Nozzle sizing help on oddball combo

Hey guys - I'm in need of some expert opinions on how much a nozzle change will affect overall volume of flow....first off, there's not much about my car that is done correctly and I'm out of money to have the system flowed. So here goes -
This is a turbo alcohol 4 cylinder Ford drag car. I just spent a day on the dyno and we got to the point where it seemed very close on fuel mixture judging by power gains/losses.
I have a single main bypass operating under boost, but a Hilborn valve downstream that pinches the return under boost.
There are 2 nozzles per runner, a .024" primary and a .055" secondary.
My problem is at the correct mixture we are running a system pressure of 300psi. Ouch!
My question is this - if all else stays the same (main and Hilborn) will installing larger nozzles reduce the pressure while holding (roughly) the same volume? I am only looking for a ballpark answer as I'm just trying to get close enough to go to the track to make some short test passes.

 

sounds to me like you have a pump that is too big. what jet do you have in the main?

 

It's a Kinsler pump, for the life of me I can't remember the model right now, but it was supposed to be a little larger than the -1 Enderle 80A I used to run (7 gpm). Main is a .093 but with the Hilborn valve pinching the return downstream of that I don't know how to guess at the end result except by pressure.

 

at what rpm is your pressure at 300 psi?. what you might need is a pump loop.you would put a t right on top of the pump with a poppet set at around 50-60 psi and a jet to bleed off fuel when the pressure gets over the popppet set presure. by using a poppet , your idle will be the same, but when your pump speed increases it will bleed of the unnesasary fuel. you can start out with a .050 jet in the loop, but you might put a smaller jet, like a 80 in your main to start, if your still on the dyno make a short pull to watch the exhaust temps, and the fuel pressure. you can keep putting a bigger jet in the loop ,bringing the pressure down and for a while it might not even effect your exhaust temps because your fuel pressure is so high. .
just my ideas fom past experience, what worked for me, might not be the right fix on someone elses problem. good luck.

 

We saw the 300 at about 8000 - and about 200 at 6000rpm and the same boost and follows the rpm from there.
I am unconcerned about idle and low speed pressure as that only runs about 20psi when not under boost.
When you say pump loop do you mean feed it back into the pump inlet or back to the tank? I eventually eliminated the high speed/pump sizer line I had to get enough volume to the motor, I am just trying to reduce the overall pressure without leaning it out at all.

 

Why would the high pressure be a problem? If delivery is about right, and the motor is happy, then the high pressure can only serve to help velocity and atomization at the nozzle. I don't see a down side?.... Also, is that Hilborn return pinch valve giving you a 1:1 boost pressure increase, or some gain value? It may well be making the pressures "look" high.

 

I'm just not used to running such high pressure and it made me nervous more than anything. I called Kinsler today and they said that pump will handle 300 no problem but they highly recommended changing the rear seal.
The Hilborn valve increases the pressure in a totally non linear curve.
I think now I have an idea about what to do with the whole system, sometimes I just need to think out loud and get some unbiased input, thanks for the help!

Dave

 

when i say loop, you can run it back under the pump or back to the tank, i always ran it to the tank. there is NO need for pressure as high as you are seeing. would you need to water your lawn with a fire hose, when a garden hose works great? i would have to look at some of my cmputer graphs, but i am pretty sure a kept the pressure below 180 psi at high rpms. don't qoute me, and DON'T try to hit a certain pressure on the nose just because someone gives you a number unless they run your exact combo.

 

Yes. That is exactly as I had thought....
You might want to enquire of Hilborn, what the actual bias ratio is for your valve. It will have a number engraved or stamped.
Your turbo MFI deal is much different than most blown MFI deals. Nothing wrong with seeing 300+ psi pressure at times with your's.

 

i guess we need to clarify something, is this a alcohol system with a barrell valve, distribution block, and nozzells, or a mechanical o.e.m. type ,computer controlled injection system.

 

As I understand things, Flanders has an MFI system with a Hilborn turbo pinch valve (backpressure valve).
The system hydraulic pressure will then be X + (boost times the boost gain factor of the valve), for net delivery pressure.
X will be a function of pump speed versus restriction (nozzle area). The boost gain pressure will be an adder in terms of system boost pressure, over and above X. Nothing out of the norm here, just a different approach (common for turbos) for fuel delivery.

 

Yes it's an alcohol system with a barrel valve for the primaries, a second barrel valve that opens at half throttle to feed the secondaries, and the usual dist. blocks and lines.
I just got back from the track and by increasing the primaries from .024" to .030" and using a high speed bleed that opens at 100psi with a .040" pill I was able to drop the pressure to about 200 while still holding the fuel curve on the rich (safe) side.
TOL - I wasn't aware there was an actual ratio for the Hilborn valve, I'll give them a call.
For right now though the car is running well, it's safe, and I can easily give it more boost if need be without worrying about being on the ragged edge.
Thanks for the input...Dave