Mini 4WD Ultra-Dash Motor Guide
Ultra-Dash is the motor people search when they want the headline RPM number. Item 15307 publishes 24,000–27,500 RPM and 4–5 A on 2.4–3.0 V, with durable carbon brushes, and Tamiya’s own copy says it pairs top speed with torque for steep slopes. That is also why it is the wrong first answer for an official race: the current official Mini 4WD motor list does not name Ultra-Dash, and two AA cells sag hard at four to five amps. This page separates the product from the rumour — what the spec sheet actually says, which chassis Tamiya lists, why official events exclude it, and what to confirm before you run one at a club.
The published numbers, not a bench myth
The official Ultra-Dash page lists input voltage 2.4–3.0 V, 24,000–27,500 RPM, and 4–5 A current consumption, with carbon brushes. It does not publish a torque band on that English page the way Hyper-Dash 3 and the Tuned motors do. Compare that current with Hyper-Dash 3’s 1.6–3.0 A or Torque-Tuned 2’s 1.7–2.0 A: Ultra-Dash asks roughly double a mid-Dash motor and about four to five times a kit FA-130. The motor is in the Monkee Mods catalogue as item 15307; treat the listing as a product identity, not a stock or price promise. For the rest of the ladder see the motor guide.
Which cars Tamiya lists
The compatible-cars line on the English 15307 page names FM-A, Super-II, Super X, Super XX, VS and AR chassis. The chassis tag list on the same page also includes VZ. That is a real ambiguity: tags are not a substitute for the kit instruction. Confirm the exact chassis family and the motor mount before buying. Ultra-Dash is a single-shaft motor. It is not a Mini 4WD PRO motor; MS, MA and ME still need the dual-shaft PRO range. If the car is a PRO kit, this item is the wrong shape regardless of RPM.
Why official Tamiya races leave it off the list
The current English Official Mini 4WD Race Regulations name a closed motor list: the kit normal motor, the Tuned family (including the “2” revisions), Light-Dash, Hyper-Dash 2 and 3, Power-Dash, Sprint-Dash and Hyper Mini. Ultra-Dash is not on that list. The regulations publish no reason for excluding the most extreme Dash motors — they are simply absent from the permitted list — though their four-to-five-amp draw through two AA cells is a practical concern in its own right. Stock Class uses the same Official Regulations except for its modification section, so a Stock Class event does not secretly allow Ultra-Dash either. Recheck the Official Regulations on the day of the race; motor lists change. The inspection process is covered in the tech inspection guide.
What 4–5 A does to batteries and heat
Two AA cells are not an RC LiPo pack. Voltage sag under 4–5 A is the usual reason an Ultra-Dash car feels explosive for a few metres and then falls off a jump it “should” have cleared: the motor is still spinning, the cells are not. Heat follows current. A motor that is too fast for the gear ratio spends more time drawing stall-adjacent current. That is a heat and break-in problem, not a reason to add grease. Official events also restrict batteries to Tamiya-branded R6/AA/UM3 cells; some club classes allow NiMH. None of that turns Ultra-Dash into a free lunch. See the battery guide before you assume a “stronger pack” is legal or even helpful.
Home tracks and organiser classes
A living-room oval or a shop practice night is not an official Tamiya tournament. Some organisers run an open-motor or “speed” class that allows Ultra-Dash and Plasma-Dash; some BMAX sheets still follow Tamiya’s permitted-motor list. Do not take permission from this article. Read the event’s own PDF. If the class does allow 15307, treat gearing and brakes as mandatory, not optional: a car that cannot finish is slower than a Hyper-Dash 3 that stays in the lane. Plasma-Dash (15186) is the sibling on the same extreme rung, not a PRO option.
Frequently asked questions
Is Ultra-Dash legal in BMAX?
Not because this page says so. Basic-MAX GP v5’s FAQ allows Dash-type motors, but v5 still follows Tamiya’s official regulations for everything it does not replace — and Ultra-Dash is not on that motor list. A local Malaysian BMAX night may still ban or allow 15307. Confirm with the organiser. See BMAX rules 2026 and race classes.
Will a shorter gear ratio make Ultra-Dash well-behaved?
A shorter (higher numerical) ratio can keep the motor in a more usable band on a technical or 3D course, but it does not cancel 4–5 A or put the motor on the official list. Change one variable and log whether the car finished. Method: one-variable testing.
Is this a good first upgrade?
No. First upgrade on a standard chassis is a Tuned motor, then Light-Dash or Hyper-Dash 3. Ultra-Dash is a specialist for organisers who allow it and for builders who already have a free-rolling drivetrain. Shop the motors category by shaft family, not by the largest RPM print on the blister.