How do the 124 abarths do in C street?
Driving impressions from the 2019 Mazda MX-5 Miata ND2 launch event are still embargoed, but there’s more than one way to skin a cat. We asked our own Andy Hollis, championship-winning autocrosser and Miata connoisseur, for some technical analysis of the new Miata’s spec sheet. We showed him the data from our own ND2 dyno testing, too. Our question? Tell us what this new Miata–and its stated 26 horsepower increase–will mean for amateur motorsports. Here’s what he wrote:
Based purely on data, the 2019 Miata is the ND model that autocrossers wanted all along. It has the same lightness, torque, and balance that the 2016 model did but without the too-early rev limiter. On most Nationals-type courses, shifting has become an annoying way of life in my 2016 MX-5 Miata. In previous Miata generations, this was fixed by the availability of longer gearing with a five-speed transmission. With the ND2, the six speed is still standard, but 2nd gear now goes to 60mph on stock tires. Autocrossers in C Street typically extend this further through use of taller competition rubber, which should now get them into the 62-63 mph range–perfect for typical courses. On slower courses where my ND1 does no shifting, there looks to be no significant advantage to the ND2. There’s a couple of lb/ft more torque to help accelerate the car, but it isn’t likely to be worth more than a tenth on typical courses.
In Street Touring trim, it is still too early to tell how much of the low-hanging engine tuning fruit Mazda has already picked for themselves. The ND2 has 3 lb/ft delta in torque that exists across the rpm range in stock form, which is likely the result of the lightened rods and pistons, along with the lighter flywheel. Adding aggressive ecu calibrations and exhaust modifications have netted existing Street Touring Roadster competitors in early ND Miatas additional power throughout the engine’s powerband. Only time will tell if those modifications will still work, or if the ND2’s power output is a result of Mazda improving things with the same methods.
The big news, according to Mazda, is the 17% increase in horsepower–it jumps from 155 to 181. That sounds like a massive increase in acceleration, but it’s a bit of a head fake since the majority of that increase comes from extending the rev limiter without losing torque. Horsepower is derived from measured torque multiplied by rpm, meaning the same engine spun faster will make more horsepower. In the lower gears, both the ND1 and ND2 Miata should accelerate the same, provided you shift at the same rpm instead of winding the ND2 out to its full 7500 rpm limiter. Yes, the new car will be faster, but that’s because you should be able to hold each gear longer.
It’s a different story at higher speeds. Horsepower is what you need to overcome drag–which is the realm of track driving. That’s where where those 26 extra ponies should work their magic. Above 100mph, the outgoing ND1 can barely accelerate in 5th gear. In the ND2, you should be able use 4th above the century mark, and 5th should continue to provide acceleration instead of just maintaining speed.
How do the 124 abarths do in C street?
If people are running taller tires on ND1s to avoid an upshift, then the ND2 will have an advantage because it will have better acceleration due to not requiring that Band-Aid. If courses are shorter, then shorter tires can be run on the ND2 (if such a size exists).
Assuming that shorter rubber does not result in less grip, of course.
MrChaos said:How do the 124 abarths do in C street?
I honestly have never seen one being autocrossed locally. And I know that at Nationals, they were non-existent
MrChaos said:How do the 124 abarths do in C street?
Worse than an ND. The 1.4L are dogs imo.
goingnowherefast said:MrChaos said:How do the 124 abarths do in C street?
Worse than an ND. The 1.4L are dogs imo.
I haven't driven a Fiat 124, but that engine in the Abarth 500 didn't really impress me much. It was a dog out of boost and the turbocharger wasn't exactly what I call responsive. It made cool sounds, but that was about it. And I recall Keith saying something about the 124s weren't particularly receptive to tuning and they couldn't get them to do what they wanted, so FM stopped developing engine parts.
It’s a different story at higher speeds. Horsepower is what you need to overcome drag–which is the realm of track driving. That’s where where those 26 extra ponies should work their magic. Above 100mph, the outgoing ND1 can barely accelerate in 5th gear. In the ND2, you should be able use 4th above the century mark, and 5th should continue to provide acceleration instead of just maintaining speed.
Well, up there, it's all about aero, assuming the two models have the same profile. Given that, top speed will be proportional to the cube root of the horsepowers:
(181 / 155)^0.33 = 5.3% higher top speed and likely also acceleration. So while it's better, it's not much. For National level drivers it's a big deal, but for trackday people, not so much. Aero improvements would do more and cost a lot less if top speed is the aim.
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