question about fuel pressure and IDC
 

Well my question will probably be the opposite of what everyone thinks... I currently have FIC 1000cc (#112ers@58psi Fuel Pressure), which IMO are tooooooo big for me at this time. soooo I am thinking about dropping the fuel pressure down to make them smaller....

The reason for this is while just crusing at 70mph my IDC is FREAKING 6%....

At 60mph it is FREAKING 4%....

Basically anything below 50mph the IDC is 2%
Yep those are all single digits...

At 155kpa (around 8psi), 5200rpm, 14* and no meth, my IDC is 40%......



I have noticed since i added the turbo my MPG has suffered about 3mpg.....



So i have been thinking about dropping the Fuel Pressure down some to make the injectors smaller, Perhaps gain back some of the MPG...


Thoughts??

If your o2s and wideband say its at the correct fueling, changing injectors or system pressure will make absolutely no difference. What is the injector pulse width in those instances?

The wideband is good, i am not using the narrow bands. VE table is dialed in for the most part at 14.7AFR

PW at 60 is 2.640 at 5% IDC
PW at 70 is 2.763 at 6% IDC

timing is in the upper 30's low 40's...

I thought injectors flowed more volume at lower pressures? Or is that the beer talking?

I think your thinking of Pumps

I think I'm thinking of beer. :)

If you drop fuel pressure, atomization suffers. It would most likely work against you. You can expect a loss in mileage with a turbo...most often it is hard to tell the difference in mileage though, if you stay out of it.

3mpg seems like a big difference to me. Have you been through the entire tank without getting into the throttle..?

I'm with atomic. I don't see how lowering the pressure would make the engine use less fuel, increasing your mpg..

Yes, lowering the pressure at the injector will lower the overall lb/hr number that the injector is able to flow, making the injector seem smaller, but that will not change the fuel demands of the engine. The engine is going to need a fixed amount of fuel at x and y to stay at stoich. If you kept it steady at 3500rpm and 50kpa, it doesn't matter what size injector or IDC you have, the injector would just have to work harder if small (higher IDC), or not as hard if large (lower IDC). So if the VE is tuned correctly and your wideband shows 14.7, then the injector is delivering the correct amount of fuel even if the IDC is small.

How hard would it be to add the narrowbands back in to your setup? I would recommend doing that. I would rather have 3 sensors tell me my fueling is ok than just 1...

the narrow bands are installed and wired up just turned off. I have thought about running semi-closed-loop, which in EFI Live is a mixture of both stock OS and Custom OS.