Got emp motor, and 650 amp alltrax controller wired up and it only runs 8mph?

[Jeffreynmandy]

I have a earlier thread about a emp motor. The installer got all my parts working, but it's only running slow at about 8 mph. It's a alltrax controller, emp motor, solenoid, and cables upgraded, with a upgrade to 48v.

I started with used parts going on a 96 ezgo series cart.

He said he's going to check the ITS in the morning, if it's not that, it would have to be the motor or controller.


Does any other knowleable people have any ideas on what it could be? It did seem to run a little slow before starting the work. But close to stock 11 mph on flat and 7-8 on hills.

I just don't want to start putting more into it than what it's worth. The guy knows his stuff, so I trust him on it.

Any help is appreciated.

[JohnnieB]

First of all, I'd call EMP and find out what the performance expectations are for the motor you have at the voltage being applied to it turning tire the diameter of the ones on the cart.

While on the phone, I'd also verify the 2-speed EMP motor is jumpered properly for the speed mode.

Checking for a 100% throttle signal to an Alltrax controller is easy.
Jack the rear tires off the ground (put on jackstands) and floor the pedal.
If the Green LED turn to Yellow, the controller is wide open and not in current limiting.

[Jeffreynmandy]

As soon as i get the cart back, I'll call emp and alltrax and get as much help as I can. Hopefully he'll have it figured out today.

It's a good sign everything is somewhat working. I'm hoping it's just a wiring or controller setting.

[Jeffreynmandy]

It was a pinched wire going to the ITS throttle. Hopefully I'll get to test it out later today.

I should have just not worried about it, i knew he could handle it.

I was worried to death because I only payed $400 to strip a wrecked cart with all that stuff in it. Charger and everything.

[chloe]

Sounds like he located the culprit. I think you're going to like that motor. With 48 volts you should see about 26, + or -, depending upon the other drive line components. It's not a pure race motor. But it is a strong, dependable unit

[Jeffreynmandy]

The cart goes pretty good. With me and me and my son on it, about 370lbs it went about 20mph up a hill that it would only go 7-8mph on before.

It runs 20-22 on flat, and out on the smooth road with a very slight downhill I hit 26mph. It gets scary and seems to get more unstable after that.


This is with stock 18" tires, they only had about 20psi in them. I may get some 20.5 " tires and 12" wheels, and see what that does to the mph.

as of now I have $2250 in it with new Trojans. I still have a charger, motor and controller I can sell. I can't get any better considering the the parts I have in it.


$850 golf cart
$800 6, 8v Trojans
$400 emp motor, 650 amp alltrax, 2awg cables
$200 installation.

[cgtech]

Do not do those "top speed down hill" runs. Your flat-ground top speed should be considered your down-hill top speed. You can overspeed and 'splode your new toy's motor (literally blow the windings outward from the center of the motor).

[JohnnieB]

If it is doing 22 MPH with 18" tires on level ground, it will do about 25 MPH on level ground with 20.5" tires.

That is a 14% increase in speed, but it is also a 12% loss in torque, so it won't accelerate quite as fast as it now does and it will slow down a bit more going uphill.

If possible, avoid low pressure tires (Especially those with a maximum inflation pressure of 10 PSI or less). Even though they are taller than 18", they might slow your cart down instead of speeding it up. Stick with tire whose max inflation pressure is 20 PSI or greater and you'll get closer to the theoretical speed increase.

Also, when you get your new tires, physically measure their height. The numbers embossed on the sidewall is very approximate at best. IE: My Carlisle Turf Master tires say 18 x 8.50 - 8 on the sidewalls, Carlisle lists a MTD (mounted Tire Diameter) of 18.3" for them on their website, but they only measure 17.04" on the cart.

Once you know the true tire height and the differential gear ratio, you can calculate the motor RPM vs MPH. Stock gears for a 1996 TXT or Medalist, is 12.44:1.

Having exploded a motor (picture attached), I agree with CG about "top speed downhill runs".
What he didn't mention was that exploding a motor tends to take out the controller also, mine did.

You'll have to check with EMP for the max recommended motor RPM, but it is probable no more than 6500RPM, which is 28.0 MPH on 18' tires and 31.9 MPH on 20.5" tires.

As you have already noticed, a short wheelbase, narrow tracked vehicle with a high center of gravity isn't very stable at speeds over about 20 MPH. What you may not have noticed (yet) is mechanical brakes on the rear wheels only, doesn't provide much stopping power at speeds over about 20 MPH.

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Overall, it sounds like you found a nice setup for you and your family. Hvae fun and be safe.

[Jeffreynmandy]

Is there an rpm gauge available for an electric motor? Since I'm building a speed cart, I may try to find a buyer for my emp torque/speed motor. It would be great for someone with a hunting cart like it came out of.


I'm in no hurry and if it doesn't sell that's ok too. It's plenty fast. But if it does, what's a good speed motor to consider with my setup? D&D or plum quick? I'm partial to plum quick, from my home state.

But if one or the other will work better for my setup, I'm open to it. I read the thread on the speed motor with high speed gears, and leads me to beleive they can make a pretty stout motor.


For now I'm content with 25mph, I'd have to look into brakes, tighter steering, and stability upgrades to go much faster.

I don't want to risk blowing the motor. I'll call emp and try to get the specifics, but they don't like that I'm running 48v on a 36v motor. It came out of the other cart that way. And it looks like it was several years old. So I should be ok for now.

[JohnnieB]

You mean RPM gauge as in Tachometer?

Series wound motors don't typically have a speed sensor installed, but there might be some out there. I e-mailed D&D and asked if they were available on their motors, so I might hear something back in the next day or so.

In general terms, the speed sensors are Hall effect devices placed close to a magnetic disk attached to the motor shaft. If the disk has four pairs of poles (8 poles total), the sensor puts out four pulses per shaft revolution, which happily coincides with the pulse rate put out by a V8 car engine, so tachometers made for cars that work with low voltage pulses, will work on a golf cart.

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From what I understand, Plum Quick rewinds stock motors for more low end torque, or more high end torque (speed), or a bit more of both, and the end product still has about the same heat dissipating capabilities of a stock motor. Of course the heat dissipation of a stock motor is likely to be sufficient unless you are pushing the performance envelope with something like a high speed motor coupled with high speed gears and turning tall tires.

A couple guys that frequent the BGW forum are using AMD 7126 motors and love them.

Also, contact Scotty at Carts unlimited:http://www.cartsunlimited.net/Home_Page.html
He is pretty good at figuring out what motor is best for a cart.
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The RPM you are turning with your setup on level ground isn't dangerous for the motor. Just don't be going down steep hills with your foot on the floor.