basic fuel injection question

[Dave1647545494]

I'm doing some getting ready planning for my new motor and everything is going to need replumbed for high pressure fuel.

 

I'm planning on running 1/2" fuel supply from the tank to the rail. On the return side does the line need to be bigger/smaller/or the same size?

 

on my carb setup I have an electric pump already so I just have to switch it out to one made for FI and I'm good, but what I'm not sure about is the fuel filter where is a good place to get a canister type(like an oil filter) rated for high pressure?

 

Are ecm's very susceptible to RF or other electric noise interference? does it need to be sheilded somehow or ist it all built in? (stock gm/delco computer)

 

 

all help appreciated

 

thanks

[BiG BeN]

return line should be the same or bigger than the supply.jegs has filters on the shelf,some have replaceable elements and are clear(bling). ECU's are generally not going to be effected by RF unless you have a 16gigawatt linear amp mounted ontop of it,but are adversly effected by dirty power.so make sure it's grounded well and you'll be fine.

[Guest chochmo]

the return line is usually a little smaller. If you are pumping fuel up there and using some of it, how are you going to need a larger return line??? I don't think an engine creates fuel... jegs has good fuel filters

[BiG BeN]

you want your FPR to be the only regulator.with a smaller line you can cause backpressure in the system,especially if your pump flows alot more than you're using.

[Guest chochmo]

depends on the type of pump you use. They make pumps that don't even need return lines, because they work like a water pump does; they can keep pumping without creating backpressure. You also don't need a larger line because you aren't going to have more fuel returning to the tank than what you ever pumped up there in the first place.

[iwishiwascool]

I bet this link will help

 

http://www.tgsi.com/fi_101.html

[Renner]

Dave,

 

In theory, you should use a larger line for the return because you don't want it to cause any pressure rises. But you will be fine running a return line of the same size, especially since I don’t think you will be running a crazy fuel pump. During idle and low speed starts is when too small of a line would make the most noticeable problems, as that is when you will have the most fuel trying to flow through the return.

 

Any place you want to put the filter after the pump and before the rails is fine, as long as it won’t get damaged and won’t drip on any exhaust if you have a small leak. The Aeromotive filters are nice because you can unscrew them and replace just the filter element, and because they have large end fittings for good flow. I would stay away from those shiny K&N fuel filters, they don’t seem to flow well and the filter elements don’t last very long before they disentegrate and clog your injectors. There are some other Aeromotive type clones under different brand names at Jegs as well that may be cheaper. Just plan ahead so it is easy to get to if you need it.

 

Putting the ECM right next to the coil packs can have some affects, but that is about it. So as long as you don’t have it right next to the coil packs or any other amps that contain large coils, ect. you will be fine.

[Dave1647545494]

ok so a 1/2 inch feed with a 1/2 inch return line I'm going to use an aeromotive pump regulator and filter and I'm going to put the computer in the glovebox so no problems there.

 

that about covers it now its time to rip out all the old low pressure lines sump the tank and replumb it all.

 

thanks to al who replied I appreciate it.

 

I'll take some pictures of before an after

[Trouble Maker]

Wouldn't restericitions in the return line causing any drops in pressure be just like restercitions in the send line causing any drops?

 

My logic is that the FPR should keep the pressure constant, or a variant thereof based upon how that particular FPR is designed to work, constant across the injector to the manifold pressure differential basicly. Any pressure drops across the supply or return line are just going to cause greater head pressure, lowering flow, causing the pump to work possible heating up the fuel. Is what I'm saying right?

[Dave1647545494]

restrictions don't drop pressure they raise it the FPR is right before the return line as long as its the same size or bigger it doesn't cuase any extra pressure build up. the reason the line nedds to be larger with a crazy fuel pump is so that the regulator does all work. the regulator should be the only restriction in the line. with an adjustable fpr you change the amount of the restriction and that varies the pressure, if the return line restricts more than the fpr you get too much pressure and you can't accuratley control it. ( I broke down and went and bought some books about high performance fuel injection so I can do this motor swap without having to stop and ask a question every six seconds) smile.gif

[Trouble Maker]

Originally posted by GAS,GRASS,OR,ASS:

( I broke down and went and bought some books about high performance fuel injection so I can do this motor swap without having to stop and ask a question every six seconds) smile.gif

Lol. I still don't see how that explains why my logic is wrong (not trying to argue, trying to understand). With an FPR you adjust the base pressure without the vacume line hooked up. I understand that it would be best to have a supply and return line that don't have a large amount of restercition for what one is flowing as to not have huge pressure differentials (drops) across them. I just don't understand how it would be determential to building a car other than the fact that for the same fuel pressure across the rail one will have a higher head pressure, which means less flow and more heat. Won't your fuel pressure still be XX PSI and you should be able to basicly keep that constant and that's what's important?

 

By drop pressure I'm thinking from the way I was first taught basic EE stuff with voltage drops. At the head basicly you have to have X pressure which will 'drop' across the entire system. You'll get a few PSI drop across the supply line, then whatever across the fuel rail from the FPR then whatever across the return line.

[Dave1647545494]

fuel pressure won't drop at the rail cuase the regulators at the end of it any pressure drop would be after the regulator and by then it doesn't matter cuase its just flowing back to the tank