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Ok so that makes a lot more sense, effectively sizing the injectors and IDC with the piggy back fuel control and you can skirt around needing the MAF adjustments to control the timing curve? Without over simplifying it.. thank you!
Not sure what you're referring to on MAF adjustments... Regardless of how you get there, the airflow signal has to match the the fuel injectors. If you install larger injectors, you need to manipulate the airflow signal to lie to the ECU by an appropriate percentage to match... (that's what a piggypack does) by changing injectors you're just moving the target.
 

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Not sure what you're referring to on MAF adjustments... Regardless of how you get there, the airflow signal has to match the the fuel injectors. If you install larger injectors, you need to manipulate the airflow signal to lie to the ECU by an appropriate percentage to match... (that's what a piggypack does) by changing injectors you're just moving the target.
Yeah i was totally confused by both of his posts as well... I dont think he entirely understands what piggyback is doing... they ARE doing the MAF adjustments (e.g., with a SAFC 2).

When you run a piggyback the ECU has no idea you put in larger injectors, so it bases IDC on an assumption you are running stock injectors, which means way too much fuel for anything larger. Thus, the piggyback applies a negative % correction to the airflow signal so the ECU thinks there is less air than there actually is, injecting less fuel. % correction will be based on actual injector size vs. stock size.

The timing issue arises because when you lie to the ECU by telling it there is less air, it is in a lower load cell on the timing map, so it is running more timing than in otherwise would, which may be too much timing depending on your boost, fuel, etc.
 

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So if I understand you,
1) by cranking (fuel) pressure and lowering IDC I would be in effect advancing timing just as I would if I were to use larger injectors in the first place?
2) What I'm confused about, not being too familiar with the inner workings of any electronics, is that I was under the impression that the ECU calculated load and thus timing advance based on the MAF signal. Is this not the case?
doctorstupid had some good questions that I didn't see answered:

1) Reading Trevor's first post, I believe he's trying to suggest that using over-sized injectors (than your setup really requires), along with a SAFC (piggyback) to modify the MAF reading, will cause our ECU's to increase timing so much that you are losing power. So the lesson learned is to go small as possible on the injector and increase the fuel pressure to keep the ECU from overcompensating the timing advance.
2) I didn't see a response, in this thread, to how our ECUs' calculate LOAD.

The most surprising thing I read in this thread are that the (old-school?) dataloggers are not calculating IDC correctly and overstating the IDC. Hopefully my LCDBC is calculating it correctly, I will have to check with BlackStealth.
 

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doctorstupid had some good questions that I didn't see answered:

1) Reading Trevor's first post, I believe he's trying to suggest that using over-sized injectors (than your setup really requires), along with a SAFC (piggyback) to modify the MAF reading, will cause our ECU's to increase timing so much that you are losing power. So the lesson learned is to go small as possible on the injector and increase the fuel pressure to keep the ECU from overcompensating the timing advance.
2) I didn't see a response, in this thread, to how our ECUs' calculate LOAD.

The most surprising thing I read in this thread are that the (old-school?) dataloggers are not calculating IDC correctly and overstating the IDC. Hopefully my LCDBC is calculating it correctly, I will have to check with BlackStealth.
There is no difference between installing a larger injector, and making a small injector flow more by raising the fuel pressure. It's the same thing... More fuel needs more correction.

Load is a calculation of air mass, RPM, and programmed VE. If you reduce the ECU's perceived air mass, you decrease load, and increase timing.
 
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