carburator explained

[bikeman564™]

I found this very interesting

 

[Thaddeus Kosciuszko]

I'm going to take a wild guess and say it's illegal to own more than six of those in Texas.

[JerrySTL ★]

Very interesting. After watching the video, it shows me why fuel injection is so much more efficient as all those droplets don't mix well with the air.

A couple of points.

He says that the gasoline molecule needs to be next to an oxygen molecule. Actually it's more like three oxygen molecules. For most gasoline engines that air fuel mixture needs to be about 14.5 to 1. As air is around 21% oxygen, that's three oxygen molecules.

I wish he'd also look a variable venturi carbs like the trusty old SU's found on a lot of British cars.

[Wilbur ★]

I understand carbs but this is a cool video. 

[jsharr ★]

43 minutes ago, Thaddeus Kosciuszko said:

I'm going to take a wild guess and say it's illegal to own more than six of those in Texas.

No, intake is unlimited.  If you were trying to install them on your exhaust, then yes, six would be the limit.

[jsharr ★]

That was cool to watch.  I could not believe the part where he asked if you could run multiple cylinders off of one carburetor.   Has he never opened the hood of an old car?  

[Ralphie ★]

I watched that last year whilst trying to get my generator running.  Interesting but the generator is still inoperative.

[maddmaxx ★]

That explains a lawn mower carburetor on a constant speed motor.

It doesn't even come close to an automobile carburetor on a variable speed motor that has to handle conditions from idle through acceleration and into top speed.  In one of those carbs there are usually 3 different fuel inlet circuits, main, idle and transition.  The main is similar to the constant speed carb, the idle is a special port that provides fuel through a narrow venturi created between the almost closed throttle blade and the throat wall next to that blade.  The third is a transition fuel inlet system just above the idle port that has a venturi created at small blade openings just above idle.  There is also an accelerator pump that shoots a fuel charge into the main jets as the throttle blade is opened.  The more rapidly it's opened the faster this charge is delivered.

In some carbs there are metering rods that restrict the fuel flow through the main jets.  These stepped rods that are pulled into the jets by engine vacuum so that the largest step is in the jet at idle and the smallest at full throttle when the intake vacuum is less.

Exactly where these ports and slots are located and to a degree their shape helps atomize the fuel into small burnable droplets or vapor.

Fuel injection, especially computer controlled beats this system hands down, but at the carbs high point they were fantastic machines that attempted to do everything as well as possible without computer control.

[JerrySTL ★]

9 minutes ago, maddmaxx said:

In some carbs there are metering rods that restrict the fuel flow through the main jets.  These stepped rods that are pulled into the jets by engine vacuum so that the largest step is in the jet at idle and the smallest at full throttle when the intake vacuum is less.

I think a repressed memory of my rebuilding a Quadrajet carb just resurfaced.

[a bunch of numbers]

2 hours ago, jsharr said:

No, intake is unlimited.  If you were trying to install them on your exhaust, then yes, six would be the limit.

[jsharr ★]

4 minutes ago, a bunch of numbers said:

[maddmaxx ★]

32 minutes ago, JerrySTL said:

I think a repressed memory of my rebuilding a Quadrajet carb just resurfaced.

Quadrajets and Carters both have them.  Holly does it differently with transition slots and accelerator pumps.

[jsharr ★]

1 hour ago, maddmaxx said:

That explains a lawn mower carburetor on a constant speed motor.

It doesn't even come close to an automobile carburetor on a variable speed motor that has to handle conditions from idle through acceleration and into top speed.  In one of those carbs there are usually 3 different fuel inlet circuits, main, idle and transition.  The main is similar to the constant speed carb, the idle is a special port that provides fuel through a narrow venturi created between the almost closed throttle blade and the throat wall next to that blade.  The third is a transition fuel inlet system just above the idle port that has a venturi created at small blade openings just above idle.  There is also an accelerator pump that shoots a fuel charge into the main jets as the throttle blade is opened.  The more rapidly it's opened the faster this charge is delivered.

In some carbs there are metering rods that restrict the fuel flow through the main jets.  These stepped rods that are pulled into the jets by engine vacuum so that the largest step is in the jet at idle and the smallest at full throttle when the intake vacuum is less.

Exactly where these ports and slots are located and to a degree their shape helps atomize the fuel into small burnable droplets or vapor.

Fuel injection, especially computer controlled beats this system hands down, but at the carbs high point they were fantastic machines that attempted to do everything as well as possible without computer control.

https://gfycat.com/daringradiantbasenji

[JerrySTL ★]

1 hour ago, maddmaxx said:

There is also an accelerator pump that shoots a fuel charge into the main jets as the throttle blade is opened. 

That's what the oil under the cap on top of an SU carb does in a way. The oil does not lube the carb; rather, it slows down the opening of the variable venturi piston which enriches the fuel mixture.

[bikeman564™]

5 hours ago, jsharr said:

That was cool to watch.  I could not believe the part where he asked if you could run multiple cylinders off of one carburetor.   Has he never opened the hood of an old car?  

I wondered that too, unless you were running tri-power

[Thaddeus Kosciuszko]

4 hours ago, maddmaxx said:

That explains a lawn mower carburetor on a constant speed motor.

It doesn't even come close to an automobile carburetor on a variable speed motor that has to handle conditions from idle through acceleration and into top speed.  In one of those carbs there are usually 3 different fuel inlet circuits, main, idle and transition.  The main is similar to the constant speed carb, the idle is a special port that provides fuel through a narrow venturi created between the almost closed throttle blade and the throat wall next to that blade.  The third is a transition fuel inlet system just above the idle port that has a venturi created at small blade openings just above idle.  There is also an accelerator pump that shoots a fuel charge into the main jets as the throttle blade is opened.  The more rapidly it's opened the faster this charge is delivered.

In some carbs there are metering rods that restrict the fuel flow through the main jets.  These stepped rods that are pulled into the jets by engine vacuum so that the largest step is in the jet at idle and the smallest at full throttle when the intake vacuum is less.

Exactly where these ports and slots are located and to a degree their shape helps atomize the fuel into small burnable droplets or vapor.

Fuel injection, especially computer controlled beats this system hands down, but at the carbs high point they were fantastic machines that attempted to do everything as well as possible without computer control.

I think Dr. Mick got hold of maxx's password...

[Bikeguy]

1 hour ago, bikeman564™ said:

I wondered that too, unless you were running tri-power

I remember the Dodge 440 with a 6 pack.  

[Bikeguy]

8 hours ago, bikeman564™ said:

I found this very interesting

I'll bet you liked the 3-D printing too.  

[bikeman564™]

14 minutes ago, Bikeguy said:

I'll bet you liked the 3-D printing too.  

[bikeman564™]

19 minutes ago, Bikeguy said:

I remember the Dodge 440 with a 6 pack.  

 

I thought of that too

[BR46]

9 hours ago, Wilbur said:

I understand carbs but this is a cool video. 

Explain this 

 

[Wilbur ★]

11 minutes ago, BR46 said:

Explain this 

Unless a part has been certified for aviation use, it can't be used.  FAA regulations. 

[Thaddeus Kosciuszko]

36 minutes ago, BR46 said:

Explain this 

 

24 minutes ago, Wilbur said:

Unless a part has been certified for aviation use, it can't be used.  FAA regulations. 

Not for sidecars, either.

If it's not certified for aviation use, then it certainly can't be used for flying the chair.

[MickinMD ★]

Back in the 60's, teenage me knew nothing about cars - my parents not owning one - but when I got a limping-along-wreck of a 1959 Chevy Impala for $300, a 283 V8 was so simple I could buy a 2-barrel carburetor rebuilding kit for less than $10 and get mine working perfectly.  Today it would be a trip to the garage.  Spark plugs properly gapped, new valve cover gaskets to keep oil from dripping down the side plus a spray can of engine orange paint and it was perfect!

[Zealot]

It’s one thing to know how it works. It’s another to see it.