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Old 11-26-2005, 11:56 AM   #1
IllNastyImpreza
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Default how the ecu works...closed loop...open loop?

where can I find some good info into how our stock ecu operates and learns?

and what is all this open loop & closed loop stuff?
I drive a 98 RS...
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Old 11-26-2005, 12:09 PM   #2
hondaeater69
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http://www.cobbtuning.com/tech/airflow/index.html

here's a good one on map vs maf i found the other day.

http://www.sportcompactcarweb.com/pr...09scc_projwrx/

This has some good info also.

If you're curious about EMS's in general (not just subarus) check out Jeff Harmans How to tune and modify EMS's.

if it's not anywhere in those two links, open loop is the ECU using AFR look up tables to determine the corresponding AFR according to MAF and RPM. IN closed loop, the ECU targets 14.7:1 using feedback from the front 02 sensor, hence the term closed loop (continuous circle of information).
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Old 11-26-2005, 12:29 PM   #3
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I think the logic inside the RS ecus might be a little different then the WRXs. Also, do the RSs even have MAFs? I thought they were just MAP... could be wrong.
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Old 11-26-2005, 12:40 PM   #4
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Quote:
Originally Posted by JRSCCivic98
I think the logic inside the RS ecus might be a little different then the WRXs. Also, do the RSs even have MAFs? I thought they were just MAP... could be wrong.

The following is an opinion on why different year model Subaru's react differently to modifications to their intake system. Primarily we're focusing on the late model Subarus which used either an air-flow system (up to 1999) or the speed-density system (2000+) in the North American market.

Before we discuss the technical details of the Subaru Intake System, lets first get familiar with the two ways Subaru has used recently to measure air flow. The first method discussed is MAF Sensors which were used on all late models until the 2000 model year. From 2000-on Subaru has begun using a speed-density system which primarily relies on a MAP sensor.

exert from the cobb article. later in the article is says something about wrx's and STi's being excluded from the above models. . .as we all know they use MAF
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Old 11-26-2005, 12:43 PM   #5
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See, I read the article a long time ago also, and it kind of confused me. The reason being is that while there is a MAP sensor on the newer cars there is still an MAF which is what drives the majority of the fueling system. This kind of clashes with this quote.

"From 2000-on Subaru has begun using a speed-density system which primarily relies on a MAP sensor."
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Old 11-26-2005, 12:50 PM   #6
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I thought the WRX used the MAP to determine boost and the MAF to determine air flow, but that you would only need one or the other on an N/A car.
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Old 11-26-2005, 12:52 PM   #7
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this article was written before the introudction of the WRX into the states, farther down in the article reads:

Starting in 2000, Subaru went to a sophisticated speed-density system in the North American market while retaining the air-flow system for their turbocharged Impreza, Legacy and Forester applications sold overseas. Also making guesses, we expect you'll see the air-flow system return when the WRX is introduced here in the US though the non-turbo applications will most likely retain their speed-density system as thus far it's proven very reliable.

I do believe all NON turbo models USDM style use MAP and NOT MAF post 2000.
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Old 11-26-2005, 12:54 PM   #8
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Quote:
Originally Posted by hondaeater69
That's a N/A (normally aspirated) reference.
" Also making guesses, we expect you'll see the air-flow system return when the WRX is introduced here in the US though the non-turbo applications will most likely retain their speed-density system as thus far it's proven very reliable."
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Old 11-26-2005, 12:54 PM   #9
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Quote:
Originally Posted by Rick Schu
I thought the WRX used the MAP to determine boost and the MAF to determine air flow, but that you would only need one or the other on an N/A car.

both turbo and NA cars can use either MAP or MAF based systems. They both have their pluses and minuses. read the article i posted on the two, it's a fairly good read.
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Old 11-26-2005, 12:56 PM   #10
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Quote:
Originally Posted by richde
That's a N/A (normally aspirated) reference.
."
yea so. It's still applicable, the logic of the two systems is still there, and the MAF based fueling system our cars use is a fairly big portion of how fueling is determined, so i linked it for the OP.
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Old 11-26-2005, 12:57 PM   #11
richde
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Quote:
Originally Posted by hondaeater69
this article was written before the introudction of the WRX into the states, farther down in the article reads:

Starting in 2000, Subaru went to a sophisticated speed-density system in the North American market while retaining the air-flow system for their turbocharged Impreza, Legacy and Forester applications sold overseas. Also making guesses, we expect you'll see the air-flow system return when the WRX is introduced here in the US though the non-turbo applications will most likely retain their speed-density system as thus far it's proven very reliable.

I do believe all NON turbo models USDM style use MAP and NOT MAF post 2000.
Dayum, caught me out by two minutes!! Ah well, I'm off to Barnes and Noble to pick up Harman's book.

Quote:
Originally Posted by hondaeater69
yea so. It's still applicable, the logic of the two systems is still there, and the MAF based fueling system our cars use is a fairly big portion of how fueling is determined, so i linked it for the OP.
At first glance it looks like they're saying that WRX's use the MAP, that's all. Yes, I know that you know, and now you know that I know that you know.
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Old 11-26-2005, 04:41 PM   #12
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Quote:
Originally Posted by hondaeater69
both turbo and NA cars can use either MAP or MAF based systems. They both have their pluses and minuses. read the article i posted on the two, it's a fairly good read.
No, I understand the differences. The WRX uses MAF based system to determine fueling needs, but it also has a MAP sensor, which I assume is to read boost+atmospheric pressure. I'm curious how does the MAP sensor in the WRX come into play - since all it should need is the MAF?
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Old 11-26-2005, 04:58 PM   #13
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The ECU uses map (manifold absolute pressure) for many different maps (different kind of "map" here), including but not limited to: boost target corresponding to RPM and TPS, and also solenoid and boost limits in relation to barometric pressure.
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Old 11-26-2005, 05:06 PM   #14
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