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Discussion Starter #1
Hypothetical what if. Say you were to put a larger size inj in and tried to force it to idle lean commanding a pulse width less than what said injector can handle ? What would you see ? Inj refuse to fire ? Stall/stick open ? Very erratic control ? Real world results firsthand would be great thanks !
 

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No longer linear response is one thing, poor cylinder to cylinder control is another. An injector needs a certain amount of time to open, especially against higher rail pressures. The injector will always "fire", but how much fuel comes out of it is another story. If the pintle never got to max lift, you don't know how much fuel will actually flow through it. It will never stick open, but it also may never open at-all.
 

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My experience is when you try and down the min opening time too low is cold cylinders on idle and when you get up in the range if you run close loop it seems to always be trying to comp.
Like Mike said if you run higher rail pressure it makes matters worse.
 

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There's a pretty good graph of what injectors do at low pulse widths at this page.

http://blog.titanmotorsports.com/?tag=bosch-1600

Here's one of the pictures:



And the blue line is one that has pretty good response at low pulse widths. But you can see as you slide down the graph that when you get towards the low end, the blue line gets a little wavy - and the red line bounces around like crazy, representing an earlier and less well behaved injector. Here, the injector can be a bit less predictable and you may have some trouble hitting the right AFR, particularly if your ECU isn't set up for handling nonlinear behavior at small pulse widths.

Then, as you go further to the left, the injector stops firing almost completely - it may leak a few drops past, but it's staying shut for all intents and purposes.

This is a bit more theory than real world, but my real world experience has been about the same. Depending on your ECU's pulse width resolution and how linear your injectors are at small pulse widths, you can end up with anywhere from "it works just fine" (if the injectors are very linear and not extremely oversized) to the AFR being a little squirrely, to an untuneable mess.
 

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Working on a brand new HOLLEY DOMINATOR EFI .
615BBC est 1150hp w/ 2 dry stages. COP, hall effect sensor, 4 mag wheel, W/ cam syn.
Has a large Accufab 8500 series (3600cfm) w/ NO provisions for any IAC .
Running 120lb Holley injectors. @ 160psi.
(2) 02 sensors in each collector before the 4" x 18" straight threw mufflers and then 18" of tail pipe. This a ALL NEW to me.....
Any advise on idle tuning with a 0.00 min inj opening time vs. 1.00?
Trying to get cleanest idle possible..... Will the opening time help this in any particular way with no IAC?
 

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Ray, there should be no problem with the 120's running at 50psi or so base fuel pressure with your engine. Those early Bosch 160's that everyone loved SUCKED! As the graph shows above, at some points decreasing the pulsewidth actually added MORE fuel! Damn I hated those pieces of shit! I knew what was happening with them but did not know why. That was all we really had to work with back then, thankfully there are a lot of better options today. :)
 

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Discussion Starter #7
I talked to the guys at Moran about this as well. I think I am chasing the problem from the wrong direction,I suspect I am going to find an install error as it doesnt appear I am down near the limits of these inj yet. Thanks for all the detailed response,Im slowly learning !
 

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Working on a brand new HOLLEY DOMINATOR EFI .
615BBC est 1150hp w/ 2 dry stages. COP, hall effect sensor, 4 mag wheel, W/ cam syn.
Has a large Accufab 8500 series (3600cfm) w/ NO provisions for any IAC .
Running 120lb Holley injectors. @ 160psi.
(2) 02 sensors in each collector before the 4" x 18" straight threw mufflers and then 18" of tail pipe. This a ALL NEW to me.....
Any advise on idle tuning with a 0.00 min inj opening time vs. 1.00?
Trying to get cleanest idle possible..... Will the opening time help this in any particular way with no IAC?
IAC is nice for a street car but you don't need it on a race car.

I think you mistyped,, 120 #/hr Holley injectors I don't think will fire of be happy @ 160 psi. Did you mean your going to kick up the base pressure and make then flow 160#/hr?

Anyway NO 0.0 min injector opening time unless you want to drive yourself crazy.

Also min opening time will depends on the voltage you run.. what battery,, 12 v or 16 v?
 

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I do drive it on the street alittle. But what im interested in is the best way to learn/figure out the best (Min open time) in regards to this thread.
They are holley's 120lb/hr injectors. Yes, the fuel is set to 60psi now = about 141.7lb/hr. I guess we should back it down(43# for now?) until we see what the duty % is when on the 2 guns. but........for now, (my thoughts where 120lb/hr injectors would max out at 43psi on the 2 guns down the road........but I will cross that bridge when we get there.... I just want to understand what's going on..... "opening timing wise"
Right this second I am on a 16v batt only, (1st time starting a new como) but shortly I will be putting in the 14V with my powermaster alternator set to 16.8amps.
I have the min opening time now set to 1.0.........no good?
 

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I do drive it on the street alittle. But what im interested in is the best way to learn/figure out the best (Min open time) in regards to this thread.
They are holley's 120lb/hr injectors. Yes, the fuel is set to 60psi now = about 141.7lb/hr. I guess we should back it down(43# for now?) until we see what the duty % is when on the 2 guns. but........for now, (my thoughts where 120lb/hr injectors would max out at 43psi on the 2 guns down the road........but I will cross that bridge when we get there.... I just want to understand what's going on..... "opening timing wise"
Right this second I am on a 16v batt only, (1st time starting a new como) but shortly I will be putting in the 14V with my powermaster alternator set to 16.8amps.
I have the min opening time now set to 1.0.........no good?
Leave it at 60 psi if that's what you think you are going to run later on.
As far an min opening time goes besides voltage it depends on the injector. Some manufacturers list the time. Maybe someone else will chime in if they know those injectors but from what I have seen @ 16 volts most will open between .6 -.8. If 1.0 is working it's no big deal. IMO more is better then less.
 

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I do drive it on the street alittle. But what im interested in is the best way to learn/figure out the best (Min open time) in regards to this thread.
They are holley's 120lb/hr injectors. Yes, the fuel is set to 60psi now = about 141.7lb/hr. I guess we should back it down(43# for now?) until we see what the duty % is when on the 2 guns. but........for now, (my thoughts where 120lb/hr injectors would max out at 43psi on the 2 guns down the road........but I will cross that bridge when we get there.... I just want to understand what's going on..... "opening timing wise"
Right this second I am on a 16v batt only, (1st time starting a new como) but shortly I will be putting in the 14V with my powermaster alternator set to 16.8amps.
I have the min opening time now set to 1.0.........no good?
The Holley 120# are in the drop down list and that will populate the off times based on voltage. Do you have this done? I have same injectors and set my min open time at 1.0 ms. Mine works fine and is always over that with 427 so I would assume yours would always be over that with your CID.
 

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I do drive it on the street alittle. But what im interested in is the best way to learn/figure out the best (Min open time) in regards to this thread.
They are holley's 120lb/hr injectors. Yes, the fuel is set to 60psi now = about 141.7lb/hr. I guess we should back it down(43# for now?) until we see what the duty % is when on the 2 guns. but........for now, (my thoughts where 120lb/hr injectors would max out at 43psi on the 2 guns down the road........but I will cross that bridge when we get there.... I just want to understand what's going on..... "opening timing wise"
Right this second I am on a 16v batt only, (1st time starting a new como) but shortly I will be putting in the 14V with my powermaster alternator set to 16.8amps.
I have the min opening time now set to 1.0.........no good?
Injector Min Open time is determined by the manufacturer of the injector. It's a static value that you don't mess with. Same for the inj dead time vs voltage. It wouldn't idle because the MAP sensor connector was loose and your plugs were likely already fouled. MAP sensor is critical to Speed Density tuning. I'm sure that now that you have that sorted out, things should go smoother.
 
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