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Old 02-19-2009, 04:55 AM   #1
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Default Gearing Vs Timming

Hi All,

I have just installed a new 17.5 in a car of mine and am in the process of sorting out the gearing.

What is the difference between increasing the timming and increasing the size of the pinion?

Is keeping the pinion small and increasing the timming going to give me more speed without effecting the low end accelaration?


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Old 02-19-2009, 06:09 AM   #2
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I believe if you increase the timing and keep the pinion the same size, you will get slower acceleration and increased speed. If you decrease the timing and keep same pinion, you will get more acceleration and less speed. If you increase the timing even more, you will have to drop pinion teeth. If I am wrong anyone, please correct me!
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Old 02-19-2009, 07:20 AM   #3
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Increase timing more low end and top end. Decrease the timing less top and bottom. Decrease pinion more punch less top end. Increase pinion more top end less punch. Increase timing more heat.
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Old 02-19-2009, 07:26 AM   #4
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I see, so the thing to do would be to set your gearing, then increase the timing as much as you can without overheating the motor.

Interesting.... I'll have to mess around with that!
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Old 02-19-2009, 08:04 AM   #5
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Increase timing more low end and top end. Decrease the timing less top and bottom. Decrease pinion more punch less top end. Increase pinion more top end less punch. Increase timing more heat.
How could increasing the timing increase both low end and top end? Everything is a trade off, where is the trade off increasing the timing? Wouldn't increasing the timing increase either top or low end, but not both?

If increasing the timing increases the KV for the same number of winds in the motor, to me that means it is increasing the overall power of the motor at expense of the torque.
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Old 02-19-2009, 08:18 AM   #6
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Quote:
Originally Posted by mattnin View Post
How could increasing the timing increase both low end and top end? Everything is a trade off, where is the trade off increasing the timing? Wouldn't increasing the timing increase either top or low end, but not both?

If increasing the timing increases the KV for the same number of winds in the motor, to me that means it is increasing the overall power of the motor at expense of the torque.
Yeah thats what i thought... you can either get torque or speed and i thought you cant increase both by timing
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Old 02-19-2009, 08:24 AM   #7
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Quote:
Originally Posted by mattnin View Post
How could increasing the timing increase both low end and top end? Everything is a trade off, where is the trade off increasing the timing? Wouldn't increasing the timing increase either top or low end, but not both?

If increasing the timing increases the KV for the same number of winds in the motor, to me that means it is increasing the overall power of the motor at expense of the torque.
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Yeah thats what i thought... you can either get torque or speed and i thought you cant increase both by timing
In my 20 years you can not or have ever been able to get more rpm AND torque by adjusting the timing....You DON'T get BOTH!!!
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Old 02-19-2009, 08:29 AM   #8
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Electric motors have a very unique characteristic...they supply maximum torque at lowest rpm. In electrical engineering terms it is expressed as infinite torque at zero rpms. You will not lose bottom end torque until you cross a threshold of advanced timing at which point the you short out the motor.
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Old 02-19-2009, 09:36 AM   #9
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simply if you increase timing you get more top end. decreasing the timing has the opposite effect, but be warned: do not go past zero degrees of timing. Thats called retarding the timing, and no one has ever done that. all the motor manufacturers say not to do it.
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Old 02-19-2009, 10:20 AM   #10
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You can't have it all so to speak. Increasing the timing will increase the overall rpm's of the motor. This will require you to have gearing slighly lower than a setup with less timing to achieve the same bottom end feel while being able to use the higher rpm's on the top end.

In general a motor that has more timing has less torque in theory. 17.5's and 21.5's prefer quite a bit of timing to maximize their use in our setups. Huge pinions are still required but as someone else mentioned, there is a threshold of diminshing return.

I recomend setting your motor at half of it's available timing setting, gear up until you find the maximum speed you can get WITHOUT overheating the motor. Than increase timing and reduce gearing in small incriments.

In general a good place to start on a Tekin for example is 20 on the motor geared for your track and motor temps. This gives you a few more degrees to play with to increase top end should that be the only thing you're lacking.

The best performance will be found with a good balance of torque and rpm's. Track size and layout will affect this setup as well.
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Old 02-19-2009, 12:26 PM   #11
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Cheers for the feed back.

I've got the timming set to 0 at the moment and the car, whilst having good accelaration, lacks top end speed. I'm using the same gearing that I was when using a 27T brushed.

Randy, that helps alot. I just bought a Venom ESC and motor, the programming card that came with the ESC had timming set to 15 degrees by default, I set it back to 0 initially.

The motor is running fairly cool, maxing out at 110 fahrenheit after 5 minutes on a hot day (with no heat sink). I'll start to move the timing up and see how it goes.

Does anyone know how the programming card manages to alter timming without having to physically adjust the motor?
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Old 02-20-2009, 07:37 AM   #12
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if you are running the same gear ratio u were running with the 27T, your car will be way undergeared, you need to gear the car up, if its a 2wd, you need an fdr around 5.0.

As for timing/gearing, this is an excellent question, i've been mucking around with my timing and gearing, there are a lot of theories going around, and that makes sense because theres a bunch of motor/esc combos, some with motor timing, some with esc timing, some with both, it doesnt seem to matter, i run the losi system and it only has 0-8 deg timing adjustment on the esc, no motor timing, but its easily as quick as any of the other motors out there, my experience is that timing helps a little but top end speed is a bit of a fuzzy term, top end speed could refer to rpm, my testing has shown that on my system, anything above 4 deg timing nets no rpm gain, with the 17.5s they get hot easily, and it doesnt seem to be as much of a black art as it could be, you're plan sounds right, you need to find the gear ratio first and keep the timing lower, you are best to creep up on it all, and keep an eye on temps, the point where you go up a pinion and the car doesnt go any faster is the limit of ur gearing because your motor doesnt have enough power to overcome the weight of the car to reach max rpm, so then try increase the timing, and see if the motor pulls it through without getting too hot, but guideline fdrs are 2wd 5.0, 4wd 5.2, truck 6.2
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