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Old 10-23-2009, 11:52 AM   #70
Scooby Guru
Member#: 32792
Join Date: Feb 2003
Chapter/Region: NESIC
Location: lincoln, ri
2003 GGA MBP
12.9 / 105+


well the question is, better fuel control compared to WHAT?

jerod's mechanical setup factors into how stable and fine-tuned his maf-load maps can be--in particular the much larger than oem maf pipe diameter, as he says.

there isn't any MORE control over the ecu. there are different controls, yes. every ROM image out there has a slightly different feature set--come include per gear boost comp, some include larger ign/fuel maps, some are smaller, etc.

never forget there is a GREAT DEAL still unknown about this ROM. we DO know that it was never meant to be street-driven.

the idea that more fine-grained control over fuel/ign maps unlocks more power is great in theory. many other aftermarket ecus offer more load cells, but this hasn't produced the results in practice.

keep in mind when you're doing a WOT run you traverse a tiny fraction of the total map surface. having 100 cells of control vs. 50 doesn't change things when you actually USE 15 of them.

having been tuning SD for the last 4+ years with the utec i can tell you a couple of things:

1) maps DO seem to be easier to tweak. they seem to have smoother surfaces and react more intuitively to changes. the bottom line is that they are easier to tune.

2) transient response seems better. i have attributed this to the faster response of the MAP sensor to changes in throttle position. in theory a true SD load doesn't require tip in enrichment, for example, because it's already accounted for. it may also mean that SD setups can contend with much longer intact tract lengths (ie fmics) which can cause transient fueling issues using oem location maf sensors.

3) they are more sensitive to accurate temperature measurement and proper compensation tables.

4) any power it "gets" you comes from either:
4.1) a better tune due to reason 1
4.2) mechanical changes you make as a result of not needing a maf sensor (ie, pulling it out of the airflow path)

5) they can be HARDER to tune idle with lumpy cams, because of the low manifold vacuum, and the scatter of that vacuum.

6) they are MUCH less forgiving wrt mods that change VE without a retune. ie, opening that exhaust cutout means you'd better retune because you're gonna run LEEEEEEEEAN.

make no mistake: subaru are no fools. maf sensors are not cheap... they're much more expensive and delicate sensors than MAP and IAT (which are already on the car). if they thought they could provide the same robustness and drive-ability with a maf-less setup then they would have. there are very real, very valid reasons they settled on maf sensor load. there are tradeoffs that cannot be avoided no matter what solution is used.
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Last edited by ride5000; 10-23-2009 at 11:58 AM.
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