With some questions posted about 17.5 Boosted racing, I think it might be a good idea to go over how I have been working with the VTX Speed Controls over the last year.

First off, we need to determine a good starting point on gearing, and probably the best way to do that with a new track or a new vehicle, is to do a little research locally and find out what optimum gearing would be Un-Boosted, which on the XXX-SCT seems to be anywhere from 84/24 to 84/27 (depending on track size, etc......)

Now, with this type of gearing setup, the motors will be warm already without timing (on the VST Motors, I have found that though temps as high as 160-170 degrees won't hurt the motor, that temps much higher than 150 will hurt performance), so we need to gear down, the more timing we add, the more we need to gear down.

Start with unboosted settings and unboosted gearing, and run 2 minutes of practice. Note performance and temps.

So lets start geared down by 10%. If we were running 84/25 un-boosted (a 3.36:1 Ratio) we would be running 84/23 (3.65:1 Ratio, about 10% lower). Run 2 minutes of practice, and note performance and temps. What we should find from out baseline is that we have more "punch", less strait-line speed, and lower temps than before.

Now, start adding some Accel Boost timing, initially, 5 degrees of timing, and lets say 8000RPM as a start point, and 15000RPM as the finish point. Run 2 minutes of practice, and note performance and temps. We should see an increase in punch, and increase in strait-line speed, and temps should be higher than that of the previous test. As of right now, don't worry about strait-line or strait away speed, we will deal with that later.

At this point, it is all about feel and drivability. With the current setup, we should be roughly the same top speed as we were with our un-boosted setup, but with more punch and bottom end. If we need more "grunt" or punch, then gear down more, and add more accel boost timing. Remember, practice in 2 minute intervals and monitor temps.

Now, it is possible to get as much grunt out of a 17.5 as a 13.5 or even a 10.5 motor without timing, so if we run into drivability or traction problems, then we can make adjustments to the RPM settings. If we went from 8k/15k settings to 8k/25k settings, we will still be adding the same amount of Accel Boost timing (lets say 5 degrees), but with the two numbers being farther apart, the VTX will be adding it much more gradual. This will be easier to drive, and will not make as much heat. The lower RPM number is one to be careful with, because if it is too low, it is VERY easy to overheat the ESC and motor. When the motors are at lower RPM, they are not very efficient, and if we are adding timing at very low RPM (under 7500RPM), it isn't very effective and we run a high risk of hurting something. Remember, if we need more grunt, gear down. We can add the speed with timing.

Everything up to this point has been to come up with a setup that is fast, drivable, with manageable temps while on the infield part of the track. Don't worry about the strait away yet. Once you have the performance needed there, with safe temps, then move on.

Once we have established a good setup that works well on the infield and is drivable, but if we need more strait away speed, that is when we use the Top Speed Timing settings. If the previous steps have been followed, start by adding 5 degrees of Top Speed Timing, with a Slew Rate of 4 Deg/1000RPM. Practice for 2 minutes and note performance and temps. We should see noticeable speed out of it, but only see single digit temp changes from out previous tests (without Top Speed Timing). If the temps are safe, you can add more TST.

Use the Slew Rate to adjust how aggressively the VTX adds the T.S.T., if the speed comes on too late, try 6 or 8/1000RPM settings. If the car wants to spin out, try less. Remember, all the power in the world does nothing if we can't drive it.

Thank you flhx some should put that in manual makes total sense now when I put my system in 17.5 boosted profile loads of top end no grunt should of geared low to make it work

Jamie, PM me your email address and I will forward you the software.

FLHX- great explanation, thanks!! One thing I want to add is that it is a bit of an experiment - just like he said, run about two minutes, and give everything a check, especially temps. Track size, layout, driving style, traction all need to be taken into account.

Hey nikos hope to meet up with you if your racing at critters on Saturday

Hey guys,

Its probably buried in this thread somewhere, but looking for some help with esc settings and gearing. Running a XXX-SCT with Viper motor and esc. I dont normally run boosted SC, so any help is appreciated.

I would like to ask, what motor are you running (17.5, 13.5, 10.5 etc.....)?

I guess I would say why to use 2 minutes increments, is to able to gauge our changes incrementally. Start with the motor at room temp, run the 2 minutes.

Why 2 minutes? Because we probably can't get enough heat in anything to hurt anything, YET!

It would be a good idea before one learns how to tune the timing features, to work with a setup we know is good, and do the 2 minute test on it, and get a baseline temp in our head so we know what is safe (I would guess approx 100-110 deg).

That way, if we are testing a new setup, and we do the 2 minute test, and we are at 125-135 deg, then we know we are going to have issues if we run 5 minutes. If we temp good at 2 minutes, run another minute. If temps are still safe, run another.

Basically, if we can run 3 or 4 minutes and keep temps safe, we will more than likely make 5 or 6.

Another thing to note, and this is especially true for those running 17.5 (blinky or open speedo) that is setup for ideal performance, we should be coming off the track at 150 or so at the end of a heat or a main. Even though a 6000mah battery will last 25-30 minutes, you will more than likely overheat the motor if you run it that long. Limit yourself two 6 or 7 minutes of practice and pull off. Let it cool.

That and don't run allot of hot laps. Some places will let you run hot laps for 5 minutes before a run. Run about a minute at first and let the car sit till the start. If you run all 5 minutes of hot laps, you will end up starting the race with a motor already up to our optimum temp. All that will happen the rest of the race is you will heat everything up even more, and it will just start slowing down.

I could be mistaken here, but I'm sure the Viper reps will correct me, I was thinking that a pretty reputable person told me the sensored 4 poles would be out early- mid December?....


Brad

As stated in the title, 13.5. Thanks

Oh sorry.

I run a 10.5 VST and 87/23 with my XXX-SCT, so start with a 87/24 or 87/25

Start with with these settings and use the above gearing. I would start with 0 deg of accel boost, 0 deg of top speed timing and see how everything feels. Do a 2 min temp check to check the gearing, if all is looking good, add some Accel Timing if you need more infield speed, add some Top Speed Timing if you need strait-away speed. Just make one adjustment at a time, and remember to monitor your temps!

Thank you

I'm running the VST 13.5 with a Tekin RS in an SC-R. The can timing is set at 30 degrees and the ESC has 40 degrees of timing. I'm running 24/78 and the motor comes off the track around 150 degrees.

I tried 26/78 but the motor was getting hot (165F+) and power would fall off after 3-4 minutes.

Stevey - see you on Saturday!! Had a good test session down there last night.

Chris - couple different things to try (its like putting a jigsaw puzzle together), Starting RPM- not to low, Throttle Freq, gearing, Timing - sometimes lowering timing actually helps. All different things to try.

Nikkos you look like the person to ask. I just set up my new vtx and all led's show it is functioning correctly. It shows it's binded correctly responding F, R, N all correct. Acknowledged profile. Even used programmer to tweak it, but I have no power to the wheels! Steering there and all wires are done perfectly. I had the wires sodered by a shop because I wanted it to look as nice as everything else I wired so well. Please help troubleshoot. It's very upsetting that an esc that seemed this easy to use is not functioning.
Thanks.

Hey Nikos,

On my SC-R/13.5/Tekin RS setup: This weekend I'm going to try 26/78 with 30 degrees on the can and 25 degrees in the ESC. The ramp I have been using is 5400-20000. I like the speed this gives me over 24/78. Hopefully the lower timing will keep the temps in check.