HPI has cleary demonstrated to the R/C world that they know how to make a high quality, affordable RTR (Ready-to-Run) car. This page may be seem outdated now that HPI is up to their RTR Nitro RS4 3. This kit comes with the 2-speed transmission included, uses shaft drive instead of belt drive, has a revised .15FE pull start motor with newer aluminum heat sink cooling head, and an easier to remove radio tray. But with thousands of the original RTR still out there and many of the hop-ups made for it compatible with the RS4 3 this page should still be beneficial. When the thought of buying your first R/C car comes to mind, maybe because you learned about it on the web or you stopped to watch a race somewhere, an RTR kit will be a huge help in getting you started. A Ready-to-Run or RTR kit means that the car if fully assembled, includes a Radio Transmitter, servos, and body. In some kits you have to glue the tires to the rims but that is it. Just add fuel, break in the motor, and go!!! It is important to buy the brand of car that your local hobby shop stocks a lot of parts for. No matter how careful you are when you drive around a parking lot or race, parts will break, tires will wear out, or in my case a Chevy Camaro will run over your new toy in a high school parking lot! The HPI RS4 RTR is a great starter kit and is a pretty competitive race car well into the intermediate racing level. The newest RS4 3 kit is even more competitive and runs side by side with most other cars out there. The most important thing I can say about this RTR kit is to buy it and drive it as much as you can before getting into an upgrade frenzy. What will happen is you will take a car that is pretty fast and handles fairly well and make it impossible to control for a beginning R/C driver. But at the same time upgrades are fun, they help you gain a better understanding of your car as you tear it apart to install new goodies, and they can improve the strength of weaker parts that might break in a hard crash. Am I confusing you yet? Just learn to be a smooth, fast driver and then worry about going faster. And one upgrade you should buy the same day you buy your RTR kit is a set of new tires. These RTR kits seem to include the worst tires possible for some reason. For about $40 you can get a set of Pro-Line or Jaco foam tires. They are color coded depending on how hard the foam is. The harder the foam the longer the tire wil last but the less traction you will get. The softest foams can keep your car glued to the track but can easily wear out in a single race day! I like running purple up front and double purple in the rear.

Engine - The car came with HPI's Nitro Star engine which runs really well. It starts easy and is easy to tune. For break in simply follow HPI's instructions. You basically start with the fuel mixture screw set on the very rich side. Rich means that there is a lot of fuel in the air / fuel ratio. As the motor breaks in you continue to lean the carb out by turning the fuel mixture screw in a tinly bit at a time. As you turn the screw you are restricting the fuel while the air flow remains the same hence the fuel mixture becomes more lean, or more air in the air / fuel ratio. Set the misture too lean though and your motor will burn up quickly. You will see the car going faster and faster each time you lean out the mixture. As long as you still have smoke puffing out of the exhaust under hard acceleration you should be OK.

Let's talk engine upgrades. For about $120, OS makes the CV-X, a great motor, both reliable and pretty quick. I bought the pull start version but I highly recommend that you buy the non-pull start version and fork out the extra money for a starter box. You can use a starter box even with the pull start engine so if you already have the pull start motor go get a starter box. I could pull the starter cord 50 times and the car won't start, I then tap it on the started box and in about 2 seconds the engine is screaming. Of all the money you spend on these cars, don't skip the starter box. Anyway, the OS engine is plenty fast, reliable, and gets good range out of a tank of gas.

The OFNA starter box is really nice. It has the connectors on it to run a glow plug ignitor which is very convienient (see photo). I connect it to a 12V car battery and can run the box and glow plug for days. You can also put (2) 7.2V battery packs in it and make it completely portable. It was about $90 and worth every penny. If you come out to our track you are welcome try our starter box. You will see how nice it is to have. Give yourself an hour or two to build the box, it comes unassembled.

Graphite Upper Deck - This really makes the car look good but it serves other purposes. Carbon fiber is extremely light yet rigid so at the same time you are making the car lighter, you are stiffening the chassis which helps with the handling. When you make this upgrade it is a good time to add the servo saver on the steering servo. Make sure you get everything required to add the servo saver, I ended up at the hobby shop 3 times before they finally gave me everything I needed, they love that though. In the photo on the right click to see the larger image and look to the right of the steering servo to see how the set up should look. A servo saver will absorb the force of a front end crash and prevent the gears in your servo from getting stripped. I think this is a good investment. Anything that makes parts last longer - I'm buying!

CVD's or Universals? - They look really cool and they provide a lot less resistance on the drivetrain of the car. MIP CVD's are about $35 but you get a big improvement in performance. I actually went with universals in place of the stock dog bones since 4 universals cost about the same as one pair of MIP CVD's. Not a must have but most racers have them. R Racing Products in CA makes Universals - similar to MIP CVD's in performance only a little cheaper as I said. The holes on them for the shaft pin that locks them in was too small so I had to drill them out. Easy enough if you have the right size drill bit. They might not all be like that though. Make sure you keep the ends cleans, even after every run, because dirt will cause the damage shown in the photo much quicker.

HPI X-Pattern radials - Tires choices can be tricky. They are also one of the most important aspects of racing for making your car handle well. Try various patters and compounds before you start stockpiling tires in your toolbox though. As quickly as tires wear out, you will have plenty of chances to experiment. HPI's x-pattern radials work pretty good. On days where the outside temperature is around 75 or 80, these tires hook up really well. Remember this simple rule, the softer the rubber or foam compound, the better traction you get but the faster the tire will wear out. Try Purple or Double Purple Foams from Pro-Line or Jaco for a good traction / wear combination. If your tires are worn out you can tune the car until you are blue in the face and it won't make a difference. Start with good tires and work from there.

Fiber Disk brake - Just look at it compared to the stock HPI plastic disc. There is a lot more surface area to wear down and the fiber is much more conducive to grabbing the brake calipers than smooth plastic. For $15 you should buy one. Your car will stop a lot quicker which means you can come into the turns faster knowing that you will be able to slow down so much better. If you never use your brake you should. While you are coasting into a turn someone else will be catching up to you knowing that they can brake hard and accelerate out of the turn.

2 speed transmission - This is a tough one. First of all, HPI's original 2 speed tranny likes to tear up the one way bearing that it comes with. This problem has been addressed with a new HPI heavy duty 2 speed for the same price. Depending on the size of the track you race at, you may or may not use the 2 speed. It may only engage for a split second but the extra little burst of speed helps and it allows for a lower 1st gear ration so accelleration is better. If you don't have your suspension dialed in, good tires, and a smooth track, the 2 speed will only cause you grief. A car that is not set up well will be very hard to control at high speeds. It is really cool to hear the car snap into 2nd gear and take off towards 50mph. But one crash at these speeds and you will definitely break something. I like having the 2 speed in there because you can always adjust a single set screw to determine when 2nd gear will engage. This way on a tighter track you can set it to not engage 2nd gear at all. If you are really serious about racing, a track that does not have enough length for 2nd gear speeds means you put in a single speed with the appropriate gearing as opposed ot just setting a2-speed not to engage.

Belt tensioners - Front and rear. Belts wear out and they are not that cheap. The tensioners probably pay for themselves after a season or two. And they look cool. The front tensioner is cheap, about $10 but the side tensioner was $35, ouch! I recommend getting both of them though. Always keep a spare set of belts with you on race day, if one breaks you are done! Most new kits are shaft drive - Finally!

Radio / Servos - Futaba 3PJS PCM - Once I bought my 1/5th scale car I had to get a new radio since the Rival AM that came with the "RTR" just wouldn't cut it. I needed 3 channels and PCM for the fail safe feature that it offers. So I took the servo that came with the Futaba 3PJS and used it for the steering on my HPI RS4. The original airtronics servo is still used for the throttle. It works just fine so I used it. Did I mention that I needed a PCM receiver since the one that came with the radio went into the 1/5 scale car, that was another $100! At least now I can use the 3PJS for both cars, it can be programmed to run up to 8 cars. Even with only 2 cars, that is the greatest feature of the radio (besides ABS brakes, traction control, and throttle/steering trim control that will make you wonder how you ever got along without them). Good FM radios start around $100 and PCM's can get over $400. The fail safe options offered with a PCM radio are well worth the money spent on the radio itself. If you have ever had your car take off out of control you know what I am talking about. With PCM, any servo connected to the PCM receiver can be programmed. In simple terms, you tell the throttle/brake servo to go to full brake if any of the following conditions occur- another radio on your channel is turned on, battery pack voltage in the car drops too low, or the receiver loses communication with the radio for any reason. Some tracks require your car to have a PCM failsafe set-up or at least a throttle return spring which is not very effective. Your radio is the only link from your hands to the car so don't go cheap. Use a Rival AM radio that is said to be "very functional" and then use a 3PJS, the decision is easy.

Lunsford Titanium Turnbuckles - Pretty expensive at $30 plus the ball ends you still need but worth it. I recommend RPM's ball ends instead of HPI's. They are much more solid. You will need 2 packages of 12 at about $5ea. That leaves you with some extra's which is good because the titanium will never break, the ball ends will (in a crash that is). Use your 4 way wrench to tighten the ball ends onto the turnbuckles, remember that one end is reversed threaded! That allows you to turn the titanium turnbuckle in one direction and make the arm extend in or out (depending on which way you turn it).

Rear Brace - Again, it looks good, stiffens the chassis and is about $10. There are aluminum ones for much more but carbon fiber will do the trick.

Spare Parts - It is good to have some spare parts on hand in case you crash early in the day and want to keep running. In your toolbox you should have belts - one of each, locktite, miscellaneous screw especially the ones used on the motor mounts in case any vibrate out, extra body pins, fresh AA batteries, a spare set of tires, and glow plugs. At first it is fun going to the hobby shop 9 times a week but it's better to be in the parking lot or at the racetrack and be able to fix a damaged or broken car then have to run to the hobby shop. Save that for the rainy days.

Summary - It is important to decide up front how many upgrades you are considering before you buy. The HPI NRS4 Racer version of the RS4 comes with turnbuckles and the fiber disk brake. No motor, body, or radio though. I ended up buying all of that stuff anyway.. If I could do it all again, I would have bought a car without an engine and radio and got the better version of the kit if one was available. But when you first get into this hobby and you are looking at a $300 RTR with your only comparison being a Radio Shack TYCO special, an RTR car is pretty hard to beat. For getting started w/o spending huge dollars I would consider an RTR kit, HPI's are excellent of course. They include everything (you only need to buy glow plugs, fuel, and glue for the tires) which will be about $300 out the door. Spend your money on tires as you need them, and then when you can afford it, upgrade to the non-pull start engine + the starter box. If you keep your engine tuned properly, a pull start version can do the trick but a non pull-start motor for about $120 will give you more accelleration and top speed. A good, consistent driver can beat just about anyone that crashes all the time no matter how much of a speed difference the two cars may have so learn to drive befor eyou turn your new car into a 1/10th scale rocket ship.