So who is going to go this route? The 2017 rules are posted and seems like we could have a similar deal to STL if anyone takes advantage of it.

https://nasa-assets.s3.amazonaws.com...--10-31-16.pdf

FWD has quite a tax break at +.6 mod factor.

Todays PTE/PTD cars could become very fun by taking out your 200#s of ballast to make up for the extra Pwr:weight.

My my current car at 2210 can run at 192whp vs 141whp. While taking limitations off brakes, tire size up to 245 vs 205, and typical nice updates including NB subframe, spindles, and bumpsteer. Can do more than double adjustables and gear ratios are also open.

Fwd cars on 245s or smaller while under 2600# and over 2200# will have 1.1 additional factor on any rwd car. Enough for a free sequential/dog box, "A" tires, or 10-12whp.

Average hp is another piece of the puzzle.

 

Wow, I'm very surprised there wasn't a break for 225mm tires, hah.

This would be a very fun class to run, but a lot of development to get towards the pointy end of it.

2400lb NB @ 208rwhp ...... average. On 245 R7s, 15x10s, front air-dam & splitter, rear wing..... damn.

 

I only skimmed the rules twice, but I'm not seeing any way for a swapped miata with an aftermarket subframe to run ST4. Aftermarket subframes work in ST1-3 with the non-production mod factor, but that mod factor can't be used in ST4. Looks like unmodified OEM subframe is required.

 

Ecotech swap

 

Yes, no way for ST4. You have to follow the

This would allow any subframe that can bolt up from the OEM manufacture. No K-swaps unless you make it work with cutting the firewall and not touching the transmission tunnel. :/

 

So NB subframes in an NA are kosher, but the V8R subframe isn't. :(

 

Indeed... Though it might be difficult to get 205-210rwhp avg from an ecotec without cams/internal work, at least on a dynojet. I think there are gains to be made just by porting the head, which would really put the current ecotec swaps I've seen over 200rwhp(peak).

Even still, in ST with 245s and aero..... you'd probably be better off running 2550lbs+ @ 220rwhp avg.

 

You have a lot better shot at it than with a bp.

 

Relocation of suspension mounting points is not permitted in ST4.


That means NO NB subframe/spindles/bumpsteer in 4. Only in 3/2/1

 

Excerpts:

Under:
2200 lbs = -0.3
2600 lbs = -0.2
3000 lbs = -0.1

Over:
3300 lbs = +0.1
3400 lbs = +0.2
3500 lbs = +0.3
3600 lbs = +0.4
3750 lbs = +0.5
3900 lbs = +0.6

245 or smaller = +.7
250 to 275mm = +0.3

windshield removal = -.3
OEM aero = +.4
Sequential = -1
A7/R1S/C91 = -1


__________________________________________________ ___

Imagine this:

OEM-aero, Ecotec, NB

12:1 base
12.2:1 2201-2599lbs
11.5:1 245 or smaller
11.1:1 Oem aero


200whp/2225lbs

Wow.

 

on 15x10s and 245s

 

EFR BP with flat 200hp from 4000rpm to 8000rpm?

 

I'd lean that way. More $$ but it would have better power area than a junkyard Ecotec.
The junkyard Ecotec swap could be "Spec ST4" thing, ultimate dirt cheap/go fast combo.

 

I also don't see 200 "average" hp from an ecotech being easy or cheap.

I dont know the exact calculations for average hp, but with really good boost control you can add/remove power in specific locations and even tune your setup per track.

 

Junkyard Ecotec would be far from optimized for ST4 but could still be quite competitive in most regions. Sort of like dyno classed, junkyard motored PTE NB1's. Butts kicked at East/West Champ but snagging wins/lap records regionally.

 

This was one of the many reasons I decided to bail on my K swap project and decided to go with the turbo BP instead.

 

I was just talking to Dan yesterday about how well a TSE turbo Supermiata S1 car crosses over to ST4.

 

Yea.

If we could get the splitter changed to 4", air dam up to 5deg and the wing raised to 8" above roofline - it WOULD be ans ST4 car!

put on some 245 Hoosiers and go!

 

Speaking of EFR's, they just showed a smaller version at SEMA called the 5951 that is smaller in every way, yet they claim it flows 95% of a 6258. It is 35mm shorter and 35% less interia.

 

We have decided to make a run at 2017 T25 in Vegas, E0 mapped from ST3.