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  #1  
Old 12-01-2020, 01:15 AM
seagull seagull is offline
 
Join Date: Dec 2019
Location: San Bernardino
Posts: 199
Default Carburetor balancer

I have a RV-12 with a Rotax. The engine has 2 carburetors that require balancing. The balancing is done with a tool that reads the manifold vacuum of each carburetor. With that information you can make mechanical adjustments to have both carburetors producing equal power.

A typical method to balance is using water columns, oil or some other fluid that is connected to the intake below each carburetor. There are electronic balancers in the $100 range with several LED's to tell you they are balanced and "OK".

I searched the internet and found a DIY project a fellow in the Netherlands designed to balance 4 carbs on his motorcycle. We communicated via email discussing using his design on the Rotax. I have built one at a cost of about $50.00. Not to difficult if you have a little electronics background.

The unit has 2 hoses to connect to each carburetor and a 5 volt USB cable for power. Internally it uses 2 automotive MAP sensors to read the vacuum. It will read in inches of mercury or millibars. The accuracy is way more than is necessary for my purposes, about 1/30th of an inch of mercury.

You can find the DIY plans here;
https://hackaday.io/project/27569-carbonbal

Mine being used reading in milibars;
https://youtu.be/4_heFd9-odA
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  #2  
Old 12-14-2020, 09:20 AM
Slightlyabnormal Slightlyabnormal is offline
 
Join Date: Apr 2020
Location: Ohio
Posts: 9
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This looks great!
Do you have any details on the changes you made for your 2 carb setup?

Thanks!
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  #3  
Old 01-08-2021, 11:22 PM
seagull seagull is offline
 
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Location: San Bernardino
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Quote:
Originally Posted by Slightlyabnormal View Post
This looks great!
Do you have any details on the changes you made for your 2 carb setup?

Thanks!
I an not sure what you mean about "changes".
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  #4  
Old 01-08-2021, 11:53 PM
larosta larosta is offline
 
Join Date: Dec 2010
Location: Redlands, CA
Posts: 180
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Interesting project, it is amazing what the open source design community brings to a problem. I have seen a lot of talent and experience brought to bear on projects like this.

I do have a question, given that you are balancing two carburetors relative to each other would a single differential pressure sensor with the each port connected individually to one of the two carbs perform the same function. It would not provide information on the intake MAP of the individual carbs but would be a pretty simple solution for balancing them relative to each other.

Just curious,
- Larosta
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  #5  
Old 01-08-2021, 11:58 PM
seagull seagull is offline
 
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Location: San Bernardino
Posts: 199
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Quote:
Originally Posted by larosta View Post
would a single differential pressure sensor with the each port connected individually to one of the two carbs perform the same function.
I don't think you could calibrate a differential sensor as accurately as two sensors that can run in parallel reading the same source at the same time.
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  #6  
Old 01-09-2021, 10:01 PM
Slightlyabnormal Slightlyabnormal is offline
 
Join Date: Apr 2020
Location: Ohio
Posts: 9
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When I asked about changes I thought you may have had to change something to make it use only 2 sensors.
I’ve built one myself now and see that no changes are necessary.
I’m having trouble locating the fittings I need to connect it to the carb crossover section. There are hose sets you can buy to use with carb mate that look like they’d work but I assumed I’d be able to find something at the local hardware store.

How do you connect yours?

Thanks!
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  #7  
Old 01-10-2021, 12:00 AM
seagull seagull is offline
 
Join Date: Dec 2019
Location: San Bernardino
Posts: 199
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I initially made fittings that went into the rubber hoses on the balance tube. I found that a nuisance to connect up so I went to this method. This method has one drawback in you have to completely clamp off the balance tube or you will show a balance when it isn't.

I drilled & tapped (2) 8mm bolts and inserted barbs. These replaced the plugs that are in the intake manifold, see photo. To balance I connect the balancer to these left and right ports and clamp off the balance tube. I have silicone plugs that cap off the ports when I am not using them.

To balance I pinch off the balance tube with these pliers available on Amazon;
search, "GEARWRENCH Small Hose Pinch Off Pliers, 3/4" O.D. Capacity - 3791"



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  #8  
Old 01-10-2021, 06:45 PM
ben barron ben barron is offline
 
Join Date: Sep 2013
Location: Fall City, WA
Posts: 148
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Id like to build one as my mechanic just left to go to PA.I like your size unit...any more details you can share?

Do you need 2 sets of plyers?
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  #9  
Old 01-10-2021, 09:42 PM
seagull seagull is offline
 
Join Date: Dec 2019
Location: San Bernardino
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To make it small I etched PC boards to integrate the display, arduino, and the MAP sensors. It doesn’t work any better small, just my preference to make things compact.

One set of pliers is all that is required since you are only blocking the air from transferring between sides.
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Last edited by seagull : 01-10-2021 at 10:29 PM.
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  #10  
Old 01-11-2021, 11:19 AM
ben barron ben barron is offline
 
Join Date: Sep 2013
Location: Fall City, WA
Posts: 148
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would you share a link to the MAP sensors and any other parts you used?
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