Racing Class Battery Capacity Motor Rating Speed Controller Rating Boost Capability (Y/N)
Offroad 4wd 4500 mah 10.5T 90 Amps N
5500 mah 7.5T 120 Amps Y
6500 mah 5.5T 120 Amps Y
Offroad 2wd 4000 mah 13.5T 60 Amps N
4500 mah 10.5T 90 Amps Y
5000 mah 8.5T 120 Amps Y
Onroad open modified 6500 mah 4.5T 120 Amps Y
Onroad stock class 4500 mah 13.5T 60 Amps Y
(13.5 boosted*) 5000 mah 13.5T 90 Amps Y
6000 mah 13.5T 90 Amps Y
Onroad spec class 3500 mah 13.5T 35 Amps N
(13.5 unboosted*) 4000 mah 13.5T 60 Amps N
4500 mah 13.5T 60 Amps N
Recommended Spec Class Package:
Etronix Pulse EX3G
Any 25C or greater, 3500mah min capacity Lipo
Hobbywing Ez-run 35A
Thunder Power 13.5
Sakura XI Sport
Body Shell & Paint
Dependant on rules
Pinion, lipo safety charging sack
Total Price - £386
The other option people get tempted with is http://www.rcracinguk.com/index.php?main_page=product_info&cPath=77_362&products_id=13611
These ready to run kits have all you need in one box but there are several problems:
We have found the brushed motors need replacing every 2 race days (about 80 mins of use) to maintain performance but they are only £7.50 each
The battery is low powered
The charger is an overnight type so no good for racing
The tyres are no good for racing
The kit comes built – we always recommend to build your kit so you know how it goes together so you can fix it if it breaks
These kits cost £230 so to get a decent battery, charger and tyres you need to add £90 to the cost (total £320) and the car will not be as quick, robust or handle as well as the recommended package.
Recommended Mod Class Package:
We do not recommend a mod class package – if you need such a recommendation, you are not experienced enough to be running in Mod class – please look at the spec class package!
There are 2 main categories of radio transmitters. Stick transmitters have 2 sticks, one you push forwards and backwards for the throttle and brake/reverse (left hand stick) and one for the steering (right hand stick). Trigger (or steerwheel) transmitters have a finger trigger which you pull towards you for throttle and push away for brake/reverse and then a wheel on the side which you rotate clockwise to turn right and anti clockwise to turn left. Which is best? Well it is down to personal preference, generally dictated by what you have used before - some people from the Playstation generation may find sticks easier as the controls are closer to a Playstation joypad. It is worth noting that using “stick” transmitters for cars is a very UK specific thing, the vast majority of the world uses Trigger type and so these are made in much larger quantities – thus its fair to say you can get more features for less money on trigger transmitters so if you are starting from scratch, trigger is probably the way to go!
There are 3 main frequencies for surface (i.e. on the floor or water!) models, 27mhz, 40mhz or 2.4ghz. These relate to the frequency at which the radio equipment operates. 40mhz and 27mhz have several “Sub frequencies”, i.e. 27.100, 27.105, 40.205. To change the frequency you have to generally change crystals – if two models are on the same frequency then they will interfere with each other. This should be avoided as much as possible as a model that is not in control is dangerous. 2.4ghz systems don’t let you choose the frequency or change a crystal, when you turn on a 2.4ghz system, it will scan the 2.4ghz band and find a sub-frequency and pick a sub frequency that is not being used. If another system is switched on, it does the same and so will see you have one sub frequency so it will pick another. In short, 2.4ghz systems will eliminate the chance of you getting interference from other radio systems. With a 27 or 40mhz system you may get interference if someone on the same sub frequency turns on their radio system. This is controlled at most clubs so that if two people use the same frequency then they are generally put in different heats so as not to clash but there is always a chance of interference.
Which should you get? The cost of 2.4ghz systems has fallen in recent times such that you can get basic entry level systems for as little as £35. That said, many people are switching to 2.4ghz so you may be able to find a good 40mhz system second hand that has many more features than you could afford on a new 2.4ghz system. A few things to keep in mind.... if you are looking to get one transmitter and multiple receivers (so you can use several different models), then check the price of spare receivers, Futaba 2.4ghz ones can be very expensive but others can be more reasonable. There are also 3rd party compatible receivers available now – for example FRSKY make a Futaba FSST compatible receiver which is around £25 as opposed to £70 for the Futaba item. Another thing to keep in mind is that 2.4ghz systems are generally not cross compatible so if you use a Spektrum transmitter then you need a Spektrum receiver. When purchasing a radio system, check if it comes with a servo for the steering. Some do, some don’t but you can generally say that very cheap systems that come with a servo mean it is a very cheap servo – which means your wheels will move slower when turning the car. If this is the case, you may need to look at a separate steering servo. The final point is that several models of transmitter have “modules”. These removable modules allow you to keep the same base transmitter (which may be a Futaba) and then insert a Spektrum Module, the module being either 27mhz, 40mhz or 2.4ghz
A basic system will have a channel reverse system and a trim for each channel. Top systems will have 30 – 40 adjustments that can be made and store settings for 10-20 different models. Rather than explain each different feature, below is a link to the manual for a Futaba 3VCS. This unit has every imaginable feature for electric and nitro cars (including ABS functions!), therefore if you see a system and are not sure what one of its advertised features is, this manual will probably tell you as there is a very good chance the 3VCS has that feature. However you will find most manuals are downloadable from the web now.
We would suggest that if you can afford slightly more than the basic system, it is worth spending the extra to get one with EPA / ATV settings and steering dual rate. These are not absolutely essential but can be a big help. For example EPA / ATV can be adjusted by good mechanical setup, dual rate can be simulated by not moving the stick all the way to its extremes!
There are 3 main chemistry compositions of batteries used in RC cars, Lipo, NIMH and NICD. NICD batteries are not really used anymore, and wont be discussed any further, if you have some the chances are they are too old to be useful anyway!
Item +ve -ve +ve -ve
Price More expensive Less Expensive
Maintenance Less Maintenance More Maintenance
Weight Lighter Heavier
Discharge Rate Higher Lower
Charger More expensive Less Expensive
LIPOs are better but more expensive. LIPOs popularity has really taken off in recent years, as such it is hard to get hold of proper racing standard NiMH packs, primarily as NIMH need maintenance as the voltage drops with time, if the voltage drops below a certain level then they degrade quickly. As such, model shops and distributers don’t want to stock many of them and so they are harder to get hold of. However you can buy cheaper, lower performance NIMH packs which are fine for beginners but you will normally want to change to LIPo at some point.
If you want to go LIPO then expect to pay between £40-£90 per pack, but you can get away with only one pack if you keep organised. For touring cars, you need a 2S pack which means 2 cells wired in series. Each cell has a nominal voltage of 3.7V thus a pack has a nominal voltage of 7.4V. This brings us to the first very important safety point with LIPO batteries. Under no circumstances should an individual cell drop below 3V or go above 4.2V. This means a 2S pack should always be between 6V and 8.4V. Lipos come in 2 different forms, saddle packs or stick packs. Saddle packs are normally used in offroad cars – these basically are where each cell is in its own case and the two cells are then wired together in series externally. Touring cars normally use stick packs, whatever you use, it should be hard cased. Softcase lipos are not allowed as they do not offer adequate protection to the cells in case of impact. Although you do not need to use lipos from the BRCA approved list, most people do. This list is normally easily found by searching for BRCA lipo approved in your favourite search engine.
There are 2 numbers which to concern yourself with, the pack capacity and the “C” rating. The higher the capacity, the longer the pack will last but for touring car racing with 5 minute heats, overall capacity is not too critical, although the higher the capacity then the higher the voltage will remain throughout the race. If you are starting out then a 3000mah pack is sufficient but the top drivers normally use 6000mah+. The “C” rating is the max charge / discharge rate for the pack. 1 “C” is the capacity in mah divided by 1000. For example, on a 5000mah pack then 1C is 5amps. The pack will normally say something between 20C and 90C, this relates to the maximum continuous (not peak) discharge current, i.e. a 50C 5000mah pack can discharge at 250amps when full. For safety reasons, never get a pack that is less than 20C as you will be drawing too much current from it when running at high speeds and loads. It is not advisable to charge at more than 1C, i.e. 5amps for a 5000mah pack. I don’t believe anyone has to charge at higher than 1C to ensure they have a full pack for the next race, sticking to 1C is the best way to look after your lipo and ensure it will last 2-3 seasons racing. If your pack states it can be charged at 2C then fine but remember it won’t last as long if you do! If you charge at 1C, then a battery takes roughly 1 hour to charge from minimum voltage (3v per cell). Rough guidance on how much capacity you will use in different classes of racing is below (all 5 minute races) – but various things can change this including temperature, grip levels, driving style, motor type etc. I have assumed that this is typical of a good club driver put use as guidance only – I also have put a typical battery specification for each application (you can always go higher!)
Racing Classs Typical Consumption (5 min race) Suggested Battery Capacity Suitable Battery C ratings (discharge C)
Offroad 4wd 2500 – 3000 mah 5500 mah 70C
Offroad 2wd 2000 – 2500 mah 5000 mah 40C
Onroad open modified 3250 - 3750 mah 6500 mah 90C
Onroad stock class 2500 - 3000 mah 5000 mah 50C
Onroad spec class 2000 – 2500 mah 3500 mah 30C
* See speed controller section for boosted / unboosted description
You can see from above that if you use 5000mah packs, you can expect to need to charge for 30-40mins between races at 1C – this is typically about as much time as you will have between rounds so isnt a major issue but it is a little bit hectic so although it is possible with 1 battery, 2 makes life easier if you can afford.
Next point is how to charge your lipo, charge it in a LIPO sack – this is a protective bag in case the lipo fails during charging and will protect you and your surroundings. Ensure you use a charger in LIPO mode – this is critical, charging a lipo battery with a NiMH charger will be extremely dangerous. See the charger section for more details
To discuss chargers, it is probably best to first discuss how to charge the different chemical compositions of batteries. To charge NIMH packs, the charger will apply a voltage to the battery to get a certain current into the pack. For a 7.2V pack the voltage will increase to somewhere around 9V, and when it is fully charged, the voltage will begin to drop. This drop is called the delta V and is normally fixed on cheaper chargers or configurable on higher end chargers. If configurable, I would suggest 3mV per cell delta V and so for a 7.2V pack (6 x 1.2V cells), this would be 18mV. So say the voltage peaks at 9V, the charger will cut out when the battery voltage drops to 9-(18/1000) = 8.982V.
A LIPO charger works a different way. If you are charging a 2S pack, the charger will charge at a certain current (you should be using 1C as explained in the LIPO battery section) until the voltage hits 8.4V . The charger will then reduce the current to maintain 8.4V until the current has dropped so low (0.1 amps), it stops charging the battery.
Due to the different ways the chargers work, you must ensure you have the correct charger, set to the correct charge mode to match the battery you are charging. Never try to charge a LIPO pack on a NIMH charger it will never end in a good way.
When looking at a charger, make sure you keep the power supply in mind. Some chargers are 12V input only so you will need a separate power supply to run the charger, some are 240V so can run off the mains and some are both.
For LIPO, I would always recommend getting a LIPO charger with balance function built in. Balance charging is where the voltage of each of the 2 lipo cells is monitored during charging and the voltage carefully maintained so that each cell charges equally. As a pack is used, one cell may be slightly better than the other so the weaker cells voltage will drop quicker than the good cell. If you don’t balance charge then you risk having one cell go over the 4.2V limit. For example you could have one cell at 4.2V and one cell at 3.5V, if you charge normally (i.e. not balance charge) the voltage would be 7.7V at the start but the charger will not stop until 8.4V. You can see one cell is already at the limit at the start of the charge and so further charging is dangerous. If you balanced charged then this situation is detected by the charger which then prevents one cell being overcharged.
Motor / Speed Controllers
There are two main technologies here. Brushed and brushless. Brushed equipment is DC based where as Brushless is AC based. The table below gives a comparison between the 2 technologies:
Item +ve -ve +ve -ve
Price More expensive Less Expensive
Maintenance Less Maintenance More Maintenance
Speed / Power More powerful Less powerful
Efficiency More efficient Less Efficient
Parameter Much more adjustable Not many adjustable
adjustment parameters parameters
For touring cars running brushed motors, you must make sure your speed controller can take a motor of the appropriate “T” number. The “T” relates to the number of winds on the rotor, the lower the turns, generally the faster and more powerful the motor is so the more current it will draw – the speed controller needs to be able to handle this current otherwise it will overheat. Brushed systems are not really used in competitive racing anymore but some mini and GT12 classes still legislate their use.
For brushless equipment, there is a lot to know about but we will try and make it easy! There are 2 main subsets, sensored and sensorless. The sensorless systems can be cheaper but are not as fast, most people use sensored systems for touring cars – so much so, we won’t cover sensorless systems any further here.
Within the band of sensored systems there are then 2 main differences between the types of speed controllers available. The basic “sportsman” speed controllers offer fixed timing which is easier to setup and set the gearing so you don’t overheat the motor – these are normally called “Sportsman” or “blinky” speed controllers – blinky comes from the fact that when in sportsman mode, there is a light that blinks to indicate it is in such a mode. The newer competition speed controllers have what is called “timing on the fly” or “boosted” or “supercharged” or “variable timing” which is where you have several settings that determine the amount of timing applied to the motor depending on its rotor speed. Timing on the fly systems can be very quick but they take a lot of practice and time to get a software setup and gearing ratio adjustments to obtain optimal motor temperatures. Similar to brushed motors, the lower the T rating of the motor, the more powerful it is. Due to the extreme speeds brushless systems can run at it is important to never rev the car off the ground other than with slight power to check it works – other wise the motor can be damaged (you can also rip the tyres apart!). It is possible to buy speed controllers where you can change the firmware on them so that you can buy one unit and change the firmware so it has either has or does not have timing on the fly capability. Why is this a good idea – well it means you can use the speedo in different classes – for example you could start off in Spec class with a non boosted speedo and change firmware to boosted if you progress to open modified.
What does timing do? Well the lower the timing, the more torque the motor can generate but the lower the top speed will be. This means the motor will be quick out of the corners when torque is needed to achieve the acceleration levels required but when you are on the straights, the speed will be lower. “Sportsman” type speedos give the option to give the motor a fixed amount of timing which is applied no matter what the speed of the motor is and so is always a compromise between torque and speed. If you put so much timing on to get top speed, you will be very very slow out of the corners. With timing on the fly systems, the amount of motor timing applied is dependant upon the motor speed, so when you are at low motor speeds, the timing can be low but when your speed picks up, the timing can increase to give the top speed as well. It is typical to have more than twice the number of adjustable parameters on a timing on the fly speedo than on a sports man type.
So what do you buy? Well don’t fall into the normal trap, a fast car does not necessarily give a quicker lap time. What you buy depends on what you can afford, what level you want to race at, if you want it to be future proof (as much as electronics can be these days) etc. It is also helpful if someone at the club has a similar speedo so they can help with settings. Before you buy, make sure you get what you need to update firmware and change settings as most of the timing on the fly systems need a separate program card or need to be connected to a laptop to program!
There are literally hundreds of possible speed controllers / firmwares etc so it is worth taking a little time over your selection. If you are using LIPOS make sure the speedo has a LIPO mode other wise you need to get a lipo cut out, this is to prevent your lipo voltage getting too low when you are running (a potential issue on long runs or using low powered lipos for racing).
Speed controllers tend to have a continuous current rating advertised. The table below gives you an idea of what continuous current rating speed controller you should look at for the different classes (note peak current can be 4-5 times the continuous rating – make sure you are looking at the correct number!). These obviously depend on what motor you are running but I have based it on something sensible!
Racing Class Continuous Current Rating
Offroad 4wd 120 Amps
Offroad 2wd 90 Amps
Onroad open modified 120 Amps
Onroad stock class (13.5 boosted*) 60 Amps
Onroad spec class (13.5 unboosted*) 35 Amps
So, you have read all that, what do most people tend to run? Please see the tables below – these give 3 levels of packages for each class – beginner (someone just getting started), Club Level (a package capable of being club champion), World (a package where you can win the world champs!) – note for open modified class you should only be running top equipment in this class due to the power involved so there is only a World package shown