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I have been slowly working the bugs out of my recent rebuild. I have just installed a larger turbo and had the primary injectors upgraded to 775's. the secondaries are 1200's. I have programmed the inj. screen to read:
front primary 71% .04 lag
front secondary .06 lag
rear primary 71% .04 lag
rear secondary .06 lag
q primary 775
q secondary 1200
pri/sec transition % 50
sec transition ms 1.500
I have slowly started changing the inj correction map to get it to idle and drive well under light load. I am still breaking in the motor. Figured this would be a good time to tune the off boost range.
What i noticed is that when you are stopped and rev the car in nuetral, it has very rough feel. For example, if I rev it to 2300 rpm and hold it there, it has a miss that doesn't go away. I tried playing with the fuel but this had no effect. This is what has me puzzled. I have a wide band and it does not change while I am adjusting the fuel. I am changing the fuel delivery in the inj/ign test area in the settings screen on the commander. You can make a total system change for fuel here. It works when I do this at idle but not when the car is free reving.
At idle, if I pull fuel out, my AFR number goes up and the idle changes. If I add fuel, the AFR goes dow and the idle changes as it gets richer. The same happens while I am driving. The problem is that this doesn't work if I am just hold ing the throttle open in nuetral. I can decrease the fuel significantly and nothing happens. The afr's do not change and the car behaves the same. If I let off the gas the car immediately dies as it tries to go to idle and starves of fuel. It is almost like the car is getting fuel some other way.
I am still having this problem and have some more info. Hope someone can help.
The car drives and accelerates fine. Very well in fact. The two problems that I am having are the one above, and this other which I am sure is linked.
If i am cruising with my foot depressing the accelerator, then I get afr's in the 13's as I have tuned. If I lift the gas just enough to create more than 500mhg of vaccuum the car goes pig rich. I have checked the cells all around these areas and they are the same. If i press the pedal down ever so slightly the vacuum rises back above 500mhg and the afr's return to normal. I noticed that while reving the engine in nuetral to 2500 rpm or so, I also create 500mgh vacuum and assume that this is why I am running real rich here too.
I also noticed that when crusing and completely lifting the throttle the duty cycle goes to 0 but my air/fuel reading will strat to go lean, then go rich for a split secound and then finally go full lean. It's like it goes down the back up a tiny bit and then all the way down. The duty cycles do not reflect this. The show 0 as soon as you lift the throttle. So what is causing the blip in the afr's. The car did not do this before. Could an exhaust leak at the manifold or v band cause this or is it stemming from the same root cause as above?
I have noticed a similar miss around 2500 rpms when in neutral.
Is the 02 feedback turned off? When I was tested for emissions, I somehow had the O2 feedback on. Tthe the contol loop seemed to take over and use some other setting or default mode instead of the AFRs I had previously tuned. This was especially noticeable in the 1500 to 2500 rpm range.
sequential is off and o2 is off. Could a bad fpr cause this? such that at a certain vacuum the fpr malfunctions and fuel pressure goes up when it shouldn't. This would explain why this only occurs at high vacuum. It only started after changing the primaries from 550 to 775. The problem is that so much else changed: turbo, wiring harness, port work, apex seals, aws removal and so forth. I need to check fuel pressure first. Keep in mind that I have not done any boost. I have also not seen my secondary injectors come online. I do not know if they are working yet
We use 850X1600"s and set front primary @ 80% lag -.4 with the default map. This gets us
very close on the tune befor changing any injector map settings. I will raise or lower the lag to fit the car, like -.4 leaner, -.3 richer etc.. Also check your injector acceleration settings and decel settings, if they are to rich they will make the car stumble with no losd. Ralph