Stock ECM
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Cruiser
Joined: Nov 2007
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From: hernando, mississippi
Stock ECM
Wondering if anyone could enlighten me with this question, what ability to adjust fuel air ratio does a stock untouched ECM have, say if you go up to altitude? is it a broadband, or narrow band, adjustment, just wondering how much it would compensate for the changes in conditions, thx to all in advance.
Road Warrior
Joined: Apr 2009
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The stock ECU will adjust for altitude. Wideband or narrow-band O2 sensor is not relevant here unless you revised your stock closed loop AFR significantly.
O2 sensors don't read AFR ratio directly, they read how much oxygen is in the exhaust and then the ECU uses math and magic to determine the AFR. They can be tricked by variations in ethanol content of fuel but are usually pretty good for altitude, other things being equal.
O2 sensors don't read AFR ratio directly, they read how much oxygen is in the exhaust and then the ECU uses math and magic to determine the AFR. They can be tricked by variations in ethanol content of fuel but are usually pretty good for altitude, other things being equal.
Road Warrior
Joined: Nov 2007
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The ECM reads barometric pressure with the MAP (Manifold absolute Pressure) sensor. When you first start up the first thing that thing does, before actually cranking, is record the reading. Thats the altitude it controles to. After that it measures load on the engine, sorta like a vacuum instrutment.
So as long as you stop and start every few thousand feet all is automatic.
In closed loop the ECM will control to 14.6 as usual.
Its out of closed loop it will run richer at altitude. Because it is controling to numbers put it for the tune at the altitude it was tuned. Less O2 with the same fuel if you go higher.
I'm not sure how much the MAP sensor will affect the tune in open loop at altitude. Thats the program inside the program in the ECM. Must do something maybe.
So as long as you stop and start every few thousand feet all is automatic.
In closed loop the ECM will control to 14.6 as usual.
Its out of closed loop it will run richer at altitude. Because it is controling to numbers put it for the tune at the altitude it was tuned. Less O2 with the same fuel if you go higher.
I'm not sure how much the MAP sensor will affect the tune in open loop at altitude. Thats the program inside the program in the ECM. Must do something maybe.
Last edited by Old Gunny; Sep 17, 2009 at 08:47 PM.
The RPM to throttle position has distinct fuel settings designed to keep a open loop system at 14.6 AFR. The barometeric pressure from the MAP provides a set enrichment/enleanment changes to those settings based on the atmospheric pressure. Again the idea is to stay at 14.6 AFR.
The Stock ECM has zero adjustability - UNLESS - you buy a tuner that can alter the settings in the ECM (or get your dealer to do it). FAV's of this are SERT and TTS Master Tune. But there there other means including augmentation to the ECM like the power commander series and ECM replacements like the Thundermax. Look below and you'll see what I did.
If you want to alter engine performance via ECM changes, keep in mind your end goals, read about your options in this and other forums for a couple of weeks, and buy what you think will achieve those goals.
...gene
The Stock ECM has zero adjustability - UNLESS - you buy a tuner that can alter the settings in the ECM (or get your dealer to do it). FAV's of this are SERT and TTS Master Tune. But there there other means including augmentation to the ECM like the power commander series and ECM replacements like the Thundermax. Look below and you'll see what I did.
If you want to alter engine performance via ECM changes, keep in mind your end goals, read about your options in this and other forums for a couple of weeks, and buy what you think will achieve those goals.
...gene
Last edited by genedjr; Sep 17, 2009 at 10:24 PM.
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Cruiser
Joined: Nov 2007
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From: hernando, mississippi
Thx for the replies fellows, so is it fair to say that a stock ecm is loaded with a rather conservative/ leaner tune for emissions and this is why alot of people go with aftermarket tuners, such as PCV, or thundermax, sert etc... to increase the engines V/E and performance?
yes.
But my goal when I bought the T-MAX was to have a ECM that I could configure/update/tune as I bought more performance parts - without having to do dyno runs. So the extra costs are balanced by not having to so a dyno run after every major upgrade.
Unlike many lucky people, I have to do upgrades one at a time. I have completed stage 1 and T-MAX. Next will be a cam, or/then big-bore, then head work. Depending on my budget at the time. Once I am done with this setup, I will probably have a single dyno run to get a finer tune, but until all this other stuff is done, T-MAX w/Autotune will allow me adaquate performance.
...gene
But my goal when I bought the T-MAX was to have a ECM that I could configure/update/tune as I bought more performance parts - without having to do dyno runs. So the extra costs are balanced by not having to so a dyno run after every major upgrade.
Unlike many lucky people, I have to do upgrades one at a time. I have completed stage 1 and T-MAX. Next will be a cam, or/then big-bore, then head work. Depending on my budget at the time. Once I am done with this setup, I will probably have a single dyno run to get a finer tune, but until all this other stuff is done, T-MAX w/Autotune will allow me adaquate performance.
...gene
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Cruiser
Joined: Nov 2007
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From: hernando, mississippi
cool, Im with you now, your unit will self adjust when it senses the changes you have made, right.
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Suggest you download the TTS tuning guide to get a good overview of how the H-D ECM works and controls fuel and timing. Go to http://www.mastertune.net/files/calibrations.asp and check under the Manuals category.
--Gary
--Gary
Last edited by user 9375875; Sep 19, 2009 at 09:08 AM.
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