Need help with fuel injectors

mob

the guy who hits on his mom
15 Year Member
Oct 3, 2003
2,566
136
104
33
Dallas, TX
I'm not saying it is how it is supposed to work. But, I do not believe fuel pressure is an input to the computer, so, it is blind there. It has a nozzle (the injector) and it "knows" the size. But, you can lie to it. Tell it the injector is 19#/hr and install one that is 24#/hr. With 50 psi fuel pressure, it will leave the injector open some period of time with the 19# injector, seeking the correct reading on the Oxygen sensor. With a nozzle about 25% larger (24# vs 19#), and pressure about 25% less (40 psi vs 50 psi), I believe the time the injector pulses for a 24# injector and 40 psi will be about the same. At least I expect it will run. Then again, the computer can adjust some based on the Oxygen sensor reading.

Seriously, if that won't work (and I'm not saying it is the right thing to do) I'd love to understand why.

I guess maybe I got confused by your question when you said "will the computer think 19# injectors at 50 psi are the same as 24# injectors at 40 psi". There is also no input in the computer for injector lb #. The computer uses things like voltage offset, high slope and low slope, breakpoint, to set the fuel trims. Different injectors have different ratings at different PSI. When you increase the PSI it just makes the injector act differently than the computer is expecting, it doesn't just think you dropped a bigger injector in there, you're just forcing a rich condition.

I couldn't find 19lb injectors at 50PSI but below is an example of ratings for a 24lb injector at 55PSI vs 30lb injector at 39 PSI. Maybe the difference isn't noticeable to us when driving but the computer knows.

Untitled.png
 

mob

the guy who hits on his mom
15 Year Member
Oct 3, 2003
2,566
136
104
33
Dallas, TX
Okay, I've wondered about this, so, let me ask you about WBO2s. Do they install instead of your O2 sensor and provide the signal to the ECU, or install in addition to your O2 sensor, in which case, I guess another fitting needs to be welded into the exhaust? Also, the big mystery with my 95 GT has always been the missing O2 sensors. The Ford dealer, and everywhere I have checked lists upstream and downstream O2 sensors for a 1995 5.0 Mustang GT. I think that is an OBD2 thing that is on 1995 V6s and 1996 and later 4.6s. But I have 2 sensors, not 4. Anyone else have this?

Wideband doesn't hook up to your stock computer, there is no input for it. The computer cant make adjustments based on an added wideband 02, it can only make adjustments from your stock O2. A wideband allows you to hook it up to a gauge that will give you a live reading of your AFR.

Aftermarket computer setups or something like a Quarter Horse allow you to hook up the wideband for data logging, but the computer doesn't actually make adjustments from what the sensor is reading. You take the reading yourself and make adjustments to the tune. Oh and you would need to add an extra bung on your exhaust if it doesnt already have one. You should always leave the stock O2 sensors in place. Without them the computer can't make adjustments.
 
Last edited:

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
23,417
8,624
203
polk county florida
Okay, I've wondered about this, so, let me ask you about WBO2s. Do they install instead of your O2 sensor and provide the signal to the ECU, or install in addition to your O2 sensor, in which case, I guess another fitting needs to be welded into the exhaust? Also, the big mystery with my 95 GT has always been the missing O2 sensors. The Ford dealer, and everywhere I have checked lists upstream and downstream O2 sensors for a 1995 5.0 Mustang GT. I think that is an OBD2 thing that is on 1995 V6s and 1996 and later 4.6s. But I have 2 sensors, not 4. Anyone else have this?
you need the 02s obviously, if the parts counter person can't find an 02 for a 95 5.0 push rod engine then they don't know how to A: input proper info B: can't properly read a computer screen.
DY1401 Motorcraft
Ok, in defence of the counter person, Rockauto lists upper/lower/right/left but same part number so they didn't comprehend what they were looking at.
 

vristang

15 Year Member
Mar 31, 2005
4,933
106
124
46
Seattle
I’m not sure of the function of the second O2’s? Weren’t some of these used as a confirmation of functionality of the cat?
I don’t think the secondary o2 affects fuel trims…???
But I didn’t realize the 95 used a secondary o2 either, lol.

The stock ecu cannot accept the signal from a wideband o2.
However, most wideband kits do have the capability to ‘simulate’ the narrow band signal to the ecu, while still running the true wideband signal to a gauge on the dash, or a data logger.
I ran this with an innovate LC-1 for a few years, using moates quarterhorse on a 2.3.
 

Bill95

Member
Apr 9, 2005
59
19
18
Virginia
you need the 02s obviously, if the parts counter person can't find an 02 for a 95 5.0 push rod engine then they don't know how to A: input proper info B: can't properly read a computer screen.
DY1401 Motorcraft
Ok, in defence of the counter person, Rockauto lists upper/lower/right/left but same part number so they didn't comprehend what they were looking at.
Even the dealer tried telling me I have four sensors, when I only have two. I honestly think there was a mid-year change, or anticipated change, in the cars or the catalog. The 1994, which I expect to be identical to the 1995, only has two O2 sensors (like my car), the 1996 4.6 SOHC has the 4 listed in RockAuto for a 1995. Again, I think it was in anticipation of OBD2.
 
  • Agree
Reactions: 1 user

Bill95

Member
Apr 9, 2005
59
19
18
Virginia
I’m not sure of the function of the second O2’s? Weren’t some of these used as a confirmation of functionality of the cat?
I don’t think the secondary o2 affects fuel trims…???
But I didn’t realize the 95 used a secondary o2 either, lol.

The stock ecu cannot accept the signal from a wideband o2.
However, most wideband kits do have the capability to ‘simulate’ the narrow band signal to the ecu, while still running the true wideband signal to a gauge on the dash, or a data logger.
I ran this with an innovate LC-1 for a few years, using moates quarterhorse on a 2.3.
To be clear, there are only two (total) O2 sensors on my 1995, Only the primary, like a 1994. Not an upstream and downstream like 1996 (or the 1995 V6). The 1995 5.0 does NOT use a secondary O2 sensor.
 
  • Like
  • Agree
Reactions: 1 users