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My injector duty cycle is going off the charts and I'm not sure why. What I have should be able to keep up no problem.
6.0 with Borg S480 with Dominator ECU
15 PSI
Fuel system is
Vic Jr with Holley 120 lbs. injectors
2 in tank Walbro 450 pumps (2nd pump comes on at 3 PSI)
-8 from pumps y'd into -10 that goes to the front
-10 y'd to -8 into the back of each rail
-8 return
Boost referenced Holley 12-848 regulator set at 58 psi base
here is a pic of the regulator/rail setup
According to the datalog the fuel pressure goes up to 72 and holds there, no drops or dips.
At about 5500 RPM the injector duty cycle starts to spike and it can't hold the commanded AFR of 11.3. That part of the fuel table is around 800 lbs/hr.
My injectors at 58 psi base are 139.4. That multiplied by 8 at 80% DC is 892 lbs/hr
Any ideas what's going on??
Last edited by squarles67; 10-17-2017 at 07:52 PM.
Does it seem to run ok up top. if its breaking up it will show a lean condition on the wideband and cause the fuel correction start adding pulse width.
Does it seem to run ok up top. if its breaking up it will show a lean condition on the wideband and cause the fuel correction start adding pulse width.
It does run ok and pull hard. It can maintain around 12.6 AFR but I'm not running it all the way out until I figure out the issue. I know the 11.3 commanded is probably too rich but I need to figure out what the issue is before I try and turn up the boost and/or really start leaning on it.
It's a new build that's been running about 6 months now and the injectors were new when I put them in.
The only filters I have are the socks on the pump pickup. I wonder if there's trash in the injectors....hmmm...something to definitely check. That would also make sense with no pressure drop.
I know the pulse width is up but check for mat air correction table and see if it is pulling below 100% of fuel table when the intake temps get up.
Something else to check when I get home, thanks. I do have it set to add fuel if IAT gets elevated but I don't believe it is getting too high. Seems like it's around 100 degrees but I need to re-check. I'm spraying 50/50 water meth to keep it in check.
I made another pass just now to check the fuel tank vent. I ran without the gas cap to make sure there was plenty of vent. Really didn't make much difference so that eliminates the vent. Fuel pressure stays steady. It was cooler today so air temp stayed around 80.
Looked at air temp from the other day and it was around 100 so no fuel was added there.
I'm going to pull the injectors and check for trash
How many milliseconds are your injectors opening for when they are maxed and what rpm when that happens? If they are opening for the correct amount of time then they are clogged because your not running a filter or your afr is just wrong.
The higher the rpm the less time the injector has to injector fuel into the cylinder. I was just wondering if your duty cycle was correct. To find duty cycle.
Take 60(seconds) and divide by 5500(your RPM)=.0109(amount of time for 1 rpm)
Multiple .0109 X2 because it takes 2 rotations of crank rotation for 1 complete 4 cycle.
60/5500=.0109x2=.0218 seconds or 21.8 milliseconds.
So your computer is atleast thinking it is holding your injectors wide open.
Now you have to find out if it actually is or more likely your injectors are clogged/faulty.
I am going to try and find the info about the bad batch of injectors for you.
Okay the injectors I was thinking of were the 1600cc CNG injectors. When the fuel would heat up they would flow like half of what they were supposed to.
Damn, looks like i gotta rethink my fuel injector sizing all together. I have same set up as you pretty much. Built 6.0l s484, same fuel system but with deka 80s...guess i should upgrade now b4 we fire it.
10-16-2017, 07:55 PM
Running out of fuel 
