When I see carb shops showing photos of the carb builder standing next to a Super flow or other type of dry flow machine I immediately get Infomercial flashbacks. You know the types of commercials that tell half truths to make their product seem better than it really is. Well dry flow is just that.. a half truth.
Gaby at Induction Specialties using a Superflow to do
what it does best. Flow cylinder heads..
With a dry flow machine you can find out two basic
1. The dry flow cfm rating of that carburetor.
2. The percentage of vacuum of the boosters.
With a Dry flow machine you can’t:
1. Map fuel curves.
2. Test atomization percentages.
3. Get an accurate cfm rating of the carb.
4. Alter the fuel curves and record the changes.
5. and more I won’t talk about.
I don’t mind people saying they have a dry flow bench, but don’t oversell its use. In my opinion its a main jet selection ball parking tool. That’s it.
Even dry flow cfm numbers can’t be relied upon as they are skewed by the development of the fuel cone. The fuel cone, which is not even in the mix during dry-testing alters the cfm based on its development vs. air speed. So the builder simply guesses the number. You see, the larger the fuel cone that develops at the booster the more air is impacted and slowed, thus a reduction in cfm and an increase in atomization. Not to mention the fuel consumes cfm which has to be calculated into the equation.
Dry flow testing is also unusable when it comes to testing metering blocks. It can't test them. Period. There are variances from metering block to metering block (just like jets) that need to be mapped and corrected. Dry flow can't do this, because it can't test the metering block or emulsion circuit of the metering block, which is the single most important part of the carburetor. Fluid is required to enable or disable the emulsion circuits and test the passages flow capabilities and the blocks fuel curve.
A dry flow machine cannot map a change to the emulsion program of the metering block and it can't map how much fuel stays in suspension at a certain air speed to tell the builder if he needs to work on the package
for the application. What good is it?
Basically let the dry flow machine do its only real available job for the builder. It can be used to select a starting main jet using a certain/hopefully known functioning metering block based on a certain vacuum signal.
To prove my point ask the builder to bolt the metering blocks and bowls on the carb and show you the newly developed fuel curve. His dry flow machine can’t do that. So the guessing begins on whether he built the blocks properly or selected the correct needle and seat or well/angle/emulsion configuration or booster passage. You can’t do any Research and Development in atomization using a dry flow machine. You also can’t verify you changed a lift coefficient or air to fuel ratio in the metering block or show the potential horsepower capabilities of your new design.
There are only a few wet-flow benches out there, but ours is the only one I know that is fully computerized and can map with accuracy inside a tenth of a main jet.
A lot of wet-flow testing and calibrating later, the completed unit is ready to ship. Its been live tested up to and beyond the horsepower level of its intended usage and its ready to bolt on and go!
Its accuracy like this that's required in today's racing scene. 10-30 horsepower is always hiding in these carburetors in atomization and fuel curve technology. It takes good equipment to find that power. Dry flow is a half truth in both cfm and fuel curve technology. There are a lot of Infomercial/snake oil salesman out there, don't believe everything you see. You have a lot of money invested in your race program, don't invest in a guess.
Thanks for reading.