Rule Change: Section 3.0 (GTS classing)

[rabbit_diesel]

Forum Moderators: please make a poll with the following seven choices:

 

NASA GTS classing rule:

1) The GTS classing rule used to be weight divided by only horsepower, and should still be. Adding the (HP+T)/2 handicap section was a mistake; get rid of it.

2) Do not change the rule -- keep the (HP+T)/2 handicap as it exists.

3) Change the rule to be weight divided by the average horsepower between the RPM of peak horsepower and 25% less RPM -- keeping most cars in the same class they are currently, but moving the current outliers to an appropriate class.

4) The weight to power ratio is just an approximation of the acceleration capability of a car. For classing purposes, just measure the actual acceleration capability in seconds to reach a specified distance, then class the cars according to that.

5) Change the rule to apply the (HP+T)/2 formula to all cars -- give a great boon to high RPM low torque engines.

6) Whatever -- I do not care.

7) None of the above.

 

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According to what I am told, the GTS classing rule was changed for the 2007 season -- that previously the rule had been weight divided by only horsepower, no exception.

 

Assuming it is true that the classing rule has in the past been changed, we then have proof that in the past 'enough' people thought the act of modification to be acceptable. Presumably, it is still acceptable to further modify this rule.

 

The question before us regards the classing rule. Do we keep it the same, or change it? If we change it, what do we change it to be?

[Lemming]

What is the difference between 2 and 5? Oh and the answer I'm looking for is not 3

[cwbaader]

#1 for me..It was a mistake when implemented and is still a mistake. It misclassifies cars. Dropping this requirement would minimize weight addition to achieve a lower class, and increase lower class participation numbers. Chuck

[rabbit_diesel]

What is the difference between 2 and 5? Oh and the answer I'm looking for is not 3

Currently, 'low torque' engines are assigned a ratio according to the weight divided by the peak horsepower [ie. W/HP]; while for 'high torque' engines the weight is divided by the average of peak horsepower plus peak torque [ie. W/(HP+T)/2].

 

Item #5 says to apply the formula W/(HP+T)/2 to all cars. In other words, no cars use the formula W/HP. (Somebody mentioned this idea, I saw it in the forum, and so I included it in the list.)

 

According to the current rules, the division between 'high torque' and 'low torque' is when the number of peak foot-pounds equals the number of peak horsepower.

 

Will

[scottbm3]

Polls on these forums do not represent the majority of the GTS racers. In the big scheme of things very few guys that race GTS participate regularly in forums and it definitely should not be used to make and or change rules. Racers should present their rule change requests to National and maybe they should send it out in a bulk email, so everyone gets a chance to respond. Then put something up for discussion.. Then everyone would know that it's up on the forum and could come and comment.

 

Personally I think the rules as they stand are fine and should be left alone including the DOT/Slick rule and the Trq/Hp rule. The Trq/Hp. rule effects very few racers and most that is does effect it is so minimal that it doesn't make much difference and I believe it was implemented to help keep the FI cars from having a big advantage. The few that complain the most seem to want their cars to be able to run in different series and want them to be competitive in all of them. Not going to happen in the real world.

 

Just my opinion as a racer that has competed in GTS for a while and run quite a few race's against all kinds of builds.

 

 

-Scott B.

[mikew968]

I'm with Scott on this...leave it as is!!

[ianacole]

All regional directors should be notifying their participants of the ongoing discussions.

 

I've created a poll for this discussion.

[Greg Smith]

EDIT-Can of worms.

[cwbaader]

Idea...Go back to the 2006 version of classification (no TQ X 2) and run for a year...then retake this poll. Chuck

[Keith Andrews]

I think every car should have the same rules. #5 sounds good to me, but in my mind it is the same as #1. But then again if #1 and #5 are the same, then why not go with #2 so...... I guess I don't mind it just like it is. The rules are the same for everyone.

[ELEPHANT1]

Given that the typical German vehicle engine is more HP than Torque....how many people, other than diesels, does this even affect? In the case of the BMW eta engines I don't exactly see a line of people waiting at the door to come and play. Chuck is the only one I know and his car is an SCCA car, not a GTS car by way of the rules he builds for. I never subscribe to rules changes to makes things nicer for those who are not dedicated to the series. If there is a legitimate claim by those who are running GTS cars and are shown to be at a disadvantage then it's at least worth a listen. Honestly, I don't recall anyone else being on that side of this....is there anyone else out there? The completely unscientific poll with few responses does not seem to indicate such. I really am curious......

 

Cheers.

[ianacole]

It would affect me, positively ... I'm able to produce upwards of 270ftlbs of torque at 225 HP ... but I'm for keeping the rule as it stands.

[gimpstang]

It also would affect me positively. Turbos can easily produce gobs of torque with moderate hp. I personally don't like the idea of two classing mechanisms for cars within the same class. IMHO cars racing within the same class should have to follow the same ruleset.

[rabbit_diesel]

....how many people, other than diesels, does this even affect?

What! No love for diesels?

 

My Rabbit is going to have a turbo-diesel. Peak horsepower will be at 4500 RPM. The (HP+T)/2 will unreasonably class my car. I have only ever raced in GTS...

 

Will

[ELEPHANT1]

....how many people, other than diesels, does this even affect?

What! No love for diesels?

 

My Rabbit is going to have a turbo-diesel. Peak horsepower will be at 4500 RPM. The (HP+T)/2 will unreasonably class my car. I have only ever raced in GTS...

 

Will

 

Well no, I just meant that we all know diesels typically produce more torque than HP...peak that is.

 

Cheers.

[ELEPHANT1]

It also would affect me positively. Turbos can easily produce gobs of torque with moderate hp. I personally don't like the idea of two classing mechanisms for cars within the same class. IMHO cars racing within the same class should have to follow the same ruleset.

 

Sure, that makes sense but the how about the other side of the argument. On one side we have a car that makes say, 200HP and 160ft-lbs torque. Then on the other it's 160HP and 200ft-lbs torque. Should they be classed differently? How so? I understand that the main point here is that lower torque cars get a freebie whilst high torque cars get penalized, if you will, but if it were to be addressed how should it be done such that it's fair to all?

 

I'm not necessarily for any rules change at all as the only complaint I've seen for changing it is from Chuck who does not have a GTS car. Others who chimed in didn't indicate it was a problem, just that it is beneficial to them. Is anyone with a dedicated GTS car making more torque than HP feel they are shafted in some way? I guess that's what I'm curious about.

 

Cheers.

[gimpstang]

Yes actually they are getting shorted. According to the rules now, the 200 hp 160 tq car will only get classed based up on hp. The 160 hp 200 tq car gets classed based upon the both the hp and tq. Two rulesets for cars racing the same series isn't far IMHO

[ELEPHANT1]

Yes actually they are getting shorted. According to the rules now, the 200 hp 160 tq car will only get classed based up on hp. The 160 hp 200 tq car gets classed based upon the both the hp and tq. Two rulesets for cars racing the same series isn't far IMHO

 

Yes, as I said, I understand that and that this is the point of this discussion. So what is the solution then? It doesn't seem like - taking the argument that higher torque than HP should be penalized in such fashion - that those of us with higher HP than torque should be "penalized" as well.

 

Cheers.

[JSirota]

Given that the typical German vehicle engine is more HP than Torque....how many people, other than diesels, does this even affect? In the case of the BMW eta engines I don't exactly see a line of people waiting at the door to come and play.

 

I'm an SCCA guy like Chuck but like to pay attention because I like to have the option to run more races. So take this all with a grain of salt, I understand that my vote carries less weight with many of you.

 

But I'd like to make a couple of points: I have a relatively modern BMW engine, an M52tu 2.8 ('99-'00 Z3, E46 328i), and it has more torque than horsepower, even in stock trim.

 

More interestingly, there is no correlation between high peak torque and a flat hp curve, which is all you really want to know here. You are trying to class cars with like acceleration ability (on a race track) into the same class. To do that, you are trying to approximate for "area under the usable part of the hp curve" and the current rule ASSUMES that a car that has a high peak torque has a flatter hp curve near its peak than the car with a lower peak torque. But ... that assumption does necessarily hold true, in fact, it is false in a significant number of real-world cases. I have done the calculations for cars in another racing series (which has all sorts of engine architectures, not just a small sample of german cars.) The bottom line is that it's a flawed assumption and therefore a flawed model.

 

The old rule (simply based on hp and weight) was a pretty good approximation of acceleration ability. The only better ones in this list are the one that is actually based on acceleration, and the one that looks at hp across a range of revs. Otherwise, they are all based on a crappy assumption.

 

Again, I've never run a GTS race (there was no one even in the class here in NorCal until 2009), so, yeah.

[rabbit_diesel]

It would affect me, positively ... I'm able to produce upwards of 270ftlbs of torque at 225 HP ... but I'm for keeping the rule as it stands.

What is the RPM of the peak torque, and of the peak horsepower?

 

Will

[ianacole]

A bit of an approximation as the dyno graph doesn't list it specifically, but:

 

Peak HP: 5250 RPM

Peak TQ: 4000 RPM

[rabbit_diesel]

Someone asked: "So what is the solution then?"

 

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In my opinion, the discussion is about a new classing rule that: keeps most cars in their current class, does not mis-class any cars, is relatively easy to comply with, and is relatively easy to administer. Realizing that this is an endeavor done by humans, it is not likely that we will achieve perfection, but hopefully whatever we do choose will be 'good enough' and be an improvement over the current classing rule.

 

The current GTS classing rule tends to mis-class cars: with engines that produce power at low RPM, and those that do not have a 'fat power curve'. This tendency to mis-class is in proportion to the lowness of the RPM at peak horsepower, and in proportion to the leanness of the power curve. It is possible for an engine to both be of a low RPM design, and to have a lean power curve -- and be mis-classed even more quickly.

 

Below is a proposed solution meets the criteria named above. The racers have to get a dynosheet, just as they do currently, so that is no increase in burden. Regarding administration of the new rule, it would be slightly more complicated: instead of just reading off the peak horsepower and the peak torque, and then using that in a formula; with the new rule one would have to draw a line at an RPM which is 75% of the RPM at peak horsepower and read the horsepower where this line crosses the curve, and read the peak horsepower, and use those two horsepower figures in the formula:

 

ratio = 2 * W / ((HP@75%) + (peak HP))

 

The intent is that the part of the power curve from the RPM of peak horsepower on down to 75% of that RPM will be decently representative of the capability of an engine, and be a rule that is relatively easy to administer. (Notice that the 25% of the power curve being selected, is well used in every gear of transmissions.) (If someone can demonstrate a part of the curve that better represents the capability, and is easy to select for most engines, I would say go with that. Today, for the sake of this discussion, let's use 75%.)

 

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The current GTS rules have an unstated assumption -- this assumption is that all German engines that might be used in a racecar will produce their peak power at close to the same RPM, and that all these engines will produce their peak torque at close to the same RPM (considerably different RPM from that of peak power). For fairly many engines this assumption is somewhat close to true, but it is NOT true for all engines. In fact, the assumption is way off for some engines, and in proportion to the degree of difference there is a classing problem.

 

For example, please consider the following set of engines and notice that they all have the same peak horsepower, the same horsepower at their respective 75% point, and the same horsepower at their respective peak torque point. Also, notice that all have essentially the same percentage 'torque rise' (which for the sake of demonstration is rather high).

 

9000 RPM, 201 HP, 117 lbft (peak horsepower)

6750 RPM, 199 HP, 155 lbft (75% point)

6000 RPM, 179 HP, 157 lbft (peak torque)

Over the 75% band, average HP = 200

Current GTS rules assigned HP = 201 (reasonable)

 

8000 RPM, 201 HP, 132 lbft (peak horsepower)

6000 RPM, 199 HP, 174 lbft (75% point)

5350 RPM, 179 HP, 176 lbft (peak torque)

Over the 75% band, average HP = 200

Current GTS rules assigned HP = 201 (reasonable)

 

7000 RPM, 201 HP, 151 lbft (peak horsepower)

5250 RPM, 199 HP, 199 lbft (75% point)

4700 RPM, 179 HP, 200 lbft (peak torque)

Over the 75% band, average HP = 200

Current GTS rules assigned HP = 201 (reasonable)

 

6000 RPM, 201 HP, 176 lbft (peak horsepower)

4500 RPM, 199 HP, 232 lbft (75% point)

4000 RPM, 179 HP, 235 lbft (peak torque)

Over the 75% band, average HP = 200

Current GTS rules assigned HP = 218 (a little high, not much difference)

 

5000 RPM, 201 HP, 211 lbft (peak horsepower)

3750 RPM, 199 HP, 279 lbft (75% point)

3340 RPM, 179 HP, 281 lbft (peak torque)

Over the 75% band, average HP = 200

Current GTS rules assigned HP = 241 (almost enough for an error of 1 class)

 

4000 RPM, 201 HP, 264 lbft (peak horsepower)

3000 RPM, 199 HP, 348 lbft (75% point)

2670 RPM, 179 HP, 352 lbft (peak torque)

Over the 75% band, average HP = 200

Current GTS rules assigned HP = 277 (more than enough for an error of 1 class)

 

Installed in identical cars (weight, driver, transmission, &c.), except with the appropriate final drive ratio such that each reached maximum vehicle speed at the RPM of peak horsepower -- these cars would be remarkably well matched.

 

But look at the assigned HP that the current GTS rules would have us divide into the weight of the car -- the cars with low RPM engines would tend to be unreasonably stuck in a higher class according to the degree of lowness.

 

If instead, we were to use average horsepower to divide into the weight, there would be no problem in classing because these cars would be grouped together.

 

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The method of average horsepower also works when comparing engines with the same RPM power band, but some engines have 'fatter power curves' than others. Please consider:

 

7000 RPM, 201 HP, 151 lbft (peak horsepower)

5250 RPM, 199 HP, 199 lbft (75% point)

4700 RPM, 179 HP, 200 lbft (peak torque)

Over the 75% band, average HP = 200

Current GTS rules assigned HP = 201 (reasonable)

 

7000 RPM, 201 HP, 151 lbft (peak horsepower)

5250 RPM, 169 HP, 169 lbft (75% point)

4700 RPM, 157 HP, 175 lbft (peak torque)

Over the 75% band, average HP = 185

Current GTS rules assigned HP = 201 (a bit high, but not bad)

 

7000 RPM, 201 HP, 151 lbft (peak horsepower)

5250 RPM, 152 HP, 152 lbft (75% point)

4700 RPM, 137 HP, 153 lbft (peak torque)

Over the 75% band, average HP = 177

Current GTS rules assigned HP = 201 (getting further off)

 

7000 RPM, 201 HP, 151 lbft (peak horsepower)

6000 RPM, 175 HP, 153 lbft (peak torque)

5250 RPM, 129 HP, 129 lbft (75% point)

Over the 75% band, average HP = 165

Current GTS rules assigned HP = 201 (an error of about 1/2 a class)

 

Using the same car earlier described and the four engines just above, the first of the four would out accelerate the others; and the rest would cross the line in the order listed.

 

Notice that the current GTS rules would assign the same horsepower to be divided into the weight, and class the cars together, but the cars are not particularly close to being equal.

 

However, notice that the average horsepower does change in proportion and proper direction, and consequently would do a better job in classing.

 

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In conclusion, the new rule would class cars much moreso according to the actual capability of the engine than does the current GTS rule. Cars with high RPM engines and with a fairly 'fat power curve' would stay in the class they are currently in. The relatively few cars with engines that produce power at low RPM, and/or do not have a 'fat power curve', would tend to be moved down a class in accordance with their actual capability.

 

The new rule depends upon the racers getting a dynosheet with a horsepower curve, essentially the same as the current rule. The administration of the new rule, is only slightly more complicated: in that one has to draw a line at an RPM which is 75% of the RPM at peak horsepower and read the horsepower where that line crosses the curve, and read the peak horsepower, and use those two horsepower figures in the simple formula:

 

ratio = 2 * W / ((HP@75%) + (peak HP))

 

Then look up the ratio in the classing table, just as is currently done.

 

Will

 

P. S. It will be noticed that in real life the peak horsepower almost always does not have the same value as the average horsepower, consequently new class threshold values will have to be selected to work with the new rule. Properly done, most cars would stay in the same class they are currently in; only the cars that do not really fit in a particular class would get moved down if their discrepancy is large enough (compared to the current GTS rule).

[mikew968]

So, you want to re-do the entire classing system because you have a diesel? I have never even run against diesel. What other cars have this issue? I could see including T and HP in the calculation for all cars but beyond that I think we are good.

[gimpstang]

So, you want to re-do the entire classing system because you have a diesel? I have never even run against diesel. What other cars have this issue? I could see including T and HP in the calculation for all cars but beyond that I think we are good.

 

 

No, I think he is proposing this change because some cars (including his) are misclassed due to having different powerbands than the majority. His proposal keeps the majority of engines where they are but correctly classes the minority.

[JSG1901]

I have to say that, as one of the people who have to actually collect and process dyno sheets--which takes a lot more effort that I would have expected--this seems like a lot of extra work for not a lot of gain. How about buying a nice GTI motor...?