U.S. Spectacular – Team Orion CRF 21 Buggy US Spec

Track Test
New nitro engines need a proper break-in and one thing we noticed when we mounted the Inferno ST-RR clutch onto the CRF 21 US Spec was that the engine has very little pinch compared to other similar motors. This should make for a relatively short break-in time but also means that you should be patient enough not to run the engine too low as it gives the feeling of being properly run it after the second or third tank of fuel.

Team Orion stated a break-in period over six to eight tanks at a very rich setting and low speeds which seems ok as long as you make sure not to run the engine too lean and with temperatures over 100 degrees Celsius. We had the feeling that the low-speed needle setting on our carburettor was a bit on the lean site as the US Spec ran very consistent with the carb fully shut. Also the temperature rose quite fast although the ambient temperature was only around 5 degrees Celsius. Therefore we opened the low-speed needle for a full turn until the engines stalled after some 10 seconds or so. After the US Spec drank its first 150 cc of RB Monster Fuel we put it on the track to continue the break-in process. The setting of the main needle seemed ok for our needs as the engine tended to bog at mid-throttle. The temperature now was around 80 degrees Celsius on the plug which and tended to fall a bit with every tank so we steadily leaned the mixture to keep the engine at around 80 degrees Celsius. With tank number eight we started to adjust the needles towards 90 percent performance. At the end we pretty much had the low-speed needle setting the carburettor was delivered with. The engine seems to have his sweet spot at around 105 degrees Celsius with a #6 Turbo glow plug and the Team Orion 3030 EFRA 2008 (#ORI88016) pipe.

When adjusted correctly it is obvious that Team Orion’s efforts to make the engine more drivable went in the right direction. The US Spec engine accelerates swiftly from low-speeds with loads of torque but is at the same time very controllable. Although meant to suit ‘new types of cars with lighter concepts’ its characteristics perfectly fit our heavier Kyosho Inferno ST-RR truggy. It was also noticeable that the ‘dieseling’ often associated with the older CRF engines is no longer an issue. Even from high revs the CRF 21 US Spec falls into idle precisely resulting in better throttle control for those drivers who tend to ‘pump’ with their throttle finger. Run-time with the smallest venturi was in the 10 minutes range with a ‘normal’ (read: not overly aggressive) driving style. So far we did not try the supplied ‘long’ low speed needle but we will in an upcoming nitro buggy test to see if it makes for the promised (even) more progressive throttle feel.

Thanks to Team Orion for supplying the CRF 21 US Spec engine.

Specifications
CRF 21 Buggy US Spec
Part number: ORI80612
Capacity: 3.49 cc
Bore: 16.26 mm
Stroke: 16.80 mm
Ports: 5+2
Weight: 330 g
Glow plug: Turbo style
Price: around 330 Euro

Review by Sebastian Suerstedt