Effect of CVT when using a Governed Engine

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Effect of CVT when using a Governed Engine

Postby The-Original-T » Fri May 19, 2017 8:39 pm

Hello everyone,

I have been chewing this over in my head a bit recently and wondering if anyone has experience of the matter,
Basically a CVT adjusts based on engine speed vs load to keep the engine speed at a consistent RPM.
The governor in the Diesel engine adjusts the amount of fuel delivered to keep the engine speed at a given RPM.

If say your cruising along and approach a hill for example could the CVT and governor potentially have a bit of a clash/overlap going on???
Just in this scenario you would want the governor to adjust first to see if the engine had enough power too keep the RPM consistent under the load first, then once the power at that rpm was exhausted at the given CVT ratio you would want the CVT to compensate second...

I'm concerned that potentially the CVT could adjust first reducing speed before the governor decides it needs to add more fuel into the engine.... obviously a twist of the throttle would help in this situation but i'm just thinking about the rideablity of the machine if you had 2 mechanical components effectively working against each other instead of in the order they should do and working in unison :shock:

Thoughts??? Anyway to compensate for this???
Or am I just talking trash??? I'm interested in your opinions :idea:
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Re: Effect of CVT when using a Governed Engine

Postby Diesel Dave » Sat May 20, 2017 12:27 am

For almost all 9/10hp motors your going to be at full power all the time (or attempting to stretch the throttle wire.....)

You will need to set the bob weights in the CVT light enough to allow the motor to keep revving, so ideally the CVT will keep the motor above 3000 rpm and the Governor will kick in at 3600.

You really need to speak with Sonke at the diesel bike rally...
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Re: Effect of CVT when using a Governed Engine

Postby The-Original-T » Sun May 21, 2017 12:02 pm

Yeah I'm planning on coming down to have a mooch around and some good conversation,
Albeit I'll be in my car (surprise surprise.... that's a diesel).
It's mine and my new girlfriends first anniversary that weekend so will be staying at a hotel I imgine as she's been good enough to agree to let me come even though it should be "our" weekend.
Not every girls first ideal of an anniversary going to a diesel bike rally so I'll only be coming for a few hours on the Saturday.
Looking forward to meeting loads of you and seeing your machines :D

I'm planning on using a Rotek V-twin in my bike and using an AJS Bobber as the donor bike :lol:
Aiming for a top speed of 80mph so I can comfortably cruise at 60mph.
That's the plan anyways we'll see what actually happens in due course :wink:
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Re: Effect of CVT when using a Governed Engine

Postby BertTrack » Mon May 22, 2017 1:04 am

The-Original-T wrote:Thoughts??? Anyway to compensate for this???
Or am I just talking trash??? I'm interested in your opinions :idea:


Well based on my own experiments. With the Track. It has no rpm control except my right hand. And i like to ride on a steady rpm. And relying on thoughts and assumptions. I can make the following cases.

The c.v.t. changes ratio because of 3 possibilities: 1 external control (will ignore that). 2 amount of pull on the belt (Torque sensing). 3 Weights only (RPM control) i haven't seen this last one in use except in the little Vespa Ciao that i used to have.

I will use number 2 as i believe it's the most common to use and i have experience with it.

When riding the Track on a hilly road with ample space i liked to experiment with a "locked" throttle position and see what happens. When going downhill the torque needed to turn the c.v.t. would drop and the ratio would gear up. Resulting in same rpm thanks to my same throttle position and the c.v.t. converting the excess power into more speed for the motorcycle. Going uphill the opposite would happen. R.p.m would remain the same and the speed would drop because it's looking to find the same torque (pull) on the belt as before.

Now to add the question of the governed engine.

It will fiddle with the throttle for you. Keeping the r.p.m constant within the engine's limits. I think the ride will be very easy with no problems between the 2 "control" systems.

The c.v.t. ratio just adjusts to the torque(pull) on the belt. So if you don't vary the engine speed than your vehicle speed will vary depending on the load.
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Re: Effect of CVT when using a Governed Engine

Postby gilburton » Mon May 22, 2017 7:54 am

Your engine will perform at it's best and the gearing will adjust to suit the conditions.
This was my theory when using one on my Robin engined MZ. On mine I had to alter the sprockets to get the best ratio but on a larger engine the extra power will probably cope over a larger range of loads as the small engine used to struggle a bit on steep hills.
As we mostly use industrial engines it keeps the revs at their optimum so keeping them reliable.
There were some posts about the Chinese based V twin clones breaking cranks but my own theory was that they didn't like the sudden torque changes when using a manual transmission. A CVT helps to alleviate that by gentle throttle openings and constant throttle and let the cvt do the adjusting.
Many years ago I had a DAF 66 and basically you just floored the throttle and let the car come up to the speed you wanted and then eased off rather than continually use the throttle to increase speed.
Modern scooters are much the same.
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Re: Effect of CVT when using a Governed Engine

Postby gilburton » Mon May 22, 2017 8:14 am

I used a CVT from an Aixam microcar and it worked on my 9hp engine so it would probably work better on your larger engine.
This thread may be of interest as you are using a V twin.
These engines don't seem to be available in the UK.

viewtopic.php?f=31&t=2902
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Re: Effect of CVT when using a Governed Engine

Postby UAofE » Thu Jul 06, 2017 6:06 pm

CVT works great with a variable speed governor. Your hand maintains a steady speed and the CVT automatically adjusts ratio as load changes. You only use as much RPM as you need to maintain target road speed.

The only major improvement to the setup (besides more power...) would be the ability to manually control CVT ratio.
Basically set the engine at 3000rpm and use the CVT to control power by increasing/decreasing load on the engine.
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