3 Blade vs 4 Blade Injectors (1 Viewer)
- Thread starter DixonFan
- Start date
mick
Nitro Member
can remember years ago talking to alan and joe hartley about injectors; it wasn't too long after the advent of the taller, modern, carbon fiber injectors; the departure from the
old style flat injector hats. the angle on the front of the injector was giving them problems as the bottom of the butterflies was not recessed far enough back in the mold, and the butterflies
would leak air at the bottom giving them problems maintaining consistent idle.
seems like all the teams, with possible exception of bill miller (last year was his last year? or is he still competing?), have gone to the 3 or 4 hole hats. the taller, one piece scoop with the butterflies
lying horizontal to the top of the manifold seem to not be in favor anymore.
old style flat injector hats. the angle on the front of the injector was giving them problems as the bottom of the butterflies was not recessed far enough back in the mold, and the butterflies
would leak air at the bottom giving them problems maintaining consistent idle.
seems like all the teams, with possible exception of bill miller (last year was his last year? or is he still competing?), have gone to the 3 or 4 hole hats. the taller, one piece scoop with the butterflies
lying horizontal to the top of the manifold seem to not be in favor anymore.
mick
Nitro Member
it is what on FC? not following you. i'm talking about TF hats. for a while, many TF'rs used the tall hat, similar to what you see on the nitro injected TAD's
Dennis
Nitro Member
I'd love to hear more about the demise of this style injector. Even in the linked video, Bruno makes reference to the importance of airflow at the hit of the throttle. With those one piece scoop and the butterflies being that much closer to the manifold, I would think that would give some advantage. There must be a reason these never really caught on.
I was told BME style (horizontal) injector blades was believed to have better throttle response, which seems quite plausible. But the advantage it gave in response is negated by the more turbulent airflow into the supercharger. With the blades just above the supercharger inlet, the air is disrupted as it flows into the inlet. The tall (TF) style injectors 3 or 4 hole give the air time to straighten and be better guided into the supercharger inlet thus having better fill of the rotors. The 4 hole injector is preferred over the 3 hole as it is thought the airflow over the car is actually wider and flatter than it is tall. I'm sure this is backed up by wind tunnel results somewhere, but I have never personally seen them. Funny cars do not get the benefit of sticking the injector up in the air but there is lots of data on how it flows over the body and the injectors and (more so) bodies are designed to take advantage of this flow. This is also the reason a FC tends to out MPH a dragster in the back half of a run. The body is more aerodynamic and therefore has less drag than a dragster does with everything hanging out in space. The dragster on the other hand has the advantage of length giving it a better weight transfer early which leads to better early acceleration and quicker ETS.
I think TF cars are roughly 200lbs lighter than FCs which also helps the early numbers a bunch.
NITRO JUNKIE
Nitro Member
Does anyone know how expensive they are?
If I’m not mistaken, I think the Aerodine folks make most scoops now. They could probably answer on social media. But surely someone on the forum can answer your question, Sam.
Z28LT1
Nitro Member
This part is untrue. Better aero will benefit ET, but not MPH. The reason the FC's are out MPH'ing TF is a dual result of better header angle and time on the box.
