Nissan LS240

iTrader: (1)

I'm running 42lb injectors in my LS1, 383cu. in. 215 afr heads, fast intake, etc. tuner said for the injectors to run at at 42 lbs I should set the pressure regulator to 43 lbs, I running it at 43lbs and haven't had any issues with the fuel but I thought the ls1 runs on 58 lbs of fuel, I'm using a aeromotive a1000 pump, 10 an lines, with a y fitting before the fuel rails going to a full bypass aeromotive regulator after the rails thats hooked up to engine vacuum.

I just want to know why he said to run it on 43 lbs as opposed to the factory 58psi. is that how its supposed to be or just something that this tuner does.

thunderstruck507

iTrader: (18)

The flow rate of the injectors is at a certain rating of rail pressure. Unless you have injectors which are rated 42lbs at 43lbs of line pressure instead of being rated 42lbs at 58lbs line pressure, that comment makes no sense to me.

What injectors do you have?

MeentSS02

iTrader: (11)

If that's how he tuned it, and it gets to the correct AFR under all conditions including heavy load WOT, don't worry about it. The higher pressure might help with fuel atomization, but if it runs well, I'd leave it alone. He might have been worried about not being able to control the idle with a higher base pressure, but it shouldn't have been a problem with that setup.

Nissan LS240

iTrader: (1)

injectors are delphi/lucas 42lb/hr at least thats whats on the receipt

dodson55

iTrader: (18)

leave the fuel pressure at 58 and them injectors i believe are 48lb at ls fuel pressure

joecar

Several points:

- your injector's flowrate is 42.29 lb/hr at 43.5 psi rail pressure;

- they will flow 42.29*sqrt(58/43.5) = 48.83 lb/hr at 58 psi;

- what rail pressure is your FPR set to...?

- is the rated flowrate measured with heptane or octane (what does the spec sheet say...?)...? if heptane, you will have to scale both of the above cases for octane (octane is denser; the injectors flow the same volume of either liquid, so flowing octane will flow more mass);

- if your FPR is vacuum referenced then the IFR table will be flat (same value in all cells); in this case measure the rail pressure with the FPR reference hose temporarily disconnected, and use this to calculate the IFR;

- if your FPR is unreferenced, the IFR table will be sloped (actually goes as squareroot), you will need the famous spreadsheet to calculate it; it this case measure rail pressure as is (unreferenced);

Your tuner should already know all that.

joecar

Also note that those are not large enough injectors to really cause any idle problems that requires running 43 psi vs 598 psi rail pressure.

But in any case, make sure your tuner has gotten all the other injector tables filled out with the correct data for those injectors.

Nissan LS240

iTrader: (1)

I don't have any issues with the motor, fuel pressure is set to 43lbs at idle, goes up close to 50 at WOT, air:fuel stays within 13-15, Geoff at EPS tuned it so I'm sure its right just want to know why run 43lbs but I kind of get it now, thanks for the explanation.

joecar

Your tuner didn't set it to 43 psi... he set it to 50 psi

(with reference hose removed your rail pressure reads 50 psi, same as you said at WOT)

(the IFR table should have been calculated for 50 psi rail pressure; if it wasn't, then the tuned VE table will correct for it (i.e. the VE table is scaled to the IFR)).

since your FPR is manifold referenced, your IFR table should be flat.