Fuel Injector Sizing

[4pointslow]

Your calibration summary and some others have unexpected values for some fuel pressures.

I can't help but wonder of they are wrong on purpose to mislead people who are just getting the info off their sites without buying anything.

 

[4pointslow]

Fuel pressure to 54.96 (55 psi)

I raised my fuel pressure to 54.96 and entered my corrections to the injector data. First test drive I could not get the HEGO test to run/pass.
I did notice a characteristic, if the load was lower (20-25) it seemed like it was going in then going right back out of the test. I was watching OBD Test State, it is 1 when not testing and goes to 2 when testing starts. At loads around 20-25 it would go to 2 and back to 1 real fast.

At higher loads around 35%, it would stay in "2" longer.(test was running longer and being kicked out)
If it did not pass it would go back to 1, if it passes it goes to 4 and stays there and the OBD tests complete goes up by 32(number for HEGO Test run/pass).

I adjusted the MAF transfer Function after doing a step test and gave it another try, the test ran and passed but it would only do that on the highway. I could not get load high enough (35) on the back roads. So it seems to want or need load to be around 35%. Of course changing MAF and/or injector data changes the calculated load value.

I must note that I stopped adjusting engine displacement to make load read 20 at Idle, after reading that it should not be done anymore. I did do it in the past. I figure that the statement may have been made when considering newer vehicles with drive by wire and Variable camshaft timing. Changing engine displacement might make it hit higher loads(35) at lower speeds if needed at some point, assuming that will help get this HEGO test to run/pass.

So I have got this thing to run/pass the HEGO tests with fuel pressure at 54.96. I am going to adjust the transmission shift points again to try to get it to go into 5th sooner and run the test at lower speeds. I also need to see where injector duty cycle is at WOT. (With all this information I can't help but think that I could put the 60's back in and get them to run/pass).

Pictures showing where load is vs HEGO test running/not passing/passing.

 

[4pointslow]

Data

some injectors do have non linear slopes

back in the day it was common to use the LPG 160 lb injectors, at low pulsewidths you could increase the pw and LEAN OUT the injector, they had very non linear low flow control

although the data may look wrong it COULD be correct, i know injector dynamics have non linear multipliers as well

You had to tell me that....
I downloaded some calibration files for the ID injectors off their site, they are in excel format.
I notice on the ID725's that the break point multiplier goes the opposite way than the other multipliers.
The ID850's and ID1000's break point multiplier goes the same way as the other multiplier.
I can understand not being linear but going the opposite direction makes no sense to me. Makes me think there are more typos.

 

[4pointslow]

scaling engine displacement to change load

[MENTION=163567]decipha[/MENTION]

My load is approximately 14% at Idle in park.
I want to scale engine displacement to change load so that it is 20% at Idle in park in hopes that I can get the vehicle to reach loads around 30-35% at lower mph, like 30-40mph instead of 50mph.
Should I just scale engine displacement, or should I scale the injector data with it? Should I scale engine displacement, injector data, and MAF transfer function?
Just trying to reach higher loads at lower speeds as an experiment.

 

[2000StreetRod]

Offset multiplier

I realized that I've tried changing high slope, low slope and breakpoint but never experimented with offset.

If I shift the above plot left the PCM will think there is higher flow and reduce the pulse width resulting in a leaner lambda. If I shift the plot right the PCM will think there is lower flow and increase the pulse width resulting in a richer lambda. I may try changing the offset multiplier (FNPW_OFFCOMP) and see what happens.

 

[4pointslow]

Scaled Engine Displacement/Inj Data to Raise Load

Load was 14, wanted 20% so 14\20 = .70
I scaled engine displacement and the injector data by .7
Without even dialing in the maf, the HEGO test ran/passed at about 35 mph in 5th gear on a back road.

STFT was adding fuel, it was not near 0% like it should be. Some things to note were that test 16 ran real fast.
16 is the test for fuel trims called the closed loop fuel test. I think when STFT and LTFT is near perfect it seems to take longer to run/pass 16. It wants to make sure Fuel trims don't exceed these limits:
Lean malfunction: LTFT > 25%, STFT > 5%
Rich malfunction: LTFT < 25%, STFT < 10%

Also STFT cycled around .90 during the HEGO test instead of around 1.00, I believe that was due to STFT being there when it entered the HEGO test.
This kind of shows that having the A/F perfectly dialed in is not absolutely necessary to run/pass the HEGO test.

Time to go step test and start dialing in the MAF again, then it's off for a WOT run to see where duty cycle goes.

 

[4pointslow]

Pegged Load at 200%

Well, the scaling didn't work so good after all. I pegged load at 200%.
I will have to scale down, and dial everything in again. lol.
At least I am having fun experimenting and may be able to get those Deka 60's to work, after getting through inspection with these 47's I have two years to get them to work. lol.

 

[4pointslow]

Duty

To top it off I pegged the Injector duty cycle too. Whoops.
And this is with fuel pressure set to aprox 55 psi, key on engine off pump running.

 

[2000StreetRod]

spark advance

Better to have the load too great and have reduced spark advance than to have the load too low and have excessive spark advance. I'm confident that eventually you'll be able to get the Deka 60s to pass. Then you can lower your fuel pressure - hopefully before that flex hose in the rear splits. Soon (if not already) you'll be the HEGO test expert.

 

[4pointslow]

SiemensDeka 60lb inectors finally passed hego test

I finished putting the 60lb Siemens Deka injectors back in last night.
Afterwards I set the fuel pressure back to 39.15.
Today I took my latest tune and entered the correct injector data, and my old maf transfer function data from when I was running the 60's before. Then I returned the engine displacement to stock, I had changed that to get load higher with the 47's installed.

I had to make two adjustments to the maf transfer function to get it close. I just did blanket adjustments to the whole thing and that was good enough to go on a road test.

It ran the HEGO test and passed!

Two of the things that were causing issues were the large injectors and having installed 4.88 gears. Both those things caused load to be lower. Making some transmission adjustments I was able to get the trans into 5th at about 28 mph and that allowed me to reach higher load values even with the 60's. The manual for 1998 Ford emissions says load has to be 20%-50% to run the test, it is more like 26-50% on my truck. Below that it would keep kicking out of the test.

The other thing that was causing issues was an offset from fuel pressure to injector data. My fuel pressure had not been 39.15 before, it was 36.15.
With the fuel pressure off as little as three psi, it throws injector breakpoint, and the high and low slope data off. I posted the equation earlier that would be used for changing fuel injector data when changing fuel pressure.

Why was my fuel pressure off? Probably because I have two fuel pressure gauges on the truck, a SnapOn fuel pressure gauge, and the factory Ford scan tool(WDS) which can measure fuel pressure and they all read a little different. My opinion is that the WDS and the SnapOn gauge are most accurate of the bunch.

After 2 years I finally conquered the HEGO test on my truck. I will not have to swap injectors for inspection anymore. More importantly though, I have gained a new level of understanding through experience.

 

[Dono]

Congratulations!
You just can't teach something like that is school. Yuo really stuck with this one to resolution.
This thread has some really detailed info in it. I'm sure it will help others (quite possibly me).

 

[2000StreetRod]

nice going!

. . . I'm confident that eventually you'll be able to get the Deka 60s to pass. . .

Like I said.

 

[4pointslow]

60's

Thanks guys!