Tuning with your Transmitter: Throttle

Tuning with your Transmitter: Throttle


   I learned many years ago that we could manipulate the settings on our transmitters to make the car work better or simply just drive better and / or easier. On today’s TX’s there are so many settings that most drivers don’t know what they do or what they are for, let alone utilize what they are capable of to help you tune and dial in your car for better performance.

    In this post I will touch on the basis of helping you tune your car by explaining what some of the adjustments on the throttle side of the transmitter are for, what they do and how you can use them to gain more performance to get your R/C to do what you want it to.

Let’s start with the basics for the throttle. The very first thing is to get your ESC or throttle servo mounted and ready to program or set up. For the ESC you will need to follow the manufacturer’s instructions on how to set it up to your radio. Keep in mind that in both cases (Electric or nitro) you will want to have your throttle settings back to factory. Trim at 0, EPA at 100% etc. Once you have everything programmed or your linkages properly aligned and centered the settings we will cover are;  EPA (End Point Adjustment) , Sub Trim and Trim, EXP/EXPO/Curve (Exponential), Brake, ABS, Speed and Punch. (Punch can be found on KO Propo Radios)

Sub-Trim/Trim:  These settings allow you to set the servo exactly in a neutral (or otherwise) position to allow the car to sit at idle. Sub-Trim allows you to make adjustments within your Trim setting to allow the trim to be set as close to “0” as possible. This makes a difference with some Transmitters where the Sub trim moves the servo in larger movements per click than compared to the Trim which is the finer setting. Some radios allow you to adjust the movement or rate per click within the Trim setting. Tech Tip: With the throttle you can use the Trim settings add some forward roll or take away drag brakes or the motor drag effect. This has been a great aid with 4wd cars and 2wd cars when the surface is a little slick to help with traction when letting off of the throttle. In the opposite you can go toward the brake side of the trim to get the opposite effects (to add more drag brake) which can aid in cornering and getting an off road car to “fly” nose down depending on how much you use. It is however a better practice with Electric cars to adjust drag brakes with the “Drag Brake Setting” on the ESC.

EPA/Highpoint: This setting allows you to set the maximum throw of the servo or ESC from 0 to full throttle. This eliminates the binding of the servo once it reaches full throw and to give you maximum operating range for your models’ throttle. With an electric car it is a setting best started at 100% when you set up your ESC both for the Throttle and the Brake. Tech Tip: You can manipulate the EPA for both an electric and nitro car by dialing back the EPA to a lesser setting than 100%. However for a nitro car it is recommended that the carburetor be adjusted for tune when you do this. With an electric car what happens is that you get less top speed but will (with most transmitters) manipulate the feel of the throttle to be smoother and gain more wheel speed control especially in an Open or Modified class. The opposite can be said of going past 100%. This will make the throttle feel a bit touchier which has been a tuning tool of mine in the low powered classes such as the Spec classes of 21.5, 17.5 and 13.5.

EXPO/Curve/Exponential: Exponential is one of those settings that was created to compensate for the arch of the servo arm to allow the driver/pilot to get back the feel of linearity for a particular control. For many years we have used EXPO to help in getting that feel that we are looking for both with Linearity of the throttle and with Control. Without a graph I will try to explain. You can manipulate Expo to give you a slower or faster reaction off of the neutral point of your throttle. Minus EXPO numbs the initial output of the servo versus your input on the throttle trigger. It does not slow down the entire throw. Gain or Plus EXPO will do the opposite. It will make the throttle react quicker in terms of feel but not speed up the servo. Your transit time stays the same from 0 to your end point. (Example: You have a Mustang and a Turbo Honda that both run 11.0. They will both get to the end at the same time however the Mustang (Plus EXPO) will leave the line quicker where the Honda (Minus EXPO) will make up it’s time later in that 11 seconds.) So, Plus EXPO will feel faster or “punchy” from center and Minus Expo will feel slower or lag off from initial throttle but both will reach the End Point at the same time. Tech Tip: You can use EXPO to help tune the reaction of your car. In example if it feels like it needs a little more punch out of the corner add more “Plus” Expo to your transmitter or If your car feels too punchy and hard to drive straight dial in some “Minus” Expo.

Speed:  On some transmitters you can lower the speed of your servo. However you cannot add to the speed. Your servo will only perform to its specifications reliant on the voltage that is being input. Why would you turn down speed? One instance would be for a beginner or when changing from a NiMH to a Lipo battery on a gas car or buggy. Other examples would be for a sweeping layout where there are no tight or quick corners that would require fast throttle input which makes for an easier drive especially in a long main event.

Punch:  (KO Propo term) This setting allows you bypass a portion of the initial input of the curve (whether linear, EXPO + or EXPO-) all the way up to 100%. In example of you where to dial in as much as 50% Punch as soon as you input throttle up to 50% of your throw the servo will bypass any EXPO setting you have until 51% where it will then resume the EXPO setting. Tech Tip: If you race spec classes or run a long sweeping track layout you can use Punch to help quicken the reaction of your throttle input which can in most cases create quicker lap times. If the track is tight or slick Punch usually will hinder traction out of a corner and should not be used. Punch can be used for these reasons but I have never effectively used anything past 10% and that is on the radical side in my opinion.

Brake: The Brake side of your transmitter setting is an EPA just for the brakes. The strength of the Brakes can be easily manipulated by adjusting this setting down. When first setting up your ESC or servo you should start at 100% for the most effective control of this function. Tech tip: Some transmitters also have an Expo setting just for the brake setting as well. For this function you can reference the above section on EXPO and set your brakes with Plus or Minus curves to help aid brake tuning.

ABS: Antilock Braking System, this function I have only seen used on Nitro cars or models with mechanical brakes. The setting provides a pulse to the servo when the brakes are applied to aid in not having the brakes lock up. It takes a bit to getting use to and I’m not aware of any Pro or Expert drives who use this function.