Thoughts on an NC ChumpCar?

Miata Parts, Intakes, Superchargers, Headers, Exhausts, Shocks, Springs, Sway Bars, Brake Kits, Autocross and track mods.

Thoughts on an NC ChumpCar?

Postby Grant » Mon Oct 01, 2018 8:42 pm

NC Miatas are classified as 500 point cars under ChumpCar rules. This means they can have:

  • Almost any free weight reduction. I'd run without a windshield E-Prod style, weld the door skins on, gut everything I could gut, etc.
  • Collector-back exhaust. I could cut the cat off and weld a pipe in its place, but could not modify the rest of the OE header.
  • Vent the hood, duct the radiator, etc.
  • Any intake.
  • Any tune.
  • Any width wheel/tire combination, street tires only (probably Hankook R-S4s). I'd probably test on both 15"s (245/40-15) and 17"s,

Any opinion on how a car like this would do? How much it would weigh? Keep in mind I'd have to run a stock-thickness radiator and stock oil cooler. With a vented hood coolant temps are usually not a problem, but oil temps can be. My friend's SC300 runs 300F+ oil temps for 14 hours at a time, and seems happy doing so... This can't be good for longevity, but it's a 2JZ.

From what I understand some clutch packs in the differential might come apart, but it would still have some torque biasing and thus probably work fine.
Grant
 
Posts: 7
Joined: Tue Sep 25, 2018 10:49 am

Re: Thoughts on an NC ChumpCar?

Postby Grant » Sat Oct 27, 2018 10:52 pm

Can anyone guess how much power an intake, exhaust and tuned NC would make with the factory header but a straight pipe welded in place of the cat?

NCs have some sort of butterfly valve in the intake manifold that can be removed, correct?
Grant
 
Posts: 7
Joined: Tue Sep 25, 2018 10:49 am

Re: Thoughts on an NC ChumpCar?

Postby Brian » Sun Oct 28, 2018 7:41 am

Factory NC header is terrible, pinched primaries, that's your big limitation on power, figure about 150 at the wheels if you do tune and everything while being stuck with stock header.

You cannot run 300 F oil temps on this motor, it just won't last and will be way down on power, need good oil cooler. Ideal oil/coolant temps are 209 F for both on this motor, run higher and you are running down on power/slower.

15 inch wheels don't fit, not even close to clearing rear control arms, even most 16 inch cannot clear. You run 17 inch.
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
Brian
Site Admin
 
Posts: 8801
Joined: Tue Feb 15, 2005 11:44 am
Location: San Diego CA

Re: Thoughts on an NC ChumpCar?

Postby Grant » Sun Oct 28, 2018 9:18 am

Thanks for the info.

I am reading stock cooler oil temps are around 260F when coolant temps are 214F? If so this sounds reasonable - oil temps should drop further so long as we can keep coolant temps down (ducting and hood venting is free).

It looks like your old car made about 145 with intake and header-back exhaust? That's not bad, as long as we can eek out a few more ponies with a tune, cat and butterfly removal.
Grant
 
Posts: 7
Joined: Tue Sep 25, 2018 10:49 am

Re: Thoughts on an NC ChumpCar?

Postby Grant » Tue Oct 30, 2018 9:13 pm

Well nevermind. For 2019 the NC is a 400-point car. That means we can do a header (I assume your PPE Longtubes make the most power?), plus either an intake manifold or cams.
Grant
 
Posts: 7
Joined: Tue Sep 25, 2018 10:49 am

Re: Thoughts on an NC ChumpCar?

Postby Brian » Tue Oct 30, 2018 9:18 pm

Longtube race header for max torque spread, or RoadsterSport 1.8 inch Max Power shorty header for max upper rpm power, combined with cams.
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
Brian
Site Admin
 
Posts: 8801
Joined: Tue Feb 15, 2005 11:44 am
Location: San Diego CA

Re: Thoughts on an NC ChumpCar?

Postby Grant » Sun Dec 02, 2018 9:15 am

Thanks, we ended up going with the 1.8 Max Power GWR header. When we dyno it I'll post the chart here.

What would you recommend for wheels and tires? We'll be running a 2xx/40-17 RS-4 in dry conditions, and RE-71Rs in wet and maybe really cold conditions. We can roll and pull the fenders, but the tops (from 11 to 1 o'clock) must not stick out past the fender. At a small penalty we can add spats to block airflow to tires.

Normally I'd default to 17x10s with 255s, but I don't know if a Miata with a mostly-stock 2.0 will be quicker with wheels and tires that wide.
Last edited by Grant on Sun Dec 02, 2018 9:24 am, edited 1 time in total.
Grant
 
Posts: 7
Joined: Tue Sep 25, 2018 10:49 am

Re: Thoughts on an NC ChumpCar?

Postby Brian » Sun Dec 02, 2018 9:22 am

Indeed I think a budget ChumpCar NC goes with 17x9, great for 235/40 or 245/40 tires in your choice. The 17x10 is certainly faster but a much tougher fit, particularly with the rules you mention, and additional gains won't show well short of big power (big 2.5 liter conversion or boosted motor). And effective gearing is a bit slow for 255mm on stockish power. Though it depends a lot on the track choice, I prefer a stock-ish power level 2.0 with gearing of the 235/40 for better leap out of the tighter corners, spread that on 17x9 for max tire sidewall stability.

Example suggestion, pics from a customer yesterday. Konig Hypergram 17x9 Bronze
Picture Courtesy Customer Steve Whitaker. Steve notes rolled fenders and 2 degrees negative camber with our Ohlins coilovers to fit 235/40ZR17 NT01 track tires shown here.

Image
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
Brian
Site Admin
 
Posts: 8801
Joined: Tue Feb 15, 2005 11:44 am
Location: San Diego CA

Re: Thoughts on an NC ChumpCar?

Postby Grant » Sun Dec 02, 2018 2:03 pm

In our experience, wider tires are actually cheaper because they don't get as hot and wear more slowly. I'm also not seeing a 245 or 235/40-17 R-S4 for sale anywhere, which sucks. Of course we could run the 255s on a 17x9.

We've got all the tools to make wheels and tires clear. What I'm more concerned about is ride height. We can alter bump travel, so the limiting factor in ride height is usually tire to body contact. We can hammer and cut on things as much as we'd like, but a mini-tub or the like would cost us points. Would a 17x10 and 255/40 require a higher ride height than other options?

I went back and looked at our daq from another car, and I'm not sure we'd want shorter gearing. It would depend on the track.

Thanks!

Oh, do you guys sell non-RPF1 17x10s? The Enkeis are all I see on your site, but I think the 6UL offset is better isn't it?
Grant
 
Posts: 7
Joined: Tue Sep 25, 2018 10:49 am

Re: Thoughts on an NC ChumpCar?

Postby Brian » Sun Dec 02, 2018 4:31 pm

Yes, all other things equal the 17x10 and 255/40 usually needs a bit more ride height, just not as much room for it top inside of the fender. But....you can limit travel with bumpstops/packers to get past that issue.

I think we have some 17x10 6UL still, need spacers depending on camber settings, more camber needs more spacer to keep those with 255 from seriously rubbing inside.
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
Brian
Site Admin
 
Posts: 8801
Joined: Tue Feb 15, 2005 11:44 am
Location: San Diego CA

Next

Return to Mazda Miata and Fiat 124

Who is online

Users browsing this forum: Google [Bot] and 2 guests