barnett87rx7

iTrader: (1)

Hi,
On my new project the fuel lines were ruptured so i decided i was going to replace all of them and the fuel pump and wanted to know how much fuel line i needed to go form tank to engine.

Acesanugal

iTrader: (5)

Not to be rude or anything, but have you gotten under the car and checked? I'll assume not only because you wouldn't have posted if you had taken a peek...

From the feed/return at the engine to fuel filter, you'll need...what like two feet maybe? Then from the fuel filter you need about eight inches, at which point the fuel line becomes a HARD line (metal) all the way back to the tank where you'll have two short hoses yet again. Seriously...look at it and you'll find this out.

Go48

iTrader: (7)

Make sure you use "high pressure" fuel line designed for fuel injected applications.

barnett87rx7

iTrader: (1)

Can i replace the hard line with a braided steel line with max 1000 psi?

Acesanugal

iTrader: (5)

What would be the point? Just replace the soft lines and be done...really. Trust.

barnett87rx7

iTrader: (1)

the hard lines cracked

Evil Aviator

Most of the 2Gen cars need their original hard lines replaced nowadays. They were not intended to last 20 years.

Sure, but AN hoses are three times more expensive than aluminum hard line, and you would need to brace it about every 6 inches. Also, it's going to look like ***, but if you are not building a show car than I guess it doesn't matter.

Now is a good time to upgrade the lines if you plan on increasing the engine horsepower. Rule of thumb for EFI feed lines:
1/4" hard line / -4 AN: 165hp
5/16" hard line: 300hp
3/8" hard line / -6 AN: 500hp
1/2" hard line / -8 AN: 1000hp

barnett87rx7

iTrader: (1)

what size AN lines would be suggested fir 300 hp? 4, 6, 8, 10, 12 AN? I can get the AN lines for 4.79 a foot how much are hard lines?

dvs71990

just answer the guys question, no need to be some uptight.

J-Rat

iTrader: (2)

300? Stock will do just fine. I carried stockers to over 500 hp.

Evil Aviator

There is no -5 AN, so you should move up to -6 AN. This is a very common size which will work well with many aftermarket fuel components.

If you have the time and money, right now may be a good time to consider converting to a parallel fuel setup if performance is a large factor in your life. Otherwise, don't worry about it.

5/16" and 3/8" plain aluminum hard line sells for about $0.75 per foot. Color anodized is about twice that much. Other than the cost and complexity, I don't see anything wrong with your idea of running AN braided hose all the way.

Yes, but his stock lines are broken. He also seems to want to convert his flex lines to AN braided lines, and I think that upgrading to -6 AN sounds like a better idea than downgrading to -4 AN.

As for 500hp on the stock lines, that may be fine for a drag car that only needs to work for a few seconds at a time. However, it will kill the fuel pump on a road car, and I would imagine that the fuel injectors would not get a stable fuel supply under rapidly-changing throttle conditions. I challenge you to reference any fuel product manufacturer's website or catalog, or any technical book written by a professional who recommends a single 5/16" OD feed line for a 500hp force-inducted engine.

J-Rat

iTrader: (2)

Mine drove on the street just fine!

Evil Aviator

What kind of fuel pump?

openrx

on the list of simple basic maintenance is replacing the short runs of flexible high pressure fuel line that's 20+ years old.

like the sections running into and out of the fuel filter, and any other location where replacement is recommended.

absolutely have to do the section feeding the fuel filter,

because the tech who last replaced it shortened the line about 1 inch and it barely reaches the filter fitting now.

these sections are no longer available from mazda as oem, i checked last week.

but high pressure flex fuel line and clamps are available from several local auto parts shops.

5/16th outside diameter is the size based on reviewing several threads here, right?

however the following comment surprises me a bit, especially since no one has challenged it....

anyone have an experienced opinion on this, either way?

i don't doubt it could be true, but why exactly would this be true?

is it a matter of corrosion from the OUTSIDE or erosion from inside or something else?

or is this conclusion about 80s hard line a result of UPGRADES to the power output which puts more stress on the original fuel lines?

is this common to all older cars with fuel injection?

inspecting the lines on my NA s4, at least those sections i can see, the lines ALL look fine, even the black flex sections, and the hard lines look pretty good.

any further views on hard line replacement where no issues are apparent, especially on a stock na ?

thanks
henry