What factors does the ECU use to switch between open-loop and closed-loop mode?

Can something as simple as a vacuum-gauge be used?

I know with carbs if you drive in such a way to keep the vacuum gauge above the opening point of the power-valve, you'll get better mileage. This is similiar to keeping the ECU out of open-loop mode.

But how can you determine if the ECU is in open-loop...

It would be nice if it was as simple as the ECU stays in closed-loop above 5in vacuum..........


Essentially, how can you use a vacuum gauge as a mpg gauge in a fuel-injected vehicle, like you can with a carb equiped vehicle.....

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Ems, I am not sure what your goal is here. Some feel that the feedback loop does not give the best mileage. So is the goal to keep it in feed back or stay out of it? I think you can tune for best mileage outside of feedback, since you can find whatever works best for your set up, and tune for that.

If your goal is to hit 14.5 below a certain vacuum reading, then simply tune those cells for the desired AF ratio. In essence you have a variable vacuum gauge in the MAP sensor which along with the fuel map allows you to set the fuel rate for each indicidual vacuum rating, and not just an on off switch.

That being said, I don't know if the Accel system does allow you to control feedback engagement with MAP readings. I know there is a minimum RPM you can chose, and a TPS setting you can chose as well. But, I not sure about the MAP reading. I have never turned mine on, accept to see if it works. It's off now.

Sam

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Same way you use a vacuum gauge as a fuel economy helper in a carbureted vehicle: Drive to keep the manifold vacuum as deep as possible. Open-loop mode is used before the O2 sensor warms to operating temperature and the coolant reaches a particular temperature, and during hard (WFO) acceleration.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Ok, I was equating open-loop with power-enrichment and closed-loop with running efficiently as possible (which may or may-not be the case)...

Generally you want a high vacuum reading and low rpms for the best mileage.

But as you lower rpms, the vacuum will also drop (same speed, same road conditions, different gears)

So at some point as you keep upshifting, the vacuum drop may be low enough to trigger the power-enrichment circuit on a carb.... which will most likely nullify your mileage gains.

With fuel-injection, basically the same thing will happen. But is the switch over to power-enrichment based on vacuum (which you can monitor) or throttle-position (a bit harder to figure out accurately) ?

Now if you have a lap-top hooked up, or a wide-band O2 sensor you can see what's happening, but I'm thinking you don't normally drive with those accessories...........

So how do you easily determine when a fuel-injected engine is in power-enrichment (other than than the obvious WOT) ?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Well, closed-loop operation gives the most complete combustion, so you're extracting the greatest possible amount of energy from the fuel. But there are times when you don't require as much energy as you can get by burning at stoichiometry; in those situations lean-burn operation can improve fuel economy. It creates emissions issues, though — NOx, mostly — and therefore needs coördination with the whole engine management and emissions cleanup system.
You are thinking in carburetion terms, where every input and every output is either binary (open/closed, on/off, yes/no) or variable only across a comparatively narrow range (gradient power valve). With even the most "beancounter-y" EFI system, there's much finer and more sophisticated control of the air-fuel ratio based on a large number of factors. Engine temperature and speed, vehicle speed, atmospheric pressure, throttle position, mass airflow and/or manifold vacuum, accessory status (P/S, A/C, etc.)...

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Well how about some rules-of-thumb.......

Inputs can vary, but say

You're always in closed-loop below 80% throttle (sometimes 85,90....)
You're always in closed-loop above 10in vacuum (5,6,8.etc)

below 1200rpm, above 5000 you're in open-loop.....


So maybe you don't catch all conditions of closed-loop, but you have some rules so that you drive by.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Those parameters are all adjustable, and I am working on that now. The answer is, I don;t know. I would like to share the various adjustments that ae available and see what you guys think. I just turned the feedback on, but have set only a few of the parameters to date.

Sam

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