How to make a TC shift into overdrive faster?

[metalthrashinman]

My GTC Tav2 30-100 seems to stick in the 'mid range' position for a longer time than I think that it should. I am trying to figure out how to get it to shift into 'high overdrive' sooner. Any suggestions? Driven spring tension settings? I have the driven spring in hole #1 right now, which is the least amount of tension (GTC does not number the holes, but I am comparing it to a Comet one that I have on another kart). When it does shift into 'high overdrive', it fees like a turbo kicking in. The kart TAKES OFF! I have plenty of smooth initial acceleration, then this pause in mid range, then the shift to high overdrive. Can't I make it shift quicker somehow?

It is very new with about 20 hours of use on it. I have cleaned it and put new belts on it...

I have a 9 tooth front sprocket, 54 tooth rear, #40 chain, 18" tires, 9hp Subie.

Thanks.

 

[redsox985]

I believe you can do that by putting the driven spring in the 3rd hole. This makes the whole unit engage at lower rpms. Blaz, am I correct?

 

[Blazkowiez]

I think the main issue here is the 6" driven instead of 7". The torque converter is working very hard with this ratio, its doing better than it was with a 10t and 48t main sprocket but it still needs time to catch its breath so to speak when driving.

Basically I feel that the clutch might be working as hard as it can in this circumstance.

 

[metalthrashinman]

I think the main issue here is the 6" driven instead of 7". The torque converter is working very hard with this ratio, its doing better than it was with a 10t and 48t main sprocket but it still needs time to catch its breath so to speak when driving.

Basically I feel that the clutch might be working as hard as it can in this circumstance.

Solution is?

I guess it would not be that hard for me to try the #3 position, but I was hoping that I would get some insight before taking it apart again...

Or do I need an 8 tooth front sprocket?

I really do appreciate everyone's help here.

 

[jr dragster T]

If you want overdrive to come on faster you want the spring in say #1 or 2. The tighter the secondary spring is, The later it opens (shifts)

 

[metalthrashinman]

If you want overdrive to come on faster you want the spring in say #1 or 2. The tighter the secondary spring is, The later it opens (shifts)

That is what I thought... Wouldn't MORE spring tension hold the belt on top of the driven longer therefore slowing down the shifting process? In my opinion, the driver would need to work harder to pull the belt up to the top of it's capacity when the driven is pulling harder against it with more tension. Correct?

Is my gear ratio still too much for the TC to handle? Will I gain the desired shifting with an 8 tooth front? Or should I look into the possibility of installing a 7" driven?

 

[modelengineer]

Why do you want it to change earlier? You will get the best acceleration if the engine is kept close to the point of maximum torque for as long as possible.

 

[redsox985]

If you want overdrive to come on faster you want the spring in say #1 or 2. The tighter the secondary spring is, The later it opens (shifts)

This is what I thought too but Blaz had just said 1 gives the latest engagement. It doesn't make sense, though, that 1 would because 3 would be the most tension and toughest to open IMO.

 

[metalthrashinman]

Why do you want it to change earlier? You will get the best acceleration if the engine is kept close to the point of maximum torque for as long as possible.

I have plenty of torque and acceleration. The kart will drift sideways, spin the rear tires with ease, and takes off like mad. It just seems to hesitate and then kick in to overdrive holding back the awesome high speed it is capable of. It's the hesitation that I wish to eliminate...

 

[metalthrashinman]

Maybe I just need to try #3 and see what happens...

 

[Blazkowiez]

My point was that these clutches are not designed for higher horsepower, they are amazing with 4-8hp engines. When you go onto larger engines like what you have they have considerable trouble operating at optimum efficiency which is most likely what you are having trouble with. I really don't care what GTC is telling people, these clutches are not made for larger engines, they'll work but it just wont be the same.

If you switch to at 8t sprocket you are just changing the gear ratio again and will gain even more torque and power which is not really what you are after.

 

[metalthrashinman]

My point was that these clutches are not designed for higher horsepower.

I completely agree with that. I cannot believe that they get away with misrepresenting their product. I NEVER would have bought it for this application knowing what I know now.

When you go onto larger engines like what you have they have considerable trouble operating at optimum deficiency which is most likely what you are having trouble with.

I think you meant 'efficiency' -- 'deficiency' is a lack of something... Sorry, my English pet peeve again..., sorry.

I really don't care what GTC is telling people, these clutches are not made for larger engines, they'll work but it just wont be the same.

I agree, obviously you can tell that by now...

If you switch to at 8t sprocket you are just changing the gear ratio again and will gain even more torque and power which is not really what you are after.

I understand that, but am looking to stop burning belts AND maintain as much top speed as I can. The 9t did not seem to lower my top speed due to the fact that the TC shifts better now. Maybe the 8t will make it work even better?

Other solutions? 40 series, maybe? I appreciate your responses, but you keep identifying my problem without offering any solutions.

We're still buds, though -- in my book.

 

[Blazkowiez]

I edited my post for the "efficiency" thing, I was writing a quick response in the middle of answering calls at the shop, don't expect all of my posts to be grammatically correct. History was my major in college, I can write my papers, and they will have flow but I always needed to bribe people to check them for me.

My only solution seems to be a series 40 torque converter, I didn't suggest this at first given the amount you've spent so far and the difficulty to find series 40 driven clutches online, drive clutches are plentiful but driven clutches seem much more rare. Series 40 should be just fine up through 18hp according to what Comet was saying during production, and I've seen them do well on GX390's running 5k rpm.

This is not saying that the clutches you have in position are worthless, they will be fantastically strong on many karts and impressive on mini-bike applications.

Price-wise this may be a better option given a series 40 belt can last 2-3 years of average riding versus 7 months on series 30. These lifespan estimates are given proper maintenance of clutches, semi level terrain, and reasonable gear ratios.

Was that better? I'll start checking you for comma splices next time homie g! Understand that all of my posts are not aimed at trying to sell people parts that I feel will make their item work the best. I am trying to give people suggestions or advice given their situation thinking that they have very little to spend.

 

[metalthrashinman]

 

[metalthrashinman]

Okay then... What makes a 40 able to handle more hp? Is it stronger springs? I know that the belt is symmetrical on a 40 as opposed to asymmetrical on the 30, but I'm sure that cannot be the only difference. Wouldn't stronger springs make the TC shift even slower? Again, please pardon my ignorance.

If I was to look into getting a 40 series, would I be able to use the same mounting plate that the 30 came with; or would another plate be necessary?

I also know that the driven 40's come in 6" and 7". Given my application, which do you recommend? I know you mentioned the 7" above knowing that I have the 30, and I understand why; but would the same recommendation hold true in the 40 series considering my gear ratio and hp?

 

[Blazkowiez]

The entire assembly is different. While the driven clutches may look similar, aside from size, the drive clutches are completely different beasts. Within the drive clutch you may remember series 30 had 2 extension springs which given action through centrifugal force would expand causing the 2 internal weight packs to ride higher on the inside of the clutch changing the gearing on the drive.

Within series 40 you will have 3 separate extension springs (much much stiffer) springs which hold rollers that drive up their own channels to create a similar motion though this requires much more force to operate which is why lower horsepower engines have trouble using series 40 torque converters.

The only belt difference is the width. Remember that series 20 and cat 88 are both symmetrical systems but are designed to hold a lower horsepower.

Questions are a good thing man, this is how we get things right. Keep asking any questions you have until you're sure this is the route you want to take.

Can you show me a 6" driven on series 40? I can't remember seeing anything but 7"...

I hope that helped a bit more.

 

[metalthrashinman]

Thanks, that makes sense.

No, I have never seen a 6" 40 series driven come to think of it... 7 1/2" is all I can find. I see that it WAS made with a 5/8" bore. Does that mean that if I can find one, I can use the 30 series mounting plate; or will it be too weak?

Do you think that a 40 will make my kart faster??

 

[Blazkowiez]

The plate shouldn't physically be able to fit the series 40 assembly to my knowledge. I believe you will be needing to construct a jack-shaft assembly or a different mounting plate where the assembly is built in.

It very well might make your kart go faster as it has the ability to transfer power more efficiently, think of how a 440 might act if someone tried to use a 904 torqueflite instead of a 727.

 

[metalthrashinman]

I see your point, but I am confused about hp vs. gearing vs. rpm.
Couldn't a 30 series handle 9 hp if it was geared with small tires, small front and a very large rear sprocket? Isn't the stress on the TC directly related to gearing vs. weight thereby meaning that the hp is irrelevant because rpm speed is similar on lower hp engines? Isn't rpm how fast the crankshaft spins, and hp is the power available behind the rpms giving you the ability to change the gearing to make the kart faster (unless the TC could not handle the gear ratio)?

 

[Kaptain Krunch]

Hp isn't really a real measurement. Hp = Torque x rpm/5252

Horsepower sells cars, torque wins races. Horsepower is just an easier way of understanding how much power an engine has

when it comes to industrial engines, they are all governed at around 3600rpm, so that doesn't matter. However the higher torque in a larger engine will simply wear out the clutches and belts quicker. I personally wouldn't worry about using one rated for 8hp on a 9hp engine.