MFI injector line size

[r lane]

I have a track car that has MFI. I was tired of dealing with the existing rigid lines, so I had a set of aeroquip lines made up. The OD of the line was .320'', am waiting on a call from the company that made them to get the ID. I had concerns over how much of an effect the ID would have on the performance of the injector as the ID of he stock line is fairly small. Pascals Law talks about that I think, and as I understood it, the ID shouldn't have effect on the pressure. Didn't make sense to me, if you are moving a larger collumn of liquid, more effort is required. Pascals law though may be about contained fluid as in a break system. I had a second set made up, but out of larger hose, .460'' as the smaller hose,' was not immediately available. Installed my second motor which had a different pump and the larger injector line. Engine would barely run. Traced some issues to a crank sensor and loose terminals on the ignition connector. Improved as it Ran fine above 4000, but stumbles badly below that. Checked cam timing, compression, injectors. I was getting ready to put the other pump on, but the injector lines were bugging me. Switched to the smaller lines and engine is now right. All of this to ask, what would be the physics concerning the sizing of the injector line. Thanks for any input. Bob

[Arlo911]

Hi Bob, I think I read on one of the MFI threads that Aaron Burnham made some larger ID fuel lines, you might want to check with him?

[356RS]

I don't have the answer for the physics concerning I.D. line sizes but I have been using "Nylon 11 High Pressure Tubing" for the MFI pump fuel lines for over 10 years. The size I use is: O.D. 4.8mm, I.D. 2.8mm with a working pressure of 800 psi. The lines have been used on engines as large as 3.8 liter MFI and have not seen any evidence of loosing any flow/pressure at WOT on dyno runs. This isn't the answer your looking for, just some data.

[r lane]

Hello Mark. That is good info thankyou. I had a set of the plastic lines and they made me nervous just looking at them. My second event, one line came apart. Thinking my next move is something that I at least think is more substantial so went with the aero quip. The first set has 4.0 mm ID approx and the engine performed well. The second set I had made is approx 5.0mm ID, whereas the stock line is approx 2.0mm. The car does not want to run well with the larger line. The 2.8 mm that you have is probably the dimension I should be looking for. Thanks, Bob