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Author Topic: Getting the best out of you Torque Converter  (Read 302 times)

Adrian

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Getting the best out of you Torque Converter
« on: 14 September 2021, 12:08:42 pm »
I guess we all install  the torque converter (T/C) straight out of the box after spending some time figuring out the best position in which to bolt it to the engine for our application.
We try to figure out the best gearing ratios and leave it at that but Bill Carter in the US CycleKart newletter has just posted the most interesting little appetite wetter I have seen for a while. It's on tuning the T/C to get the best out of it for your Kart given its weight, your weight, driving style and what you use it for.

My biggest issue with the Renault for example is due to it’s overall weight which results in poor acceleration out of the corners, where it really matters. That is why I am tweaking the engine a bit to take it up around the 10h.p. level.
So here I am spending all this time, effort and money on the engine whilst totally ignoring the real gains that can be had by tuning the T/C.
I am not going to lift Bobs article so pop across the Altantic  and read the article for yourself, the least we can do.
Many thanks Bill.

It’s prompted me to look into the subject and when I really know what I am talking about, I’ll write an illustrated article.

The main thing is to have the clutch bite at around (above a bit actually) the engines max torque.
A standard T/C starts biting at around  2,200 rpm and since max torque on a standard GX200 is around 2,600 rpm, we suffer the engine being pulled down below max torque, resulting in  low acceleration, significantly less then it could be if only the T/C cut-in at around the max torque. On my rebuilt engine that's going to be round 3,500 rpm so something has to be done.
Well the good new is that you can quite simply get the T/C to-cut in at that point by changing the springs within the clutch for some Blue/silver springs and you can change the spring in the output clutch (not sure of the correct names for these parts but I will find out) for a stronger one and you can change the tension of that spring too.
Also, the weights in the clutch can be changed so there are a whole bunch of alternatives to have a go at.

I have just ordered a set of blue/silver springs and the yellow spring for the other end on Gemini's advice. That should give me a biting start of 3,600 rpm (max torque)  and the stronger yellow spring will hold it down keeping the engine in it's power band longer but allowing ten thousand rpm so yippe!
In Bills posting he included a spring engagement chart for the 20 and 30 series T/C's and Gemini have promised to send me one which explains things a bit better.

I must point out that this information is for my use only and MUST NOT be used by anyone in CycleKartsGB.

It’s not all about winning you know!   
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StefanN

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Re: Getting the best out of you Torque Converter
« Reply #1 on: 14 September 2021, 01:22:11 pm »
Funnily enough I’ve just machined my Zinc weights to just under 280g (from 340g) which should get them to engage at 2500 on the blue springs.    The torque gain is marginal but thought I’d give it a go.   I have tried Aluminium weights on blue garter springs (3300 rpm) which kept it in a lower ratio for longer but didn’t help much with engine and was unrefined when pulling away.

Will be interesting to see if I’ve machined off anything important!

I’ve increased the preload on the chain end to keep it in a lower ratio longer but haven’t tried changing that spring - this improved acceleration and I suspect increased belt wear.

Adrian

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Re: Getting the best out of you Torque Converter
« Reply #2 on: 14 September 2021, 10:17:38 pm »
Well done that man.
My engine now has a 1.3:1 set of rockers (pressed steel ones), a billet rod and flywheel and a 22mm Makuni with jets supplied by GX tuning and a ten thou head gasket so it should pull in excess of 10hp and rev a lot higher than the standard engine. I think around 6,000 rpm with max torque at around 3,600rpm so in theory at least it sounds like it should pull well off-the-line and have a good top-end speed to. I hope so.
The engine going in the Wee Beastie is the one supplied by GX tuning (I put it in the Renault for the speed trial) and that has a claimed 10+hp. even though it's on a re-jetted standard carb.
I was going to use it with a centrifugal clutch but i have changed my mind and I am using a T/C now.
I have a spare 22mm Makuni somewhere, in tricky condition so I will be sorting that out and fitting it to the Wee Beastie. She is a cartoon car that is very recognisable but I though it might be fun at shows in particular to have her pulling wheelies which she will do. So according to Gemini, there is a set-up of springs for the clutch and a spring for the driven bit which the kids use for drag racing (so eat yer heart out Jim lad!
 
 
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jim

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Re: Getting the best out of you Torque Converter
« Reply #3 on: 16 September 2021, 07:21:58 am »
I think that engine will make some good power Adrian and would have easily shown mine a clean pair of heals. I now have a Jimmy de Fish tail silencer which will go all the way to 11. Your gonna need a blower to beat the Fish lol.

jim

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Re: Getting the best out of you Torque Converter
« Reply #4 on: 16 September 2021, 07:37:51 am »
Another pic of the Fish


Seven racer

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Re: Getting the best out of you Torque Converter
« Reply #6 on: 16 September 2021, 02:05:34 pm »
I really hope so!

On the down size it's more weight and drive chain complexity, on the plus side there's a 1.3 to 1 reduction on the drive.
The biggest issue I'm finding at the moment is that the output shaft is inboard of the input, so I might be having to put a layshaft in.
The £50 option doesn't include the cables and lever though, so I went for the full version, but that still only cost around £119.

jim

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Re: Getting the best out of you Torque Converter
« Reply #7 on: 14 November 2021, 01:26:52 pm »
Adding a forward and reverse gearbox with built in reduction may help get more from the TC. Here's one I put on an old chassis recently.

Seven racer

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Re: Getting the best out of you Torque Converter
« Reply #8 on: 14 September 2022, 08:16:13 pm »
Wondering if you can steer me in the right direction on the reverse box Jim, I've hit a small snag as the spacing between chain drive and TAV belt differs between the engine and reverse box.
It appears that my input shaft to the gearbox has a shouldered section at the end, of about 9mm, which pushes the top TAV pulley out further.

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Because of the close proximity of the engine to the chain wheel, I can't just move the engine across, as it will foul the chain.

Thus I think there are three options,
To drill out a short section of the TAV top pulley to fit over the 20mm section of the shaft.
To take the gearbox apart and get the 20mm section turned down to 16mm
Or less likely, put a spacer on the engine end of the TAV drive to push the bottom pulley out the required 9mm, but there's not a lot of shaft anyway, so this seems the least desirable option.

Did you have a similar issue? Or does your set up allow you to move the engine across?

Peter


jim

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Re: Getting the best out of you Torque Converter
« Reply #9 on: 15 September 2022, 06:05:19 am »
Hi Peter, I drilled the tav pulley to fit over the 20mm gearbox shaft. I also removed a bit in the centre of the engine pulley to get more purchase .

Seven racer

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Re: Getting the best out of you Torque Converter
« Reply #10 on: 15 September 2022, 08:32:08 am »
Thanks Jim,
That seemed the easiest way to me, as I can 'ghetto' engineer it, but I thought it best to check first, most helpful,

Peter