help !!! why is my injector dutycycle jumping all over the place ?? fast ,385 chevy,procharger 15 # boost,38# injectors !! 11.5 target airfuel !! it will read 70,80 100,130,and fall to 20 in the second gear !!! or third !!!! it goes up and spikes and falls to nothing !!!! thanks guys !!!!
injector dutycycle jumping around ????
- Thread starter suns68
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With 15# of boost on a 385, are 38# injectors big enough? When the ECM is trying for 130% DC, it sounds like you are running out of fuel.
Also, we'll need some more information (and fewer exclamation points) to help you- how much O2 correction do you have? Under what conditions are you seeing 20% and 130% - are you racing at WOT? Has your VE table been relatively well calibrated?
-Bob Cunningham
Also, we'll need some more information (and fewer exclamation points) to help you- how much O2 correction do you have? Under what conditions are you seeing 20% and 130% - are you racing at WOT? Has your VE table been relatively well calibrated?
-Bob Cunningham
Craig Smith
That was easy!
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You are WAY out of injector. Once the calculated pulsewidth value gets too high, it basically rolls back over to zero, kinda like an odometer does when you exceed its limits.
You should look into a set of 55 lb/hr injectors. I think you will kill that motor trying to run it much more with an inadequate fuel supply.
You should look into a set of 55 lb/hr injectors. I think you will kill that motor trying to run it much more with an inadequate fuel supply.
thanks ! again !
thanks bobc455 and craig smith ! i love this fast stuff , but i think we all need a little help here and there ! i think craig hit it on the head , it did all of this jumping around in second gear at wide open ! bobc455 was right there too ,, 1st data was 6.3 corr at 5300 rpm ,19.00 degress of spark ,injector duty was 7.9%,!! at 6125 injector duty was 165%, but air fuel was 11.25 at target of 11.5 , then o2 corr was 22.7 , at 8.4# of boost !!! my fuel pressure was off 10 pounds after setting all winter , but i think you guys are right ,, i need bigger injectors !!!! i do have 2 good pumps and to lines to fuel rails !!! ps , it does have a 4000 stall , and i think the lower numbers didnt have time to react !!! what ya guys think ! thanks again ! suns68
thanks bobc455 and craig smith ! i love this fast stuff , but i think we all need a little help here and there ! i think craig hit it on the head , it did all of this jumping around in second gear at wide open ! bobc455 was right there too ,, 1st data was 6.3 corr at 5300 rpm ,19.00 degress of spark ,injector duty was 7.9%,!! at 6125 injector duty was 165%, but air fuel was 11.25 at target of 11.5 , then o2 corr was 22.7 , at 8.4# of boost !!! my fuel pressure was off 10 pounds after setting all winter , but i think you guys are right ,, i need bigger injectors !!!! i do have 2 good pumps and to lines to fuel rails !!! ps , it does have a 4000 stall , and i think the lower numbers didnt have time to react !!! what ya guys think ! thanks again ! suns68
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!!!!!!!!!!!!!!!!
Like Bob said.. get over the exclamation points. We get the idea.
Craig is right on w/ the "blowing it up" suggestion.
Why would the fact that the car sat over the winter, cause the FP to drop 10psi??
I'd suggest you look at that first, and correct the problem.. That alone is more than enuf to blow it up.
Once corrected, check to be certain that the boost is referenced to the FPR, so that you get the # for # rise w/ boost.
As for the inj size.. John, and everyone else is correct, NOT CLOSE! [Note: only 1 ! in the entire post.]
At 2 atmos of air, the engine thinks it's 770 CI.
Assuming only 700FWHP, a BSFC of .6, and a DC of 85%, you are looking at an inj size of 62PPH. John's shot at 65's or 72's is where I'd go.. You know well, that you won't be satisfied w/ 15psi for long, and w/ the 72's, you'll have a little cushion...
The 700FWHP is probably low too.. That's less than 2 HP/CI.
maybe 83's??
Back to workin on my HEMI!!
Like Bob said.. get over the exclamation points. We get the idea.
Craig is right on w/ the "blowing it up" suggestion.
Why would the fact that the car sat over the winter, cause the FP to drop 10psi??
I'd suggest you look at that first, and correct the problem
Once corrected, check to be certain that the boost is referenced to the FPR, so that you get the # for # rise w/ boost.
As for the inj size.. John, and everyone else is correct, NOT CLOSE! [Note: only 1 ! in the entire post.]
At 2 atmos of air, the engine thinks it's 770 CI.
Assuming only 700FWHP, a BSFC of .6, and a DC of 85%, you are looking at an inj size of 62PPH. John's shot at 65's or 72's is where I'd go.. You know well, that you won't be satisfied w/ 15psi for long, and w/ the 72's, you'll have a little cushion...
The 700FWHP is probably low too.. That's less than 2 HP/CI.
maybe 83's??
Back to workin on my HEMI!!
ok , i get it ,, to many !!!!!
ok guys, i get the idea abought to many !!!!!!! .im looking into why fuel pressure was down and looking into bigger injectors! chuck you are right , 15 #s of boost is only good enough for now . down the road i do plan on a bigger blower or turbos ! ( look , only one ! ) thanks again guys for all the help , im done tunning untill new injectors are here . ps , thanks john and chuck for reply !!
ok guys, i get the idea abought to many !!!!!!! .im looking into why fuel pressure was down and looking into bigger injectors! chuck you are right , 15 #s of boost is only good enough for now . down the road i do plan on a bigger blower or turbos ! ( look , only one ! ) thanks again guys for all the help , im done tunning untill new injectors are here . ps , thanks john and chuck for reply !!
You might also want to address the fuel pressure issue- if you have insufficient fuel pressure /volmue, the new injectors won't be the full solution.
If you reference your fuel pressure to vacuum/boost, you will see the pressure drop at idle, but it should rise as you step on the throttle (and the vacuum decreases / pressure increases). However if your pump is not capable of generating sufficient pressure anymore, it's time to replace (or rethink) it.
What kind of car is this in? Do you have an external pump or intank pump? Which pump is it?
This sounds like it's gonna be one kick-ass machine when you get the right fuel delivery!
-Bob Cunningham
If you reference your fuel pressure to vacuum/boost, you will see the pressure drop at idle, but it should rise as you step on the throttle (and the vacuum decreases / pressure increases). However if your pump is not capable of generating sufficient pressure anymore, it's time to replace (or rethink) it.
What kind of car is this in? Do you have an external pump or intank pump? Which pump is it?
This sounds like it's gonna be one kick-ass machine when you get the right fuel delivery!
-Bob Cunningham
fuel pressure issue
thanks bobc455 for your reply , i hope it goes faster , im sure it will with all of you guys on here , (way to smart for me ) but im learning !i have 3 pumps , first is procharger pump with 1/2 inch line to fuel rail , 2 is in tank pump runs to bosch pump like the procharger pump , thats on the factory lines . i have a hobb switch that kicks on bosch pump at 5 # off boost , procharger pump runs all the time ! i think my regulater is going week , over the winter it droped pressure to 35 #at idle with vaccum . ! im working on it tomorrow , but im for sure getting new (bigger) injectors ! thanks guys P S 89 firebird formula ,6.81 1/8 mile at 110mph best to date ! Now its got new cam ,fast ecm , want to see what it will do now , might be slower ! later thanks again guys ! love the site !
thanks bobc455 for your reply , i hope it goes faster , im sure it will with all of you guys on here , (way to smart for me ) but im learning !i have 3 pumps , first is procharger pump with 1/2 inch line to fuel rail , 2 is in tank pump runs to bosch pump like the procharger pump , thats on the factory lines . i have a hobb switch that kicks on bosch pump at 5 # off boost , procharger pump runs all the time ! i think my regulater is going week , over the winter it droped pressure to 35 #at idle with vaccum . ! im working on it tomorrow , but im for sure getting new (bigger) injectors ! thanks guys P S 89 firebird formula ,6.81 1/8 mile at 110mph best to date ! Now its got new cam ,fast ecm , want to see what it will do now , might be slower ! later thanks again guys ! love the site !
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Re: fuel pressure issue
Originally posted by suns68
i have 3 pumps , first is procharger pump with 1/2 inch line to fuel rail , 2 is in tank pump runs to bosch pump like the procharger pump , thats on the factory lines . i have a hobb switch that kicks on bosch pump at 5 # off boost , procharger pump runs all the time ! i think my regulater is going week , over the winter it droped pressure to 35 #at idle with vaccum
A suggestion for a bit more simplicity and safety....
The 1/2" line is plenty to feed the engine. I'd stick w/ that, and add 1 good external pump such as the Aeromotive.[Pt # 11104 covers up to 900HP forced ind. and # 11102 is good to 1250]
Do away w/ all the other pumps feeding pumps, turning on w/ hobbs, etc.
A problem w/ the current system is, IF 1 component fails, the engine will continue to run, only w/ insufficient fuel volume. This can result in "driving over the crank", blowing head gaskets, etc...
Whereas, a single pump quits, the engine quits, and lives to "fight another day"!< only 1.
Also, having one pump feeding another is not good,as the in tank may not be able to out produce the Bosch external, and you have a external trying to pull thru a restriction..[or vice versa]
The other side of the coin is, the internal fails, then the external is in real trouble, it's inlet is blocked w/ a bad pump.. NOT GOOD.
Same thing if the Bosch fails, the internal can't push thru it like it should.
HTH,
Just sharing my experiences.. kinda as in BTDT!!
