Optimal T4 Parameters for Maximum Speed

Hi All,

I’m running a 2006 e4 with a T4 motor controller and have been able to change some of the settings to increase the speed. I first increased the top speed regulation point (function 21) up to 255, tested it and increased the speed 2ish mph. I then decreased the rolling radius (function 13) down to the lowest it would go without throwing the “error 14” which was 085. With this change I was able to get up to 33-34mph GPS.

Reading the other forums it seems like the only other thing I could change to increase speed is gear ratio (function 16) but reading a post from @LithiumGods it sounds like 13 and 16 are correlated so when I tried to move this value down even 1 point it threw the “14 error”.

I’m running 110 Volts and know I have the power to keep going up but I feel the vehicle cut off my speed, and I see the spedo get to the top mph and cut me off…

Reading the forums it sounds like I may be able to get a little more on the top end by changing the field weakening, but I’m not super stoked about that because it sounds like I would lose some power and I live in a hilly area, so my question is: is there any other parameters I could change to increase my top speed or do I just need to buy a MM?

All of your assumptions are correct . Weakening field makes a shunt motor turn higher rpm’s but thats not your problem . The problem is you have a 12.44 gear ratio . Once your speedo hits 26 mph it wont go any faster , the controller starts slowing you down . More power or rpm;s wont help . There are a few things you can do . Install taller Tires so you increase your rolling diameter and get more distance per rpm . Change your gear box to 10.35 ratio for more top speed or install a magic magnet so that the speedo doesn’t read 26 mph .

Once you stop the controller from slowing you down you can weaken field for even more rpm if needed . But at this point you are running more rpm’s than your motor was designed for . I dont know where the upper limit is before It has a problem .

@LithiumGods thanks for the response this is very helpful, and I was kind of thinking this was the case.

Do you know if there are any dangers of running the motor at this high of RPM? I would rather go the more inexpensive route to just get a MM, but if there is a chance you think it would damage the motors maybe I should just get bigger tires? Let me know what you think and thanks for the help.


I have never seen a motor damaged from high rpm . Oldhouseboater says he has . Its your call .

My 2009 with a T4 controller limits me to 26 indicated which is 27 via GPS with my slightly larger tires. I’d like to get just a few more MPH (30?). Is the magic magnet the way to go? What do I need to buy and do to program the controller as mentioned in this post?



Is it holding back at 26mph?

Yes, Inwo. It takes off quick but a limiter seems to kick in at 26.

Magic Magnet device romoves that limit.

Great! Thanks, Inwo.

I’ve just edited all my questions out after researching the forum. Do you have any Magic Magnets in stock? Will PayPal asap.

Thanks again!


1 Like

Yes, $135 with a note.

David. Is this the same thing? This one looks programmable.

Yes, a scam site copying a very old version of my device. I am the inventor and only builder.
Only authorized re-seller is R4F website.

Ahh. Got it. Is the latest one programmable with pinouts or does it just half the speedometer effectively doubling the speed?

Is there any risk of burning out the motor by going too fast or will 72 volts just not be able to push it?

Thanks for your patience!


It can be set for any ratio in 16ths up to 1/2.
Limiting speed to were you feel comfortable.
Hot rodding has risks. I have not personally seen a motor grenade from over speed. I CAN see that wot down hill, set to 50mph (1/2), could certainly blow up commutator.
Default setting is 25/40 ratio. For speedometer correction to kph. 0-40mph displayed range.

David. I really like that the ratios can be set to our comfort zone. I’m assuming there are clear pinout instructions for nitwits such as myself.

I sent the PayPal a few moments ago and am looking forward to not holding up traffic in our gated community. :wink:

Thanks for all your help!


No instructions. Just plug it in.
I will explain settings, or go to Ride4Fun website.
He calls it calibrator.

Hi David- I’m biting at the bit to get this MM installed. Do you have a tracking number so I can be looking for it?



Not showing a payment under that name.

No worries, David. It just came in shortly after I posted. (I ordered it from my wife’s account, “Something Borrowed”.)

For anyone that wants to know, I just installed David’s (Inwo’s) Magic Magnet and it works great! I’m thrilled! Though you may see others trying to pass theirs off as the original, don’t buy it. It’s scamalicious.

Results: My 2009 e2 used to limit itself to 26 indicated (27mph actual due to larger tires). Now it cruises at a top speed of 33 mph (GPS verified) with an occasional 35 mph on a very slight downslope. (I don’t want it going any faster than 35 so I would take my foot off the accelerator as necessary on a major downslope.)

Also, David’s tip to correct the speedometer by clicking it over to Kilometers works perfectly. The numbers on my GPS and the speedometer were always within 1 of each other after doing so. Just ignore that your odometer is doubled and it says “kph”. No need to get into the controller IMO.

I didn’t see any way to adjust the speeds incrementally (no pinouts) but that is moot/unnecessary since my 5HP motor maxes out long before I could possibly overspeed it.

Bottom line, this was a very inexpensive way to get an additional 6-8 mph by simply unplugging the motor cable and inserting the Magic Magnet in between using two fool-proof plugs.

Thanks for developing this, David. It is a Godsend!



Yrah, Daves an alright guy.