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2015 GTS Rules changes

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JSG1901

GTS Rules changes for 2015

 

For 2015, the NASA GTS rules will include three changes, two of which are minor, and one of which I believe will be considered major. This document has been written to explain the logic and intent of these changes. Because, as you will learn, we are still working through a few details, the final written version of the rules will not be available for another week or so. However, that doesn't mean we can't share with you the details of this year's changes.

 

Let’s start with the easy ones:

 

General availability of tires

 

The new paragraph covering this rule reads as follows:

 

All tires, whether DOT-approved or not, must be commonly available to all competitors from typical national retailers (for instance, Tire Rack), or directly from their respective manufacturers. This is to be interpreted to mean that special compounds not generally available to all competitors are not permitted.

 

The intent here is simply to disallow individual competitors working with tire manufacturers to create one-off or very-limited-run tires not available to other competitors.

 

Additional sequential gearbox penalties

 

Last year we added a 0.2 lb/hp penalty for racing sequential gearboxes. For 2015, we have extended that penalty to include Porsche’s PDK, BMW’s DCT, Volkswagen’s DCT, and other similar gearboxes. Specifically excluded are Porsche’s Tiptronic, BMW’s SMG, and older conventional “automatic” gearboxes.

 

Change the method of calculating minimum race weight

 

This is quite possibly the biggest rule change ever made in GTS, and one we, as series directors, do not take lightly. Because of that, and because the changes we are implementing will likely touch each and every GTS racer in some way, I would like to take some time here to discuss not only the specific changes we are making, but also the reasoning behind them.

 

A changing playing field

 

When GTS was first created, the idea was to provide a series where German cars could race one another with minimal limitations on the modifications that could be made to those vehicles.

 

Rather than have a highly-regulated points system like the ones used to assess modifications in NASA’s PT and ST classes, and unlike the restrictive limits set in the various spec classes, GTS has always been comparatively wide open in its acceptance of performance modifications of virtually all types. It was, and remains, the ideal series for drivers who like to tinker with their cars in search of increased performance.

 

Other than a penalty for using full racing slicks (as opposed to DOT-approved tires), the only real performance limitation in the original GTS rules was a power-to-weight ratio used to determine each car’s minimum allowed racing weight based on its peak horsepower (and in some cases a combination of horsepower and torque).

 

The point of using the power-to-weight ratio was to equalize, as much as possible, acceleration between the cars in each class. Cars with more power had to carry more weight, while those with less power could run at lower weights but, at least in theory, all of them would accelerate more or less the same.

 

From that relatively level base, performance differences could then come from differences in driver skills, suspension setup, etc.

 

This very simple set of rules lasted for many years with very few changes. Since originally written, we have added additional penalties for tube-frame construction and for sequential gearboxes (which were unheard of in amateur racing when GTS was originally formed), but not for much else.

 

But since those early days, technologies and, in particular, engine management systems have advanced significantly, making it possible for engines to do things that were essentially unthinkable just ten years ago. It is these new capabilities that have had the biggest effect on our decision to change the minimum weight calculation.

 

But before I get any further into the details of the new calculation, it’s important to clear up a few misconceptions related to horsepower and torque because these, too, inform our decision.

 

A quick aside about horsepower and torque as they relate to racing

 

While there has been a great deal of talk both ways regarding torque and horsepower, the truth of the matter is that torque is a measure of force, while horsepower is a measure of the rate of application of that force.

 

The bottom line is that what matters for acceleration is horsepower. And, just so there are no misconceptions, 200hp at 2,000 RPM has exactly the same ability to accelerate a car as 200hp at 8,000 RPM.

 

Engine speed is absolutely unimportant except to the extent it has a role in the computation of horsepower because torque is multiplied by RPM as a part of the calculation that results in horsepower. Because of this multiplication by RPM, 100 lb-ft or torque at 2,000 RPM does not create nearly as much horsepower as 100 lb-ft of torque at 8,000 RPM. But once you have a given horsepower value, it will do exactly the same amount of work, regardless of engine speed. 200 horsepower is 200 horsepower, and horsepower is what matters for acceleration.

 

Given that, the first thing we can say for certain is that the current GTS calculation, which averages torque and horsepower when the torque is higher, is flawed. This part of the calculation unnecessarily penalizes high-torque cars because, as I have already explained, it is only the horsepower that matters in determining the ability to accelerate.

 

Therefore, the alternate minimum weight calculation that is used when torque is higher than horsepower should be removed from the rules.

 

But if the goal with setting minimum weights is to level the playing field in terms of individual cars’ ability to accelerate, we also need to consider more than just each car’s peak horsepower. Let me explain why:

 

The unfair (but legal) advantage

 

Our current rules have no restrictions on what modifications drivers may make to their engines or their related components. Because of this, and because of the sophistication of modern ECUs and electronic throttles, several companies and numerous individuals have found ways to quite legally give themselves an enormous advantage in terms of raw acceleration on the track.

 

Consider the graph shown below:

 

GTSGraphZoom.gif

 

This is a graph of two different GTS3 cars, one (in blue) a normally-aspirated engine running unrestricted, the other (in green) an oversized engine that has been electronically throttled back to maintain a particular maximum power level. I should note that these lines represent actual values from actual GTS cars.

 

What is shown here is the percentage of maximum horsepower for each car across the upper 30% of that engine’s RPM range. This is roughly the part of the power band that’s used when these cars accelerate through the gears, shifting at or near redline.

 

Note that the green car never drops below 97% of maximum horsepower across the entire spectrum, while the blue car only briefly makes it up to that value. Keep in mind that this is a graph of relative horsepower, and that horsepower creates acceleration. If both these cars peak at 250 horsepower and compete in GTS3, both cars will be assigned the same minimum weight: 250hp x 11.0lb/hp = 2,750 lbs. But with significantly more horsepower over the usable RPM range, the green car will have an enormous advantage in actual acceleration.

 

To be clear, there is nothing here that is against the current GTS rules. The modifications that tuners have been able to make to create power bands like that shown here are, frankly, brilliant, and provide an absolute advantage on the track that is perfectly legal with the rules as they are written today.

 

But while this kind of modification is legal, it is not in the spirit of the GTS power-to-weight rules. The intent of these rules was to equate, as much as reasonably possible, the acceleration between all our various GTS cars. Which brings us to the need for a change in the method of calculation.

 

A new method for calculating minimum weights

 

The example shown above is a good illustration of the challenge facing us, but the chart is somewhat misleading as it over-emphasizes the differences between the two cars by not showing the full 100% of the horsepower range. The chart below shows the whole range:

 

GTSGraph.gif

 

Looked at this way, the differences between the two cars seem smaller, but there is still a clear advantage of one over the other. But is that really enough to matter? In fact, it is.

 

Over the full 30% of the rev range shown in this chart, the green car makes, on average, 99% of its maximum power. Ninety-nine percent. At a peak of 250 hp, that means the green car averages 247.5hp across the top 30% of its rev range. That’s a remarkable feat of tuning.

 

By comparison, the blue car averages just 91% of its peak power over that same range, or 227.5hp.

 

So, on average, the green car makes 8.8%—20 more horsepower— than the blue car all the way across the most important part of the power band while being allowed to run at the exact same minimum weight.

 

It seems clear from this example that what we should be considering is not the peak horsepower of each of these engines but, instead, the average area under the curve across the most-used part of the power band—that is, the part of the power band shown in the charts here.

 

You may be wondering why we have settled on the upper 30% of the rev range. After reviewing gearing charts for dozens of transmissions from the various manufacturers of GTS-eligible cars, we discovered that the average drop in RPM between gears as those cars accelerate from 50-150 mph fell into a range of about 25% to 40% of maximum revs. Given that, 30% seems a balanced and reasonable compromise, and it is this 30% that is shown in the graphs above and which figures into our calculations below.

 

To truly level the playing field, either the green car (in this example) should carry a bit more weight, the blue should be allowed to run a little lighter, or each should move a little each way.

 

And in essence, that’s what we are doing with the minimum weight calculations for 2015.

 

Although we are still finishing up the software to support these calculations, GTS will provide an online calculator that takes inputs of the usual data (GTS class, type of tire, sequential gearbox, etc), plus RPM values for every 1,000 RPM across the useful part of your car’s power band—which is usually the top 50% or so of the rev range. In addition, there will be inputs for redline RPM and horsepower, and for maximum horsepower and its corresponding RPM value.

 

From these values, the calculator will identify the optimum 30% of the power band, break it into 10 equal increments, pro-rate the horsepower values for each of those increments, and then average them.

 

Because the resulting average horsepower values will be lower than the peak horsepower numbers we use today, the ratios for each class will be adjusted accordingly. Our goal in this adjustment is to find a balanced value for each class, where roughly half of our cars will need to add weight (or reduce average power) and about half can take weight away.

 

As series directors and competitors ourselves, we recognize that the changes outlined above will not make everyone happy. What we hope is that all GTS competitors—even those who find themselves having to race a little harder as a result of these changes—will appreciate these changes as helping to match today’s realities to the spirit of the GTS rule set.

 

Thanks for your interest and participation. Good luck out there this year.

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Jimax

Thanks for a clear explanation. I haven't fully digested it all yet, but it seems like a fair way to balance out the advantages of tuning. I'm glad to see that GTS evolves over time.

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mcdonaldsracing

So wait a minute....what rule change proposal was this last part taken from? Furthermore, what proposal dealing with a hp/wt change had a majority of responses "for" a change??? I'm sorry, but I seem to be unable to find such a proposal Also, what is the point in suggesting rule changes if the powers that be are just going to create their own rule without giving the racers a voice on the change??? I chose GTS b/c of its simplicity and openness in allowing creative ways to gain an advantage. GTS isn't about budget racing if you want to run up front. If you want to race competitively on a budget, then move to a spec series. Moving away from the simplicity, to me, is against the spirit of GTS! Now, we're having to come up with special formulas and tools that are so complicated that they aren't even ready yet??? OR, maybe they aren't ready yet b/c this specific proposal was never, in fact, a "proposal" to begin with? How about some clarification on some of these points please, or do the opinions of the racers even matter?

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J Smith

I agree with McD's...where did this come from? I didn't see anything in the "discussion period" topics that got overwhelming support for a change?

 

 

And:

"Note that the green car never drops below 97% of maximum horsepower across the entire spectrum, while the blue car only briefly makes it up to that value. Keep in mind that this is a graph of relative horsepower, and that horsepower creates acceleration. If both these cars peak at 250 horsepower and compete in GTS3, both cars will be assigned the same minimum weight: 250hp x 11.0lb/hp = 2,750 lbs. But with significantly more horsepower over the usable RPM range, the green car will have an enormous advantage in actual acceleration."

 

On paper, you can make an argument that this could be true. Well, having raced against "non-detuned engines" with my "detuned" engine, I can guarantee you the acceleration advantage is minimal to non-existent. It most certainly is not "enormous".

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Brad Waite

I'll provide my opinion on the change before it has been biased by the knowledge of the specific impact on me and my cars. I think this makes a lot of sense and thank Scott for the detailed explanation. The simple rule set of wt/hp is still in place, we're just using an average hp rather than the highest point. Still seems pretty simple to me, and does seem like a more fair representation of a car's potential in relation to others in the class. As long as the class ratios are correct after the change, this doesn't seem like a bad move.

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dbryant61

Thanks also for the detailed explanation. As one with a non-programmable engine, I've definitely seen the difference in acceleration as tuned cars walk away. 8-10% does not sound like much, but neither does 2 seconds a lap.

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JSG1901

Actually, the opinions of the racers matter very much. But, while the views shared by the racers (and others) who participate in our rules change discussions are weighed heavily in our deliberations, they are not the only consideration in our ultimate decisions. Above everything else hangs the question of is what is best for the long-term success and competitiveness of GTS.

 

In this year's rules suggestions there were three different proposals hovering around the topic of how to better equalize GTS cars, ranging from eliminating torque as a consideration, to changing the formula used to compute minimum weights, to restricting by how many classes a car could be detuned. In other forms, this subject has been brought up before the group for five or more years in a row now, so the issue is nothing new.

 

What is new, and what makes it time for a change, is the breadth of the differences in power that have been made available to some but not all of our racers over the last few years through the programmable throttle controls available in a minority of our vehicles.

 

While the final solution we have implemented does not specifically follow any of this year's three suggestions, we believe it addresses the core concerns of all of them and, more importantly, is the correct move for the long-term success and competitiveness of GTS.

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jcrist

I never went faster than I did with the 2.8 wide open. I had a GTS2 detuned S54 engine and never came within a second of the full tune 2.8 M50 engine. As long as overall horsepower can be measured and a situation like what happened at Nationals in ATL with GTS2, the best drivers will win regardless of detune. Josh Smith dominated 3 in an E46.(DAMNED near podiums in 4 at Mid Ohio). Unless you have super wheel bearings, drivers win. Now yall go bury your heads in some Ross Bently

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mcdonaldsracing

So that shouldn't be proposed to the racers first before y'all decide what's best for us???

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Greg Smith

I agree with the previous concerns of "where did this proposal come from?".

 

With that said, I've already thought of two pretty good ways to legally skirt around these proposed(finalized?) changes. What I'm thinking of would be a much larger advantage that the current detune disparity.

 

EDIT-Also, track side dynos just got a whole lot more complicated and time consuming.

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7VO-VOM

I agree with McD and JSmith. This is a horrible rule change that did not come from the proposals.

 

Like Greg Smith, I already know how to get around the rule. This rule gives the highly tunable cars a bigger advantage not smaller. Let the arms race begin!

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cstreit911
I've already thought of two pretty good ways to legally skirt around these proposed(finalized?) changes
Like Greg Smith, I already know how to get around the rule. This rule gives the highly tunable cars a bigger advantage not smaller. Let the arms race begin!

 

I'm having trouble understanding the above comments. I assume you are interested in helping GTS since you are concerned about the source and intent of the rule. If you are interested in participating, gentleman, since Scott has stated it has not been finalized, now's your chance to point out the flaw. Please show the math so it can be well understood.

Edited by Guest

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7VO-VOM

My car will have a V8. Even though this rule makes me spend money that I'd rather spend elsewhere, it gives me more of an advantage, not less. Why would I help craft it to cost me more money for less advantage? My only advice will be to not change the rule. In fact, I think all 3 changes are failures, not that the first matters.

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cstreit911
My car will have a V8. Even though this rule makes me spend money that I'd rather spend elsewhere, it gives me more of an advantage, not less. Why would I help craft it to cost me more money for less advantage? My only advice will be to not change the rule. In fact, I think all 3 changes are failures, not that the first matters.

 

You've answered your own earlier question. You can understand that not all changes can come from drivers (As you asked about) because as you've just demonstrated, a drivers allegiance is to his/her self and not GTS.

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Cobra4B

I have no dog in this fight, but couldn't I artificially bump my rev range to make the "top 30%" an RPM I don't need to use. Then make my car unlimited below than then choke it back below that RPM and gear it accordingly. No matter how you make the rules people will push them to the bleeding edge.

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cstreit911
I have no dog in this fight, but couldn't I artificially bump my rev range to make the "top 30%" an RPM I don't need to use. Then make my car unlimited below than then choke it back below that RPM and gear it accordingly. No matter how you make the rules people will push them to the bleeding edge.

 

Clarifying question ... Do you mean to say if you normally ran a 7000 max RPM motor (where the top 30% would normally be 4900-7000) and then bump your rev limit "artificially" above that. You would build an engine that could sustain 10,000 RPM's on the dyno every time they checked it (because then the top 30% range would be 7000-10000 RPM which is not where you normally drive?)... ...and then tune the HP very low in that 7000-10000RPM range?

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nasaDEchamp
I have no dog in this fight, but couldn't I artificially bump my rev range to make the "top 30%" an RPM I don't need to use. Then make my car unlimited below than then choke it back below that RPM and gear it accordingly. No matter how you make the rules people will push them to the bleeding edge.

 

Clarifying question ... Do you mean to say if you normally ran a 7000 max RPM motor (where the top 30% would normally be 4900-7000) and then bump your rev limit "artificially" above that. You would build an engine that could sustain 10,000 RPM's on the dyno every time they checked it (because then the top 30% range would be 7000-10000 RPM which is not where you normally drive?)... ...and then tune the HP very low in that 7000-10000RPM range?

 

 

The 30% in your example is if you take it to 10K max...no need to. The lower your max rev's are the shorter in actual rpm range your 30% equates to. So if you hit your max at 6500, you can extend your max rev to say 8500 (on an s54, this is trivial) and a 30% range below 8500 would be from 5900-8500. Your "real power is only from 5900-6500 and everything past the peek has a sharp drop off. So you don't need to build an engine that revs to 10K at all. You used the edge case in your example. There are many ways to engineer or strategize on how to retain max pwr through out the race RPM band.

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flink

This is switching GTS from a "peak power to weight" class over to an "average power to weight" class. One can either agree with that change or not. I think it's a good change. But then I haven't spent kilobucks on a detuned S65! It's a bummer for those people who have made the investment - they're just going to have to drive it harder

 

The proposed scheme for implementing "average power to weight" seems pretty good and sufficiently simple. I think the "every 1000 RPM" thing should be made more fine-grained. That's only like 3 data points - having to type in 5 or 10 numbers is not too onerous.

 

The detuned engines will still have some advantage - it's better to make your max power over a 5000RPM band than over a 2500RPM band. But the advantage is less.

 

Obviously some smartypants can come along and tune the engine to have massive dips in output every 1000RPM. This can be immediately detected from eyeballing the graph, so perhaps some verbiage to prevent this sort of thing is needed.

 

 

btw, there's a tpyo: "plus RPM values for every 1,000 RPM across the useful part" should read "plus HP values..."

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joe149

As someone who likes to race but not 'tinker' with my car to make it faster, this proposal makes complete sense to me. Scott, thanks for the great explanation and the obvious work you've put into this.

 

However, the way I see it, this simply gets down to what kind of series we want GTS to be. Folks who are happy to win by improving their cars will likely be against it. Folks who want to race in series that controls costs and provides more 'equal' racing will likely be in favor of it. Since I fall into the latter camp, I am in favor. But then, I'd prefer we adopt Toyo's spec tires - they last longer than the Hoosiers I've ended up using for performance reasons.

 

So, is GTS a cost-controlled driver's series, or a more open and competitive car series?

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7VO-VOM
My car will have a V8. Even though this rule makes me spend money that I'd rather spend elsewhere, it gives me more of an advantage, not less. Why would I help craft it to cost me more money for less advantage? My only advice will be to not change the rule. In fact, I think all 3 changes are failures, not that the first matters.

 

You've answered your own earlier question. You can understand that not all changes can come from drivers (As you asked about) because as you've just demonstrated, a drivers allegiance is to his/her self and not GTS.

Absolutely not. I said my advice would be to not make a change the existing 2014 rule. Don't change to a rule that gives me a bigger advantage. The current rule is fair. The new rule is not fair. If I told you what I would do to get around it, it would not be fair to me.

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7VO-VOM

I do find it ironic that one of the main reasons argued for changing the HP/TQ/WT rules was to encourage (not discourage) new turbocharged BMWs that had more torque than horsepower. These are brand new cars that cost more in street form than most fully built GTS cars. However, the goal of this rule is to stop people using 2-15 year old BMW V8 engines because they have a torque curve advantage.

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Who's to say on a given dyno sheet what 30% to look at?

What will the heuristics be for that decision?

Who's to say how to pro-rate each of 10 new interpolated data points?

 

Isn't this unfair to people who can't tune their engine and change their redline to benefit the calculation that will be applied?

 

*******

 

The statement that the current de-tuning is "unfair but legal" is puzzling.

 

Which brand was unfairly not allowed to de-tune their engines?

 

I missed the exclusion mentioning that brand in the 2014 rule set apparently

Edited by Guest

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John Graber

I see both sides of this issue and have been torn myself, waffling back and forth several times since I first ran in GTS in 2006.

 

Ultimately I do believe we need to either provide limitations on some items or penalize for them. If we don’t do something the series will die a slow death as investment and development of a few will chase away many. Power delivery is just one component. The “sequential” penalty is another, and perhaps someday there will be an Aero component….. I am for providing an avenue to equalize cars, to some degree but certainly not like in PT, so the focus is more on the driving. Not a lot of pushback on the “sequential” penalty, and it’s basically the same thing. Spend $$$ on a faster shifting transmission, or $$$ on a better curve and tune.

 

To me this is about providing better competition and growing the series. I agree with both concepts.

 

I appreciate the (clearly) thankless effort Scott and all the Regional Series Directors put into this amateur club racing series. Ultimately I may or may not agree, but that’s another story.

 

When do we get the details?

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Brad Waite

I would suggest before people go out and install a V8, or spend money coming up with the "new tune" to take advantage of the new rule set, they stop and think about the spirit and intent of the rule change. Clearly, the series is trying to protect the wt/hp rule set that the series was founded upon and moving to an average is a good step in that direction.

 

My guess is if efforts are made this year to work around that rule, the 30% range may be expanded to a broader segment of the rpm curve, or a different section of the curve may be chosen for measurement rather than the upper 30%. I think our time and money would be better spent accepting the avg. hp change and working on our racing skills rather than a tuned advantage.

 

This has nothing to do with controlling cost in the series in my opinion. There are still many expensive choices that can be made from car choice to building a motor to maximize power, albeit average power. I have always been a protector of the GTS open rule set and don't think this erodes that philosophy.

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bimmerhead

From a practical standpoint, I'm wary of the unintended consequences. Those that have the resources will now explore different (and likely more expensive) means to gain a competitive advantage.

 

Has a real-world impact analysis of this change been done? It's one thing to say certain cars are eligible to run at a reduced weight, but in reality can they? One successful GTS racer in my region claims that while on paper, this rule change would offer a nice weight break for him, he's at a loss as to where he'd get it. I have ECU-controlled TBs, and from what I can see, I will actually be able to reduce the weight of my car slightly, but that will mean a re-tune.

 

From a philosophical standpoint, the biggest reason I built a GTS car was the simplicity of the rules - and why I never built a BMW CCA Club racer, even though I am a died-in wool bimmerhead. I am not convinced this isn't the first step down the slippery slope into what I consider the current deplorable state of virtually all spec series.

 

What's next? Do semi-trailing arm suspension cars get some kind of break, since their suspension design is inferior to a multi-link? Do cars running narrower tires get a break over cars with wider tires since those cars have an assumed grip advantage? Do cars with higher drag coefficients get a break over cars with lower drag coefficients? And on and on, with the whack-a-mole game that is the nightmare of virtually all other spec series.

 

The fact of the matter is that some cars will always have an advantage on paper. The reality is, IMHO, at the amateur level we're racing at, the driver is the biggest variable.

 

From my perspective, this rule change will only cost us racers money and not change the landscape at all.

 

Cheers,

-jerry

 

 

 

 

Just my 2 cents.

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