I have a 2005 GEM e-4 car with a 5 hp GE, standard motor on it. I want to upgrade to a 7.5 hp motor. I understand that the GE motor has a 4 pulse tachometer on it and the 7.5 hp motor (ride 4 fun) has a 2 pulse tach on it. What I don’t understand is as both motors have 72 volt armatures in them and the GE gives 4100 rpm at 72 volts and 7.5 gives 6000 rpm at 72 volts how does the controller deal with the tach information. The tach must provide information to the controller on when to go into regenerative mode. If the armature is at full voltage (full speed of 25mph) then the only way the motor could overspeed is by an overhauling load (like going downhill). What is the relationship between the tachometer and the motor’s speed? Is the motor speed regulated by tach feedback? or is it only used as spillover information for regen to start. Given the 2 pulse per rev tach the feedback / regeneration would only come on at 12,000 rpm which is way over the base speed (72volts / 6,000 rpm) of the motor. I assume there is no field regulator used on these motors, all speed is by armature voltage control. So, does the controller even need a tach feedback with the 7.5 hp motor? It doesn’t provide any overspeed protection. I also understand the controller cannot be reprogrammed to accept the 2 pulse / rev tach. Finally, a 5 hp at 4100 rpm has the same torque and a 7.5 hp at 6,000 rpm. Other than speed the 7.5 hp motor doesn’t bring any more torque (power) to the application. Sorry for the length of this, just trying to understand. What am I missing? Thanks, Gerry
The reason the R4F has a 2 pole tach for GE T3 and T4 installations is to enable it to obtain Cart speeds greater than 25 MPH which is hard programmed into these controller models. If you install a 2 pole magnet in the stock motor it too would be capable of higher speeds. (magnets are available) The downside is that 2005 to 2013 GEM cars have a 12.44 gear box and the stock motor wont take high RPM’s that many owners need to meet their top speed goals. This is one of the reasons Polaris went back to the 10.35 box in 2014.The R4F motor lives at up to 7000 RPM’s. The smart thing to do is swap out the 12.44 gearbox for a 10,35 or even better an 8.9 to 1. With these gear boxes you can run 35 MPH with a stock motor,
A 2 pole magnet reads at 1/2 the MPH on the speedometer. However R4F will rebuild your controller to read real speed for a charge. Control settings for top speed, ,regen functions ,etc. require different parameters to accomodate the 2 pole magnet. R4F includes reprogramming with the motor sale.
My Cart has an 8.9 gear box and a R4F 7.5 motor and easily exceeds 40 MPH without any strain. I have it programmed for 35 MPH to retain reasonable range.
Hope this answers some of your questions.
It was my understanding that the 2005 car had a 10.35 box in it. I have the stock 12 inch wheels which gives 66" circumference. If you do the math at 25 mph this gives 4,100 rpm of the motor which the GE is. I assume that they chose a gear ratio that gave speed of 25mph at the base speed of the motor (4,100 rpm). I spoke to R4F and they didn’t mention reprogramming my controller, in fact they said it couldn’t be done. I still don’t understand how they can get more “power” out of their 7.5@6000 (or 7000) when a 5hp at 4,100 has the same torque. The car seems torque limited, on any significant grade (maybe 10%) it chugs along at 20 mph. Does this make sense to you?
Mid 2002 thru had 10.35 gear box. 2005 went to 12.44 when they updated the car design. are you sure your machine is a 2005?
The controller can easily be reprogrammed for more power. To get more speed you have to use a 2 pole magnet to fool the controller.
T1 and T2 controllers in the older machines could also be programmed for more speed. Didn’t need 2 pole magnet.
These cars are programmed for flat land. They are programmed to provide 25 MPH with as much range as they can possible get. To get 25 MPH in hills more available amps must be programmed and this eats into range. You would be amazed how much performance you can get out of a 5HP motor. With your gear box it can be a climbing fool.
Below is a chart to show the relationship between motor RPM and gearbox ratio. You will note that 12.44 gears exceed Motor Manufacturers RPM Rating at 25 MPH.
Higher ratio more power/torque Lower Ratio more speed less power/torque
Motor RPM with stock 21 1/2 inch diameter tires
… … 25 MPH 30 MPH 40 MPH
8.9 GEAR BOX …3480… 4176… 5568
10.35 GEAR BOX …4047… 4856… 6475
12.44 GEAR BOX …4864… 5837… 7783
14.76 GEAR BOX …5771… 6926… 9235
My GEM car is a 2005 model. I have the original GEM factory sales document . It says it has a Dana Spicer Differfential. Originally sold on 7/21/2005.
Some of the components inside the GEM car have manufactured dates on them. All of the components were manufactured in 2005. What do you do if R4F says the controller can’t be reprogrammed? What do you do then?
Go with Marlon at MZMotorSports He has been a forum contributor for years.
OK will do, thank you.
hi
2006 also has 10,35
12,44 comes in 2007
2006 Parts book has 12.44 part # 0613-00634
2005/2006 parts book has 10.35 #0613 00249 12.44 #0613 00863 14.76 #0613 00873
I’ve reprogrammed a few gems i’m pretty sure one was a 2005 (could have been a 2006) reprogramming shouldn’t be a problem . there is 2 parts to this you need to understand . 1st is power . you can program your controller to send more power to your 5hp easily . this is wha the factory does with the 6 passenger that has the the 5hp motor . that’s what I did with my cart , changed the parameter to the same as a 6 passenger . it well accelerate faster and climb better on hills . but this well not increase top speed . the controller simply calculates your speed . the controller takes gear ratio , rolling radius , and motor rpm and calculates speed , if its over 25mph it pulls out power . that’s it . so if you change any one of the parameters you can fool your cart into going faster . your speedo wont show over 25mph but with a gps you can see your real speed.
these are you choices :
put in an aftermarket motor with a 2 pole sensor, instead of the factory 4 pole sensor . this only sends half as many pulses to your controller . this makes it think the motor is turning at half the speed it really is . your speedo well now read 1/2 of what your real speed is. unfortunately i’m unaware of anyone that makes a 2 pole sensor for the stock 5hp motor
2nd. go into your controller and change either the gear ratio input or the rolling radius . ex: tell it your gear ratio is 20% higher then it is . now when your speedo says 25 your really going 30 . you can also accomplish part of this by just adding taller tires to your cart .
if you do have the 10.35 gear box , you can reprogram your controller to 30mph and be turning the same motor rpm as a stock cart that came with the 12.44 @ 25mph ( see rodneys chart above)
[quote=kinghappy;25854]I’ve reprogrammed a few gems i’m pretty sure one was a 2005 (could have been a 2006) reprogramming shouldn’t be a problem . there is 2 parts to this you need to understand . 1st is power . you can program your controller to send more power to your 5hp easily . this is wha the factory does with the 6 passenger that has the the 5hp motor . that’s what I did with my cart , changed the parameter to the same as a 6 passenger . it well accelerate faster and climb better on hills . but this well not increase top speed . the controller simply calculates your speed . the controller takes gear ratio , rolling radius , and motor rpm and calculates speed , if its over 25mph it pulls out power . that’s it . so if you change any one of the parameters you can fool your cart into going faster . your speedo wont show over 25mph but with a gps you can see your real speed.
these are you choices :
put in an aftermarket motor with a 2 pole sensor, instead of the factory 4 pole sensor . this only sends half as many pulses to your controller . this makes it think the motor is turning at half the speed it really is . your speedo well now read 1/2 of what your real speed is. unfortunately i’m unaware of anyone that makes a 2 pole sensor for the stock 5hp motor
2nd. go into your controller and change either the gear ratio input or the rolling radius . ex: tell it your gear ratio is 20% higher then it is . now when your speedo says 25 your really going 30 . you can also accomplish part of this by just adding taller tires to your cart .
if you do have the 10.35 gear box , you can reprogram your controller to 30mph and be turning the same motor rpm as a stock cart that came with the 12.44 @ 25mph ( see rodneys chart above)[/quote]
Not that I would try it but how does one know if his controller can be reprogrammed and how does one go about reprogramming it. I like your solution about fooling the controller with the gear ratio.
I bought the software and cable and learned myself . the software is not the easiest thing to use , so it took me a while to figure it out . marlon on this forum sells the software and does phone support with it. there is probably a few individuals on this forum that you could probably send your controller to and for a fee have it done . i’m not set up to do it out of a cart . I only do them while they are installed . maybe marlon himself would do it for you .