Torque converter rating and engine hp

[Acavet]

The torque converter on my dunecycle is rated for up to 8 hp however I have located a 10 hp motor that I would like to install.

I don't want to change the torque converter, which will fit the new motor. What effect will the added hp have on the existing converter.

Will this setup work?

 

[Doc Sprocket]

It will probably be okay. What make/model is your CVT? The shaft size is appropriate?

 

[Acavet]

Its a comet torque converter, fits 3/4" shaft using #40 chain.

The motor is a Briggs and Stratton 10 hp also with 3/4" x 2 5/16 shaft.

 

[OzFab]

Its a comet torque converter, fits 3/4" shaft using #40 chain.

The motor is a Briggs and Stratton 10 hp also with 3/4" x 2 5/16 shaft.

Strange, I have an 11hp B&S with a 1" shaft. (just saying)

The fact that a cvt rated for your engine would fit a 1" shaft I would say you will be ok with the smaller one; if toystory says it'll be ok then it will be ok

 

[Doc Sprocket]

Which model Comet?

 

[Acavet]

10 hp comes in both 3/4" and 1" shafts

http://willardssmallengines.com/sho...que-converter-kit-41-10-tooth-3-4in-bore.html

 

[Doc Sprocket]

Okay- So it's a TAV2 (30 series). It'll be fine.

 

[Acavet]

Thanks didnt want to have to make to many changes....

Here are a few before pictures. I have a new set of turf saver tires and wheels coming, a new torque converter and soon the new motor. What you see in the pictures is pretty much 70's stock.

 

[OzFab]

10 hp comes in both 3/4" and 1" shafts

Good to know, thanks. 10hp must be the crossover point.

That thing looks awesome I bet it's loads of fun

 

[Acavet]

I identified the wrong motor earlier in my post, I said 10 hp B/S the motor is a 10 hp Tecumseh. I've looked at so many different ones the last few days I'm starting to get them confused.

 

[spyder1968]

IMO...the 30 series would hold up to the power........as long as you are NOT overgeared ! those look like pretty tall tires. what size axle sprocket is on that bad boy?

 

[Acavet]

The tires on it now are 21x10x8's the new tires are going to be 20x10x8 turf saver style.

I will have to do some counting on the sprocket to give an answer about gearing. The setup is torque converter to jack-shaft, jack-shaft to differential.

I'm trying not to change to much right now as I just want to get it back up and running for the summer. The motor selection was more about suitability than my desire for added horse power. The 7 hp motor that is on it right now was built back in the 70's and the new motors of the same size are setup differently.

 

[spyder1968]

Do you know if it originally drove well, or did it tend to be real slow taking off from a stop? Sprocket sizes would definitely help.

 

[Acavet]

The torque converter has never worked 100% since I bought it 10 years ago, so its difficult to say just how good the take off is. With faulty converter it takes a bit to get moving.

Here is a diagram of the current ratios, showing the different teeth count on the motor, jackshaft and differential.

What do you think?

 

[spyder1968]

Okay, first off, I am assuming in the above diagram this is all chain and sprockets correct? If so, you do not have a torque converter, you have a jackshaft with a gear reduction. A torque converter would have (usually) one belt and one chain.

If I did the math correctly on the reduction, you have a 16.64 to 1 gear ratio. Even with your 7hp motor, it should have plenty of torque. More than likely, the top speed is not going to be very quick.

Please take a pic of your engine, from the crank side, so we can be sure. To make a long story short, I would install the motor and make sure it runs well, before doing anything else ... THEN address the gear issue and make changes, if you feel it is lacking speed or torque, etc.

 

[r_chez_08]

*8.4:1 ratio if I have done the correct maths (bloody American spelling )
Ratio sounds ideal.

 

[Acavet]

There is a comet torque converter, just didn't draw it in. The torque converter is attached to the motor. The diagram shows the teeth count coming off torque converter at the motor.

I would assume it was designed primarily for off road and hill climbing and not for top speed.

Is R Chez 08 suggesting that the ration would be better off at 8:1?

What is the formula for determining the ratio?

 

[r_chez_08]

You have a 8.4:1 ratio if my maths is correct.
(Jackshaft input / engine or tc output) x (axle/ jackshaft output) :1
So-
(32/10) x (42/16):1=
3.2 x 2.625 :1 =
8.4:1

Hope that makes sense.
I had a 6:1 ratio with similar sized tires and only a 6.5hp with a tc.
It was OK, needed more oomf for hills etc.
Now going to a 7.5:1 with nodded 6.5hp and tc.
Your setup will have plenty of bottom end, as your motor is more powerful and ratio is higher.