fuel split for 14-71

i have been doing quite a bit of research and figured i would ask everyones thoughts on this. we run an altered with a 526 hemi and 14-71 HH. the blower is an older SSI(B rotor) that makes 40-42 pounds. i am trying to make things more efficient for this season, and since i can't afford a new blower i wanted to get every ounce i can out of what i already have. we run 6 nozzles in the hat, 2 in the back of the blower, and 8 in the manifold. the average size of the hat nozzles is smaller than the manifold nozzles. my thoughts were to put alot more fuel in the hat, and through the blower to hopefully cool the ail charge a little and seal the blower a little tighter so i could make more boost. i wanted to run a smaller nozzle in the manifold...........is my thinking right on this? does this make sense, or am i totally lost here? can someone please give me a little insight on what kind of split i can get away with here? what % of fuel should go where?
thanks,
Darren Russell

 

I tried that over the last couple of years, and still believe that it should work, but we weren't able to run any quicker. I think if you load the clutch hard enough, and perhaps back the barrel valve off a bit to compensate, it should seal the blower better. We were up to the low 60's in the hat, and went correspondingly smaller in the manifold, but the car seemed to be dogging it on the starting line. As I said, maybe I should have backed the barrel off a bit; the rotors would see the extra fuel once the throttles are wide open anyway.

 

Darren,
Keep in mind the more boost you have, the more fuel pressure you need to push the fuel through the port nozzles. Manifold pressure is trying to push the fuel back up the lines.

 

The thought of putting as much fuel as you can through the blower to cool the intake charge is a good idea. The problem is that, as you put more fuel through the blower there will be less space for air in blower. This can be tuned for, by taking fuel away, but it starts to defeat the purpose of the blower by decreasing the flow of air through it and decreasing the potential energy that can be released from the air.
If you would like to decrease the air temperature past the blower then you can reduce the heat additions of the air due to friction. This can be done by having your rotors coated with a friction reducing coating.

 

Are you saying that a friction reducing coating is going to reduce friction against the air that is being pumped, or are you saying that the blower rotors are rubbing against the case?

What about using the nozzle bodies with the check valves instead of the check valve in the distribution block. Wouldn't this reduce some fuel lag to the port nozzles or would it be so insignificant that you wouldn't notice?

 

Last season i first ran with 45% on hat and 55 % on port ; Bae 456 , 14-71 HH , 50 % over , converter dragster . On computer the int temp was in the 150-160 deg. range , then i switch for 60% in the hat (Don Gerardot upright) and 40% in the port . The temp drop to 120-125 deg. range and lower my ET by .15 .
Just my experience

Claude

 

WJ,

It reduces the friction from both. As the air passes by the rotor there is friction between the air and the rotor, and internal friction in the air due to internal shear created as some of the air slows down against the rotor, this generate the boundry layer.

Also the rotors will rub each other in spots, especially after a few bangs. The tips see friction against the rotors and housing from the pressure it takes to create a seal due to microscopic surface imperfections. Friction coatings reduce these imperfections and the tendency for the air to slowdown as it passes by the surfaces in the blower.

This will not however reduce the temperature increase from the air becoming pressurized that is reduced with the addition of fuel to the air.

 

I've been trying to figure this out over the last couple years also. What I do know is Fred Mandolini and Brian Knox of Sassy Racing Engines put more fuel thru the blower than in the ports.
One of these years I'll have a blower dyno and I'll find out for sure, but I have to think there is a happy medium. A spot where more sealing(more hat fuel) is a diminishing return because of the air thats being displaced. I run about 60/40, 60% of my fuel goes thru the hat. I can't really go anymore because with ft discharge the distribution is so uneven and I already have a port nozzle at .024". Soon a setback blower will help that.

 

Hi Mike
I'm talking jet area

 

Mike
Is it possible to calculate that mathematicaly, with fuel pressure and boost press. or the only way to have the real % is to work with 2 flowmeters on the car .
Claude

 

Jet sizes

The port nozzles are smaller in area than the hat nozzles, so they have more pressure, I don't think the blower will affect the port nozzles flow. Randy Anderson's roots fuel set up has 10 nozzles up top, and one in each port. I'm not positive, but I think 2 of the top ones have check valves, don't know what pressure they are. P/S remember the KISS rule

 

What is the utility of the check valve nozzle

Thanks
Claude

 

Mike
In a pressure system , if the pressure is doubled , does the amount of liquid is doubled too.
in other words ; if the fuel pressure is 100 lbs and the boost press is 50 lbs , does the amount of fuel is cut in half . (in the port )

Thanks
Claude

 

Thanks Mike

Claude

 

The two that have the check valve don't flow till the fuel system gets to a pre set pressure, I'm guessing it's like a hi speed enrichment to cool the blower.
Mike i see what your saying, but that would be only when the valve is closed, when the valve opens the piston is sucking air from the port so it's not as much as you think. Plus if you use the old style nozzles ( not the aerodynamic ones ) they act like a venture so it's even less.