BCCR Swap Formula

[The Aero Man]

In the BCCR, the raw swap formula is shown. This is the exact formula stated in the BCCR:

 

 IF[16 - (weight / (HP + hpAdd) ) > 0 ]
 THEN [ 0.032 * (16 - (weight / (HP + hpAdd))) ^6] + 50
 ELSE + 50

 

Why is it that I get a different answer on the online calculator than on a spreadsheet? Also, it it really supposed to be to the sixth power or is it supposed to be multiplied by six?

[ABR-Glen]

You are probably using the wrong value for hp+hpadd, which should just be your new hp. You wouldn't be the first to make that mistake. If not, then post the numbers you are using and we'll check.

[The Aero Man]

The weight is 2048 per the online calculator, and the two HP ratings off of Edmunds are 116 and 140. 

[enginerd]

9 hours ago, The Aero Man said:

In the BCCR, the raw swap formula is shown. This is the exact formula stated in the BCCR:

 

 IF[16 - (weight / (HP + hpAdd) ) > 0 ]
 THEN [ 0.032 * (16 - (weight / (HP + hpAdd      140       ))) ^6] + 50
 ELSE + 50

 

Why is it that I get a different answer on the online calculator than on a spreadsheet? Also, it it really supposed to be to the sixth power or is it supposed to be multiplied by six?

 

[mender]

Make: Mazda
Model: Miata
Year: 1992
VPi: 250
Car Weight: 2048
Original HP: 116
New HP: 140
Points Added to VPi: 50
--->NEW VPI: 300

[espog]

I just realized that the NA8 miatas weigh just as much as NA6 miatas. At least on the swap calculator. Yet one has a bigger motor, bigger brakes, bigger rear diff. Thats why one is a hundred more points. Huh?

[The Aero Man]

I personally don't agree with the 1.8L cars being 100 more points. The 1.6L has a diff with a shorter final drive, which is good for most tracks that Champ drives at. The brakes can be replaced for free under the 2X Rule, and there is a 10 hp advantage at the wheels.

 

As for the weights, they probably don't weigh exactly the same but they are very close. The 2048lb that they got is really light, I knew a guy who was trying to get his NA8 down to 2200lb for the limit, and could never get the car that light.

[JDChristianson]

46 minutes ago, The Aero Man said:

I personally don't agree with the 1.8L cars being 100 more points. The 1.6L has a diff with a shorter final drive, which is good for most tracks that Champ drives at. The brakes can be replaced for free under the 2X Rule, and there is a 10 hp advantage at the wheels.

 

As for the weights, they probably don't weigh exactly the same but they are very close. The 2048lb that they got is really light, I knew a guy who was trying to get his NA8 down to 2200lb for the limit, and could never get the car that light.

Aummmm. That 1.6 diff is a viscous pile of fragile poo poo.   The best way to get good at changing  a miata differential is to endurance race a 1.6.    And the 1.6 might have less usable torque than a Honda 

 

and your correct, there's not that much weight to take out after you put in a cage, fire system , and cooshirt cooler. 

Edited May 13, 2018 by JDChristianson

[The Aero Man]

Just now, JDChristianson said:

Aummmm. That 1.6 diff is a viscous pile of fragile poo poo.   The best way to get good at change a miata differential is to endurance race a 1.6.    And the 1.6 might have less usable torque tag a Honda 

 

and your correct, there's not that much weight to take out after you put in a cage, fire system , and cooshirt cooler. 

Yeah the 1.6 diff is fragile, if you want that ratio look at the NB's. Honda's have really good power to displacement ratios, so yes in some cases. Just checked Edmunds, and the curb weight was 2264lb.

[hotchkis23]

21 minutes ago, The Aero Man said:

Yeah the 1.6 diff is fragile, if you want that ratio look at the NB's. Honda's have really good power to displacement ratios, so yes in some cases. Just checked Edmunds, and the curb weight was 2264lb.

We went through 4 or 5 NA6 diffs in a season.  Could really only get about ~6-7 hours of really pushing it out of them.  Found out the front seal is only rated up to about 500 degrees F.  We took temps that were considerably higher and wouldn't you know, the front seal would fail and then KABOOM!  Lots of fun.  On a plus side, we got it down to swapping them in and out in about ~30-40 minutes depending on how hot it was under the car.

Edited May 13, 2018 by hotchkis23

[The Aero Man]

30-40 minutes are well worth the 25 points that you could spend on a new diff that you don't need to replace three times in a 24 hour.

[espog]

On 5/13/2018 at 4:02 PM, The Aero Man said:

I personally don't agree with the 1.8L cars being 100 more points. The 1.6L has a diff with a shorter final drive, which is good for most tracks that Champ drives at. The brakes can be replaced for free under the 2X Rule, and there is a 10 hp advantage at the wheels.

 

As for the weights, they probably don't weigh exactly the same but they are very close. The 2048lb that they got is really light, I knew a guy who was trying to get his NA8 down to 2200lb for the limit, and could never get the car that light.

I was not talking about points difference. I was trying to say that more motor, more brakes, and more rear diff, means more weight. It may not be much but there should be a difference.

 

As far as weight goes i got my na8 under the 2048 that they have listed, but it is fairly gutted. It still does "looks" like a car though. It has all of its body panels and a roof.

[The Aero Man]

How much of the car is gutted out? I mean, the rules say everything else must be stock, but I guess this is an exception to take out what ever you want?

[wvumtnbkr]

23 minutes ago, The Aero Man said:

How much of the car is gutted out? I mean, the rules say everything else must be stock, but I guess this is an exception to take out what ever you want?

Uh, yes.  Take entire car apart.  Put back only what is necessary to be a racecar.

 

If you can get your car sub 1k and meet all the safety rules, go for it.

 

The rules don't say you need to leave all the parts in the car.

 

He'll, there is a 60% body rule for a reason.

[espog]

33 minutes ago, The Aero Man said:

How much of the car is gutted out? I mean, the rules say everything else must be stock, but I guess this is an exception to take out what ever you want?

Doors are just skins, no little triagle window no crash bar no lock but kept door handle to open. Have bumper covers but no plastic crash structure. Cut support on trunk. Cut seat belt towers. Cut wall between cabin and trunk. Took everything off that does not make car go, turn, or stop.(ac, heater, power steering pump, kept rack, head lights, parking lights, headlight motors, pully for ac power steering, airbags, extra wiring no longer needed, entire interior, all emissions stuff). I even took off rear tail lights and replaced with two third brake lights zip tied to roll cage. I cut off all the little studs that everything was bolted down to. Not much but everything adds up. I even have lightweight rims and flywheel. Im sure there is stuff i forgot.

Edited May 15, 2018 by espog
Spelling

[The Aero Man]

Wow...   

[wvumtnbkr]

Wow, what?  

 

That is not abnormal.  

 

Light weight is the best mod to make laptime.  It's also the cheapest.

 

Swiss cheese the crap out of your ride!

 

Go to a race and look at the podium cars.

[Wittenauer Racing]

16 minutes ago, wvumtnbkr said:

Go to a race and look at  the podium cars.

 

Or atleast, what's left of them

 

In all seriousness, some cars have a lot more dead weight than others, but you'd be surprised how much glass, OEM exhaust and wheels weigh!

[Bandit]

On 5/13/2018 at 4:22 PM, JDChristianson said:

 And the 1.6 might have less usable torque than a Honda 

Ouch 

[JJordan]

On 5/14/2018 at 8:43 PM, wvumtnbkr said:

Uh, yes.  Take entire car apart.  Put back only what is necessary to be a racecar.

 

If you can get your car sub 1k and meet all the safety rules, go for it.

 

The rules don't say you need to leave all the parts in the car.

 

He'll, there is a 60% body rule for a reason.

Bit of a thread-jack here, but where in the rule book do you read that you can gut the car out?  It is pretty clear that the car needs to be stock with the exception of things that are either free or have specific points associated with them.  I don't see that it says gutting the car is OK, once you start hogging out stuff it really isn't stock anymore.

[enginerd]

31 minutes ago, JJordan said:

Bit of a thread-jack here, but where in the rule book do you read that you can gut the car out?  It is pretty clear that the car needs to be stock with the exception of things that are either free or have specific points associated with them.  I don't see that it says gutting the car is OK, once you start hogging out stuff it really isn't stock anymore.

There are many rules which limit what you can ADD to the car... you will have a lot harder time finding rules which limit what you can REMOVE from the car.

 

I don’t think you’ll find any rules which say the car itself has to be stock. Certain parts (trans /drivetrain) do have rules about being stock.

Edited May 20, 2018 by enginerd

[JJordan]

Section 4.3.3 states that points may be assigned for any non-stock component that substantially increases performance.  4.4.1 and 4.4.2 note that all non-stock items need to be declared and there is no such thing as a free item.  Gutting the car out is certainly a performance enhancement so therefore it should be part of the point structure.  This is where I fail to see how it is allowed to be done, unless its part of an un-written rule that people have just assumed to be correct.

 

If you want to get really harsh about it 4.4.3 states that any component found to have part numbers ground off will immediately go to EC.  If the part is missing, I think the part number is also gone.

 

[Ian]

51 minutes ago, JJordan said:

Section 4.3.3 states that points may be assigned for any non-stock component that substantially increases performance.  4.4.1 and 4.4.2 note that all non-stock items need to be declared and there is no such thing as a free item.  Gutting the car out is certainly a performance enhancement so therefore it should be part of the point structure.  This is where I fail to see how it is allowed to be done, unless its part of an un-written rule that people have just assumed to be correct.

 

If you want to get really harsh about it 4.4.3 states that any component found to have part numbers ground off will immediately go to EC.  If the part is missing, I think the part number is also gone.

 

 

Have you ever looked at any cars at a race?

 

The ground off part number stipulation is for parts, or assemblies a person is claiming as factory.  Like a cylinder head, or brake caliper.

 

A removed passenger seat, isn't a non stock item.  That is the point of the 60% body rule.

 

If there are parts on your car you can lose to save weight, see that they're lost.

[Chris Huggins]

@JJordan

 

champ forum troll of the year award nominee

[JJordan]

Not trying to cause trouble, but yes, I've seen the cars and I don't follow the logic.  Trying to build a car that is both fast and legal.  Since it doesn't say you can, I assumed you can't and was looking for how the rest of the field was reading it.

 

Never considered that things outside of fenders and hoods were considered body work.  Always assumed bodywork covered the skin of the car, not the structure and interior.