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Old 07-09-2007, 11:32 PM   #1
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Default Injector Duty Cycle

I seem to recall someone posting that the OEM computer goes to 100% injector duty cycle at WOT. Can't find that thread. Anyone confirm? This would help with my fuel calcs for increasing line pressure in boost.

Just waiting on an electronic fuel pressure gauge to come in then I will start playing.

The engine rebuild took me 9 months due to various parts hold ups. Does run well now at 9 psi. Only done 900 kms so far.
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Old 07-09-2007, 11:35 PM   #2
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i think it is above a certain rpm, (maybe 4500??) but that may only be for 1.6's i don't know crap about 1.8's

wait for one of the more experienced members to post because i'm speaking out of my ***
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Old 07-10-2007, 01:29 AM   #3
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you dont want to go over like 80%~85%
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Old 07-10-2007, 03:19 AM   #4
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I don't have any control over the factory ECU for the injectors. My Turbolink only controls a 5th injector. I will be raising fuel line pressure when in boost to get 12.5:1 afr or there abouts through the ECU controlled injectors then hopefully finish of the afr with the 5th injector. A bit crude but I have to stay with the factory ECU due to our arcane DOT requirements.
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Old 07-10-2007, 08:46 AM   #5
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the stock ecu floods us full rich but never hits even close to 90% DC much less 100% 100% dc on any injector is bad. The rrfpr idea is a good one i suggest you swap in some 300CC injectors if you need more fuel than the 5th injector can supply. still about 75 psi Fuel pressure should make that 2560's max power available to you. GL
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Old 07-10-2007, 09:20 AM   #6
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My 1.6 ecu would go 90-95% ijdc at WOT.

Can't comment on your overseas, newer 1.8 ecu.
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Old 07-10-2007, 09:25 AM   #7
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realy damn i wouldn't expect that.
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Old 07-10-2007, 11:35 AM   #8
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I just checked some EMU datalogs. There are a few spots where the input injector duty cycle was up to around 90% - 92%, all at >7000 RPM and around 10 PSI.

Bear in mind that 90% at 7000 RPM is the same injector duration (in ms.) as 45% at 3500 RPM. The apparent duty cycle increases with RPM for a given load, since the crankshaft cycle time decreases.
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Old 07-11-2007, 12:08 AM   #9
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So heres the plan then. Fit the fuel pressure gauge when it arrives (Airmailed from the US today apparently). Use the Digital FMU to increase fuel line pressure through the auxiliary pump on a rising rate to about 75 psi at peak boost. Gradually increase the boost to 12 psi and see what the data log shows for afr on the wideband trace. This is all on stock 265cc injectors. I can make minor adjustments using the 5th 440cc injector if necessary but I would keep this minimal as I worry about even cylinder dispersion.

Just wish the Zeitronic Zt-2 would talk to a Windows PDA. A notebook in the car is awkward. They have software for a Palm but not the PDA that I have.
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Old 07-11-2007, 09:04 AM   #10
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that should be plenty of fuel for 14 or so psi easily enough to max the flow of your 2560
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Old 07-11-2007, 08:11 PM   #11
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Yes, the Garrett site calculator puts me in a good part of the turbo map at 14 psi. I will gradually work up to 12 psi first.
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Old 07-26-2007, 02:05 AM   #12
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OK. The Autometer Electronic fuel gauge is in, mounted in the far right dash vent (right hand drive). The stock pump runs at 60psi with the engine running, non return system. It flows 2310cc per minute open hose, no back pressure. So I have plenty of overhead fuel volume. The auxiliary pump kicks in at 0.1psi boost and fuel pressure immediately jumps to 80psi on the minimum setting from the digital fmu. This does not seem to translate into an immediate rich mixture on the WBo2 reading. I have reduced the 5th injector start point to 5psi boost and duty cycle to 30% as a rough starting point. The auxiliary pump easily achieves 100psi at about 45% output from the fmu. Don't know how high it will go as my gauge only reads to 100psi.

Will be data logging this weekend on some deserted roads around Corryong. I hope to achieve 12psi Saturday, with the wife driving!
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Old 07-26-2007, 09:34 AM   #13
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you are throwing to much fuel dude cut the aux back until 3 psi and then leave the pressure alone 80 psi with 5 injectors even the stock ones and good cooling is more than enough for 283 or so bhp 230 or so whp maybe 13 psi. given a flow of (265cc apeice *4)*.9) +((440)*.8) * 1.15= lots of fun trust me.
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Old 07-26-2007, 11:12 AM   #14
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Quote:
Originally Posted by Pitlab77 View Post
you dont want to go over like 80%~85%
RC Engineerings way of selling more injectors.

Frank
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Old 07-26-2007, 01:25 PM   #15
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Quote:
Originally Posted by fmowry View Post
RC Engineerings way of selling more injectors.

Frank
more like I want my butt covered in case of a hiccup in my system
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Old 07-28-2007, 03:35 AM   #16
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Default Zeitronix Pinouts

My Zeitronix computer connector RJ12 to DB9 is faulty. The yellow wire and brass pin were not seated. Kept getting error readings, fail to start etc. Pulled the DB9 end off to look and now I don't know which pin hole the yellow belongs in. The black was properly seated in pin hole no.2 so I know that is right. Could someone with a Zeitronix take a look at their adapter and tell me what pin holes are being used? You will probably need a magnifying glass if your eyes are anything like mine.

When it did work I was starting to adjust the fmu to get 12.5 afr at 10 psi boost. Still had plenty of fuel available, although I am up around 95 psi fuel pressure in some sections of the boost curve. I have five increasing pressure ranges available on the fmu to cover whatever boost range I am using up to a max of 15psi boost. The slider adjusters are very sensitive over a small distance of adjustment. The fuel pressure goes from 80psi to 100psi with very little movement of the slider. Just something else to learn I guess.

Really could have done without the DB9 connector failing.
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Old 07-28-2007, 11:19 PM   #17
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Zeitronix replied to my email overnight. If anyone needs to know DB9 pinouts are black to pin 2 and yellow to pin 5. Now it is collecting data again we will start the callibrations.

It does look like I will need some fuel through the 5th injector if I stay below 100psi in the supply line and go above 10psi boost. This surprises me as I was hoping to rely on the oem injectors for 99% of fueling up to 12psi boost. Will see.
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