etzilon

The intent of this thread is to discuss NASA PT/TT activities, how mods affect class and points, etc.

This is my first year doing TTs. I run with the NASA TX group in TTD (#145). Since we don't have that pesky white thing called snow, we already had our first event in January. It was challenging and fun driving on a track I had never run before.

Here's NASA TX schedule for 2013:
Jan 19-20 MSR Houston (Race, TT, DE)
Feb 16-17 Harris Hill (Comp School and Instructor Clinic)
March 16-17 MSR Cresson (Race, TT, DE)
April 19-21 TWS (Race, TT, DE, Enduro)
May 4-5 NOLA (Race, TT, DE)
June 22-23 Hallett (Race & TT)
Sept 5-8 Miller Motorsports "Nationals" (Race & TT)
Sept 20-22 TWS (Race, TT, DE)
Nov 2-3 Eagle’s Canyon (Race, TT, DE)

My plan is to attend all TT events except "Nationals"

kbrewmr2

baahhh Nationals is fun

MagnusRacing

iTrader: (2)

Yes, I'll be going to nationals this year since it's once again closer to California. I went in 2009-2010 and it was great. Miller is a nice track. You should go if you can - it's not THAT far.

etzilon

We shall see... we shall see...

MagnusRacing

iTrader: (2)

A friend of mine who moved to Texas keep asking me to come to some of the Texas events... we'll see with me as well!

MagnusRacing

iTrader: (2)

Dyno Reclassing - This can be a very useful option for cars competing in NASA TT and PT. As we know the NASA National Time Trial / Performance Touring Director, Greg Greenbaum, has a secret formula for determining your race class and minimum weight based on dyno results (must be from a Dynojet Dyno). He won't release how he determines this to anyone - not even his assitant directors (I should know as I am one!).

Often a Dyno Reclass is very useful because it eliminates any "points" taken for motor modifications or weight reduction and instead assigns you a maximum rear horsepower rating you must not exceed and a new minimum weight (weight is with driver). Also, you can't spend "points" to reduce this minimum weight once you have reclassed - you may not go under in any way.

Just FYI the "base" minimum competition weight/class (with driver) for a 2004-2008 RX-8 is PTD at 3045lbs if you do not dyno reclass. PTD has a maximum ADJUSTED power to weight ratio for ALL vehicles of 14.25:1 - once you factor in the "Adjustments" for the RX-8 you can run up to 229rwhp and you will still not exceed the max power/weight ratio of the class. We know that getting the renesis motor to that level without massive porting or forced induction is not really possible but if you happen to have a VERY powerful motor NOT doing a Dyno Reclass might be to your advantage. Dyno testing for TT and PT cars that are not Dyno Reclassed are rare but I've seen it done - particularly at Nationals. The base class for a 2009-2011 RX-8 is PTD* and for a 2009-2011 RX-8 R3 PTC. Same 3045 min weight. If you have one of these newer RX-8 models you really should dyno reclass right away. The 2009 and later RX-8s really don't have much of an on track performance advantage so why they're base classed so much higher is a mystery.

To help people determine if a Dyno Reclass might be useful for their RX-8 I thought I'd compile a list of the known Dyno Reclasses done for RX-8 race cars so far:

MagnusRacing: (2005 RX-8): PTD/TTD with 213rwhp and 3065lbs min weight OR TTD/PTD with 215rwhp and 3095 min weight

Etzilon: (2005 RX-8): TTD* with 207rwhp and 2900lbs min weight OR TTD** with 214rwhp and 2895lbs min weight as long as final class is TTC or higher

Arca ex: (2005 RX-8): TTD with 200rwhp and 2935lbs min weight OR TTD with 210rwhp and 3025lbs min weight OR TTD* with 218rwhp and 3055lbs min weight

Robert D.: (2004 RX-8): PTD with 185rwhp and 2760lbs min weight OR PTE** with 185rwhp and 2900lbs min weight (final class must be PTD or higher)

Lee P.: (2004 RX-8): PTD with 200rwhp and 2935lbs min weight OR PTE** with 200rwhp and 3030lbs min weight (final class must be PTD or higher)

DocgaterX8er: (2004 RX-8): PTD/TTD with 197rwhp and 2890lbs min weight

Darnellm (2005 RX-8): PTE**/TTE** with 204 rwhp and 3090 min weight ( final class must be TTD or higher)

Dennis H. (2005 RX-8): PTD** with 208rwhp and 2810 min weight

If anyone else has been dyno reclassed in a NASA TT or PT car please post your results here.

olddragger

iTrader: (3)

how do they handle the engines redline? Do they go by the manufacturers recommendations?

MagnusRacing

iTrader: (2)

The Dyno Reclassing only takes into consideration the engine redline in the following way:

The Dyno Operator must indicate on the Dyno Certification Form that either:

A) The rev limiter of the motor was reached during the dyno test

or

B) The dyno graph must show decreasing horsepower past the peak horsepower reading for at least 300rpms


For example the ECU on my RX-8 has been reflashed for a 10,000 rpm limit. My dyno results show the HP curve from 3000rpm to 9500rpm. The graph shows a peak power of 210hp at 8800rpm which then drops off to about 180hp at 9500rpm. Since the curve is decreasing for more than 300rpms past the peak horsepower this is considered an acceptable dyno test. I can can make my rev limit anything I want as long as I show that the motor has reached peak horsepower.

etzilon

I assume it is ingredient X of the Secret Sauce.

I have neither a reason to believe nor a complaint that Greg's approach isn't fair or isn't consistent yet it is still a black box. I can only believe it has to do with a perceived chassis/suspension advantage together with some sort of "X pounds equals Y HP", etc.

etzilon

etzilon: (RX-8, 2005): TTD* (i.e. +7) with 207rwhp and 2900lbs min weight

Here's another option I was given: max 214 rwhp, Minimum Competition Weight (w/driver) of 2895 lbs -> TTD** (+14 points) as long as Final Competition Class is TTC or higher.

Arca_ex

iTrader: (10)

Awesome thread.


After seeing some of the other dyno reclasses I think I might shoot off another email after I get an official dyno. Still aiming for 210RWHP, but instead of running 275 Hoosiers I think I'll opt for 255 hoosiers which gives me 6 points back. Then ask Greg to give me a weight for my car at whatever HP it makes, with a base class of TT-D* and minimum competition group of TT-C. Hopefully it comes back at around 210HP at ~2900lbs.

Then I'll be:
+7 for one star
+10 Hoosiers
+1 Tire Width
+3 Shocks (Coilovers)
+2 Springs (Coilovers)
+2 Sway Bars
+3 Splitter
+4 Rear Wing
+2 Canards
+2 Add Rear Diffuser
+2 Side Skirts
+1 Vortex Generators

Which is +39 points total, moving me up one class which is maxed out in TT-C.

Now you may say, hey why don't you go for TT-D** base class for even less weight by losing all the aero stuff that may not do a whole lot, the canards, rear diffuser, side skirts and vortex generators, but I need to either be able to ballast up or have a different tune for the time attack series that I run in which has a 15:1 power to weight cap for my class. Have to make compromises to run in both TT-C and Time Attack. I should be very dominant in Time Attack but TT-C will be a good battle. There are usually 7 to 10 competitors and everyone is within like a 3 to 4 second spread with the middle of the pack all being within about a second of each other.

Arca_ex

iTrader: (10)

Also one other thing I'd like to add, is to keep in mind that the power to weight ratios that are not to be exceeded for the class is an ADJUSTED number. Your raw power to weight isn't the number you go off of for the class limits. The guide for finding your adjusted power to weight is on the last pages under Appendix B of the Time Trials Rules found here: NASA Time Trial

For example:

If my car makes 210RWHP, has only 255mm DOT tires for modifications, and has a competition weight of 2986 my raw power to weight is 14.21, and if we were going by raw power to weight, this means I would not be able to participate in TT-D which has a cap of 14.25 lbs/hp.

But after adjusting:

14.219 Raw P/W
+0 for Body Type (Not sure on this one, see question later in post)
+0 for Transmission
+0 for Drivetrain
+0.4 for Tire Width
-0.25 for Weight

We get 14.369 for the adjusted power to weight, which is legal for competition in TT-D.


Now for someone who might be able to answer my question about the body type, could we get away with classifying it as a four door sedan? I might email Greg about this. If it is considered a 4 door sedan that would be another +0.4 to the adjusted power to weight which is a pretty decent advantage...

etzilon

Ha! I put it down as a "sedan" on my first reclass try (as per DOT?). It seems to have pissed Greg off.

etzilon

This is a snippet from Greg's email:
what you have done is put numbers down to reach the limit on Adjusted Wt./HP Ratio for the class, and then give yourself 20 points to play with. It doesn't work that way.



I was just doing what I thought was right... Ignorance is bliss, I guess.

Arca_ex

iTrader: (10)

Well you can't ask for Power, Weight and Base Class, most of the time you can pick two and he'll give you the third. For example in my next email I'll give him my Power and what base class I would prefer and he will use his super secret formula to give me a weight.

etzilon

The only conclusion I made is that the adjusted weight/power ratio is just one input to the super secret formula.

Notice how when calculating adjusted weight/power ratio, weight is actually accounted for twice, tires influence it too, etc.

Based on the above, I thought that adjusted weight/power ratio (instead of actual) would define the class but it doesn't, it just influences it.

Arca_ex

iTrader: (10)

Yeah it doesn't define it, have to take into consideration that he thinks about how good the chassis is as well as how many points you have for modifications and such. I will be nowhere near my adjusted power to weight cap which is 12.0 lbs/hp. I'll be more like 14.0 I think but I'll have a ton of points to use and our chassis is considered advantageous since it comes stock with things like LSD that we don't have to take points for, and the suspension geometry is a lot better than most of the older cars competing, etc. Usually most of the time everything ends up pretty fair in the classes here after it's all said and done.

MagnusRacing

iTrader: (2)

Yes, the RX-8 is a Sedan. It has four doors and four seats. We should get the +0.4 power/weight modification. Etzilon - did Greg tell you it's not a sedan?

etzilon

He didn't. However, at 210HP, 2,900 lbs and 255mm wide r-comps the adj p/w ratio would be 12.26 which I would expect to be TTD no stars, not TTD*.

Arca_ex

iTrader: (10)

I don't think you understand how the stars work, they eat up your points in return for what is usually a better power to weight. He already said that TTD no stars at 210 HP would be 3025 lbs weight limit. Doing a base class of TTD* means that I have a 7 point penalty right from the start, but my minimum weight is likely to be lower.

Also you're not doing your math correctly. Adjusted power to weight for 2900lbs and 210hp assuming 255 dot tires and 2 door coupe is 13.86

Also if Greg didn't tell you it is a sedan then we don't know for sure.

etzilon

Oh... You got that right. I really don't understand it and I'm not ashamed of it at all

Understood. That's the base class. How do we (or Greg) come up with base classing numbers from scratch? Power and weight only? I don't know how.

Duh... I meant 14.26 if you consider the RX8 a sedan (13.86+0.4)

MagnusRacing

iTrader: (2)

We don't.

As the 2013 Time Trial Rules say on page 7 regarding the minimum adjusted weight power ratio for each class: "These minimum 'Adjusted Weight/Power Ratios' are not a substite for base classing followed by calculation of Modification Points to determine the final competition class. They are an additional limitation placed on vehicles to help achieve a level platform for competition in each class."

For base classing all we can do is provide the national director (Greg) with our dyno results and wait for his magic calculations. I'm hoping that by showing the results of RX-8s that have already been dyno reclassed this can be used to help anticipate what options Greg might make available.

MagnusRacing

iTrader: (2)

Just make sure you don't run the 255/35-18 Hoosiers as there is an exception specific to this tire that makes it the same points as a 275 tire (because they run really wide).

I did really well with this exact tire in 2011 and got a whole bunch on contingency at the end of the 2011 season in anticipation of the next. Then Greg changed the rules for 2012 and I ended up with a bunch of free tires I couldn't use.

Arca_ex

iTrader: (10)

Yeah its going to be 255/40R17

etzilon

Since I am TTD*, I am going with 225/45/17 NT01s. I had to buy a set of 17x8 Enkeis :-(