. Peak torque however gives a window to the power band. If you just had peak hp to deal with then those looking to optimize would build low hp massive torque motors. Then they would use the unlimited gearing to try to rectify the lower hp number with big torque.

 

Now chuck your 140hp 180ftlbs motor maybe weak vs some GTS2 cars, but compare that to a 140 hp/140 ft-lbs 944 motor and you WILL have A MASSIVE edge. That extra 40ft-lbs will help you in the mid range and shove you forward out of every corner.

 

Not just that consier a 400hp 400ft-lb turbo motor vs a 400 hp -280 ft-lbs NA motor. That big torque motor will have an edge most places.

 

So to try to put a lid on it some what the rules makes said they would figure hp and torque in their numbers. This way a high hp low torqe motor gains a bit why a big torque low hp motor pays the a little bit for the extra torque and presumeably wider power band.

 

Now even then it just may be that some cars are not suited well in the GTS classifications as they are built. Really you try to run that 325e motor, but may be the best thing to do is just to swap the head for a better flowing one so you can gain some "free" hp. I bet 20-30 more hp is there easy with a 325i head (or whatever the right one is for this swap) and the associated weight penalty would only count for 1/2 that power due to probably no change in torque.

 

GTS is all about no rules and free for all. If your car is not optimized for the class it is in there is nothing stopping you from modding all you want to try to make it compeitive or shift it to class where it can be.

 

If you just want to run with a stock motor and limited chassis mods swap that eta engine and try to run spec E30 or try PT where you will probably have a more favorable base classing for the low revving eta motor.

 

 

Now if you just want to run you optimzed ITA BMW run in NASA GTS you will need to deal with the limitations of the ITA rules just accept it. There is no way to have a car optimzed for GTS and ITA. You will need to pick one.