breath in

N

NateDogg

Guest
hey, top end airflow question here. How does these throttle body spacers affect EFI engines. I can see the affects of carb engines having it, but just twising air above helps just as much?
 
What kind of throttle body? With fuel injected at the throttle body or in front of an port injection set up using a plenum "top"?
 
Well, all in all plenum is plenum. I like it to be 125% of cylinder displacement in an ideal world....seems nothing is ideal anymore. In a case where it is TBI where you have a spacer under a throttle body injector, you still want it to be tall enough to prevent the fuel from bouncing off the floor of the plenum. In the case of a TPI then spacers would be used to help get that 125% ratio.

....be carefull about keeping the plenum and runners separate. If the spacers extend the length of the runners, make sure they will be an ideal length for the rpm at max hp. If you know where that point is I can help you determine runner length.
 
lets say 6000 rpm peak.

hmm, what about these "power tower" deals, spinning just air around in a EFI engine, I can't see where it would help. So its all about the 125% volume of the displacement. Is there a curve for that?
 
LMAO!!!!! You mean those JC Whintey things?

I'll get you an f(x) function for runner length.
 
haha, yeah. I knew you love those. Seemed a little over reality with their claims, made me wonder, heh.

Just found a article on nhra.com and moroso has one made out of plywood for heat transfer, huh, seems like a cheap and easy way to experiment.
 
This will work for runner length and is not propreitary:

RL = 3E-07x^2 - 0.0067x + 44.808

RL = runner length
x = rpm

note: ^2 means squared

Remember, runner length is from the seat to the end of the air horn. The best way I have found to measure the length, just in the head is to form a wire along the floor from opening to seat. Measure it. Do the same to the roof. Add both together and divide by 2. You may want to do the same for the intake runners, or or injector air horns, or if using webers, to the end of their air horn. That is ideal length.

As for those spinners......paper weight? LOL!
 
heh, expensive paper weights eh.

thanks for the fx, will try it out this week.
 
I think I figured out the 3E-07 E part of it and the runners came out to roughly 117%
 
Don't consider the runner volume as part of plenum volume. Treat them completely separate.

What runner length did you come up with?
 
You must log in or register to reply here.
Back
Top Bottom