JC565Ford wrote: ↑Tue May 30, 2023 1:07 pm
SchmidtMotorWorks wrote: ↑Thu May 25, 2023 7:57 pm
I had an interesting discussion with a CFD engineer.
He said that of course the curved duct will flow more.
and
If the fuel is dropping out in either design,
the solution would be to have smaller fuel drops.
Is that always possible with carbs ?
Annular discharge boosters help. but they can only do so much.
You’re ultimately limited by the fact that the fuel in the float bowl is at atmospheric pressure and the difference is that vs whatever the pressure is in the carb booster.
A “low pressure” fuel injector might be at 5bar (which a lot of aftermarket systems are), but the port injectors Formula One used prior to the current PU’s were cap at a rules limited 100bar (and they made power with ever increasing amounts) and figure a gasoline DI injector is around 150 bar.
At the end of the day fuel being forced through 12+ orfices injectors at 100 bar plus, plus whatever the port pressure is at that point, so there is a delta P component, is going to have a larger Joule-Thomson effect.
FYI Honda had a 24 hole injector at 100 bar, and an average droplet size of 17 um, at 100 L/h flow rate, and was worth 20hp over what they had before. Droplet size on a carburetor, that I kind find, ranges 50-200um depending.
Carburetors only make good WOT power because they rely on the plenum to beat it into submission, and often they’re compared against systems where the injectors are 6-8” closer to the valve. If you look at the Ilmor Indy Car engines from the early 1980s up until they went to DI, they injected with injectors through the plenum roof aimed at the bellmouth. Without rules dictating position, Pro Stock builders would absolutely do the same.
I’m really surprised we haven’t seen people in the aftermarket use the current DI pumps to drive high pressure port injectors, like F1 did. Cosworth was testing 200 bar on the dyno and it worked great for them (these were the 20,000 rpm engines, so besides evaporative cooling, they needed to deliver 110hp / cyl worth of fuel in 166x a second, and have it so said fuel could have stable combustion in an almost 4in bore).
Some cool work they did:
D4E19504-18E4-48F5-B3B7-3928B6DF1316.jpeg
You do not have the required permissions to view the files attached to this post.