http://www.fullsizechevy.com/forums/...d.php?t=145234

thought you guys might be interested in this thread over at fullsizechevy.com . They did flow testing on a stock TB, flowed close to 575cfm stock, i imagine porting and polishing w/ the injector spacer and an open element could really open it up, maybe 625-650?

 

There was discussion further down the thread about it being unrealistic becuase it was a dry-flow test. No cones of fuel spray being shot from the injectors during the test to disrupt airflow like you would see in a live application.

I'm not a flow expert but I can certainly see that further reducing airflow by a significant margin. Not just becuase of the fuel droplets displacing air volume but also becuase it generally "disrupts" smooth airflow into the bores.

 

Wet flow displaces roughly 1.5% of the air by volume --- so it's negligible on airflow data. The math has been shown here on TGO (by me) before. At anywhere in the 12:1 to 15:1 range of air:fuel by mass, the volume of air displaced by wet-flow fuel is insignificant. If you want to adjust dry-flow measurements to wet-flow conditions, you can multiply the cfm numbers by 0.985.

As far as smooth airflow -- the airflow is always turbulent especially at part throttle. Calculate the Reynold's number and you'll see why.

The flow measurements on that web site confirm what Ken73 already measured on his flow bench, using TBI units from a Crossfire engine. That info was also reposted here on TGO by me if you search for the threads.

Finally some thought questions -- when carbs are flow tested, do you think they are flow tested in dry-flow or wet-flow? And would it matter? FWIW.

 

Good info. IIRC Holley flows their carbs/throttle body units wet.

 

Wow I almost missed this post. Thats some very good info, if nothing else it's going to give us a direct A to B to C comparison between stock, ported, and 2" throttle bodies. Also very interesting that the pod spacer really helped, but removing the pod didn't do as much. Can't wait to see what the 2" unit does.

 

I'm in the process of designing a TB unit that uses foggers (extreamly fine dropplets) instead of injectors. There is not a need for injector pulses, or complex electronics. A high pressure constant flow pressure regluator, used with an anolog air flow meter, and a few other componets I cant disclose yet. Got the idea in part from NOS foggers, and watching mosquito chemical foggers. They operate at 100 psi with tiny high pressure pumps. I have a Briggs and Stratten 10hp engine with a working prototype fogger system on it, has alot of bugs right now but hope to have one on a 350 soon. If you think about it makes fuel injection alot simpler, constant fuel flow, fine mist mixes with air to burn better, little electronics to operate it.

 

The fogger idea might not work as well as you expect it. It'll work equally as well but there are some things to consider about engine air flow. 1st is that the air entering an engine is never constant flow, the intake valves close so in effect an injectors "pulse" timed correctly would be better than a constant flow where the air flow had slowed down. 2nd is the fact that fuel boils into vapor at a relatively low temperature. Once it becomes vapor it's mixed extreamely well with the air (duh). The intake valve, piston, cylinder wall, and combustion chambers are all VERY hot. Enough to instantly vaporize fuel in "mild" hp/liter engines like many v8's. The important part of making horsepower is the quenching done in the combustion chamber and piston to head clearance. In otherwords, everybody should be focusing on getting ENOUGH fuel and not HOW. That is my opinion.
The good idea about a fogger would be the cylinder to cylinder distribution. This can be pretty much cured with a properly placed TBi, warm intake, higher fuel pressures, and the least about of IAC counts possible at idle and part throttle.