30 series torque converter tuning questions

[pghp8ntballer]

Hey everyone, I am new to karts. I understand how the 30 series torque converter driver weights, garter springs, and driven spring changes affect rpm engagement but I want to know what the results of these changes are...

How will it change operation of the kart through hilly/pretty rough terrain?
Is it better to have a higher engagement for these activities or low engagement?

What changes beyond rpm engagement can be expected by switching to cast aluminum driver weights from zinc? Does the engine rev faster, etc?

if larger than stock (+ 3 to 4 inches) diameter tires are in the plans, how would you adjust the torque converter to accommodate for this assuming the stock sprockets are left unchanged?

I'm sorry if the questions aren't clear.

Thanks!

 

[Brianator]

Welcome to the forum!

In order to help you best we can you'll need to give us as much info as possible. Motor plus mods (if any), if governed/ungoverned, tire size (true height), gearing ect. For rough and hilly terrain you want the driven set in the #1 hole, if no numbers on it you want to set it in the hole that holds the most tension on the spring which delays shifting and keeps it in a lower "gear" longer. Chances are you want to keep the driver clutch setup stock which should start to engage at about 2300 rpms. Rarely would you want lower rpm engagement as that will put it well below the torque peak and youd only want to raise the engagement rpm if you have a high rpm motor. Here's the spring/weight chart so you can get a better idea. You can't really compensate for tire size without changing physical gear ratios btw, let us know what you have and we'll move forward

 

[pghp8ntballer]

It’s a bone stock 2012 hammerhead mudhead. 6.5 hp 208cc. Stock knock off 30 series torque converter.

So I know it is governed with a screw at the throttle assembly on the engine and/or at the gas pedal. I highly doubt it’s electronically governed because there isn’t any control modules. How else could it me governed.

I already adjusted the driven spring to the tighter setting and noticed the change in low end torque for the better. Not much but better. Thinking about getting a yellow driven spring.

I will see if I can get the other info today for the sprocket tooth counts and current (and desired) tire sizes.

 

[Brianator]

You can drill a fourth hole fyi. With driven springs keep in mind different ones can be wound different ways and could require the driven to be flipped around which will require you to realign it

 

[pghp8ntballer]

So this kart has:

10 and 60 tooth sprockets
420 chain
6” driven pulley
Tires 16” stock but current diameter with wear is 14-⅛”
Looking to put 19” rear tires in it, not sure of actual tire diameter since I haven’t bought them yet.

Anything else?

 

[bob58o]

Ideally you want the driver unit to engage at peak TQ (2000-2300 RPM is fine for a stock engine).
And you want to be shifting into “highest gear” / overdrive as the RPMs climb to peak HP. If peak HP is at 4800 rpm, you don’t really want to be fully shifted until you get to 4800 RPM. If the engine is governed to 3600 RPM, then you want the shift out to occur near, but at less than 3600 RPMs.

A camera app with gps speedo pointed at a tachometer while you do some testing could possibly help you see how and when it is shifting.

Great info here about tuning these types of CVTs with these types of engines.
https://www.cogentoa.com/article/10.1080/23311916.2017.1398299.pdf

 

[Brianator]

Someone else should chime with their opinion but you MAY be okay. I have a 6.5hp with a 30series, a 5.4:1 gear ratio (not ideal) and 19" tires, I can tell I'm stressing the belt out a bit and the TC gets hot fairly quickly but so far its holding up. Check out this live app (KartCalculator - app.kartcalc.net) it will take weight, gearing, rpm and tire size into account. I think you'll have better overall results with a larger rear sprocket, I wish I could get larger than a 54 tooth on my machine.

 

[pghp8ntballer]

Brianator: thanks for the real world info. I was looking on BMI karts last yesterday and can’t find any sprocket with the same bolt pattern, so I might be stuck with 60 tooth. My small sprocket doesn’t quite match to the comet type C ones with the ¼” hubs as shown in the product pics on bmi karts website. The hubs on my small sprocket are about 3/16”, but I guess I could shim it if I wanted different sprockets to change gearing.

What gear ratio is good for hills? The higher the better? Trade off being lower top speed?

Bob58o: I found the manual to my engine: max governed rpm is 3850.

I did some reading on here last night about disabling/removing the governor. I understand the do’s and don’ts and dangers.
But I have some questions: what exactly gets removed? Just the governor weights? The entire linkage assembly through the case? How does the linkage hole get sealed if it’s removed? How does removing the governor affect the oil splasher? Is there a way to then electronically limit rpms?

 

[Brianator]

Lower gear ratio is better for hills, the confusing part is that a higher number is actually a lower ratio (ie 6:1 is lower than 5.4:1). I couldn't find a sprocket either, I ended up getting a 40 chain "weld on" sprocket, enlarged the center hole with a hole saw and drilled mounting holes. Fyi 40 and 420 are the same pitch.

You need to go inside the motor to remove the plastic gear/ weights and rod. Most guys tap threads and install a bolt, I suppose you could JB weld it shut also. There are posts going through the whole process and videos on YouTube as well. Removing the governor shouldn't affect the oil splasher