I think the cleanest way to do my direct port kit is with 2 nitrous and 2 fuel rails. But, I don't want to pay ~$300 for them. I don't see any reason I can't make a set (I have access to a lathe and a mill). Does anyone know the inside diameter of the some of the aftermarket rails. I want to make them (especially the fuel) as small as possible so they can pressurize faster. I don't plan on going over a 250 shot with it.

Thanks
Dustin

 

how about some PVC??

 

You do not want to make fuel or nitrous rails "as small as possible." The smaller you make them, the larger gradient you will have in pressure from cylinder to cylinder, and the more variance you will have in the power made in each cylinder.

One way to maximize pressure buildup AND minimize cylinder-to-cylinder variations is to feed the rails from both ends.

 

That would look nice wouldn't it

Injuneer:

Thank you for pointing that out. I had not thought of that before. I see what you are saying about a pressure gradient as there liquid (N2O or fuel) goes past each port. I don't understand how the inside diameter changes this pressure gradient. I was mostlly worried about creating a large volume that would take a long time (relative to the N2O) for the fuel to pressurize.

If I want to feed the rail from both ends I can do it by putting a T on the solenoid and plumbing to both ends right? I would like to avoid buying more solenoids if I could.

So does anyone have a recomendation on what inside diameter would be good to use?

Thanks for the help
Dustin

I just realized that if I put a solenoid at each end of the rail (and a Y before them) if one of my fuel solenoids fails, the rail would still pressure up and it probably wouldn't cost me a motor.

 

Something someone pointed out to me, since you have to drill/tap your own rails no matter what, place the inlet in the middle of the rail and plug both ends, this will distribute the fuel/n2o more evenly and pressurize better, the two outside cylinders will get slightly less fluid, but its better than going in on the end and the opposite end of the rail gets less and less as you go down.

 

i had never thought of that either. this is a good thing to keep in mind if i ever do DP. Thx for the info.

 

The pressure drops as you get farther down the rail, because of "friction" from the fluid flowing in the pipe (rail). That friction is VERY ROUGHLY proportional to the area of the rail..... double the diameter of the rail and the pressure loss per unit length drops by a factor of 4. The pressure gradient will always exist... making the diameter larger reduces the magnitude of the gradient, to the point where it is no longer "significant".

 

Thanks, I see what you are saying now.

I have a couple more questions.

1.) Is the pressure gradient a percentage of the original pressure? Or, Is there a constant pressure drop across each port no matter what the original pressure was? If it is a constant figure, then I will probably have little effect on the N2O side, (ie if it is going to drop 2 psi after each port from the original 1000psi) then it is a very small delta, but if it drops say 10% (regardless of original pressure) after each port, then I would have a large pressure drop by the time it got to the end. I am wondering if I could feed the fuel from the middle and the N2O from the end with little adverse effects.

2.) At what point do I run into trouble from the rail taking too long to pressurize? I just made a spread sheet where I can adjust all of the variables (flow rate, size of rail etc.). I assume the pump is pumping at free flow until the rail pressurizes (100 gph in these figures). If the rail is .15" diameter it should take 0.0661 s to fill. If it is .25 " diameter it takes 0.1836 s to fill. if it is .35"diameter it takes 0.360 s to fill. My point is that the time the rail takes to fill increases exponentially with the diameter of the rail. .36 s seems lke a long time to go with no pressure in your fuel rail.

Thanks a ton for the help, I am learning a lot.

Dustin

 

Might wanna check this out, I might just be using this instead of the $265 NX rails. Not positive if it will work, but dont see why not.

Fuel Rail Extrusion

 

The price is right, thats for sure. It would be nice to know the diameter of the inside of the rail.