The V8 Owners Forum -

Just a general query, say if I was running a -6an line from the fuel pump to separate fuel rails on a V8 (so not like an RV8) would it be better to use a Y-block and split the -6an feed to each fuel rail, with the other ends of the fuel rails going to a FPR with a single return to tank.

Or would it be better to go in one rail, down, then across to the other rail?

I'm thinking the former?

The general consensus seems to be that a parallel system (i.e. Y piece) should provide a more even fuel pressure distribution across injectors, while a series system will potentially show a lower pressure at the end of the run compared to the start, therefore Parallel is supposedly "better", especially on batch injection where you cannot compensate for the reduced pressure in the downstream injectors.

However, I suppose it depends, like many things, on the power output expected, pump flow rate, pump peak pressure, injection method, etc. Series seems a potentially slightly cheaper, and less clutter, option if the system is up to delivering suitable pressure to the last injector.

volospian wrote:The general consensus seems to be that a parallel system (i.e. Y piece) should provide a more even fuel pressure distribution across injectors, while a series system will potentially show a lower pressure at the end of the run compared to the start, therefore Parallel is supposedly "better", especially on batch injection where you cannot compensate for the reduced pressure in the downstream injectors.

However, I suppose it depends, like many things, on the power output expected, pump flow rate, pump peak pressure, injection method, etc. Series seems a potentially slightly cheaper, and less clutter, option if the system is up to delivering suitable pressure to the last injector.

Thanks that's what I suspected. Power is going to be around 300bhp and system is more than up to providing the juice.

I've seen various people giving out various power figures, from anything over 400bhp to well over 1000bhp before parallel is a "must", although I don't see how a specific HP figure is an accurate indication anyway. I suppose the reality is that, for the most part, you probably need to do the maths and see what the figures say, rather than listen to internet "experts"

If you ask me, far from being the amazing mine of information it is constantly billed as, the internet has actually reduced the amount of accurate knowledge we have at our fingertips. Like the old adage about a man with more than one clock never knowing the real time we now have instant access to a million different opinions, none of which are based upon fact or experience.

volospian wrote: If you ask me, far from being the amazing mine of information it is constantly billed as, the internet has actually reduced the amount of accurate knowledge we have at our fingertips. Like the old adage about a man with more than one clock never knowing the real time we now have instant access to a million different opinions, none of which are based upon fact or experience.

Are you sure that is the case??
Best regards
Mike

chodjinn wrote:

volospian wrote:The general consensus seems to be that a parallel system (i.e. Y piece) should provide a more even fuel pressure distribution across injectors, while a series system will potentially show a lower pressure at the end of the run compared to the start, therefore Parallel is supposedly "better", especially on batch injection where you cannot compensate for the reduced pressure in the downstream injectors.

However, I suppose it depends, like many things, on the power output expected, pump flow rate, pump peak pressure, injection method, etc. Series seems a potentially slightly cheaper, and less clutter, option if the system is up to delivering suitable pressure to the last injector.

Thanks that's what I suspected. Power is going to be around 300bhp and system is more than up to providing the juice.

Really wont matter unless the rails are very tiny diameter.

Just do whatever looks or is neatest and easiest.