You’re not alone in wishing your E-Z-GO RXV had a little more top speed. There are a few ways to get the speed upgrades you desire and in this article I’ll explain the pros and cons of each.
Dealer Programming 
By far the easiest way to achieve a higher top speed from your RXV is to purchase it that way. Now I’m going to assume that since you’re here reading this article you’ve probably already purchased your RXV. In the future however if you're buying from an E-Z-GO dealer then just ask them to crank up the speed, most will do this free or for a small charge. You see they have access to a hand held programmer or a passkey that can turn up the speed on your cart, typically 19.5 mph. There are ways to trick the controller of your RXV into thinking it's going slower thereby making your cart faster but in this technician's opinion I don't think it worth the risk. The RXV needs to know its speed for the electronic braking to work correctly and when it comes to brakes I don’t take any chances.
Tuner / Speed Chip / Freedom Mode 
The most economical way for the DIYer to gain speed is to purchase a FastRXV Tuner. Now I may be a little biased on this one but stick with me. A Fast RXV Tuner is as simple as it gets as far as installation goes. Turn off the cart, plug the tuner into the diagnostics port, turn on the cart and wait for a solid orange light, turn off the cart and unplug the tuner. That's it! With a stage 2 tuner you would be running a swift 25.5 mph, and even more speed with taller than stock tires. We typically run 20” tall tires on our RXVs and usually see 29 mph.
High Speed Gears 
Next up we have high speed gears. The gear ratio on the EZ-GO Electric RXV is 12.44:1, the lower the first number the faster you’ll go. The Standard high speed gear set is 10:1, that will get you around the 35mph mark. There are a few downsides to high speed gears and first is the cost. Just shy of $500 for just the gears! Unless you are mechanically inclined and have a press youre going to need a golf cart shop to install these. A 2 - 4 hour install time means you’re most likely going to be around $1000 all said and done. There's also the issue of lost torque, with a set of high speed gears your ability to climb hills will decrease significantly.
High Performance Controllers
Upgraded controllers are a fantastic way to increase both speed and torque, my favorite by far is the Navitas AC Controller kit for the RXV. Installation on this is pretty difficult if you haven't replaced a controller before but it’s about as easy as it can be for a high performance controller kit. The instructions are very detailed and the technical support is top notch. The cost for one of these kits is all over the board. I've seen them for as low as $799 to over $1000. One important thing to note here is if you have a factory lithium battery pack from EZ GO, this kit will not work for you. Also a lot of aftermarket lithium battery packs don't produce enough power for the Navitas kit.
Taller Tires 
Lastly we have taller tires, stock tires are 18” tall. If you go up in tire diameter you'll get a few extra miles per hour. It's not much but going from 14mph to 17mph could be all you need.