49 replies to this topic

[Grant]

If the car needs a fan, we'll run a fan. It isn't a big deal.

 

I don't plan on running Daytona. However, my friend's fan-less SC300 has finished second, first and first the last three races there.

[Grant]

We can do an intake manifold or cams, but not both. Dynotronics recommended the intake over the cams, especially as we can alter cam timing without points.

[Grant]

We took the (nearly-stock) car out for a rain track day today. We put a lot of time on it and it performed very well considering its tires are absolute junk. It was very easy to drive at the limit in the wet; my only handling complaint is the steering is too boosted for good wet feel.

 

With equal pads front and rear, the RX8 brakes have too much rear bias (they increase the rear piston from 35 to 43 mm). Trail braking wasn't an option even in really tight corners. I'll end up running more aggressive pads in front, which will hopefully fix this.

After a few hours of lapping, the rear end started doing some strange things. It felt like the right rear would occasionally grab, slowing the car down and making cornering much more interesting. I'm guessing this is the Tochigi-Fuji LSD coming apart? The rear suspension, brakes, hubs, etc. are fine. Is there any way to make these things last in endurance racing? If not we'll have to weld it, or pay the points for an upgraded LSD like a Quaife.

 

Thanks.

[Grant]

Here are my experiences tuning the car: https://forum.miata....d.php?p=9196897

It made 164whp SAE with no muffler, a 2.5" mid-pipe, the 1.8 GWR header and the airbox pulled apart.

[Steve Scheifler]

I’d like to see the results but it seems I would need to join that site. Perhaps repost here?

[Grant]

Ok, here's the miata.net post:

 

 

We did some dynojet tuning on my Champcar-to-be (2009 6-speed) this weekend with an ecutek racerom setup. It's going to be a racecar, so we need every last horsepower.

Here are the runs we did Friday night. The first was done as the car rolled on to the dyno: stock except for a catless 2.5" mid-pipe, GWR 1.8 header and a 12.5 AFR target. It made 157 SAE. For the next pull I removed the part of the airbox the MAF attaches to, and set it on top of the lid. It made 160. Then I removed the muffler, and the car made 164:

 runs_2-3-4.jpg   86.36KB   2 downloads

We wanted to be able to tune VVT without worrying about running into any knock, so today we started by getting the AFR a consistent 12:1. However just as in the last pulls, commanded AFR did not follow actual AFR (regardless of the state of the airbox). This confused us. Were the OE MAF or injector tables not calibrated correctly? The fuel compensation table is all zeroes. We ended up tweaking the load calibration tables until the AFR curve was flat-ish, but this struck us as something that shouldn't be necessary.

Anyway, on to VVT tuning:

 runs_11-15.jpg   79.59KB   1 downloads

As you can see, we picked up power from 4,350 to 6,750.

I wish I could say what the final VVT settings we settled on were, but my ecutek dongle was slowly failing throughout the day.  It made tuning very difficult, and eventually stopped working completely. So I have no way to even open my tunes. Why do they need a dongle separate from the cable? I wish HPTuners did imports...

Next we messed with AFRs. The motor didn't seem to mind different settings here, so long as it was between 12 and 13:1:

 runs_23-24-26.jpg   83.6KB   0 downloads

So we left it at 12.5 and moved on to timing. We added a degree everywhere, and set the advance at 7,500 to the 7,000 column's. It picked up a bit of peak power, and quite a bit under the curve:

 

 runs_26-27.jpg   84.63KB   0 downloads

 

Unfortunately at this point the ecutek dongle failed completely. I don't know what was wrong with it; it got progressively more USB device errors throughout the day. I'm tempted to open it up and see if a solder joint came lose, but that would surely void the warranty.

Though the car didn't make much more peak power today than it did yesterday, I believe this is due to differing conditions. Almost every run today was less than Friday's best, regardless of the tune. Dynos don't correct perfectly for weather, so the back-to-back runs should be more indicative of gains.

MAP dropped as low as 97 kPa, so there might be another two hp from a real intake with a smooth elbow and no neck-down for the MAF. We're going to make a ram air setup which pulls directly from a hole in the front bumper.

Anyway, I have some questions for other tuners here:

• Why is the car using the Safe Mode fuel maps? Is it because it has no secondary O2 sensor? Is there any downside to this? I'm not using ecutek's map switching because I want to preserve the factory high det map switch functionality.
• Why doesn't the car not hold a commanded AFR? It was more consistent with the lid on the airbox, but not what I'd expect from an almost completely stock MAF car. Maybe I should just run speed density? The fuel compensation table is zeroes.
• Are these results typical?

Thanks for any help. Oh, STD corrected results were 167 for run 4 on Friday, and 168 for run 27 today.

 

 

[Grant]

Mods, can this thread be moved to the new ChampCar / WRL forum? Thanks.

[Camaro67racer]

Was this the White/Red NC running at Sebring last weekend?

[Grant]

No, our car is silver and we're still building it. It's currently at KSR Performance & Fabrication for the roll cage. It'll be easily recognizable as it doesn't have a windshield, frame, or roof.

We've only run it at the Firm in Keystone Florida, in nearly stock trim. I think our first race will probably be Road Atlanta with WRL in July.

 

We've been very happy with how the car has been turning out. The NC chassis is really great. Attached is a photo of the stock fenders easily tucking a 17x10 6UL (we'll run 255/40-17s). We think it'll be just under 2,000 lbs with a full tank of gas, but it will take a lot of nickle-and-dime weight reduction to get there.

Attached Files

•  17x10_6UL.jpeg   178.84KB   4 downloads

[Krusovice]

I’m late to this but I’ve done a lot of ChampCar/WRL. I’d suggest before you go for power make the car as reliable as possible. And then get really good at managing time on track. If you haven’t rented a seat with a good team, do that before spending any money on engine mods. You’ll stand a much better chance of having fun and being competitive learning from experience than adding a few Hp.

FWIW, I’ve won more endurance races on mileage-unknown stock engines than fancy ones.

(Of course, if you’ve done a few races you might already know this.)

[Danny Steyn]

IMO if you are making under 200HP running 255's is going to be too much tire and slow you down - 235 is more than enough even for my STL at 205HP

[Michael Novak]

IMO if you are making under 200HP running 255's is going to be too much tire and slow you down - 235 is more than enough even for my STL at 205HP

Danny, It seems to be hard to tell with the 200TW tires. Sometimes if you put alot more tire down with 200TW it appears you can get closer to Hoosier grip.

[Danny Steyn]

Danny, It seems to be hard to tell with the 200TW tires. Sometimes if you put alot more tire down with 200TW it appears you can get closer to Hoosier grip.

 

Good to know Michael - did not factor the 200TW into the equation - silly me

[tburas56]

The 225 45 15 is more then enough tire for a Miata that only weighs 2250 soaking wet. We have been running 205s with no problem, one set of tires 14hrs at Sebring.

[Grant]

IMO if you are making under 200HP running 255's is going to be too much tire and slow you down - 235 is more than enough even for my STL at 205HP

 

Great info, thanks. Our last dyno with a completely stock engine, GWR 1.8 header, 2.5" exhaust, and custom intake, and a lot of dyno tuning was 171whp SAE on a dynojet 248. Weight with a driver and full tank should be just under 2,250 lbs. We're now thinking of mostly running WRL, which means we'll need to make 180whp on a dynojet to hit GP1 class limits. I'm hoping to get there with an intake manifold and maybe a custom header, but that could be wishful thinking.

 

We can test 255s on our 17x10s vs. 225s on the stock wheels. With our low weight and wide tire we were hoping to be able to run a softer compound like an RE71R or Rival 1.5S.

 

Anyone know where to get adapter axles to run RX8 hubs and spindles with the NC diff?

[Grant]

The 225 45 15 is more then enough tire for a Miata that only weighs 2250 soaking wet. We have been running 205s with no problem, one set of tires 14hrs at Sebring.

 

Have you tried 225/45-15s? In the car I won two Sebring races in, the tires (Star Specs) probably could have gone 56 hours (though it rains the last few hours of each race). We found wider tires to last much longer and so significantly reduce running costs. I'm not sure this will be true with the Hankooks since unlike the Star Specs they seem to cycle out.

 

This said, if we could fit 15x9s and run 245/40-15s, I'd do it.

[Camaro67racer]

 

Anyone know where to get adapter axles to run RX8 hubs and spindles with the NC diff?

 

Call Tom Neel at The Parts Group. I believe he had developed this several years ago.

[Grant]

He was the first person I called. Unfortunately he doesn't offer this service anymore.

[Adax]

I heard rumor that the RX8 axles from an automatic work - but have never verified this.

[Grant]

Unfortunately RockAuto says the differential-side spine count differs between the RX8 automatic and NC axles. World Challenge talks about using the RX8 outer joint with the rest of the Miata axle, so maybe no machine work is needed. I'll take them apart and find out.