Classing a Factory Five 818R

[David K]

Hello

 

Has anyone classed the 818 yet?

On the east coast they run under STR3 rules.

 

According to my calculation, I got a correctin factor of +1, so adjusted pwr of 10:1.

At 2000lbs race weight, I would be allowed 200whp - is this correct?

 

What happens if Im at 8:1 for example? Do I get bounced to STR1?

 

And what happens after 5.5:1? Super Unlimited?

 

 

Thanks n advance

 

David

[Bnjmn]

Just do the math to get to the "adjusted" lb/hp ratio that you can run.

If you want someone to check, then post up all the correction factors you used and your proposed setup.

I am not sure that you can race it without a more substantial cage, but the FF cobra guys get away with a similar setup so maybe you will be ok (will need to check that with your regional compliance person).

[David K]

I justhave 2 adjustments

 

.4 for 275 dot

And

.6 for the weight.

 

That takes me from 9 to 10

 

At 2000lbs I can only have 200hp?

[kbrew8991]

PM me your email, I'll send over the MS Excel calculator sheet I built.

[kbrew8991]

did some tweaks to make an STR specific tab if anyone else wants it. Again - PM me your email so I can fire it off to you as an attachment

 

At 2000lbs min weight, 200whp, and +0.4 adjustment for 275 DOT tires, I get an adjusted hp/weight of 9.80, over the class minimum of STR3, so legal. Comfortably so.

 

Raw hp/weight is 2000/200 = 10.000

 

Adjustment for weight -0.600

Adjustment for skinnier tires +0.400

Net adjustment is -0.200

 

Adjusted hp/weight is 9.800 (raw 10.000, then net adjustments -0.200 = 9.800)

 

If it were me, I'd look at running just a tiny bit heavier to hit the next higher weight break point and do 2051lbs min weight so the weight factor is a little less harsh. Could dyno as high as 224whp and just squeak under the bar with the same adjustments. You'd probably want to aim to only dyno in the 21X range though to avoid accidentally blowing over on the dyno post-race however. Going to 245 tires (wheel size is free, so stretch 'em!) lets you run even higher, 234whp would squeak under the bar, probably aim to be in the high 22X range. If you stick with just 2000lbs as your min weight you can still dyno a little higher at 217whp and still squeak under the bar but you may want more margin than that of course. Or go whole-hog and make that 0.60 hit for weight count and pare some more weight off, 1951lb min and 212whp comes out good with 275s, 221whp with 245 tires.

 

Here's the math on all those:

2051lbs, 224whp = raw 9.156. Net adjustments with weight & 275 tires is -0.150; 9.006 adjusted

2051lbs, 234whp = raw 8.765. Net adjustments with weight & 245 tires is +0.250; 9.015 adjusted

2000lbs, 217whp = raw 9.217. Net adjustments with weight & 275 tires is -0.200; 9.017 adjusted

1951lbs, 212whp = raw 9.203. Net adjustments with weight & 275 tires is -0.200; 9.003 adjusted

1951lbs, 221whp = raw 8.828. Net adjustments with weight & 245 tires is +0.200; 9.028 adjusted

 

Just be sure to leave yourself a margin on those min weights & max whps as applicable. A few lbs insurance and a few whp left on the table is better than a DQ for sure.

 

I think in terms of starting with RAW hp/weight, and then think of positive adjustments as credits (and thus "good") and negative adjustments as hits (and thus "bad"), and then see how that compares to the class minimums. Some people work just fine going the other way, and that's fine if your brain works like that and it makes more sense to you. In the end both of these ratios are like golf, lower is "better" but don't want to be too good or you'll fall in a faster class. But just make sure that you separate the concepts of adjusted hp/weight and raw hp/weight. Your raw can be all over the place, but the final adjusted has to be in the right range or you're not legal for the class - as evidenced by the 5 what-if scenarios a couple paragraphs up, 5 different raw hp/weights but the adjusted are all right there together at the limit.

 

Overwhelmed yet, or did that help?

 

Did some barely legal numbers for STR1 just for giggles:

1951lbs, 342whp = raw 5.705, net adjustments for 275 tires & weight is -0.200; adjusted is 5.505

2000lbs, 350whp = raw 5.714, net adjustments for 275 tires & weight is -0.200; adjusted is 5.514

2051lbs, 363whp = raw 5.650, net adjustments for 275 tires & weight is -0.150; adjusted is 5.500

 

Any of those sound fun!

 

SU is super crazy, sky is the limit there....

[ILIKETODRIVE]

I think you originally got 10.0:1 because you were slightly confused. You take a hit for your weight but you get help because of your tire size.

 

9.0:1 +0.6 (for weight) -0.4 (for tires) = maximum 9.2:1 PTW

(NOT +0.6 and +0.4 = 10.0:1 PTW)

 

At 2000lbs and 217whp, you would be just over 9.2:1 PTW.

[kbrew8991]

And there's one of those guys that works backwards

 

(I will admit it makes finding the absolute min/max values if you hold the other variable constant a little easier, though it's tougher to illustrate the concepts of the class with imho)

 

In the end the biggest thing is to keep straight which is ADJUSTED and which is RAW. That'll help you compare apples:apples better (ie your adjusted vs adjusted class limit)

[ILIKETODRIVE]

And there's one of those guys that works backwards

LOL yup!

[David K]

I think I get it now..

 

I was taking all the hits and plusses and added that number to the allowable ratio, i.e. 9:1

So in that case I thought it was 9.2 was allowable

 

Instead, you make all the adjustments to your raw power/weight

 

 

I guess my brain works sideways

 

D

[kbrew8991]

if you're working "backwards" and going from adjusted to raw like Iliketodrive, then you need to flip the signs - that can confuse some people too. Just make sure you keep talking the same language / keep going the same direction all the way through though or you'll end up with an unbalanced equation and/or lost.

 

(That's another plus to working "forwards" and going from raw to adjusted like a normal person no having to flip the signs )

 

It's a little bit confusing ruleset at first glance, but once you work through a couple what-ifs and/or classify a few different cars it gets alot clearer

[SixStarCars.com]

Skated right over this and started a new post... sorry.

 

Good to know someone else is building one and doing the math also. We were close on our guesstimate based on the first iteration of the FFR car as tested.

 

Also good to know that my current build in my WRX is almost perfect, I make 223/263 on E to the wheels. Dial that down a little to compensate for driveline loss and I'm darn close!

[David K]

Hopefully the car was on E and not you...

[C.Plavan]

Sub'd

 

 

Because of this in the garage.....

[SixStarCars.com]

With today's rule changes I'm even more confused than I was before!

 

Can I just keep the car in STR-3 for 2014 and be happy?

[kbrew8991]

STR and ST merged, so STR is no more. Which is good for more competition, as it combines both fields which were eerily similar and can get along well with the right correction factor tweaks.

 

I've almost got the excel calculator tweaked for the update.

 

The big thing to pay attention to is that the FF818 is still considered a non-production vehicle. Not much else changed for the math on y'alls cars, just that extra little correction factor to equalize production/ST and non-production/STR type cars.

[kbrew8991]

Did some math for a FF818 for 2014

 

(note: NOF aka "no other factors" in this post actually means no other factors besides the non-production vehicle factor)

 

at 2,000lbs min weight

ST3 max 215whp with 245 DOTs, NOF. 206whp with 275 DOTs, NOF. 200whp with any DOT, NOF.

ST2 max 250whp with 245 DOTs, NOF. 238whp with 275 DOTs, NOF. 229whp with any DOT, NOF.

ST1 max 363whp with 245 DOTs, NOF. 339whp with 275 DOTs, NOF. 322whp with any DOT, NOF.

 

Are there any typical mod factors listed that you guys may normally take? I'm assuming the Subaru engine you guys are using is 2.0L and bigger and/or turbocharged, using a normal car-type transmission with an h-type shift pattern, stuff like that. My math accounts for the tires - again I'm assuming you guys are going to use some sort of DOT approved tire but if that's not normal I can do it the other way with the non-dot factor and widths instead.

 

Oh and double-check my math of course, this was done with the very very BETA version of the excel sheet. Which missed some cells, hence I've already edited these numbers once haha oops!

[SixStarCars.com]

ST3 would be a 6hp hit, add 49lbs. Pretty much puts the weight right on par with X Prepared in Solo.

 

Our engine will be a 2.0 to keep things cheap and simple. No fancy trans, or traction control. Aero that the car comes with, front splitter, rear diffuser, big nasty wing.

 

Hoping to run A6s.

[Emmanuel B.]

Ken, can I get a copy of the update spreadsheet as well?

 

Thanks.

[kbrew8991]

send me an email and I'll reply with it - brewer (dot) ken @ gmail. com

 

note - you can run at any weight and power so long as the ratio works out. I did 2,000lb min weight because that's what you asked about in your initial post

[SixStarCars.com]

I'm excited! Honestly I'm going to shoot for ST3 but whatever happens happens. Ballast is easy, I'm not trying to shave lbs on the build either so it should be close to FFRs car around 2k. The power... well that's pretty much stock for an EJ20 with a TD04L, I can turn the boost down, worst case I can run a restrictor.