P Limited Tuning Tips by David Newland
There’s been a divide between NAMBA racers as of late, concerning opinions over the quality of the P-Ltd motors. As part of my effort to help, I’d like to share my philosophy and what I do with P-Ltd Setups. If you find yourself unsatisfied with this class, burning up motors, etc, there are some things you can do to help your situation, or at least create an acceptable level of failure. If anyone has a question, please let me know. Ask here or send me a PM.
I’ve mentioned in a few posts about racing mentality. This is a big part of my success with P-ltd classes. You need to ask yourself if you’re willing, able and have the desire to setup, tune and race differently. If not, maybe P-Ltd isn’t for you.
You may actually find the end result of my process boring, and that’s OK. We racers come in a lot of different shapes and sizes. And, NAMBA has other Power Parameters that may fit your needs. Just know that my goal here is to help keep P-Ltd viable. At this point in time, it is my opinion that we do not need a “better” motor on the list. If that happens, it will just be a matter of time when that motor if flogged into a crispy mess, too.
1) Motor Temperature. We all know that P-Ltd motors are temperature sensitive. We know that they will be happy at a certain temperature, then go nuclear at a slightly higher temperature. However, some racers fail in how they check the temperature, have an incorrect temperature threshold, or just say, “Well, it didn’t burn up that heat, I’ll keep running it. That white smoke really didn’t smell like anything too serious”.
I don’t data log. I’m not against it, but I just don’t. I feel checking motor temperature is more important and I’m comfortable with my ability to test a motors temperature and set a realistic threshold. And, with the different production runs, motor quality is going to vary from time to time. Therefore, the “envelope” is going to shift. Don’t be on the edge of the envelope or you will burn motors. You do not allow yourself any room for mistake or different motor variance.
125 degrees. That’s my comfort level with regards to end bell motor temperature. And, I test that during open water when I’m the only boat on the water. That way, when I’m racing, the boat will run looser due to other boats on the water making wakes, etc. I verify this after a race, too.
I know what 125 degrees feels like on my finger. I also verify and somewhat calibrate/validate my feel with a temp gun. If you don’t have one, get one. You should, at a minimum, be laying a finger across the end bell after every P-Ltd run you make. Use the temp gun on occasion, too.
2) Testing a new boat/motor/setup. Standard rules apply here, but with even more emphasis on runtime and prop selection. With regards to prop selection for the first time, you need to start with something familiar, or something that you know will work, or something your partner knows will work. It must be a conservative prop selection. Start small and work your way up.
If you run 1 lap with the boat and the setup isn’t right, bring it right back to shore. Don’t run it more because it’s not going to get better. Immediately. Back to shore. Get the trim figured out and run it again. If it’s not right, immediately back to shore. Keep checking the motor during this time, too. Don’t say, “I just don’t want to un-tape it AGAIN!” Do it. Un-tape it and check.
Once you get it trimmed and the motor was giving no obvious signs of stress during your quick runs, recharge and run the boat for 60 seconds. That’s it. And pin the throttle. If you have to let up during this 60 second run, your setup isn’t right. It’s too loose or your turn fins aren’t set right. If it’s too fast to WOT for 60 seconds, prop down. Recharge, make a setup change, and run it again.
Once you nail down a WOT 60 second run, test the motor heat. If you want more info, recharge your pack. If you ran for 1 minute exactly, your pack recharge will tell you an average amp draw. 1000 mAh put back into the packs = 60 amps on average. 1200 mAh = 72 amp average. 1300 mAh = 78 amp average. That’s about as high as I’ll go. Maybe 80 amps, but it starts to be a game of Russian Roulette with the motor.
Now, remember, you’ve done your homework to select a safe prop to start testing. If the motor is ambient, move up a prop. It shouldn’t be, but if your motor is hotter than 125 degrees, prop down. Or, start eliminating drag (loosen the boat up, use a shorter rudder, smaller turn/skid fins, going from aluminum to stainless turn/skid fins, etc).
Rinse and repeat. Take notes. Keep a spreadsheet of your known setups, hull type, prop, ESC, cells.
3) Speed. I couldn’t tell you how fast any of my P-Ltd boat are running. I’ve never GPS’d a boat. Speed is not important to me. Chasing MPH is not important to me. With rare exception, anyone who posts a MPH is either wrong on the number, or wrong for testing the way they do.
Yes, I’m talking about you. Stop posting how fast your boats are. Wait, do it so I can get a chuckle.
We also have to make 12 turns during a typical sprint heat (which many racers greatly miss the target tuning here, me included), so SAW speed is barely relevant. I also feel it’s a mentality that some racers have that tend to have problems. Burn motors, for instance. Maybe they are chasing MPH, maybe they want to be faster than the next guy. Than all of the guys. Maybe they want a P-Ltd boat that can pass on the outside. I don’t recommend that mentality.
I have calculated the statistics. You have a better chance at winning the class by NOT having the fastest boat. This is counter-intuitive, I know. Slow down. You’ll do better. And save money.
4) Known setup. Once you’ve tested your boat and are comfortable with its handling and ability to get around the course and the motor temperature is good, resist the urge to continually tinker with it. Now, I know we are racers and we like to tinker/improve, but I will say that my P-Ltd setups get locked in and I rarely make changes. If I do, I do it very carefully. Minor changes then I tell myself I need to leave it alone. I will clean up props, sharpen things here and there, but I just won’t keep trying different props to chase MPH. After all, I don’t even know how fast my boats are going, anyway.
99% of the time, I never add more prop to a boat mid-race. Even during club racing. Good things rarely come from it. If you find yourself wanting to make a prop change mid-race, resist the urge. Remember, you don’t have to be the fastest boat on the course. Finish out the day and wait for your next test/tune session.
