HPI Racing - Nitro RS4 Racer 2 Updates

These are building tips that HPI team drivers and other fast racers have found will increase the effectiveness of your Racer 2 kit!

How to Rebuild Your Engine!
Learn how to change your Nitro engine's piston and sleeve with seven pages of detailed pictures and rebuilding tips! Essential for all Nitro car and truck owners! Click here to start!

How to Make Your 15FE Engine Run Cooler!
If you run your HPI Nitro car or truck hard, your engine will benefit from better cooling. We'll show you how to install the #1703 or any option engine head. Useful for most HPI Nitro car and truck owners. Click here to start!

How to Upgrade the Carburetor on Your 15FE Engine!
For race-tuning your Nitro car or truck, a 2-needle carb is very useful - detailed pictures show you how to upgrade your 15FE stock carburetor to our #1634 2-needle carb! Useful for most HPI Nitro car and truck owners. Click here to start!

Add a belt roller guide
Nitro racers can add a bearing-equipped roller guide onto the front pulley mount. Our #72060 Aluminum Pulley Mount and the most recent version of the plastic mounts have an extra hole that allow the installation of a pilot shaft or screw that can hold bearings against the front belt. This is not an essential feature, but some racers like the option to do this modification. Parts used for the pictures below: one 3 x 15mm metric cap head screw (#Z545), one 3 x 5mm metric binder head screw (#Z515), one servo saver shaft 4 x 10mm (#A168), two 4 x 8 x 3mm ball bearings (#B017) and a few 4 x 6 x .3mm washers (#Z695). You can use different screws and parts that those listed, but these are the exact parts shown.

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Vibration-proof your fuel tank
Use machine screws, locknuts and old shock o-rings to make bushings for your fuel tank. This will help prevent the formation of bubbles in the fuel lines as you run the car. See the arrows in the picture below for the location of the o-rings.

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Lower Your CG!
Racers are always looking for a way to lower their Center of Gravity (CG). HPI Factory Team Drivers mount their Nitro car throttle servo below the graphite upper deck, as well as removing the thick aluminum washers that space the graphite battery tray above the upper deck. This lowers the center of gravity quite a bit on the Nitro car kits.


Use the same screws and nuts, just move the throttle servo mounting ears under the graphite upper deck.	You can use Shoe Goo to attach rechargeable batteries to the graphite battery tray.

Use a Fake Transponder
Use a "fake transponder" (available under many different brand names) to balance your car when tweaking or testing setups. Because the weight of a transponder can affect side-to-side balance, it's helpful for experienced racers (who can feel the difference when driving) to use fake transponders. Buy one or make your own using lead weights, tape and a nylon zip tie. Make a loop of the zip tie and strap the weights together, then strap the zip tie to the lead. The finished fake transponder should be .75 oz or roughly 22g.

Fill it up...halfway
When balancing your car for racing and tweaking, it's usually best to fill the fuel tank only halfway. This allows you to make adjustments with confidence that a full or empty tank won't affect the balance of the car.