Our Corvette Z06 can only be used for Time Trial events, which means the placement of the transponder is irrelevant. We found a spot near the trunk to mount our transponder to the undercarriage at the correct 12-inch height.

Completed racing laps are difficult to earn. To accomplish one, you have to drive all the way around the racecourse, avoid 60 other maniacs racing around you, not have a mechanical failure, and most importantly, have a working transponder that will give you credit for the lap.

There are essentially two choices for racers when it comes to purchasing a transponder, either the direct-powered MyLaps — formerly AMB — transponder or the rechargeable MyLaps transponder. The direct-powered unit requires 12-volt power from the vehicle to work while the rechargeable unit is independent. There are pros and cons to each system, which we will explore in depth here.

MyLaps and NASA give you the choice when you purchase a transponder to use either a hard-wired unit or a rechargeable unit. There are pros and cons to both systems, but I believe the rechargeable units will save you money and ensure every lap is counted.
MyLaps and NASA give you the choice when you purchase a transponder to use either a hard-wired unit or a rechargeable unit. There are pros and cons to both systems, but I believe the rechargeable units will save you money and ensure every lap is counted.

 

DIRECT-POWER UNIT

Fans of the hardwired unit claim that the great thing about this system is once you wire it into your car you never have to think about it again. Haters of this system talk about how the transponder will kill your car’s battery over time. Racers have tried to fix this power-loss issue by installing an on/off switch on the dashboard. Inevitably, the driver will forget to flip the switch on and head out onto the track with the transponder off. Without power to the transponder, that session doesn’t count. I have seen numerous drivers doing a head slap at the base of the tower while staring at the grid sheet and exclaiming, “I don’t have a qualifying time because I forgot to turn on the transponder!” Of course, those drivers always claim it was the fastest session ever, which, based on Murphy’s Law, it probably was.

A simple solution is to wire the transponder so it comes on when you start the car (see February 2014 Speed News, Page 58 for install story).

The other issue with a direct-wired unit is normally they are mounted and wired to a single car. If you have different racecars, you have to purchase a separate transponder for each one. The current price for one is $489.95. Yes, you read that correctly. Do you think the price is a bit steep? Do you understand what a monopoly is? Try winning a race without one. Can’t do it. So get out your checkbook.

 

RECHARGEABLE UNIT

Fans of the rechargeable unit love its portability. Stick it inside one car and go racing, then grab some tie wraps and fasten it to another car in about 30 seconds. One transponder can track your laps and progress on a multitude of cars — and you have one MyLaps account to track all of your progress. This is the biggest advantage of the rechargeable unit.

Another advantage of using the rechargeable transponder is all of your lap times are assigned to your number and tracked on the MyLaps website. So, if someone calls you and asks, “Will you drive my car for me in this race?” you can use your own transponder to track all of your sessions regardless of whose car it is.
Another advantage of using the rechargeable transponder is all of your lap times are assigned to your number and tracked on the MyLaps website. So, if someone calls you and asks, “Will you drive my car for me in this race?” you can use your own transponder to track all of your sessions regardless of whose car it is.

Another advantage is the ability of the transponder to function separately from the electronics of the racecar itself. With a hard-wired unit, if your car has an electrical glitch and loses all power just as your car crosses the start/finish line —where the transponder loop is placed — your lap doesn’t count.

I know on my team we actually shut cars down completely in an attempt to clear engine codes and other computer problems during a long straightaway, where inevitably the start/finish line is located on a lot of tracks. With a rechargeable unit, we don’t worry about the vehicle’s electronics or remembering to flip on a transponder switch. The battery-powered transponder does its thing, lap after lap for us.

I will warn you that with a rechargeable system comes some responsibility. You have to remember to charge the transponder before your race weekend. The good news is a charge lasts from four to five days, so the entire weekend is covered. This little bit of responsibility has caused some teams big grief. They go to the track, leaving their transponder in the shop charging. Teams forget to put it back in the car before the race or they show up at the track with a dead transponder and they forgot their charger. You can see how issues quickly arise. Luckily NASA usually has one for you to rent.

For my team to remember to charge the transponder, it comes down to organization, checklists and a charger at home, at the shop, in the motorhome and a spare charger in the radio charging station. Yes, we are a bit paranoid about not having our transponder charged. Laps are hard to earn, so we want every one to count. We charge all of our spotter radio batteries and our transponder together so we can ensure it gets done.

We use a toolbox converted to a radio charging station to recharge all of our electronics (Check out the Toolshed Engineer column from the November 2012 issue for the build of the box). Inside the box, we have our transponder charger ready to go.
We use a toolbox converted to a radio charging station to recharge all of our electronics (Check out the Toolshed Engineer column from the November 2012 issue for the build of the box). Inside the box, we have our transponder charger ready to go.

On a rechargeable unit, to see how many days you have left on a charge, just look at the little blinking light on the front of the transponder. It blinks in succession. Three quick green blinks and then a long pause and then three quick green blinks again means you have three full days of transponder use. If you see a slow red blink you are on your last day of charge (but the transponder is still working).

Inside our toolbox charging station, we plug our transponder in at night to get a fresh charge before a race weekend. The number of blinking green lights in succession indicates how many days are left on the transponder charge.
Inside our toolbox charging station, we plug our transponder in at night to get a fresh charge before a race weekend. The number of blinking green lights in succession indicates how many days are left on the transponder charge.

The biggest advantage to the rechargeable unit is being able to use it in many different vehicles. My transponder has been used in more than 10 cars. Each one of the cars I race has the plastic transponder mount in it ready for action. This has saved me thousands of dollars. Why buy another $489.95 transponder when a spare plastic mount is just $8 from I/O Port Racing Supplies?

Here is the easy-to-install $8 transponder mount. I have one of these in every one of my cars so each vehicle is ready to accept my rechargeable MyLaps transponder whenever I go to the track.
Here is the easy-to-install $8 transponder mount. I have one of these in every one of my cars so each vehicle is ready to accept my rechargeable MyLaps transponder whenever I go to the track.

 

MOUNTING LOCATIONS

The mounting location of your transponder can directly affect its ability to work correctly. MyLaps says the system should be placed 12 to 24 inches above the ground. I agree, because I have seen transponders mounted too low not work properly. The transponder signal will go through fiberglass and can be mounted in the interior of a Corvette, but my recommendation is to have nothing between the base of the transponder and the track surface. Why chance it?

For wheel-to-wheel racing, you should place the transponder at the front of the vehicle just far enough away from the area of minor crash damage — these things aren’t cheap. NASA claims for close finishes, they will do a photo finish to determine the winner, as opposed to a transponder finishing time, which would be advantageous for the person with a transponder in the front. However, I don’t always see a photographer at the finish line of every race, so my advice is to get the transponder as far forward as is safely possible.

Here you can see a rechargeable transponder, attached to the frame rail near the front of the car with a clear, unobstructed view of the ground. In this position, the transponder is protected from collision damage, but is located near the front of the vehicle for timing.
Here you can see a rechargeable transponder, attached to the frame rail near the front of the car with a clear, unobstructed view of the ground. In this position, the transponder is protected from collision damage, but is located near the front of the vehicle for timing.
A rechargeable transponder easily mounts to any car. Want to take your hotrod grocery getter to the track just to see how it does compared to your “real” racecar? Zip-tie the transponder to your street car and catch your lap times during a Time Trial session.
A rechargeable transponder easily mounts to any car. Want to take your hotrod grocery getter to the track just to see how it does compared to your “real” racecar? Zip-tie the transponder to your street car and catch your lap times during a Time Trial session.

For time trial racers, the longitudinal placement in the vehicle doesn’t matter because your lap time is relevant to your own fastest lap. For those Smokey Yunick wannabes out there who want to design a transponder mount on a chain and a servo that will move the transponder from the rear of your car on one lap to the front of your car on the next lap to make the track several feet shorter — the length of your car — during a qualifying run, knock your socks off. The average speed at the start/finish line is 112 miles per hour, which is 164.3 feet per second. At that speed, a car length would only take off 0.09 seconds a lap from your qualifying time.

For the 25 Hours of Thunderhill, teams are required to have two separate transponders for each vehicle. NASA recommends that the transponders not be mounted near each other because it is difficult for the timing and scoring system to grab multiple signals at the exact same moment. I know this claim to be true. Teams should mount their primary transponder number near the front of the car and their secondary number toward the rear of the vehicle. Our team uses one rechargeable unit and one direct-wired unit in our cars at the 25 — just to cover all bases since we are paranoid people.

Our Nissan Sentra SE-R does wheel-to-wheel battle at the 25 Hours of Thunderhill, where two transponders are required. We mounted the primary rechargeable transponder as far forward as possible and the hard-wired secondary transponder toward the rear of the car.
Our Nissan Sentra SE-R does wheel-to-wheel battle at the 25 Hours of Thunderhill, where two transponders are required. We mounted the primary rechargeable transponder as far forward as possible and the hard-wired secondary transponder toward the rear of the car.

So I leave it to you, rechargeable versus direct-wired. Pick your poison. In either case, mount the transponder correctly to ensure you get credit for every lap, and, oh yeah, remember to turn it on or to charge it!

This diagram shows the best places to mount your MyLaps transponders for the 25 Hours of Thunderhill, where two transponders are required. The best height is between 12 and 24 inches from the ground with nothing between the bottom of the transponder and the track surface. For two transponders, it is better to have one at the front of the car (the primary one) and a secondary one near the rear of the car. The separation of the two transponders on the same car helps the timing and scoring system work as it should.
This diagram shows the best places to mount your MyLaps transponders for the 25 Hours of Thunderhill, where two transponders are required. The best height is between 12 and 24 inches from the ground with nothing between the bottom of the transponder and the track surface. For two transponders, it is better to have one at the front of the car (the primary one) and a secondary one near the rear of the car. The separation of the two transponders on the same car helps the timing and scoring system work as it should.
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Image courtesy of Rob Krider