ezgo downhill speed

[racercdd]

i have a new to me 09 ezgo pds 36v, not lifted, new batteries. the uphill speed isnt as fast as my last cart. it was a lifted 2000 pds. but going down hill my old cart would kick in an engin brake, the new one doesnt. going down hill it feels like its just coasting, if i lift off the throttle it doesnt change speed at all, go back on the throttle and it doesnt speed up at all. seems wierd to me. is that normal?

[JohnnieB]

It depends somewhat on the controller type and what mode it is in, and how steep the hill is.

Stock PDS controller limits the motor's RPM and cuts back on the duty-cycle of the PWM output to the motor when the Max RPM for the PDS mode it is in, is reached and if the motor RPM exceeds the Max RPM for the mode it is in by more than a few percent (IE: Going downhill - with or without the pedal pushed), the controller turns on the regen braking to limit Motor RPM.

As for uphill speeds, it depends on tires height and the condition of the battery pack, if both carts have(had) stock PDS motors and Stock PDS controllers (with the same EZGO part number)

FWIW: EZGO started putting a slightly different controller in PDS carts in late 2008, but I'm not sure if there was any performance difference. (The later controller would shift between PDS modes without cycling the Run/Tow switch. Other than that, I'm not aware of any differences.)

If the 2009 has an aftermarket controller that does not use a motor speed sensor, by careful going downhill WOT (Wide-Open-Throttle), I exploded a stock PDS motor that way.

[HARDWOOD]

Mine is factory everything except 0 ga wires ( all of them ) and a 6" lift with 12/23" tire wheel combo. Downhill it will not run faster than 23 mph.....is that about normal ?

[JohnnieB]

Originally Posted by HARDWOOD

Mine is factory everything except 0 ga wires ( all of them ) and a 6" lift with 12/23" tire wheel combo. Downhill it will not run faster than 23 mph.....is that about normal ?

A PDS controller limits motor RPM to about 4400 on level ground in Freedom mode and not much more than that downhill.

What PDS mode are you running in?

Mathematically, 23" tires will give you a 20% increase in speed on level ground and downhill.

What was the max speed downhill with stock height tires?

Also, measure your tire height. The numbers stamped on the sidewall is very approximate to say the least. (Can vary be an inch or more)

[HARDWOOD]

Freedom Mode.....I have a stock controller and solenoid for now but changing those very soon. I'm taking my motor to PQ this week , I live in Sc and they are only about an hour and a half away. I'm also going to do the 42 volt upgrade and order the combo pack from Scotty. My batteries are a few years old and I never knew anything about charging them properly until very recently so they aren't much. I did a few laps at my shop and its either uphill or down there is no flat land LOL. Up hill was 18mph steady an downhill was 23.

[JohnnieB]

Originally Posted by HARDWOOD

Freedom Mode.....I have a stock controller and solenoid for now but changing those very soon. I'm taking my motor to PQ this week , I live in Sc and they are only about an hour and a half away. I'm also going to do the 42 volt upgrade and order the combo pack from Scotty. My batteries are a few years old and I never knew anything about charging them properly until very recently so they aren't much. I did a few laps at my shop and its either uphill or down there is no flat land LOL. Up hill was 18mph steady an downhill was 23.

Get the Super-Duty (400A continuous/1000A peak) solenoid from Scotty, it works at 36V, 42V and 48V.
It will handle just about any controller, motor and battery pack you're likely to install, unless you go into drag racing.

Ask PQ what the max recommended RPM is for your motor and don't exceed it going downhill.
I explode a stock PDS motor going downhill WOT with a DCX400 running 42V, which took out the controller when it went.

Give me you exact (measured) tire height (or circumference) and I'll tell you how many RPM your motor spins per MPH.
(If they are exactly 23.0", which they most likely aren't, your motor spins at 181.8 RPM per MPH.)

Or you can install a tachometer, using the motor speed sensor as an input.
(I'm in the process of installing one on my cart)

---------
Level ground is a rarity around here also.

[Hecky50]

JohnnieB, that tach sounds like a nice deal. Will you do a write up on it??

[JohnnieB]

Originally Posted by Hecky50

JohnnieB, that tach sounds like a nice deal. Will you do a write up on it??

I'm planning to.

Contrary to what the EZGO manuals say, the output from the speed sensor is 4 pulses per revolution. (Magnet disk does have eight poles, but that is only four pairs of poles, so the output is 4 per rev rather than 8 like the tech writer at EZGO assumed.)

Therefore, a tach set for a V8 ought to show true motor RPM when it is fed by the output from a PDS type speed sensor.

I have an automotive type DMM with an RPM function and used it to measure my motor RPM when I was running a stock PDS controller and motor. Just connected the test leads into the backside of J5 Pins 1 & 2 and I got a RPM reading that matched my calculations for motor RPM vs GPS Speed with the tire height and gear ratio I had.

My DCX controller doesn't use the speed sensor on my motor, nor does it provide power to it, so I have to feed it from a voltage source. Probable 12V from a DC-DC converter and add a pullup resistor for the output. (See Attached)


I've got the stuff, just haven't found the ambition or energy to put it all together.

--------Added------------
The third pic is the Tach I'm using. Stewart-Warner Ultra Shift Light

I'm going to set the amber LEDs to come on at 6,500 RPM, which is the Max recommended RPM for my motor.

[UroGator]

Originally Posted by JohnnieB

I'm planning to.

Contrary to what the EZGO manuals say, the output from the speed sensor is 4 pulses per revolution. (Magnet disk does have eight poles, but that is only four pairs of poles, so the output is 4 per rev rather than 8 like the tech writer at EZGO assumed.)

Therefore, a tach set for a V8 ought to show true motor RPM when it is fed by the output from a PDS type speed sensor.

I have an automotive type DMM with an RPM function and used it to measure my motor RPM when I was running a stock PDS controller and motor. Just connected the test leads into the backside of J5 Pins 1 & 2 and I got a RPM reading that matched my calculations for motor RPM vs GPS Speed with the tire height and gear ratio I had.

My DCX controller doesn't use the speed sensor on my motor, nor does it provide power to it, so I have to feed it from a voltage source. Probable 12V from a DC-DC converter and add a pullup resistor for the output. (See Attached)


I've got the stuff, just haven't found the ambition or energy to put it all together.

--------Added------------
The third pic is the Tach I'm using. Stewart-Warner Ultra Shift Light

I'm going to set the amber LEDs to come on at 6,500 RPM, which is the Max recommended RPM for my motor.

Very nice JohnnieB. Can't wait to see the write up. I am looking to add a tach as well.