• 2019/09/01
  • OTHER(海外)

RE Miata’s 2019 Bonneville effort struggles with loose salt

This year Bonneville Speed Week, a speed challenge that is held annually on a huge salt lake in the highlands of Utah, started on August 9th. Sumito “Sam” Okamoto, who lives near LA in California, is a self-made Bonneville challenger. He brought his machine out to the venue as he has for the last several years.


His Bonneville Challenge Machine, which swaps the 13B naturally aspirated engine used in the North American specification FC RX-7 into an NA-MX-5 Miata, recorded 174.756 miles per hour (280.2km / h) at Bonneville last year, but struggled with a gear ratio unsuited to the conditions. For this reason, he replaced it with a RX-8 use 6MT, with a 6th speed of 0.87. The RX-7 standard 5MT, which was designed based on the premise of long highway driving, has a gear ratio in which the 4th and 5th gear are spread too far apart. Thus the thought was that a close-ratio 6MT would allow for further acceleration and he went in expecting it possible to break a target speed of 188 mph (approx. 300 km / h). He participated in the F / GMS class, for modified sports cars mounted with naturally aspirated gasoline engines with a displacement of between 2-liters and 3 liters.


Okamoto left Los Angeles on August 8 with a friend who lives in California and a staff member from Japan who participated at his own expense. The RE Miata on the trailer was drawn by a CX-9 loaned from Mazda USA and traveled over a distance of approximately 650 miles (1,040 km) for over 13 hours. After arriving at Wendover on the border between Utah and Nevada, the group headed to the Salt Flats to check the condition of the competition track. As expected, the rain on the previous day resulted in terrible salt conditions in the pit area, with more than a few large puddles. The group participated in the opening ceremony, but due to poor salt conditions, the organizer announced that the course would open on Monday the 12th in anticipation of fine weather on the weekend, which left the group at a loss. This resulted in several entrants giving up and packing it in at this point. Okamoto-san and his team decided to improve a few points indicated by the official responsible for the safety check of the RE Miata.


Based on last year’s results, the RE Miata was supposed to be able to run 5 miles on the long course this time. However, even on Monday, the salt conditions were not good and the course was not opened until Tuesday 13th. The next day, entrants packed into the long course early in the morning as it opened, creating a long line. Then, there was an accident involving a fallen motorcycle on the long course where the salt was loose, and the course was closed immediately. Okamoto’s team moved to the short course about 10km away from the pit area. There they waited for their turn. Then when it looked like they were finally going to get a run, the official signaled them to “turn off the engine” at the start line. The oil cooler clamp had become loose and was dripping oil on the salt. While they were repairing that, it had reached 5:00pm and the day’s runs ended. According to the team schedule, Wednesday was to be the last day of the salt challenge, and all the helpers would have to go home. Therefore, they went to the start line early in the morning and managed to finally get a start in the RE Miata. However, the normal short course, which usually consists of 2 miles after a 1-mile run, this time had a mere 1.25 miles (about 2 km) from the start due to the salt conditions. It seemed that it would be almost impossible to break 188mph with this distance. However, they decided to carry out a run to test the how well the 6MT matched the engine and car body. As a result, their long awaited first recorded run was completed in just 40 seconds. They recorded a mere 140mph (225km/h). After several months of preparation, and 5 days after leaving LA, their long-awaited challenge run was over before it began. With this one run, Okamoto and his team finished this year’s Bonneville Challenge.


Mr. Okamoto went on to say, “This year, the salt was bad which was unlucky. However, in the section that I was able to run, my impression was that the 6MT is really good from low to 5th gear compared to the 5MT due to its close ratio and if we were able to run up to 3 miles with good course conditions, we could achieve 188mph I think.”


This year was disappointing, but the challenge of the “men covered in salt” is likely to continue next year.


Text and Photos by Sam Okamoto


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