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2021 Rules Time--How about no changes?


Greg G.
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re: flat power curves.  having had both, i can tell you that what matters is the area under the curve. whether it's flat or not is a function of how you decide to maximize that area.  same car, same weight, same avg hp will show the same accel/speed traces in the data. the WRL rule is ridiculous

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Theoretically, I would argue that for a power limited car (low power, lots of tire), a flat power curve would be beneficial, and for a tire limited car (high power and/or not enough tire), a traditional sloped power curve would be beneficial.

Why...

The low power car can easily use full throttle when leaving a slow corner.  having more power (and thus generating more energy) at the beginning of the straight is more valuable than at the middle or end of the straight, because the acceleration that it generates then pays dividends all the way down the straight.
Additionally, a flat power curve may allow you to downshift less, and therefore upshift less on the following straight, saving time.

The high power car would struggle to use full throttle when leaving a slow corner.  Therefore, having a flat power curve would be useless, because they would then be able to use even less of the throttle %, so that potential power would be lost.  Therefore, over the course of the straight, they would end up generating less energy, and therefore less acceleration than if they had had a traditional power curve.

 

Of course, overall these differences are miniscule, and ST should not have a flat power curve modifier. 
The current average HP calculation method does a very good job of creating equivalence between different engine types.

For WRL, where most cars are lower power, I can see how this type of rule might be beneficial.  I am not familiar with their power/weight calculation method.  If they are just using peak HP, and then adding on this flat power curve modifier, then that makes sense.  But we don't need it.

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WRL uses weight / peak power plus modifier.  So a 2800 lbs car with 241 horsepower and up to -0.4 modifier would be 11.2:1.  Or, with a traditional power curve, it could make 250rwhp.  That's really not much of a penalty for having a flat power band.

Using the ST4 formula, assuming a >7k rev limiter, a 2800 car with a flat 241 power band would be 11.6:1.  A traditional power curve with, say, a 20 hp drop every 1k RPM could make 223 @ 6250 and 259 @ 8000 RPM.  (223 + 228 + 233 + 238 + 244 + 249 + 254 + 259).

So the ST rule has a greater penalty for flat power band cars than WRL already.  Plus it doesn't have any ambiguous language like "flat horsepower power curve."  (what's flat?  1 rwhp drop over 500 RPM ok? 2 rwhp?)

 

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  • 1 year later...

    When it comes to 13.5:1 power levels which I run in GTS2 with an S54 swapped car, flat is definitely a disadvantage. A few other racers have also discovered that it’s more beneficial to make the curve more peaky at the top of the rpm range. With my ST3 tune I have found that with my S54, flat doesn’t work that great for racing with the ST3 calculator. I find myself struggling to complete passes since the top end is backed down. After switching to a more natural and peaky tune, it made for a better race setup for me. Where I think the “issue” is with the ST/TT calculator is there is no factor for tq. So you end up with large displacement engines or turbos that are capable of basically maintaining their peak flat hp from 4500 to 7k rpm. Whereas lower displacement cars have a much smaller peak operating window. Even my “flat” tune is only 1250rpm of peak power. So I get half the rpm range at peak yet my avg ends up being basically the same avg as an engine with 2500rpm of peak power. 
 

     So I think the challenges are less related to having a flat curve, and more related to how long a particular engine is at that peak whp. Just setting some generic “flat” mod will actually even further disadvantage a lower displacement engine that has a somewhat flat curve. 

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  • National Staff
On 1/14/2022 at 6:44 PM, daytonars4 said:

    When it comes to 13.5:1 power levels which I run in GTS2 with an S54 swapped car, flat is definitely a disadvantage. A few other racers have also discovered that it’s more beneficial to make the curve more peaky at the top of the rpm range. With my ST3 tune I have found that with my S54, flat doesn’t work that great for racing with the ST3 calculator. I find myself struggling to complete passes since the top end is backed down. After switching to a more natural and peaky tune, it made for a better race setup for me. Where I think the “issue” is with the ST/TT calculator is there is no factor for tq. So you end up with large displacement engines or turbos that are capable of basically maintaining their peak flat hp from 4500 to 7k rpm. Whereas lower displacement cars have a much smaller peak operating window. Even my “flat” tune is only 1250rpm of peak power. So I get half the rpm range at peak yet my avg ends up being basically the same avg as an engine with 2500rpm of peak power. 
 

     So I think the challenges are less related to having a flat curve, and more related to how long a particular engine is at that peak whp. Just setting some generic “flat” mod will actually even further disadvantage a lower displacement engine that has a somewhat flat curve. 

If your "flat" tune only spans a 1250 rpm range, then that is a function of you not spending enough money to build the power up high enough to then throttle tune it back down to a flat HP range of 2-3K rpm.  I'm not saying that is what you should do, but that is what is and can be done under the rules.  Or, you could comply with the other ST4 rules and drop from ST3 to ST4 and get that flat power band for a longer time.   I'm guessing that we have gone over the Max Tq versus power under the curve discussion hundreds of times, and I guess one more time.  Max Tq does not mean a damn thing by itself.  Having a high Max Tq at 2000 rpm where the car never operates doesn't improve speed on track.  A locomotive engine has humongous Max Tq, but you won't find one in a race car.  When you add in rpm to Tq, you get HP, which is what provides the power necessary to move an object.  So, when you say there is no factor for Tq, what you really mean is that there is no factor for a car with very long usable flat HP RPM range--or basically calculus and measuring the entire area of the HP curve.  We decided that calculus was just a slight step above what our typical competitor was capable of, and would have made tuning pretty difficult.  So, we came up with our formula that helps the situation, and we limited the ability of competitors to legally cheat the formula by not providing too wide of an RPM range that is used for calculations.  Because a car with a 10 speed close-ratio transmission could theoretically have huge HP for 1200 RPM, and then dump power before and after that range, and if driven correctly, would be at a huge advantage.  That would be the same thing even if we did the calculus and measured the entire area under the curve.  The answer to a narrow band of power is better (granted can be very expensive) transmission choices.  Ultimately, the only fair racing--driver to driver--is in 100% identical cars, with 100% identical setups, with cars swapped between drivers after every session on track, and new tires every session. 

And, just to throw this in, any rule set that has arbitrary and subjective limits like "flat horsepower" would never fly in NASA.  Might as well just make a dart board with NASA Officials photos on it and post it on Facebook.  Then watch how many hits each official gets for the subjective decision of whether a HP curve is flat or not. 🤣

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  • Greg G. unpinned this topic

Yes @Greg G. you are saying exactly what I’m acknowledging. The ST power calculation is more catered to the high displacement cars that easily exceed the ratio for the base class such as LS’s that can achieve the 2500-3k useable peak power. Even with a stroked $20k S54 I can’t achieve that same powerband, which is why I think we are starting to see more LS swapped BMW’s. BMWCCA allowing that in their new classes will probably open the floodgates on that. The LS combined with the fact that ST only mods a 335 tire the same as a 285 heavily skews the ruleset toward that setup for ST3. The fact the combo worked well at Daytona (which is a track that skinner tires would have the best chance) kind of hints at what to expect at lower speed with higher mechanical grip tracks. 
 

Since you did mention ST4 and I agree that’s where S54’s become the “overdog”…. Balancing power and tire size really are the top things that matter in these classes. I have never understood the logic behind not allowing a car such as an e36 to run fenders which provide the same tire coverage/track width as other top cars in class such as the Corvettes and E46’s. It’s a restriction that is only putting the older more narrow chassis in class at a disadvantage. Just not following the logic behind that when tire size is already limited.  I see so many NASA publications highlighting cars in their ST4 marketing material that don’t even follow the fender rules. 

Edited by daytonars4
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