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PostPosted: Sun Oct 15, 2017 7:29 pm 
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daytona,

I drive a 350z de, they are also thinking of moving the minimum weight to 3100 for 275 tires, so at that weight with 6 points my car is out of st4. I hope they make the correction to the base ration and make it a true 12:1 class
Many of us have brought up this concern, you can see it in previous post.



daytonars4 wrote:
Going to 6 data points will have a significant impact on avg hp, so if that’s the direction please consider a comparable adjustment to the base ratio. Many of the cars that have been racing in ST4 (e36’s/350z’s/S2000’s etc) are already at or beyond what they can reach for power to weight. Without an adjustment expect this to become more of an E46/E92 M class which I don’t think is the intention.

GTS chose to not use a 3k rpm band in the averaging bc it allowed too much room for tuners to make adjustments to exploit it. If someone has a sequential which can stay primarily around a 2k rpm range it’ll make a mockery of this revision. But I guess since sequentials aren’t a concern in ST4 it doesn’t matter as much.


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PostPosted: Mon Oct 16, 2017 8:51 am 
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daytonars4 wrote:
Going to 6 data points will have a significant impact on avg hp, so if that’s the direction please consider a comparable adjustment to the base ratio. Many of the cars that have been racing in ST4 (e36’s/350z’s/S2000’s etc) are already at or beyond what they can reach for power to weight. Without an adjustment expect this to become more of an E46/E92 M class which I don’t think is the intention.

GTS chose to not use a 3k rpm band in the averaging bc it allowed too much room for tuners to make adjustments to exploit it. If someone has a sequential which can stay primarily around a 2k rpm range it’ll make a mockery of this revision. But I guess since sequentials aren’t a concern in ST4 it doesn’t matter as much.


Daytonars4 - when you say that 'many of the cars that have been racing in ST4...are already at or beyond what they can reach for power to weight...' do you mean that by now using 6 points at 500 RPM increments it will be difficult to make the car competitive as the avg hp will now be much lower? In my case (running a e36 m3 with @234 avg hp) I am already coming in about 100lbs over on weight. 2 more data points would bring my avg down to around 220, which would make it really tough to be close to an ideal weight. Is that why you would also be suggesting to make an adjustment to the base ratio? Just trying to understand the implications of 6 vs 4 data points for the avg.

Jon B
NorCal ST4


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PostPosted: Mon Oct 16, 2017 9:56 am 
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clock wrote:
Alan_Wolfe wrote:
Just to be clear and accurate about this:
4 data points covers 1500 rpm range
6 data points covers 2500 rpm range


While that is probably the intention, that is not how the math was set up.

The Interval of the evaluation = the partition size * number of points. So 4 points x 500rpm evaluates a 2000rpm interval, and 6 a 3000rpm interval. You can't arbitrarily make the evaluation exclusive of the lower partition.

The ST rules describe a Riemann Sum(https://en.wikipedia.org/wiki/Riemann_sum) when they add up the points as a means of evaluating different curves against one another(dividing by the constant 4 does nothing). One problem is that a LEFT sum (as opposed to RIGHT, or MID) is codified in the rules by 8.2 "If any of the above data points at higher RPM than Max HP RPM do not exist due to redline, then those potential data points will not be used in the calculation of Avg HP". LEFT sum is an OVERESTIMATION of area under the curve PROPORTIONAL TO THE SLOPE OF THE CURVE. A flatter curve means less of an overestimation.

This will not go away by adding more points.

Without even getting into the "race-ability" advantages of a flat curve(which we should not, because it too difficult to quantify), you can now see why so many people have chosen to tune their cars as flat as possible: because the ST rules math will give engines with a steep power curve a weight ratio disadvantage right off the bat.

As I suggested, the best way we can deal with this is to decrease the partition size, which increases accuracy. Simply increasing the interval does nothing.

Poor 4 cylinder NA. I feel your pain... And wait until the Rotary shows up. Poor poor rotary.


If the calculation is in fact using a Riemann Sum Approximation, then we should go to using 100 rpm intervals instead of 500 rpm intervals. This would increase the accuracy of the Approximation, especially for motors that do not have a flat HP curve. It would also reduce the difference between left rule, right rule, or midpoint rule approximations.

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PostPosted: Mon Oct 16, 2017 10:28 am 
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Alan_Wolfe wrote:
clock wrote:
Alan_Wolfe wrote:
Just to be clear and accurate about this:
4 data points covers 1500 rpm range
6 data points covers 2500 rpm range


While that is probably the intention, that is not how the math was set up.

The Interval of the evaluation = the partition size * number of points. So 4 points x 500rpm evaluates a 2000rpm interval, and 6 a 3000rpm interval. You can't arbitrarily make the evaluation exclusive of the lower partition.

The ST rules describe a Riemann Sum(https://en.wikipedia.org/wiki/Riemann_sum) when they add up the points as a means of evaluating different curves against one another(dividing by the constant 4 does nothing). One problem is that a LEFT sum (as opposed to RIGHT, or MID) is codified in the rules by 8.2 "If any of the above data points at higher RPM than Max HP RPM do not exist due to redline, then those potential data points will not be used in the calculation of Avg HP". LEFT sum is an OVERESTIMATION of area under the curve PROPORTIONAL TO THE SLOPE OF THE CURVE. A flatter curve means less of an overestimation.

This will not go away by adding more points.

Without even getting into the "race-ability" advantages of a flat curve(which we should not, because it too difficult to quantify), you can now see why so many people have chosen to tune their cars as flat as possible: because the ST rules math will give engines with a steep power curve a weight ratio disadvantage right off the bat.

As I suggested, the best way we can deal with this is to decrease the partition size, which increases accuracy. Simply increasing the interval does nothing.

Poor 4 cylinder NA. I feel your pain... And wait until the Rotary shows up. Poor poor rotary.


If the calculation is in fact using a Riemann Sum Approximation, then we should go to using 100 rpm intervals instead of 500 rpm intervals. This would increase the accuracy of the Approximation, especially for motors that do not have a flat HP curve. It would also reduce the difference between left rule, right rule, or midpoint rule approximations.



I don't think it needs to be this complicated. I plugged the four numbers from my peaky power curve into the Trapezoid Rule (average of the right sum and left sum / very little error) and came with 0.1% of the arithmetic mean of the 4 points. Try the same with your actual numbers and see what you get. I think you'll find that the "add 'em up and divide by 4" approach is close enough for government work.

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PostPosted: Mon Oct 16, 2017 1:23 pm 
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Rafael.
You have a lot to say for someone who only race one race weekend, this whole year. You talk a lot about car disparity, tires ect. But not sure what you are trying to gain? If you put Andrew Kidd on stock tires, he will still be faster then you are. I ran the same times you did back in April, on used NT01 tires, on basically stock street car, in my first ever race. You keep going on about car disparity, which i believe should be left for those, whom actually are racing in the series, consistently, with competitive times. I wouldnt think to start asking to change the rules because i got beat every race, but also know my skills are not on par with the leaders in this ST4. Unless you start coming out, and racing every weekend, i do not see how you plan on getting faster. You can look in the race from April where i followed you half of a race, and perhaps you can take some notes. https://www.youtube.com/watch?v=pKZ9IB_4bcg&t=3s

On another note, congrats on everyone that came out and race NWC, it was fun, clean racing. Glad i got a chance to get to know, and race with so many of you, looking forward to next season, and hope you all can come out and race more.

Martin
S2000 #58


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PostPosted: Mon Oct 16, 2017 2:11 pm 
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esr wrote:
only reason I am considering it is for lack of a good fast spec series


Fair enough given "fast" is very subjective.

esr wrote:
I drive a 350z


Wait...what?!? Um NASA SpecZ. Please direct your energies at building up your region's SpecZ field if you want a "fast" spec series. Our local guys did that and now we have upwards of 20 entries at events and very tight racing (and we're a relatively small region). You come off as the guy who doesn't want to do any (serious) work, wants the rules written to match his personal needs and to hell with whatever is best for the growth of the class/sport, and thinks if he just shouts whatever nonsense the loudest (and most frequently), he'll get his way. Then bitches when he still gets beat at the one event he actually shows up to because clearly everyone else must be cheating. :roll:

Also could you please learn how to quote when you reply. Your posts are a PITA to read.

Edit: Fixed link to go to class view.

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Last edited by DarkGift on Tue Oct 17, 2017 5:36 am, edited 1 time in total.

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PostPosted: Mon Oct 16, 2017 2:57 pm 
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jonb94118 wrote:
daytonars4 wrote:
Going to 6 data points will have a significant impact on avg hp, so if that’s the direction please consider a comparable adjustment to the base ratio. Many of the cars that have been racing in ST4 (e36’s/350z’s/S2000’s etc) are already at or beyond what they can reach for power to weight. Without an adjustment expect this to become more of an E46/E92 M class which I don’t think is the intention.

GTS chose to not use a 3k rpm band in the averaging bc it allowed too much room for tuners to make adjustments to exploit it. If someone has a sequential which can stay primarily around a 2k rpm range it’ll make a mockery of this revision. But I guess since sequentials aren’t a concern in ST4 it doesn’t matter as much.


Daytonars4 - when you say that 'many of the cars that have been racing in ST4...are already at or beyond what they can reach for power to weight...' do you mean that by now using 6 points at 500 RPM increments it will be difficult to make the car competitive as the avg hp will now be much lower? In my case (running a e36 m3 with @234 avg hp) I am already coming in about 100lbs over on weight. 2 more data points would bring my avg down to around 220, which would make it really tough to be close to an ideal weight. Is that why you would also be suggesting to make an adjustment to the base ratio? Just trying to understand the implications of 6 vs 4 data points for the avg.

Jon B
NorCal ST4


Yes John B, you are explaining exactly the issue I’m describing. You don’t want to turn ST4 into a class where people have to run built motors or carbon panels etc. So the ratio needs to be within reasonable reach of the target cars for the class.


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PostPosted: Mon Oct 16, 2017 3:01 pm 
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Rafael,
You have a lot to say, for someone who only raced one weekend this whole season. Basically, you come out, raced once in April and have not shut up ever since about car disparity, but not sure what you are trying to gain. if you put Andrew kidd on stock tires, he is still going to be faster then you are. Actually pretty sure the spec miata guys are faster also.
I ran the same time as you did on used NT01 on basically a street car, and in my first ever race. You talk a lot about car disparity but no driver disparity. Unless you start coming out, and racing i dont see how you plan on getting faster, regardless of what car you are in. You can look at the race from April where i followed you for half of the race, perhaps you can take some notes. https://www.youtube.com/watch?v=pKZ9IB_4bcg
If you do not want to put the work in on your car, then just come out and have fun. Which this is what we have all been doing all season long.


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PostPosted: Mon Oct 16, 2017 3:11 pm 
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ESR, are you coming to Sonoma? Come to the last nor-cal race of the year.


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PostPosted: Mon Oct 16, 2017 4:01 pm 
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ianbarberi wrote:
Dave Schotz wrote:
Chris, I posted my incar of the start...

Dave, I'd love to see your video, but I don't see a link. Where is it posted?

-Ian

Ian,

I saw that Dave Schotz posted two videos:

Time Trials https://www.youtube.com/watch?v=TJq5wkwA9sc
Sunday ST4 race start https://youtu.be/wCMacEY3Smo

and Nasa Speed News ST4 race is at https://youtu.be/H_nibYdBmuY

- Jim

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