Series or parallel opinions

krhonn

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I'm soon to start installing a level 2 fore return system on my car to run e85. My question to you all is what route you took or would take (series or parallel) and why?
Thanks in advance, Kenny.
 

JeremyH

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Its a largely debatable subject there are so many ways to do it and really no way to definitive prove one is really better than the other at automotive flow rates and pressures. You could argue from a fluid physics standpoint that you have a better chance for equal pressure to each injector with rails in parallel. But you would need to ensure equal lengths of line from the feed split as well as from each rail back to the regulator which can be tricky in an engine bay while finding a good spot for the regulator, also more line and hose ends are needed. On the flip side you could say when you split a feed line either with a y block or through a regulator to now feed two lines with more volume that you can limit the actually flow through each path as you push the system even when pressure is maintained. On paper you could debate the physics of it all day, in the end you have to kind of try to make the system not work and cause a pressure difference between injectors regardless of the chosen setup. You will have an issue from maxing out injectors or maxing the fuel pumps long before your route method would cause an issue. Consensus is parallel may be better when pushing north of triple digit power put I have seen dead head and series setups handle the same flow power. So in the end just set it up how you like and how it makes sense for your setup.

That being said, the fore level 2 kit is setup for rails in series regulator after rails, so the fittings and hose ends included in the kit are intended for that method. Its one of the easiest and most common ways done, its cheaper, less fittings and works great. 9 out of 10 Fore kits I install are set up that way from basic setups to 1000rwhp on e85, including my own car is setup that way. A few tips to optimize the setup would be to keep the line from each rail as direct and short as possible and make sure the regulator is not too far from the second rail outlet usually no more than 2-3 feet away. Pressure drop through 8an line/rails is about 1psi for every 6-8ft from friction. So as the fuel travels away from the fuel hat there is some line and filter pressure loss but the regulator being at the end after the rails almost completely nullifies that effect as that's where the pressure is maintained back from and any flow or pressure change from injectors firing or pumps kicking on or off is instantly adjusted for by the regulator.
 

krhonn

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This is great information you've posted thank you. I was leaning more towards the series with regulator after rails do to it looking cleaner and more straight forward.
JeremyH when you wired your pumps up what color wire do you splice into? I've heard the purple/another color and I've heard the yellow/grey wire. From reading the purple/other color is a continuous feed with the key on. The yellow/grey wire kicks pumps on while cranking.
 

JeremyH

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Technically you could use any key-on power source. Preferred method is use the stock inertia wire as your trigger to retain the inertia switch function in case of an accident. The wire color depends on the year of your car.
 

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