PSI Screw Hat Fuel ??

Same in mine (80's) in the hat. I also have a 20 number spread between the front and back. The backs are 20 or more bigger and the plugs read good like this.

 

Many thanks to those who have responded both online and offline about the hat fuel thing with a screw !.....

Sounds like maybe the hat fuel delivery is not as critical as I may have thought. I'm still going to go ahead and try an "electronically" controlled hat fuel scheme to fit in with the rest of the overall ECU controlled fuel scheme.

I am still confused in one sense though. I hear of a lot of PM and ADRL guys talking about working around messed up port distributions with their screws. If the hat fuel is not the culprit, then what is the culprit in their case? Sorry, I'm just not understanding this. If the hat fuel/air is well homogenized coming out of the screw, and if the port nozzles are reasonably balanced, then I can't picture where their problems are coming from? Is fuel distribution generally a problem with screw deals, or have these people just done some things to author their own problems?

Thanks.

 

More fuel pressure, smaller nozzles, better atomization?

Is the best information here from all of the fuel going in the hat or ports, to still to run higher fuel pressure, smaller nozzles and it will make better power through better atomization? I have gone back to nearly 50% in the hat and 50% in the ports, and all seems good for now. If this is bad, let me know what to change? Our fuel temps and air seem really cool going in the intake. THANKS! Jim

 

Agree totally with the bold underlined section in the post above. What sort of fuel back pressures do people typically see through a run with MFI & a barrel valve wide open?

In this current project I'll have 16 port EFI's in a constant 120 psig fuel loop (with boost bias pressure added to that), and the hat fuel devices [whatever they turn out to be....] will either be part of the same fuel loop or on a different fuel loop with their own pump/regulator. My goal is to be able to map out the port fuel (with per cylinder trim ability) independantly of mapping out the hat fuel (bulk batch mode). My thinking is along the lines of, does the hat fuel really always need to be a fixed % of the total fuel going into the motor (as with MFI) or are there better alternative approaches? I'd go even higher with the port pressures for the exact reasons that Blown5402 touched on, but the electromagnetics of the port EFI's that I have just won't play well past 120 psig differential pressure, give or take.

All ideas that I've wanted to explore for some time. Just getting around to them now. Things move slowly at this end. Too much other crap gets in the way first it seems To those who have responded both on & off line THANKS ! ITA is a great resource !......

 

140#s and higher for manual fuel systems

I know this is just one opinion, but we are still real low (140#s) on our fuel pressures for now, compared to many we race with. Some are from 250#s to 300#s and some even higher with really small nozzles. I just always think about the smaller nozzles plugging easy and hurting a cylinder. I have seen several fuel lines from the distribution blocks break also. I realize the fast cars are onto something, but we are crawling and starting to walk that direction now-THANKS! Jim

 

22 nozzles to 24 nozzles

TOL, we are running 22 total nozzles now and going to 24 this season. Atomization is also better and ETs picked up quite a bit too-THANKS! Jim

 

Blown 5402, do you find that your port stagger is decent with 50+% fuel through the hat? What OD do you run? Do you run the PSI bottom plate or have you gutted it out?

Thanks.

 

Small nozzles = easy to plug and high fuel pressure. High pressure can lead to elevated pump wear which highly increases the possibility of getting those little pieces of end plate/gears stuck in your nozzles. This can be worse with your electronic fuel injectors because there are little tiny screens that plug fairly easily. To complicate matters, if your electronic injector gets crap by the screen and it hangs the injector and you lift at the 1320 and go back to idle, you run the risk of blowing the rod out of that hole (it's happened). I would run MFI nozzles in the hat and put a couple on checks (they make nozzle checks) if you are worried about distribution during idle and use your electronics to control your cylinder to cylinder. If you plug one of those electronic ones in the hat and the rotors get a little hot, they will stick and the blower will be junk (this has also happened). I seen a pretty neat injector with specific electronic injector placement for the screw some time ago, thinking it had 3 progressive blades; would this happen to be yours?

 

I think I need a fuel injection lesson or maybe I’m just reading this wrong.

I can understand if you make the nozzles smaller and reduce the total area of fuel flowing to the engine smaller that the pressure will increase given the same pump output and bypass size. Just making the nozzles smaller but giving the engine the correct a/f ratio by adding more nozzles that are smaller would give you the same effective fuel to the engine which would do nothing except make some of the nozzles smaller and prone to clogging as some have said. The only way I can see to raise the pressure and give the same a/f ratio the engine wants (based on an already good tune) is to raise the pump output.

Am I missing something here? Always open to schooling in this stuff.