Did a carburetor bench tester ever exist?

[m-mman]

You can attach an engine to a dyno or test stand, and operate it outside of the car

You can put a distributor into a bench tester and simulate it's operation in a running engine. 

 

Was there ever such a thing as a carburetor bench tester?

I am imagining a 'vacuum cleaner' device that would suck air through a carb to test/prove the operation of the many circuits.

A sensor in the device that could verify that the carb was dispensing a 14.7:1 air fuel ratio would prove that every thing was functional. 

 

The problem I see would be that in testing a carb, it would make an extremely explosive mixture and any spark from something like the vacuum motor would be disastrous. 

 

I have never heard of such a thing but in the history of auto technology you never know. Anybody ever heard of one?

[carbking]

Pictures in my "virtual carburetor museum":

 

Hygrade carburetor and fuel pump repair and test station

 

Jon.

[keithb7]

The Chrysler Engineers did a ton of carb research work with Ball & Ball. Ball & Ball  had early, not before seen, test labs. They had steam jets running steam through venturis. They plotted fuel burn compared to measured air flow. Chrysler engineers spent a lot of time in the Ball & Ball lab. Later on Chrysler purchased Ball & Ball.

[Str8-8-Dave]

Still using carburetor flow benches today...

 

 

[m-mman]

Hummmmm . . . . 

The flow bench seems to measure air volume but no fuel ratio or atomization. . . . 

 

The Ball & ball you said used steam forced down the carb. (like supercharging) but is that comparable to vacuum testing like it would be using on an engine?

Again this would test air movement (and perhaps they could sample vacuum/pressure at the venturis?) but then they would calculate(?) the fuel flow and mixture?

All this seem to be more for research not testing a carb rebuild before installation. 

 

Jon not sure how your device functioned. It seems to be made for in shop service, did it bench flow a carb with fuel in it for testing? 

[joe_padavano]

1 hour ago, m-mman said:

Hummmmm . . . . 

The flow bench seems to measure air volume but no fuel ratio or atomization. . . .

 

The device you are asking about is called a wet flow test bench and is still in use today for both carb and cylinder head testing. Carburetor OEMs like Rochester and Holley used them, though today CFD is the preferred analysis tool.

 

 

New wet test flow benches are available today.

 

http://dambest.com/catalog/product_info.php?products_id=179

 

 

[carbking]

The carburetor and fuel pump rebuilding and testing station on my site had testing procedures and tools for service (volume, fuel leaks, vacuum leaks, etc.).

 

The carburetor companies testing with the wet flow bench did NOT use fuel (dangerous). There is another non-flamable material (no, I do not remember its name) with properties (other than the ability to burn) simiilar to gasoline that is used with the wet flow bench.

 

I have custody of the Carter Carburetor Company flow test files. Lots of folks consider "flow testing" as to determine the CFM of the carburetor; but for the most part, Carter was interested in the volume of liquid and air used at a specific vacuum point from which an air/fuel mixture could be determined. 

 

Jon

[joe_padavano]

36 minutes ago, carbking said:

The carburetor companies testing with the wet flow bench did NOT use fuel (dangerous). There is another non-flamable material (no, I do not remember its name) with properties (other than the ability to burn) simiilar to gasoline that is used with the wet flow bench.

 

I suspected as much. Atomized gasoline is not the safest thing to have blowing around. We use similar non-hazardous "referee fluids" when flow testing rocket propulsion systems - for example, liquid nitrogen instead of liquid oxygen. I'm not sure what the appropriate referee fluid would be for gasoline - it would need to have similar density and viscosity. This is another reason why most OEMs use CFD modelling today.

Edited July 21, 2020 by joe_padavano (see edit history)

[edinmass]

Having never had access to a flow bench, we keep a few cars around the shop of different displacements to test most of our carbs. After doing fifty of the same unit for let’s say.......a Pierce Arrow A eight, you develop enough experience to be able to hit it on thr mark the first time. With factory and carburetor manufacturers specifications, all you need to do is adjust for E10. Having the ability to tune a car with a chassis dyne and a five gas machine is an incredible asset.......you can get hard data to determine what is actually happening.

[m-mman]

2 hours ago, carbking said:

The carburetor companies testing with the wet flow bench did NOT use fuel (dangerous). There is another non-flamable material (no, I do not remember its name) with properties (other than the ability to burn) simiilar to gasoline that is used with the wet flow bench.

 

Ah ha! Now I am beginning to understand how it is done. Fascinating 

[carbking]

OK - Holley used a fluid called Stoddard Solvent, which has the exact same specific gravity as gasoline.

 

Jon.

[Frank DuVal]

aka, Varsol.

[edinmass]

Interesting thread........but remember, with a flow bench, the results are as only as good as the operator, and his experience. Using a bench like that without the knowledge of someone like Carbking is almost useless. I find most cars that have replacement carbs are starving for fuel, or so over carbureted that’s they don’t run right. There were engineers with limitless experience, and skilled ten times more than most “experts” today..........and people just Cavalierly make changes thinking they know better than the people who built the cars new. In 99.9 percent of all circumstances, going back to stock configuration is you best option.

[jvelde]

Ed, you could change your "handle" to edinmask - just kidding!

[joe_padavano]

54 minutes ago, edinmass said:

Interesting thread........but remember, with a flow bench, the results are as only as good as the operator, and his experience. Using a bench like that without the knowledge of someone like Carbking is almost useless. I find most cars that have replacement carbs are starving for fuel, or so over carbureted that’s they don’t run right. There were engineers with limitless experience, and skilled ten times more than most “experts” today..........and people just Cavalierly make changes thinking they know better than the people who built the cars new. In 99.9 percent of all circumstances, going back to stock configuration is you best option.

 

I don't disagree with you, but testing a carb on a carb flow bench has nothing to do with how it performs on a given engine. The carb flow bench is only for assessing the performance of the carb - atomization at specific pressure drops and flows, etc. How a specific engine with a specific carb runs in a certain vehicle with specific gearing is not something you get from a carb flow bench, nor is the flow bench intended to provide that info.

[m-mman]

1 hour ago, edinmass said:

remember, with a flow bench, the results are as only as good as the operator, and his experience. Using a bench like that without the knowledge of someone like Carbking is almost useless.

 

Absolutely!  Any test device only gives you a number. It takes a skilled person to understand the numbers and make adjustments. 

 

21 minutes ago, joe_padavano said:

I don't disagree with you, but testing a carb on a carb flow bench has nothing to do with how it performs on a given engine.

 

True also. A flow bench will provide a guaranteed amount of CFM but bad rings, burned valves and slow timing will not duplicate the textbook engine performance characteristics. 

 

I was trying to conceive of a device that might prove a carb off the vehicle such that it could be eliminated from the diagnostic process as having been shown as functional. 

 

I was also thinking about a carb mass rebuilder exchange operation (like in the old days) Might they have proven each carb on a flow bench before being released in an attempt to reduce warranty claims and returns?

 

Ed's prior description of a chassis dyno and 5 gas analyzer would certainly prove the operation of the complete set up.

But if you could test each part before assembly, then when everything is proven individually and  brought together, theoretically it should only need a few adjustments. Unlikely, nothing on a car is that easy. 

[joe_padavano]

16 hours ago, m-mman said:

A flow bench will provide a guaranteed amount of CFM but bad rings, burned valves and slow timing will not duplicate the textbook engine performance characteristics. 

 

I was trying to conceive of a device that might prove a carb off the vehicle such that it could be eliminated from the diagnostic process as having been shown as functional.

 

A carb flow bench won't even tell you if a carb is properly matched to an engine that doesn't have mechanical problems. It will only tell you how the carb performs when subjected to a specific set of flow conditions. Things like jetting, choke settings, power valve, secondary opening, etc. need to be worked out on the real engine since they depend on load, ignition timing, cam profile, etc. The carb flow bench will tell you if the carb is functioning as designed, but not if that "design" is correct for a given engine.

[carbking]

It is my thought that some may misunderstand the reason(s) for using a flow bench.

 

The major reason was carburetor design, although racing teams may also use them to test modifications (again, design).

 

The carburetor companies, designing carburetors, were interested in very precise measurements of A/F ratios at specific values of vacuum. A secondary function was the CFM available at different values of vacuum, although many look only at WOT CFM. However, CFM figures, at best, are ambiguous. Anyone that believes a carburetor rated 500 CFM will actually flow 500 CFM still believes in the tooth fairy! The engineers did NOT do thousands of tests to determine an exact venturi size and associated air horn and throttle sizes to obtain an exact CFM figure; rather they used standard diameters, measured the CFM, and submitted the results to marketing. Then marketing would assign a CFM value to the carburetor, depending on the needs of the company in the marketing line-up. For years, I have contended the world's foremost expert on CFM was Mark Twain  I am unaware of anyone making the statement before Mr. Twain, but he stated "figures don't lie, but liars figure!".

 

Anyone interested in CFM numbers might enjoy this section from my website: CFM ratings

 

What I know of SOME of the carburetor mass rebuilders is that they had very little interest in warranty/returns. They had agreements with their distributors that a certain percentage of sales were going to be returns, and the distributors "ate" those issues. The units were not returned to the company. Trying to "prove" each unit, would be expensive, raising their "rebuilt" prices above new prices.

 

Basically, the flow bench is more of a laboratory tool for design, than a practical service tool.

 

Jon.

Edited July 22, 2020 by carbking (see edit history)

[joe_padavano]

17 minutes ago, carbking said:

What I know of SOME of the carburetor mass rebuilders is that they had very little interest in warranty/returns.

 

Sadly, this is true of rebuilders of many items. It all comes down to cost/benefit. So long as the cost of returns is lower than the cost of improved quality, that vendor will continue to build and sell crap. In many cases, even the higher cost of a "premium" part has nothing to do with increased quality of manufacture. The higher cost simply goes towards "insurance" against returns. I've seen this at NAPA, for example, where the higher price "premium" item is identical to the lower cost one. The price difference only covers the added costs of the three year warranty vs. the 90 day warranty.

[Bloo]

This is why it is ALWAYS better to rebuild/overhaul/adjust what you have rather than using exchange parts. Using exchange parts, best case, you wind up with someone else's problems. Worst case, you wind up with something that has been beat up or had unknown modifications done by the rebuilder to "prevent comebacks".

 

This last situation is extremely common with carburetors. It leaves the car owner in a really bad situation because he (or some previous owner) probably turned in the old one for a "core charge". He must then locate one that has not been through the "exchange" program, and rebuild it or have it rebuilt by someone competent. In some cases it can drag out for years.

[Frank DuVal]

I learned to rebuild carburetors almost 50 years ago because my friends bought rebuilt ones from the parts store and over 50% were crap. Odds seemed in my favor to do my own! Worked out very well for me!😉

[edinmass]

9 hours ago, Frank DuVal said:

I learned to rebuild carburetors almost 50 years ago because my friends bought rebuilt ones from the parts store and over 50% were crap. Odds seemed in my favor to do my own! Worked out very well for me!😉

 

 

I agree.........off the shelf rebuilds are a total was of time. Only problem is, as more time goes by, there are fewer and fewer people left doing good work............I lost my carb rebuilding guy 20 years ago............so now I end up doing all of it, as I just don't know anyone who I trust to do it anymore.