Parallel vs Series Fuel Rails?
08-15-08, 10:29 AM
#1
Parallel vs Series Fuel Rails?
I've seen most of the write-ups for fuel systems switch the fuel flow through each of the rails from a parallel to a series flow setup, but what is the reason for doing this? Is it just for a more even distribution of pressure between the rails? Does it help to dampen out pressure fluctuations more? It seems like the parallel setup may be more likely to have problems though, in case one of the rails becomes plugged, theres a greater restriction in one than the other, or a line gets kinked then the majority of the fuel will pass through the other, starving the one for flow. Has anyone noticed (or solved) fuel issues by going with one setup over the other?
08-15-08, 05:15 PM
#6
^^That's the main reason^^
But I don't really have any data to contest that as I made the parallel mod for my own personal reasons (because I wanted to get the hang of doing AN fittings)
But the "theory" is with larger secondaries (1600's, not those little 720's
) in a series system they may not have adequate flow behind them to fill the large hole an open 1600 creates. but with the feed split to both primary and secondary, it becomes easier.
but like I said, I have no real data.......my honest guess after years of running the parallel system is that a series stock style system would work very well, I just have no idea at which point (fuel flow or horsepower) the series system starts to lack.
But I don't really have any data to contest that as I made the parallel mod for my own personal reasons (because I wanted to get the hang of doing AN fittings)
But the "theory" is with larger secondaries (1600's, not those little 720's
) in a series system they may not have adequate flow behind them to fill the large hole an open 1600 creates. but with the feed split to both primary and secondary, it becomes easier.but like I said, I have no real data.......my honest guess after years of running the parallel system is that a series stock style system would work very well, I just have no idea at which point (fuel flow or horsepower) the series system starts to lack.
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08-16-08, 11:12 AM
#10
Ok, thanks for the responses. I've only got 1000cc's for the secondaries and havent had a problem with them in the stock series configuration, so I think i'll keep it that way when I put in the new FPR. my plans arent THAT big for this car anyway, just a nice healthy 250-300 at the wheels.
Classic, doesnt the 2ndary rail come after the primary in terms of fuel flow? In that case, only one of the 2ndary injectors would be seeing this "void", which would be the same as if it were a parallel setup. If you had ridiculously large primaries and secondaries it would seem to make sense to do a parallel setup, but with smaller primaries it shouldnt make a difference (and because of flow losses, the primaries would see a higher pressure than the secondaries anyway, so you could in theory flow a little bit more fuel to the engine for a given injector size).
Classic, doesnt the 2ndary rail come after the primary in terms of fuel flow? In that case, only one of the 2ndary injectors would be seeing this "void", which would be the same as if it were a parallel setup. If you had ridiculously large primaries and secondaries it would seem to make sense to do a parallel setup, but with smaller primaries it shouldnt make a difference (and because of flow losses, the primaries would see a higher pressure than the secondaries anyway, so you could in theory flow a little bit more fuel to the engine for a given injector size).
08-17-08, 12:08 AM
#11
Ok, thanks for the responses. I've only got 1000cc's for the secondaries and havent had a problem with them in the stock series configuration, so I think i'll keep it that way when I put in the new FPR. my plans arent THAT big for this car anyway, just a nice healthy 250-300 at the wheels.
Classic, doesnt the 2ndary rail come after the primary in terms of fuel flow? In that case, only one of the 2ndary injectors would be seeing this "void", which would be the same as if it were a parallel setup. If you had ridiculously large primaries and secondaries it would seem to make sense to do a parallel setup, but with smaller primaries it shouldnt make a difference (and because of flow losses, the primaries would see a higher pressure than the secondaries anyway, so you could in theory flow a little bit more fuel to the engine for a given injector size).
Classic, doesnt the 2ndary rail come after the primary in terms of fuel flow? In that case, only one of the 2ndary injectors would be seeing this "void", which would be the same as if it were a parallel setup. If you had ridiculously large primaries and secondaries it would seem to make sense to do a parallel setup, but with smaller primaries it shouldnt make a difference (and because of flow losses, the primaries would see a higher pressure than the secondaries anyway, so you could in theory flow a little bit more fuel to the engine for a given injector size).
hm... your running a stand alone. just do the parallel man. its not a problem duders.
08-18-08, 11:03 AM
#12
Classic, doesnt the 2ndary rail come after the primary in terms of fuel flow? In that case, only one of the 2ndary injectors would be seeing this "void", which would be the same as if it were a parallel setup. If you had ridiculously large primaries and secondaries it would seem to make sense to do a parallel setup, but with smaller primaries it shouldnt make a difference (and because of flow losses, the primaries would see a higher pressure than the secondaries anyway, so you could in theory flow a little bit more fuel to the engine for a given injector size).
08-18-08, 11:22 AM
#13
I ran 21psi on a T04S 60-1 with fuel lines in series no problem, 720/1680 with rewired Supra TT pump. The stainless parallel fuel system mod is nice, but IMO not "necessary" to keep your fuel pressure from dropping off, although I would recommend an aftermarket FPR for consistent fuel pressure under all levels of engine load. And injector staging is mostly a function of the way you have tuned your EMS.
