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Home > Video > Video Display > HPI Trophy Nitro Buggy Speed Test

HPI Trophy Nitro Buggy Speed Test

Several previous videos were starred with man's best canine friends, often chasing the buggy. So I just want to do see how fast (or slow) this buggy actually goes, in its current set up and environmental conditions. In order to make sense of the results, let's go through the build first. 

Buggy is based on RTR waterproof HPI Trophy 3.5 Nitro Buggy. Engine has been upgraded to K4.6 HO still using pull starter and limited by 8.5mm (orange) restrictor. This doesn't mean she will run faster. In fact, a Nova or OS 3.5 will out-run her easily. Even the stock engine, if tuned right will probably go faster. However, the torque of the K4.6 HO is great fun and very fast off the line.  

Front and rear shocks are upgraded to big-bore shocks with Losi oils. All dog bones replaced with CVDs including wheel shafts and drive shafts. 17mm hex wheel hubs are extended to give more stability. 

In order to better handle the higher torque of the K4.6 HO engine, diff gears are upgraded with spiral bevel gears in both front and back diffs. These are basically the truggy diffs. Clutch consists of 14T clutch bell and Losi's 4-shoe carbon-aluminium clutch. Center diff gear is standard 46T. [2016-01-30 Update] With 14T replaced with 16T, top speed was 53.9km/h.

Two sets of tyres were used - badlands & Losi step-pin tyres. Changing wheels wasn't planned but some splitting from the rims was noticed in the badlands which prompted the change. The badlands have subsequently been re-glued.

Both throttle and steering servos are Futaba BLS servos and radio is Futaba 4PL/receiver. Body shell is strengthened with tape. Speed logger is Garmin forerunner 101 with its own 2xAAA battery supply. All these upgrades and add ons resulted in a pretty heavy vehicle at almost 4kg when batteries are installed and fuelled using Losi tyres and just over 4kg with badlands tyres installed. Fuel is race prep 25% nitro. 

Weather and field condition: It was a warm sunny 31c afternoon, level ground albeit uneven at places, with dry short grass. I had to change location after the tyre change. Wish I could bash and do this at a golf course lawn but doubt anyone will let me. 

Admittedly, it would be faster running on race track or hard surface. Grass creates drag and resistance and raises temperature as a result. In addition, the upgrades and modifications were not for the sake of speed. Even my old Tamiya Nitro Blaster with much smaller FR15S (2.5cc) engine and 2 speed transmission has a higher top speed (just under 55km/h) than the Trophy. 

Anyway, let's see how fast it can go and hope you enjoy watching this experiment as much as I did putting it together.

[2016-01-21 Update] Found a couple of issues with the buggy which hopefully explains a little its high temp. Rear anti-bend rod has come lose rubbing against rear drive shaft because the tapered collar are worn out. Front drive shaft is rubbing against fuel tank. Noted was also a hole in the  silicon exhaust gasket. Both problem have been rectified. Also upgraded 14T clutch bell to OFNA 16T along with clutch bearings which are worn. Just need to find time to do another test. :)

[2016-01-30 Re-Test] Had many issues but managed to test it today. Pull starter gave up and exhaust gasket was torn. Top speed recorded today was 53.9km/h. Still have really good speed off the line which tells me I can up the cutch bell gear further. Anyway, intention of the hop-ups weren't for race (it would be disqualified for the K4.6 alone) but for bashing and just general fun of mucking around with this platform. It fits both bills really well and is loads of fun. I am happy with 53.9km/h and this concludes the this experiment (unless I gear it up further in time).
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