Plumbing fuel -- Series or Parallel?

[JoeMag]

Is there any issues with plumbing fuel rails in series vs parallel? Lines do not seem long enough that you'd see any pressure drop from one rail to the other.

[JoeMag]

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[r lane]

Not speaking from scientific knowledge, but I don't see how one would differ from the other. Pascals law about pressure being equal all through a contained system. Bob

[dannobee]

The "series" one in your diagram is used by most if not all manufacturers.
I've seen it both ways. I prefer the cleaner look of the series method.
Practically, like Bob said, it likely doesn't make a difference, assuming there's enough flow/pressure at the end to keep the regulator returning fuel to the tank.

[targa72e]

Something to consider . Porsche had in their stock systems a damper. With batch firing multiple injectors at one time it could cause pressure pulses in the fuel system. The damper effectively isolated one bank from the other to lessen the pressure pulses. The fuel system is not static pressure. If using aftermarket ECU then sequential would be preferred for many reasons and reduces large pulses as multiple injectors are not firing at once. unless the rails are undersized I think both layouts should work equally well.

john

john

[JoeMag]

Thanks gents... interesting data on the pressure pulses. I’m running sequential injection...

[dannobee]

The dampers weren't limited to Porsche. The problem of omitting one is that the injector closing causes a water hammer effect, not different from pipes banging in an old house when you turn off a faucet. Except in a car, the "ping ping ping" noise is transmitted through the fuel line and can be heard by the driver. The damper helps eliminate the noise.

[r lane]

I have some understanding of the physics of engines and chassis, but addmittently, am often monkey see monkey do, so I love the frequent enlightenment received from cogent information that populates this site. I have a twin plugged, EFI 3.3 Turbo that ran full sequential initially. In trying to sort out running problems that cropped up a few years after the build, I changed to phase sequential. Engine seemed to like that better, and didn't have to run as rich at low rpms. Not really sure why I chose full sequential initially. The difference in the 2, and I need to look at my old notes, but I think the phase fires every 360 as apposed to 720. On paper that sounds better to me as you have a shorter injector time which I take as better control, but considering the varying speeds of the engine components and air and fuel, figuring out on paper is a start, and then let's go try it. Thanks for all your good info guys. Bob

[jonathant]

Joe,
FWIW, the 986 and 996 use a series flow fuel system, just like in your left picture. They are coil on plug EFI, 250-350HP, in-line fuel filter, and no fuel damper.

[winders]

I have a new 3.6L race engine build with AT Power ITBs and Injector Dynamics 1050x injectors. I am using a single Bosch 044 fuel pump, AN-6 lines, AEM fuel pressure regulator, and an Injector Dynamics ID F750 fuel filter.

I did a lot of asking around about this parallel vs in series controversy with people that build a lot of high output air-cooled engines with ITBs. The consensus is that the parallel setup is better. It is a must use with our 6 cylinder air-cooled engines in some situations. Those would be 600+ HP situations. That would be because of inconsistent fuel flow concerns.

But, the "in series" setup is perfectly fine with most normally aspirated setups and you will not giving up any performance. In fact, the simplicity of the setup means there is less to go wrong with hoses and fittings.

When I plumb my engine fuel lines, I will be using the "in series" configuration. Why? Because there are no downsides and some upsides.