30 replies to this topic

[Keith Andrews]

I want to make sure I'm calculating a 99 SM correctly for PTE to run E3 in a NASA enduro.  Any help is appreciated.

 

I calculated for PTE as follows:

 

Tire SM6 at +10 

Tire size 205 vs. base of 235 at -7

Non OEM sway bar +2

Non OEM springs +2

Non OEM shocks +3

 

Total  -  10 points 

 

So that gives me 10 points under the maximum of 20 that would bump the car up in class.  Can I use 9 of those points to reduce the weight of the car?

 

Base weight with driver is 2400 lbs.  

 

Can I reduce that by (125 lbs. = +9) and for +9 points to be at a total of 19points?  So my race weight would be 2275 w/ driver.  I don't think that's doable but I'm wondering if I'm figuring it correctly.

 

This is the first time I've run through PT classing.  Please let me know if I have messed it up.  

[chris haldeman]

Keith you missed a lot of points. Torsen is considered an added limited slip +2 I think
Also exhaust is a few in the end an sm prepped car will usually have 2-3 points left over and yea that can be used too reduce weight.

[Todd Lamb]

SM is classed as E3 and is must run SM rules. I supposed you could try to class it as PTE, but why bother?

[Keith Andrews]

Keith you missed a lot of points. Torsen is considered an added limited slip +2 I think
Also exhaust is a few in the end an sm prepped car will usually have 2-3 points left over and yea that can be used too reduce weight.

 

Thanks, I read that as putting a LSD in a non-LSD car but ok +2 and yes I see + 2 for non OEM exhaust and +1 for CAT removal.  Thanks for the help.   

[Keith Andrews]

SM is classed as E3 and is must run SM rules. I supposed you could try to class it as PTE, but why bother?

 

 

Agreed on the SM.  

 

Why bother?  It's 44 degrees and it's been raining all day 

[Chad Martin]

The reason people do it is to pull the restrictor plate on 1.8L cars. SM directly cross classes into E3, but you must run the restrictor plate.  You are allowed to run any DOT tire.  Any spec miata prepped to the limit of the SM rules is a PTD car, thus E2 if you want to use PT as its non-enduro declared class.  Classed as a PT car your tire choice comes into play...

 

It does somewhat depend on the year....but this is how it works out. Two things to keep in mind first you cant get points back for running heavier and two this is only potential SM mods, not all cars have all these of course:

 

1.6L car base PT class is PTF** at 2182lbs

 

Engine

+1 Intake (Cone filter)

+3 Exhaust (+2 cat back, +1 for cat removal)

+2 Fuel Pressure Regulator

+6 If any of the SM legal "pro motor" head work is done (this one is debated back and forth and probably depends on the regional PT director or tech director's discretion, i am both in my region and i don't apply it simply because it's not enforceable in any realistic way)

 

Suspension

+2 Sway Bars

+2 Springs

+3 Shocks

 

Aero

+3 Chin Spoiler

 

Drivetrain

+3 LSD

 

Chassis

+2 bump steer mod (if employing one OR both of, rack shims and "R" model tie rod ends)

+3 for chassis bracing (if updated to the 97 sub-frame braces)

 

Tires (base class tire size is 215)

+8 205 RRs (9pt tires -1 pt for size)

+9 205 SM6s (10pt tires -1 pt for size)

 

Potential total of 38-39 pts....more than 24 puts it in PTD

 

 

1.8L 94-97 car base PT class is PTE at 2330lbs

 

Engine

+3 Exhaust (+2 cat back, +1 for cat removal)

+2 Fuel Pressure Regulator

+6 If any of the SM legal "pro motor" head work 

 

Suspension

+2 Sway Bars

+2 Springs

+3 Shocks

 

Aero

+3 Chin Spoiler

 

Drivetrain

+3 LSD

 

Chassis

+2 bump steer mod (if employing one OR both of, rack shims and "R" model tie rod ends)

 

Tires (base class tire size is 235)

+2 205 RRs (9pt tires -7 pt for size)

+3 205 SM6s (10pt tires -7 pt for size)

 

Potential total of 28-29 pts....more than 19 puts it in PTD

 

NB 99+ chassis cars base PT class is PTE at 2400lbs

 

Engine

+3 Exhaust (+2 cat back, +1 for cat removal)

+2 Fuel Pressure Regulator

+6 If any of the SM legal "pro motor" head work 

 

Suspension

+2 Sway Bars

+2 Springs

+3 Shocks

 

Aero

+3 Chin Spoiler

 

Drivetrain

+3 LSD

 

Tires (base class tire size is 235)

+2 205 RRs (9pt tires -7 pt for size)

+3 205 SM6s (10pt tires -7 pt for size)

 

Potential total of 26-27 pts....more than 19 puts it in PTD

 

 

All that being said, if you are heII bent to pull your restrictor for enduros your best bet will be to re-baseclass the car by getting 3 dynojet runs without it and sending them along with your minimum weight to Greg (National PT director).  He will reclass the car and you wont have to take any engine or weight points...i believe most cars then can squeeze into PTE sans restrictor plate.

 

EDIT: Fixed 1.6 max points before jumping to PTD

[Todd Green]

1.6L car base PT class is PTF** at 2182lbs

 

 

Potential total of 38-39 pts....more than 25 puts it in PTD

How are you arriving at 25 points for PTD?  You have 39 points to move up a class.  (Minus the 14 for **), so it should be > 25 puts your in PTE (one class up from PTF) no?  59 points for two classes, so the limit would be 59-14 or 45 unless I'm missing something.  Also people should be aware of the 16.50:1 minimum adjusted weight to power ratio.  It's really easy to go over that.  (I really hate that it isn't hp+tq/2.)

[Keith Andrews]

The reason people do it is to pull the restrictor plate on 1.8L cars. SM directly cross classes into E3, but you must run the restrictor plate.  You are allowed to run any DOT tire.  Any spec miata prepped to the limit of the SM rules is a PTD car, thus E2 if you want to use PT as its non-enduro declared class.  Classed as a PT car your tire choice comes into play...

 

It does somewhat depend on the year....but this is how it works out. Two things to keep in mind first you cant get points back for running heavier and two this is only potential SM mods, not all cars have all these of course:

 

1.6L car base PT class is PTF** at 2182lbs

 

Engine

+1 Intake (Cone filter)

+3 Exhaust (+2 cat back, +1 for cat removal)

+2 Fuel Pressure Regulator

+6 If any of the SM legal "pro motor" head work is done (this one is debated back and forth and probably depends on the regional PT director or tech director's discretion, i am both in my region and i don't apply it simply because it's not enforceable in any realistic way)

 

Suspension

+2 Sway Bars

+2 Springs

+3 Shocks

 

Aero

+3 Chin Spoiler

 

Drivetrain

+3 LSD

 

Chassis

+2 bump steer mod (if employing one OR both of, rack shims and "R" model tie rod ends)

+3 for chassis bracing (if updated to the 97 sub-frame braces)

 

Tires (base class tire size is 215)

+8 205 RRs (9pt tires -1 pt for size)

+9 205 SM6s (10pt tires -1 pt for size)

 

Potential total of 38-39 pts....more than 25 puts it in PTD

 

 

1.8L 94-97 car base PT class is PTE at 2330lbs

 

Engine

+3 Exhaust (+2 cat back, +1 for cat removal)

+2 Fuel Pressure Regulator

+6 If any of the SM legal "pro motor" head work 

 

Suspension

+2 Sway Bars

+2 Springs

+3 Shocks

 

Aero

+3 Chin Spoiler

 

Drivetrain

+3 LSD

 

Chassis

+2 bump steer mod (if employing one OR both of, rack shims and "R" model tie rod ends)

 

Tires (base class tire size is 235)

+2 205 RRs (9pt tires -7 pt for size)

+3 205 SM6s (10pt tires -7 pt for size)

 

Potential total of 28-29 pts....more than 19 puts it in PTD

 

NB 99+ chassis cars base PT class is PTE at 2400lbs

 

Engine

+3 Exhaust (+2 cat back, +1 for cat removal)

+2 Fuel Pressure Regulator

+6 If any of the SM legal "pro motor" head work 

 

Suspension

+2 Sway Bars

+2 Springs

+3 Shocks

 

Aero

+3 Chin Spoiler

 

Drivetrain

+3 LSD

 

Tires (base class tire size is 235)

+2 205 RRs (9pt tires -7 pt for size)

+3 205 SM6s (10pt tires -7 pt for size)

 

Potential total of 26-27 pts....more than 19 puts it in PTD

 

 

All that being said, if you are heII bent to pull your restrictor for enduros your best bet will be to re-baseclass the car by getting 3 dynojet runs without it and sending them along with your minimum weight to Greg (National PT director).  He will reclass the car and you wont have to take any engine or weight points...i believe most cars then can squeeze into PTE sans restrictor plate.

 

 

Thanks for taking the time to fully explain the process.  It's those fine points that you pointed out, I was curious about.  

[Chad Martin]

How are you arriving at 25 points for PTD?  You have 39 points to move up a class.  (Minus the 14 for **), so it should be > 25 puts your in PTE (one class up from PTF) no?  59 points for two classes, so the limit would be 59-14 or 45 unless I'm missing something.  Also people should be aware of the 16.50:1 minimum adjusted weight to power ratio.  It's really easy to go over that.  (I really hate that it isn't hp+tq/2.)

 I agree with you on the fact that max HP being the only thing taken into consideration is kinda lame.  I drive an RX-7, so imagine my frustration.  I myself think that it should be some simplified area under the usable (RPM) HP curve based on the cars actual gearing...but i suppose that would just glass peoples eyes over in about 1 millisecond.

 

So for the 1.6L car it is PTF +14 base (each * is 7) So you have 5 more points before you jump to PTE.  +6 puts you in PTE Then another 18 before you jump to PTD.  So, 6 points or or more means PTE, 25 or more means PTD.  So i guess my phrasing should have been more than 24 points puts you in PTD.  The 1.6 is a goofy base class but i think they offset it and justify by having a considerably lower competition weight than the spec miata 2300lbs.

[Todd Green]

I myself think that it should be some simplified area under the usable (RPM) HP curve based on the cars actual gearing...but i suppose that would just glass peoples eyes over in about 1 millisecond.

Agreed. That's why I'd hope at least for a hp+tq/2. Or minimally: max(hp,tq) which is simple to calculate even for non-math people
 

So for the 1.6L car it is PTF +14 base (each * is 7) So you have 5 more points before you jump to PTE.

I see...I was looking at 20-39, but 20 is the boundary for bumping, not 39. Had I written those rules, I would have started the chart via 0-19. I tend to think along the lines of what is the highest number of points I can use before I bump, not the minimum number of points before I bump.

[john mueller]

SM is classed as E3 and is must run SM rules. I supposed you could try to class it as PTE, but why bother?

 

Matter a lot.  If you 'map' in via SM it has to be 100% SM, including the tires.  If you map in as a PT car you have the ability to modify the car based on the number of points available.  This can make a big difference.

[Rob Burgoon]

Matter a lot.  If you 'map' in via SM it has to be 100% SM, including the tires.  If you map in as a PT car you have the ability to modify the car based on the number of points available.  This can make a big difference.

 

You can get clever.  If you map in as a SCCA non-national SM, you've got open tires.

[Chad Martin]

It's open tires anyway for SM cross class into E3.  (At least, within the confines that it must be a DOT tire)  You could run BFGs or A6s if you wanted...they must fit on a 7" spec miata compliant rim though.

 

As a PT car you can change width and compound but it will affect the PT class which affects the cross classification.

Edited by Chad Martin, 12-06-2013 09:15 AM.

[Glenn Davis]

I thought the 99+ was a PTE*

 

Just checked.  The MX-5 is PTE*, not the 99-05.

Edited by Glenn Davis, 11-30-2013 03:35 PM.

[Chad Martin]

The +6 for head work is very likely to be applied at the championship sprint races.   Again it's just regional discretion that I don't apply it for enduros, both due to untenable enforcement (I'm not going to make a competitor tear down their motor on a friday before a weekend of sprint races), and minimal effect on the outcome of a 3+ hour race with fuel stops, etc.

 

But, if a Dyno is available a prime target would be a winning E3 spec miata for max P:W ratio check...

[john mueller]

The 3-hour races in Western Endurance Race Championship (WERC) are sprint races, the 25hour is starting to go that way too.

The 25hr is now all about the best prepped car that had the right amount of luck not to have hard contact or a random fluky mechanical failure, those are the cars that wins the class'.

 

Lap times are important (10%), but staying out of the paddock / pit road (50%), not getting pit penalties (20%) and staying on the tarmac (20%) are way more paramount in an WERC endurance race that is longer than 4hours...  Times will become important when the teams all have the reliability a few of top WERC teams are seeing now.  I guess since we run these races so frequently in NASA Nor & So Cal it has morphed into what GrandAm had become.

 

Don't get me wrong I'm all for enforcement of the rules, but until there is parity within the class'  of how to prep, run and manage these longer races, tech becomes less of an issue (IMHO).

[Johnny D]

bump

[Chad Martin]

Update for the 2014 NASA Performance Touring rules:

 

NASA published pre-approved dyno re-base classing for spec miatas to more easily cross class into PT and thus enduros.  (note that these reclasses are not necessarily a reflection of actual spec miata performance but instead likely a sweet spot in the classing equations)

 

It is important to note once you elect to use these reclasses you MAY NOT use additional points to lower the weight any further than these values.

 

1.6L Miata with not more that 127 DynoJet WHP base PT class is PTE at 2295lbs

 

Engine 

Engine Modifications are unlimited (except forced induction)

 

Suspension

+2 Sway Bars

+2 Springs

+3 Shocks

 

Aero

+3 Chin Spoiler

 

Drivetrain

+3 LSD

 

Chassis

+2 bump steer mod (if employing one OR both of, rack shims and "R" model tie rod ends)

+3 for chassis bracing (if updated to the 97 sub-frame braces)*

 

Tires (base class tire size is 235)

+2 205 RRs (9pt tires -7 pt for size)

+3 205 SM6/7s (10pt tires -7 pt for size)

 

Potential total of 21 pts....more than 19 puts it in PTD

 

 

1.8L 94-97 car with not more that 128 DynoJet WHP base PT class is PTE at 2355lbs

 

Engine

Engine Modifications are unlimited (except forced induction)

 

Suspension

+2 Sway Bars

+2 Springs

+3 Shocks

 

Aero

+3 Chin Spoiler

 

Drivetrain

+3 LSD

 

Chassis

+2 bump steer mod (if employing one OR both of, rack shims and "R" model tie rod ends)

 

Tires (base class tire size is 235)

+2 205 RRs (9pt tires -7 pt for size)

+3 205 SM6/7s (10pt tires -7 pt for size)

 

Potential total of 18 pts....more than 19 puts it in PTD

 

NB 99-00 cars with not more than 130 DynoJet WHP base PT class is PTE at 2390lbs

 

Engine

Engine Modifications are unlimited (except forced induction)

 

Suspension

+2 Sway Bars

+2 Springs

+3 Shocks

 

Aero

+3 Chin Spoiler

 

Drivetrain

+3 LSD

 

Tires (base class tire size is 235)

+2 205 RRs (9pt tires -7 pt for size)

+3 205 SM6/7s (10pt tires -7 pt for size)

 

Potential total of 16 pts....more than 19 puts it in PTD

 

NB 01-05 cars with not more than 130 DynoJet WHP base PT class is PTE at 2405lbs

 

Engine

Engine Modifications are unlimited (except forced induction)

 

Suspension

+2 Sway Bars

+2 Springs

+3 Shocks

 

Aero

+3 Chin Spoiler

 

Drivetrain

+3 LSD

 

Tires (base class tire size is 235)

+2 205 RRs (9pt tires -7 pt for size)

+3 205 SM6/7s (10pt tires -7 pt for size)

 

Potential total of 16 pts....more than 19 puts it in PTD

 

*  I have suggested to the national PT director that the update to the 97 subframe braces be included as a no-points modification for 1.6L cars.  I have not heard back but i think he will accept this, thus the fully built 1.6L car would remain PTE without any modifications from SM trim.

[Caveman-kwebb99]

Also there needs to he zero points for fuel pressure reg. as iy.would.already be in. the hp of the car

[Chad Martin]

Yep, i took all the engine stuff out...