860 Performance

iTrader: (1)

I've been messing around with a 4bbl spray bar set-up, and hole sizes in the spary bars have me going crazy.
I started by just bench flowing water throgh the fuel side, and was very surprised to find out how uneven the distribution is. Here are actual #'s of the 'stock' bar. Testing done with a 41fuel jet @12psi. This was done by flowing for exactly 2 minutes, and the measureing the water in a graduated cylinder.
Front 1&2- 160ml/min
cyl 3&4- 190ml/min
cyl 5&6- 210ml/min
Rear, cyl 7&8- 260ml/min
The holes in the 'stock' spray bar all pin-out between .051-.055" They are not in a partictular pattern, just crappy craftsmanship.

So, I decided to make a new spray bar with holes decreasing in dia as they get towards th rear. So I made a set that had a
.053
.047
.043
.043
This bar flowed very well. All cylinders were now within 15ml/min.
Front 1&2- 205ml/min
cyl 3&4- 200ml/min
cyl 5&6- 190ml/min
Rear, cyl 7&8- 205ml/min


So I thought I was done, and just just messing around giving it shot after shot for no apparent reason, until all of a sudden the flow got all messed up, and it started only flowing through the rear 2 holes with a airated pattern. I kept trying it and about 1 out of every 10 shots it only flows out the rear two holes, while the other 9 shots flow perfect. What happens is, sometimes the flowing water pulls a venturi across the front holes and actually pulls air into the tube, instead of pushing water out. This happens about once every 10 shots with a.041 jet, and happens about 50% of the time with a .031 jet, and never happens with a .052"+ jet. This would be disasterous if it happened during use for obvious reasons.
I hooked up the origional spray bar after seeing this, and it does the same thing.


So it seems like I still need to decrease the hole size in the bar, but I'm wondering anyone has experimented with this before? If so, what size holes did you end up with? and for what size shot?

WE TODD DID

iTrader: (2)

What plate are you using?

860 Performance

iTrader: (1)

This was a spay bar install directly into the manifold.
Here are a few pics to show what I'm talking about.

Most of the time it flows like this:



but every once and a while it does this
:

Nick@HSW

iTrader: (4)

I wish more people would flow test their stuff...Especially a single directional tube and I hate to say it but this is exactly why I'm not a fan of spray bars set up like that. Spray bars rely on reversion to fill the tube and distribute. This unfortunately is a prime example of what happens with little reversion of the flow. Not all single runner systems are like that. I've seen 1 that had such horrible flow that the last hole in the run was completely dead lol nothing like such large orifices to completely prevent reversion!! I could go into why eliminating the need for a single directional device that relies on reversion is so beneficial but that would just de-rail this thread. The un-deniable fact is that they suck for even flow, so how can you fix what you're dealt, right? And I will be the first to admit that ALL of these are fixes. There is no 1 single answer that will cure something that might not be the "best" set up and keep in mind that I'm addressing your current set up as some spray bars that act differently from what you have going on now will not benefit from the below answers. Matter of fact they might be detrimental. Well bumping up pressure will get you the reversion to fill the tube quicker and still maintain a decent flow at the primary openings, but that will also start to drown out the holes closest to the "dead end" with excess. This might also require a full revision of the current fuel system...$$$. You can stagger the hole orifices, which it looks like you started to do, but then you might run into distribution issues if the main tube ID is too large. Since we can't create a continuous flow, a dual feed system would be beneficial, but now we're looking at an increased distance between the two bars. More holes with way smaller diameters will also help, but being so damn close to the intake floor, now you're going to run into cylinder distribution issues. Do you see where I'm going with this? Every "fix" of a bad system just results in a potential issue and please don't take that as its helpless, it just takes time and $$. But then again, sometimes its easiest to just start over.

Easiest solution would be to just ditch the fuel and put it at the injector but I don't think that's an option since she's missing some holes at the bottom of the runner.

So...

What size jet are you looking to run? Ballpark it.
What size ID tube is it?
What pump are you using at 14psi? You sure it didn't change pressures on you?
What are you using to regulate your flow on the bench? Deadhead or bypass?

Nick

860 Performance

iTrader: (1)

Nick,
Agreed with most every you stated, reversion does suck for even distribution. Especially when these systems try to have a big range of shot sizes.
Here are the answers to your questions:
-Fuel jet is a .041,
-FFP in the car is 9.5-10 psi depending on weather conditions. its on a return system.
-FFP on my test set-up is 12psi. No regulator at all, just a holley blue pump, which seems to hold 12psi flowing or not.
Tube I.D.=.124"
Vinny

Noyzee

iTrader: (37)

make sure you take the water out of the motor before you fire it up

Nitro Dave's Nitrous Outlet

iTrader: (25)

Vinny,
One of the guys shot me a link to this. I can tell by looking at the job who did it and I know it was not us.

I am slammed at the shop right now but I will try to get back on the board and respond to this later tonight.

In my opinion there could be many reasons why your test showed the results they did and reasons for certain things you are seeing.

Dave

860 Performance

iTrader: (1)

Cool thanks man!
or give me a call if thats easier.

WE TODD DID

iTrader: (2)

Need to get rid of that spray bar. The distribution, and atomization will not be so great.

860 Performance

iTrader: (1)

The atomization is actually great once the nitrous is activated, the nitrous & fuel paths intercept in close proximity of the bars. Really no different than any other spray bar or plate out there.
As far as distribution goes, thats the point of flowing it. Even distribution is the reason for custom set-ups like this, and both the fuel and N20 are right on target for the runners.

860 Performance

iTrader: (1)

Update:
After revision 4, I have something that is working very well. It now has even distribution, and does not ever venturi/ cavitate.
I have made the holes smaller, and still stepping them down at each set of runners.
Also, I noticed the biggest thing that helped prevent the venturi across the first set of holes was to increase the distance from the jet to the first set of holes.

As a side note, we are very lucky to have some fantastic board sponsors here. I think its great when they go out of their way to help out even when its not their parts that are causing grief.

Nitro Dave's Nitrous Outlet

iTrader: (25)

Vinny,

There are a few things working against you in the testing which may have you chasing an issue that is not there. I am going to share some basics here online and then discuss the rest over when you and I talk for obvious reasons. (Don’t want to share our hard R&D)

1.st In the way you are testing your flow results can have several factors that can produce different results. Using a non certified flow gauge is not an accurate way to measure flow. Voltage spikes or drops to the fuel pump can alter flow numbers as well. Pump flow can alter as well due to how the pump works. Even in a perfect flow environment if you were to take a digital certified gauge on a flow bench and flow a one orifice jet discharge over and over and measure it the chances of the measurement being different from time to time are highly likely.

2nd. There is no way you can reproduce the same atmosphere as to when the motor is in use. In your testing for closer results you should have blown the spray bar out and dry each time it was flowed. Something as simple as a water droplet stuck to the hole can change direction. In an engine’s real atmosphere the spray bar is sucked dry shortly after firing. You have to keep in mind that the air velocity cutting across the spray bar tube creates vacuum pulling the fuel and drying it out. In your testing you are also missing the fact the nitrous cuts across the fuel discharge and colliding with the fuel creating suction as well.

There are so many factors that come into play. This is just the simple version. We do a lot of spray bar set ups and companies have produced plates for years with spray bars tube in. I run spray bars on my own cars and I would not due it if there was an issue with them. Of course being properly done is the key as well as knowing which intake’s flow properly with a spray bar feed discharge and which ones do no not.

As to the comment about reversion, reversion has nothing to do with this.

Dave

Nitro Dave's Nitrous Outlet

iTrader: (25)

Smaller holes become more precise but the chances of cloging become greater. Be careful..

860 Performance

iTrader: (1)

1.st- I agree with your comments on small fuel pressure gauges, the small fuel pressure gauges are all junk. You could hook 10 up in a row, and they will all read different. I use the NX certified master Flavor-Flav gauge, and actually trust it.

2.nd I know the atmosphere is way different at WOT. There is no way to reproduce that, but a simple bench flow test is important, to see if its even close. How many times have I seen flow paths totally miss runners, or have a clogged hole etc. so there is something to be learned from simple bench flow tests.
I feel if it looks reasonable, then run it, and checking plugs is the final say.