HPI Racing

HPI Trophy 3.5 nitro is a fantastic platform, loads of fun and great for hobbyists – This is a long term review. I have owned a HPI Trophy 3.5 buggy for 6 years now. That said, this review is still relevant for consumers regardless… Read more

whether you are in the market for a rc vehicle, new to the hobby or is also a proud owner of a HPI Trophy 3.5.

1. HPI Trophy 3.5 nitro buggy is over a decade old but still current - When I bought this nitro buggy, it has already been around for years hence was an old product because HPI has not released anything significantly new for years. Still it is a current model! While HPI would tell you there are many new products, they are built on existing platforms with new lexan body shell and decals. Specific to the Trophy 3.5, the only change was an engine change (not an upgrade) and making it water proof. It is really the same platform. However, HPI as a company has had several significant changes in the last few years and is under new ownership, which explains why engineering has become stagnant. Perhaps some actual new products will come out soon.

2. Standard 1/8 platform - Whilst the popularity of 1/10 scale especially for racing has grown substantially over the last 5 years or so and 1/8 scale truggy such as Savage which is an awesome platform has become vastly popular because of their toughness, ability to do tricks and bash-ability. 1/8 is still the interchangeable platform where you could swap many parts between brands and models without issue. Therefore, for a hobbyist who love to tinker, the amount of stuff you can do is practically infinite.

This is the reason I still very much love this buggy. My HPI Trophy 3.5 isn't really the Trophy 3.5 that came in the box anymore. The only thing that are still original include little more than the base aluminium plate, arms and the wing. The nitro engine has been upsized 2x. Two shoe stock clutch replaced with TLR 4 shoe combination aluminium and carbon crutch. All shocks are replaced with big bore shocks and sway bars added to both front and rear. Diffs are changed with toughened gears and thicker oil. All bevel gears are changed to spiral gears. All dog bones replaced with CVD rods. All servos upgraded to digital brushless tough servos. Radio changed to support ABS and huge bunch of other things. Hubs are extended to give her a wider wheel base for stability and so it can take larger wheels. Suspension tuning with different oil, camber angle, toe-in/out angle, link position, you name it. The receiver box was changed back to original style so I can just open it without a hex key and lock it with clips. Fuel tube is lengthened and oil filter and pump added. Even all the screws are changed to stainless steel. Last but not least, a HPI DBox2 drift gyro was added just for fun, and it sure is! It practically have all truggy parts inside using a large truggy engine in a small reliable, tough body. The only reason I didn't change the arms and steering knuckles is that I was convinced that doing so will break other parts in the event of a crash hence not worth it, and they add weight too. There is some play in the wheels but that is ok as a basher.

Because it is so standard, the number of hop-ups and compatible and after-market parts is enormous. I know some even added truggy wheelies wheels despite they will practically never be used because it is a 4 wheel drive. If it were possible, I would have added 3 speeds transmission and slip diff like I have done before with another buggy. I have kept the pull starter rather than investing into bump starter box or tiger drive despite my old buggy has a tiger drive and I love it.

3. HPI Trophy 3.5 is textbook design - Afaik, it is a carbon copy of Kyosho MP777. All the parts look the same! And that was a great racing platform. There is a very large amount of literature about this vehicle. The biggest difference one might find is that another rc vehicle may use a pivot ball steering knuckles rather than c-hub. Thats about it!

4. Size does matter - As tempting as it is, 1/8 truggies and 1/5 vehicles like the Bajas are just too big for me personally. Everything are more expensive with them. Their larger size and heavier weight demand more grunt so engine and everything else have to be beefier to meet the performance of a buggy. Yes, truggies especially two wheels ones can do wheelies and tricks. But personally, I am in it for the engineering of it hence why I tinkered and changed so many parts. In recent years, several manufacturers have started making 1/8 petrol / gasoline truggies, hoping to build on top of the popularity of the Baja, but they have failed to capture the market. The interest didn't last long enough for this new line of product (the gasoline engines) to evolve to become as reliable as its nitro counterpart.

5. Cheap - The HPI Trophy 3.5 is relatively cheap. Easy to get parts, infinite compatible hop up options and cheap parts. This is the reason why I was able to change so much in mine.

Electric vs Nitro Electric platform is much simpler. You only have one spur gear, a fly wheel, an engine, one servo and radio and batteries. There are no brake discs, no clutch, no pull starter / tiger drive / bump starter, no air filter, no tuned pipe, no nitro fuel, no glow plug, no glow starter required and no need for throttle / brake servo you need just on parts alone. From operation and maintenance standpoints, for a nitro vehicle, one might think about throttle exponential curve so the clutch grabs quicker, spend hours on cleaning, tuning the engine, replacing clutch shoes or the whole clutch, whichever is cheaper, when it wears out, watching engine temperature to not let it get so hot and melt the bearings inside the engine that usually use nylon retainers for the bearing balls. Nitro is a much dirtier platform. Electric on the other hand is so clean. Engine does the braking. Instant thrust. It even reverses. You need a fancy transmission mechanism to do that in a nitro / gasoline vehicle.

But, and this is a BIG but, I do absolutely love nitro! Learning about 2 strokes engine. The satisfaction of tuning up the engine, replacing bearings in the engine, trying out different clutch to improve performance, trying different fuel, etc. Then there is a great deal of smoke and roar from the engine as it revs. Great fun for an enthusiast or petrol head! I do have an electric buggy, the way brake and reverse work really confused me at the beginning. Electric buggies do go faster than nitro.

Unlike some, I don't do crazy jumps to test out the limit of how strong the plastics are. I have only ever broken one c-hub steering arm because of a smash. The limit I push is in terms of handling and driving performance. For this reason, I have cooked engines before, chewed up diffs and worn down clutches. A little dirt in the engine can quickly wear out the engine sleeve against the piston. Melting the engine bearing will cause leakage. Much worst still, the piston rod will most likely bend, snap and shred into dust inside the engine digging deep gouges in the engine sleeve and piston killing compression. That's a hobby! In fact, of late, there is a very big obsession about speed, most manufacturers are making 6s or even 8s electric vehicles that would do 60+, 70+ or even 100+ mph.

HPI D-Box2 is fun but may be challenging to set up – I have had a HPI D-Box2 for years, first using it in a nitro vehicle and then migrated it over to through a couple of electric vehicles. I also have… Read more

a newer gyro unit from SkyRC, the GC301.

HPI D-Box2 is 80% more expensive than this SkyRC GC301 gyro at about $90 at my local hobby store, compared with listed price of $49 for the SkyRC GC301. It must be mounted on the narrow side making it heaps less stable unless you can tape it to side of chassis like in the case of HPI Savage cage chassis. The HPI D-Box2 is really sensitive. While it provides sensitivity mode 0-3, I have always had it at level 3 - the least sensitive mode. Still I have the gyro sensitivity knob set to less than 40%. The knob is adjusted by a small flat screw driver / supplied gyro set up tool and it is pretty loose although I have never found it lose itself setting while bashing the vehicle.

The unit is 33% larger than the SkyRC GC301 gyro at 26.5mm x 27mm x 10mm and 65% heavier at 9.5g. If you like to add a bit of light or colour, its clear orange casing and bright red LED is great. It is waterproof with rubber cover over the sensitivity dip switch and knob. When turned on, it takes about 3-4 seconds before it is ready.

Sensitivity must be set on the unit rather than via radio like you can with the SkyRC GC301. There is no reverse switch although it can be reversed by mounting the unit upside down. Pretty elegant design which also explains whey the unit must be mounted on the narrow side.

Despite nitro vehicle introduces much more vibrations than electric vehicles do and therefore two layers of double sided tape is supposedly required, I had really good luck with it mounted in the radio box with the receiver. Not so lucky when I tried to mount it to my electric vehicles, partly because my electric vehicles are markedly faster. I have now mounted it to an electric Tamiya vehicle, outside on the side. It is a much slower vehicle and the magic has returned. It does lean a little after a while but it is more than bearable. I am loving the ability to drift with it. And I also love the red LED which adds some interest to this vehicle for which I have also added a full lighting kit.