I know when everyone upgrades thier fuel lines they use braided SS lines. Why is that? Why not just use some solid line basically just like stock but larger?

Also, how do you replace the nipples at the top of the tank? I've seen people use AN fittings but I dont know how they attached them. Do you have to weld them in or what?

Thanks,
STEPHEN

 

You can do it either way. Making your own hard line can be time consuming as the tube would need to be bent to shape. Stainless line can just be cut to length and easily routed. Either option would work fine. A nicely bent hard line fuel system would look neat though.

 

Hard line would be difficult because of all the bends. Earl's and Aeroquip among other make rubber lines using AN fittings that are cheaper.

You can attach braided line to the nipples coming out of the tank using double hose clamps or a fitting that has a hose clamp inside of an anodized fitting (forget what Earl's calls this fitting but can look it up if you need it). I used one of these fitting on my return line going to the tank. If a high pressure line, you must use double clamps for it to hold.

I used a bulk head fitting on the supply line coming out of the tank.

There are some pics of my set-up at:
http://ourworld.cs.com/_ht_a/talvendi/id19.htm

Jack

 

(Aluminum) hard line was not safe for fuel injection pressures up until recently.  In a crash, the hard line (especially aluminum) will tend to crack versus AN lines.


-Ted

 

Does anyone know if the aluminum hard lines will fit into the AN fitting ends? Or does the use of the hard lines require special ends to fit onto AN fittings?

Does anyone know where to get the hard line fittings?

Huy

 

What about usings high pressure thick copper lines?

Also, at what point do most people think a upgrade is needed? The more I look into it I'm not so sure the stock lines will cap me off unless I'm making over 550rwhp.

STEPHEN

 

I don't think volume is a problem but the system should have a lower pressure drop. This is not proven but taking to Kinsler about the stock size and -6, they said I should see a lower pressure drop from the pump to the rails.

If anyone has a spare stock fuel system sitting around, this would be an interesting test to see.

Jack

 

Pressure shouldnt be much of a prob for me. I'm going to be running a pump capable of high pressures anyway.

Maybe I'll just stick with the stock lines till I have a problem with them. It sounds like a lot of people replace them when its not really needed and I'd rather spend that money on some other things.....like a wet kit lol

STEPHEN

 

sorry to hijack the thread like this, but just curious if anyone knew the answer to my question.

Will the hard lines mate right into the same aeroquip fittings that are used for the SS flex hoses?

 

hah, stephen, i want to hear about what's next, because it's obviously something big, heha. check your PMs.

 

Yes, hard lines can mate to the "AN" stuff that costs big bucks. You have to get tube nuts, tube sleeves and a flaring tool. I did all my lines with alumn hard line and "AN" style ends. You can get a bender also to make nice bends and make it look awsome or you can simply bend it with your hands. The aluminum hard line is pretty flexible and easily bent.

 

Have there been any good threads on the HP capability of the stock lines?

I was just getting into this with my tuner and he seemed to think I would need to upgrade my lines at my hp level.

I measured all the general sizes of lines used a while ago and didn’t really get a response from others what each was capable of any comments or experiences with what each system can yield safely with acceptable pressure drop in the system.

I am just going to cut and past an excerpt from the post I am talking about.

I have a question for you guys, has anybody came up with a good idea of how much flow area we need to properly feed the upgraded injectors that we are running?

I have been considering if I should move up to 8 from 6 but really don't know if I should. what are the stock lines capable of safely providing in terms of capacity to the injectors?

These are some rough estimates of the sizes and percentages greater than the stock system bottlenecks.

-8 = 9.6mm=.378"
-6 = 7.5mm=.296"
stock fpr=6.2mm=.246"
stock banjo bolt=6mm=.236"
stock hard line=6.3mm=.251"

so to go from stock to 6 it is 1.56 times the flow area.
to go from -6 to -8 is 1.63 times the flow area
and to go from stock to 8 is 2.56 times the flow area.

So how much flow area do we really need for a given HP range, assuming standard fuel pressures?

what is just right and what is excess?

Any thoughts?

 

I know this will be overkill on 99% of the cars out there, but I'm going run a monster of a fuel system, when $$ will allow.

I'm going to sump the stock tank. From the two ports of the sump, I'm going to run -8 lines to two 100ish micron fuel filter, (One for each line.) then each line will hook up to a Ground Zero fuel pump. (The one that Ralph Friend sells.) Each one should be good for around 475rwhp. After the pumps, I'll run a -6 fuel line to the engine bay where each line will have a 10 micron fuel filter, then each fuel rail will get its own -6 line. Finally into a fuel pressure regulator, and back to the tank. Way overkill, but according Ralph, something like 90% of the cars he tunes has some type of fuel problem.

So basically, it'll be a year or two until thats finished. CJ

 

My mechanic made his fuel line from 3/8 inch aircraft fuel line ( steel tubing, 2200 lbs test .The pri rail has custom made ends with 3/8 tubing as does the sec rail .The line starts at the fuel pump connector and runs to the SX fpr .He got a bender to do the job for about $50 , the tubing is about $ 1 per foot .All tubing ,rubber hose and clamps cost about $ 40 .The line runs where the stock one was . The fuel pressure guage nipple is built in with no extra hoses and clamps .

 

seems to me that the fuel line should have the same ID as the ID of the fittings on the fuel pump you are using. I believe (could be wrong) that changes in cross section will have some negative effect, reduction in size will restrict maximum output, and oversize will reduce pressure or increase strain on the pump without flowing more. Anybody have some fuel pumps handy they can measure.

If you are VERY concerned, use a hi-vol\lo-pressure pump from your tank to a sealed fuel canister on your firewall. Then mount your hi-pressure FI pump next to it. Now you have minimal pumping losses (shortest lines possible), and no problems from sloshing fuel in the fuel tank. Don't forget to put a return line from the top of the cannister.

 

I measured pressure drop in my entire fuel system a while back. I have -6 (3/8) from tank to bosch pump, -6 from pump to a 10micron filter, through the fuel rails then returns to tank through a 5/16" line. With a pressure gauge at the outlet of my pump the pressure drop was 6psi (regulator not hooked in for test).

 

The main reason for flexible lines likely has to do with engine motion vs the rest of the car. On V-8 cars as the engine mounts wear out the engine can move a great deal. Hard lines all the way would rip apart when the engine started to move. I'd put my money on the same reason for the RX-7.

-Trent

 

Of course rubber lines are used to connect the hard lines from the body to the hard lines on the engine .

 

Yeah, no one is running hard lines from the car to the engine.

 

Yea, in my example it was "just like stock". The stock goes to rubber just before the engine and also just before the fuel tank.

STEPHEN