Why is my injector DC so high?
Why is my injector DC so high? Haven't had the car on the dyno yet but went to the track Friday night. Based on the numbers it ran, 131 mph and 3350 race weight, its making a little under 600 rear wheel horse. My fuel system is twin 320lph pumps, -8 feed, 120 lbs. injectors, 52 psi fuel pressure , on E85. AFR was in the mid 7's. I was seeing 115-120% duty cycle. All the injector calculators say these should support way more power than this. What would cause the DC to be so high?
Leaning it will help some.
I'd double check the injector data in the tune file.
And make sure both pumps are on and working.
Boost referenced FPR?
Make sure the fuel pressure is actually rising with boost.
Ron
I'd double check the injector data in the tune file.
And make sure both pumps are on and working.
Boost referenced FPR?
Make sure the fuel pressure is actually rising with boost.
Ron
The tune is set as 120 lbs flow rate. Using HP Tuners. Is there something in the tune or scanner setup that would/could cause an inaccurate duty cycle reading?
Yeah, both pumps are running. The second is on a pressure switch that kicks on at 1 psi boost. I've also tried bypassing it and running both pumps constant, no change. The FPR can be boost referenced, but it's not currently set up with a pressure line. Just seems like I shouldn't be anywhere near maxing out these injectors yet, even without raising the pressure further.
Yeah, both pumps are running. The second is on a pressure switch that kicks on at 1 psi boost. I've also tried bypassing it and running both pumps constant, no change. The FPR can be boost referenced, but it's not currently set up with a pressure line. Just seems like I shouldn't be anywhere near maxing out these injectors yet, even without raising the pressure further.
I'd flow the pumps and and verify gph. Take the line off where it goes into the wye before the rail and flow it from there. Could have a weak pump. Then I'd hook up the line to the regulator to up the pressure with boost. I'd try those two things before anything else.
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9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
The tune is set as 120 lbs flow rate. Using HP Tuners. Is there something in the tune or scanner setup that would/could cause an inaccurate duty cycle reading?
Yeah, both pumps are running. The second is on a pressure switch that kicks on at 1 psi boost. I've also tried bypassing it and running both pumps constant, no change. The FPR can be boost referenced, but it's not currently set up with a pressure line. Just seems like I shouldn't be anywhere near maxing out these injectors yet, even without raising the pressure further.
Yeah, both pumps are running. The second is on a pressure switch that kicks on at 1 psi boost. I've also tried bypassing it and running both pumps constant, no change. The FPR can be boost referenced, but it's not currently set up with a pressure line. Just seems like I shouldn't be anywhere near maxing out these injectors yet, even without raising the pressure further.
And are you sure you've set your wideband calibration to that of E85 with that 7 AFR number ?
When the DC showed 115%, the injectors show 23.3 to 23.8 msec (depending on exact afr), 14 pounds boost. At idle they are at 1% DC and 1.6 msec. I don't know what would be expected though, do those pulse widths sound normal? Yes, the wideband is set for E85. Normal driving it reads mid to high 9's.
I flowed the pumps a few weeks ago coming out of the tank and they were ok. I'll test them again at the motor end to make sure I don't have a restriction or something.
I flowed the pumps a few weeks ago coming out of the tank and they were ok. I'll test them again at the motor end to make sure I don't have a restriction or something.
Last edited by BOOSTAT4500; Jun 7, 2015 at 08:20 PM.
Make sure its firing all 8 cylinders. If your running on 7 you'll be using about 10 cylinders worth of fuel making up for the lean condition created, the power loss having to be made up, etc.
On The Tree
Joined: Jul 2005
Posts: 125
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From: North Dakota
[QUOTE=BOOSTAT4500;18835369]The tune is set as 120 lbs flow rate. Using HP Tuners. Is there something in the tune or scanner setup that would/could cause an inaccurate duty cycle reading?
What are your 120lb injectors rated at 43 or 58 base pressure? You said your running 52PSI base pressure.
If there rated at 43 psi (3bar) and your running 52 psi base pressure they should be set to 131.2 in the Flow Rate vs. KPA in hptuners.
If there rated at 58 psi (4bar) and your running 52 psi base pressure they should be set to 113.6 in the flow rate vs. kpa in hptuners.
EDIT **I was assuming you were running a boost referenced fuel pressure regulator** Are you?
What are your 120lb injectors rated at 43 or 58 base pressure? You said your running 52PSI base pressure.
If there rated at 43 psi (3bar) and your running 52 psi base pressure they should be set to 131.2 in the Flow Rate vs. KPA in hptuners.
If there rated at 58 psi (4bar) and your running 52 psi base pressure they should be set to 113.6 in the flow rate vs. kpa in hptuners.
EDIT **I was assuming you were running a boost referenced fuel pressure regulator** Are you?
Last edited by johnminer; Jun 7, 2015 at 10:44 PM.
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From: Ohio
Its obviously not your only problem, but that is a pretty big problem.
Either boost reference the regulator, or up your base pressure to ~66 PSI (your dual pumps can handle it).
9 Second Club
Joined: Nov 2003
Posts: 13,616
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From: Norn Iron
When the DC showed 115%, the injectors show 23.3 to 23.8 msec (depending on exact afr), 14 pounds boost. At idle they are at 1% DC and 1.6 msec. I don't know what would be expected though, do those pulse widths sound normal? Yes, the wideband is set for E85. Normal driving it reads mid to high 9's.
I flowed the pumps a few weeks ago coming out of the tank and they were ok. I'll test them again at the motor end to make sure I don't have a restriction or something.
I flowed the pumps a few weeks ago coming out of the tank and they were ok. I'll test them again at the motor end to make sure I don't have a restriction or something.
Either way, values as high as 24ms are huge if that is the actual value being sent to the injector, from anywhere around 5000rpm your injectors will be static open.
You need to boost reference the regulator, and you also need to monitor fuel pressure under load, and also voltage/current at the pumps may do no harm of pressure under load isnt doing what it should
If you really had 20ms+ and a true 52psi in the rail with a 120lb injector that thing wouldn't even of ran at that level
I see two possibilities. The injector filters in each injector are plugged up or the injectors are not what they thought they where
I see two possibilities. The injector filters in each injector are plugged up or the injectors are not what they thought they where
Running a Versafueler driver box and stock ecm.
The injector pulse was around 5500 rpm, so yeah, static open.
I'll get the tune data changed to match up better. The VE table is pretty good everywhere, so I don't think that's the bulk of the problem. I'm new to tuning turbos though, so I could be wrong.
The regulator is not boost referenced, so I'm leaning towards fuel pressure drop being the biggest issue. I'll get that hooked up and see what happens. I also just bought a pressure sender for the regulator so I'll be able to monitor what's going on.
I just installed all new filters in the injectors. I did buy them second hand though, so hopefully I wasn't lied to about what they are.
Thanks for the help and ideas guys!
The injector pulse was around 5500 rpm, so yeah, static open.
I'll get the tune data changed to match up better. The VE table is pretty good everywhere, so I don't think that's the bulk of the problem. I'm new to tuning turbos though, so I could be wrong.
The regulator is not boost referenced, so I'm leaning towards fuel pressure drop being the biggest issue. I'll get that hooked up and see what happens. I also just bought a pressure sender for the regulator so I'll be able to monitor what's going on.
I just installed all new filters in the injectors. I did buy them second hand though, so hopefully I wasn't lied to about what they are.
Thanks for the help and ideas guys!