Hat vs Port Nozzle Percentage

I know this has been discussed in several threads before but I can't find a definitive answer for what I'm looking for searching through prior posts.

I calculated my nozzle numbers and I'm running about 51% through the hat and 49% through the port nozzles. Four nozzles in the hat and four in the blower. Single nozzle to each port. 14-71 STD helix SSI Roots.

My questions are:

1. What is the optimum setting for the hat to port ratio?

2. How much increase do you think I'll get changing to the answer to #1?

3. What is the smallest port nozzle that you would use safely?

4. What is the smallest hat nozzle that you would use safely?


I have a safe tune now but want to tweak it to get the most out of what I have but not burn my stuff up. Just bought 240 plugs so I can tune away.

Thanks.

Tom

 

Mike,

Appreciate the input. I made a typo as I do run six nozzles in the hat and four in the blower case along with eight in the ports.

Yeah, I'm concerned that the port nozzle size would get too small if I went to something in the 30's to achieve the 70-30 split or so that I've seen some recommend. My comment about the hat nozzles was really about what I have in the back of the blower case as they are 36's at this time. I really don't want to plug a nozzle and I guess that is my main concern. We filter the fuel going into the cell and also System One it before the Barrel Valve but I know stuff can still plug up a small nozzle.

I am computing the total area of the ports and the total area of the hat plus blower case and then comparing them against each other. I have about 130 PSI during the run. Just trying to squeeze out what I can with this combination as it sits now.

Thanks.

Tom

 

I have had better success running larger port nozzles than hat nozzles.

 

max percentage

hey, we just took a drill bit to all the nozzles, added 100 percent nitro, and it fixed all the lack of acceleration problems! but dont buy more than 1 gas tank of fuel, you wont need it!

 

Mike, I am very likely the exception. I am messing with a Pontiac powered funny car, the Dirty Bird. (a real Pontiac motor, not a Big Chief) So, I wonder if the wedge chamber, 2 middle exhaust valves type head (like a sb chevy) has anything to do with it liking fuel squirt into the runner, and why it is not so picky about making the blower happy? I hear what you are saying and know you are right about the cooling, sealing, and such. Most everyone agrees with you, except my obscure, oddball motor. This is one thing she is positive about, and she will mess up my time slip if I try to be normal.

 

Dave,
Travis Quillen runs the pontiac wedge engine , with twin turbo forced induction. He has down heaps of R & D with Rodney Butler from Butler performance. Travis's can be contacted : travis@quillenmotorsports.com
cheers
Ash

 

port nozzels

I tried it last year, had no success it kept puddling large amounts of fuel in the cyls. It was something I had to try, + I had 2 good fuel syst. guys try to help me out. They both said the same thing Mike did.so If you do try it, please be very careful. It could end up very costly, + ugly when you can't get out all the unburnt fuel in the cylinders.

 

OK, so maybe the chamber shape and heat concentration issues shouldn't matter, as long as it is getting the proper a/f ratio. Believe me, it has been run with the same fuel volume, and been run on both sides of what is proper. If there is a problem with the intake instead, I would love to know what the problem is, since I made it. We are running a 14-71 hh retro, set waaayy back, about a foot, so that the opening is in the middle of the engine. This apparently has been effective in treating all eight cylinders fairly. Tuning by rod bearings, and by plug readings, my port nozzle sizes wound up very near the same size. The engine has also proven to be very resistant to detonation, even when getting lean. Now, I have been concerned as to whether the plenum is large enough, and maybe that is the peculiar thing that is giving peculiar results. I don't think runner cross section is an issue, it is about 4 sq. in. on a 475 ci engine. Sigh. Why is my motor so weird?

 

Thank you Ash. I will check out what Travis has come up with. I did talk briefly with Dave and Rodney Butler about a turbo motor they were fooling with about a year or two back. Sounds as though I need to do some more interrogation.

 

Well, I didn't say anything was wrong with the intake, as it is obviously working very well. Fuel distribution is very good, and even when the majority of the fuel was going in the top, the engine required very little adjustment with port nozzle sizes. It is shaped just like many other top performing intakes also. I only said that apparently this motor is peculiar. Peculiar as in functioning better in a way different than some people say that it should. I originally stated that I had better success with larger port nozzles. Success. I am not the only one to have had this experience as I have heard others with roots blowers say the same thing. It is very common for screw blower motors to run double the fuel volume into the manifold as they do on top of the blower. I know the screws are a completely different animal and do not heat the air nowhere near as much, but this fact has to add some validity to my experience.

Theories: 1. Maybe because the engine that we are running is essentially a small chevy with severe heat issues, perhaps it is more important to inject cool fuel directly into the head. 2. Fuel that is atomized by the nozzle gets turned back into larger drops by all of the contact and torture of grinding through the blower. Maybe this head is able to keep what is sprayed into the runner somewhat atomized at the point of combustion. 3. Smaller displacement engines like this one run more boost from the same displacement blower and therefore the port nozzle flow is reduced in overcoming manifold pressure. Larger nozzles compensate. I have not calculated how much this effect would be so I don't know if this is worth considering. I appreciate the input you gave and I am sorry to be so long winded.

 

Dan, I'll take that one under advisement. I thought the holes in these nozzle thing-ies looked kinda small. .187" drill in each one should be just about right, right? That would match the hose size or do we need bigger hoses and bigger holes?

 

big ol hoe

we gave up adjusting nozzles and jets, forget all that! just hook up the line straight to the port and all problems solved! no reason to overcomplicate things so much. geeeez