Like most people I'm not too thrilled with the design of the fuel rail system. I'm planning on buying 2 6" pieces of aluminum fuel rail and tapping it for 5/16" barbed fittings (3/8" NPT). I'm assuming that 3/8 NPT -> barb 5/16 exist. I found em.. on ebay

Does anyone know what the exact OD of the fuel injectors are? I'd like to use 5/16" high pressure fuel line on everything.

I'm pretty sure I'll have to fab a bracket to support the extra weight of the fuel rail. I'm surprised the stock fuel rail is floating.

I'll also tap a 1/8" NPT for the fuel pressure gauge.

I've seen a fuel rail kit on the market, but it costs $170 or so. I can build this for ~$30.

Yarin

I'm not sure why you want to work so hard. The stock rail is simple and effective. They deliver plenty of fuel for my 2270.

Dave

I know the stock rail can flow enough fuel, i'm more concerned about the safety of the rail. There seems to be a lot of conflicting info regarding proper hose diameters, 90 deg elbows vs. straight, etc etc.

I need all new elbows, so why not build a new fuel rail. It's cheaper and safer. Plus there is no easy way to mount a 1/8" NPT fuel pressure gauge on the fuel rail. I'd rather minimize the number of fuel hose clamps.

I guess i'm overly cautious in redoing the system to prevent any possibility of a fuel leak.

I agree that the stock design has problems. In my case, one of the short hoses from the aluminum rail to the injector was very slightly bent, causing a restriction. The amount of restriction changed with the slightest movement, and as a result, I had a very annoying bucking while trying to accelerate through the mid RPM range. Easy to fix w/ fresh hose, but a real PITA to track down.

Sounds like you're still going w/ those short rubber hoses. So definitely make sure they are straight and under no load when youmount the rail to the bracket.

Oh, and be sure the rail is CNC machined from aircraft-grade billet aluminum and anodized in a pukey color.

QUOTE (jsteele22 @ Feb 21 2006, 09:56 AM)

I agree that the stock design has problems. In my case, one of the short hoses from the aluminum rail to the injector was very slightly bent, causing a restriction. The amount of restriction changed with the slightest movement, and as a result, I had a very annoying bucking while trying to accelerate through the mid RPM range. Easy to fix w/ fresh hose, but a real PITA to track down. Sounds like you're still going w/ those short rubber hoses. So definitely make sure they are straight and under no load when youmount the rail to the bracket. Oh, and be sure the rail is CNC machined from aircraft-grade billet aluminum and anodized in a pukey color.

Are you using the factory style bent injector hoses or straight fuel line? If its the latter i would imagine that could cause the flow restriction that you described.

Cap'n... is 5/16" hose an acceptable size for the barb fitting on the injectors?

Fuel injection is something that needs to be looked over carefully. Keep in mind that no one has spent more money into engineering cars than Porsche has. So if you feel that you want to try something thats not "Porsche," be careful. Just my 2 cents.

QUOTE (nbscooters @ Feb 21 2006, 12:52 PM)

Fuel injection is something that needs to be looked over carefully. Keep in mind that no one has spent more money into engineering cars than Porsche has. So if you feel that you want to try something thats not "Porsche," be careful. Just my 2 cents.

Agreed. But is this a Porsche design or VW design? I think technology has changed significantly and costs of materials have dropped enough to allow for the modernization of areas like fuel delivery. Early fuel injection isn't flawless.

I always look at things from an engineering perspective.

The stock set-up if fine, but what I did is made steel lines to go from one side (3/4) to the other (1/2), used stock clamps and I got real VW fuel hose...not the braided shit...the stuff they use now on the WC cars. It's expensive (like $7./FT) but it's real good hose.

I'm pretty anal about checking my hoses (I have aftermarket FI) and I've never found a leak yet.

QUOTE (nbscooters @ Feb 21 2006, 12:52 PM)

Fuel injection is something that needs to be looked over carefully. Keep in mind that no one has spent more money into engineering cars than Porsche has. So if you feel that you want to try something thats not "Porsche," be careful. Just my 2 cents.

Porsche didn't engineer the 914 EFI system, Bosch did, and it's pretty much exactly what you'll find on Type 3 VWs, too. No one uses hoses and bent tube fuel rails anymore, they use O-ring'd injectors with a solid fuel rail. EFI technology has progressed somewhat since 1967, when the D-Jet system was designed.

If you're going to go to a new fuel rail, I'd consider dumping the D-Jet injectors entirely and go to a modern injectors, which are generally cheaper, too. You could probably sell the D-Jet injectors on Ebay for 50%-100% more than you'd spend on their replacements. This eliminates two more hose-barb connections (between the injectors and the fuel rail). This makes the fuel rail fabrication easier, too. The replacement injectors could also be selected with much lower flow rates, too.

That said, the D-Jet system, as long as the hoses are replaced once in a while, has been very reliable. Many 914s and Type 3s are still driving around on the same fuel rails that they left the factory with 30-35 years ago. That kind of reliability is pretty hard to argue with. I plan to stick with the stock fuel rails and hose-barbs on my setup, if only because the (relatively) low pressure hose is easy to get, and as long as good hose and clamps are used, doesn't leak.

QUOTE (lapuwali @ Feb 21 2006, 01:06 PM)

QUOTE (nbscooters @ Feb 21 2006, 12:52 PM) Fuel injection is something that needs to be looked over carefully. Keep in mind that no one has spent more money into engineering cars than Porsche has. So if you feel that you want to try something thats not "Porsche," be careful. Just my 2 cents. Porsche didn't engineer the 914 EFI system, Bosch did, and it's pretty much exactly what you'll find on Type 3 VWs, too. No one uses hoses and bent tube fuel rails anymore, they use O-ring'd injectors with a solid fuel rail. EFI technology has progressed somewhat since 1967, when the D-Jet system was designed. If you're going to go to a new fuel rail, I'd consider dumping the D-Jet injectors entirely and go to a modern injectors, which are generally cheaper, too. You could probably sell the D-Jet injectors on Ebay for 50%-100% more than you'd spend on their replacements. This eliminates two more hose-barb connections (between the injectors and the fuel rail). This makes the fuel rail fabrication easier, too. The replacement injectors could also be selected with much lower flow rates, too. That said, the D-Jet system, as long as the hoses are replaced once in a while, has been very reliable. Many 914s and Type 3s are still driving around on the same fuel rails that they left the factory with 30-35 years ago. That kind of reliability is pretty hard to argue with. I plan to stick with the stock fuel rails and hose-barbs on my setup, if only because the (relatively) low pressure hose is easy to get, and as long as good hose and clamps are used, doesn't leak.

I concur....

The stock injectors can only handle what? 26 psi? Newer injectors are available that can handle much greater pressures and deliver fuel much faster. And can be had for a minimal amount of time and effort.

QUOTE (yarin @ Feb 21 2006, 12:37 PM)

QUOTE (jsteele22 @ Feb 21 2006, 09:56 AM) I agree that the stock design has problems.  In my case, one of the short hoses from the aluminum rail to the injector was very slightly bent, causing a restriction.  The amount of restriction changed with the slightest movement, and as a result, I had a very annoying bucking while trying to accelerate through the mid RPM range.  Easy to fix w/ fresh hose, but a real PITA to track down. Sounds like you're still going w/ those short rubber hoses.  So definitely make sure they are straight and under no load when youmount the rail to the bracket. Oh, and be sure the rail is CNC machined from aircraft-grade billet aluminum and anodized in a pukey color. Are you using the factory style bent injector hoses or straight fuel line? If its the latter i would imagine that could cause the flow restriction that you described. Cap'n... is 5/16" hose an acceptable size for the barb fitting on the injectors?

5/16 is too big, IMO. That's 8mm, fuel hose was 7mm, now 7.5mm. 8 fits just a bit too loose. The Cap'n

The stock fuel rail is fine, and floating is fine. The special elbows are not necessary. (I know, some will say huh?? There's a reason they did it, etc.) But if you just use FI hose about 2" long between the rail and the injectors and leave the rail floating, it will not be a problem. At least from my experience on my car, it is absolutely not a problem. At that length, the bend is extremely minor - certainly not enough to cause restriction or kinking.

That being said, I applaud you for thinking about ways to make new designs. If that's what you want to do, go for it.

I have noticed several posts lately where people say you shouldn't try anything different than what the factory engineers did. Because after all, they know best. Rubbish. Don't get me wrong, of course the factory engineers smart... But these cars are 30 years old and plenty of better ideas have come along. And plenty of things about the design of the 914 have been shown to be bad. And plenty of things about the 914s have been improved upon by guys in this very club.

Personally, I wouldn't get hung up on the fuel rail thing. But I love to see people engineer and implement new ideas. And share them!

QUOTE (alpha434 @ Feb 21 2006, 01:10 PM)

I concur.... The stock injectors can only handle what? 26 psi? Newer injectors are available that can handle much greater pressures and deliver fuel much faster. And can be had for a minimal amount of time and effort.

Well, you're concurring for the wrong reasons.

The stock D-Jet injectors actually flow too MUCH for near-stock engines, so better flow really isn't the aim. Rather, by using O-ring injectors that plug into spigots in a modern-style fuel rail, you're eliminating two hose-barb connections per injector. The higher operating pressure is also desirable from an atomization perspective, as long as you engineer the rest of the fuel system to operate at the higher pressure, too. Again, IF you're going to go to the trouble to make modern style fuel rails, I'd go that extra mile to do the rest of the system to modern standards, too.

Again, however, the "outdated" D-Jet way of doing things seems to have worked well for the last 30 years, so the reliablity concerns over the extra connections and the free-floating fuel rail seem to be unwarranted.

QUOTE (lapuwali @ Feb 21 2006, 02:06 PM)

If you're going to go to a new fuel rail, I'd consider dumping the D-Jet injectors entirely and go to a modern injectors, which are generally cheaper, too. You could probably sell the D-Jet injectors on Ebay for 50%-100% more than you'd spend on their replacements. This eliminates two more hose-barb connections (between the injectors and the fuel rail). This makes the fuel rail fabrication easier, too. The replacement injectors could also be selected with much lower flow rates, too.

Just got 8 brand new Bosch injectors for my Ford truck for $37.50 including tax and shipping

These use the o-rings on top and bottom (fuel rail is still a steel tube, not sure of the diameter, but it's not that much bigger than the 914 parts)