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Old 05-20-2008, 08:57 PM   #1
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96 HX owner with a scanguage 2 sg2 questions

Im a new member, 96 hx, sg2

i drive 35miles one way to work 3 days a week 210 total

my first tank was 546 on 10.6 gal. without sg2

after installing a sg2 I drove home and back into work.

these are my observations and questions. This site has been a wealth of info and i find my self reading searching and wondering (aka not what im sposta be doing.)

1. i noticed when I let off the gas in gear i get 9999 this is fuel cutout correct?

2. is any fuel going to the motor? or is cutout the wrong term?

3. i have noticed that acceleration in a gear too high is bad for fe is this correct?

any other sg2 tips or observations would be great

I still have a egr fault and some other issues im working with on the car. its been babied for that tank due to a possible clutch issue. when i hammer the gas it tends to slip i dont have time to do a clutch right now so ive been easy on it.

Tires are inflated to 40 (checked every 4 days)
new front clip was installed in the middle of the tank
along with new wheels and tires.
cv joints are new
new right bearing installed


I'm reading more about lean burn.
and the vtec e synloid. thinking of installing some indicators or monitoring it in some way.

kb
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Old 05-21-2008, 06:19 AM   #2
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Yes, that is fuel cut you're seeing. My civic holds fuel cut down to about 1200 rpm. It's using no fuel during that time.

Note that the scangauge will be inaccurate for the time it's running in lean burn. It reads air flow and calculates fuel used from that, assuming a standard fuel-air ratio. Lean burn changes this ratio, but doesn't tell the SG about it.

You'll get the best mileage by accelerating at low-ish rpm and high load/throttle. Not quite to full throttle - there are diminishing returns above about 3/4. Then, when you're at speed, you can cruise gently and use lean-burn.
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Old 05-21-2008, 07:51 AM   #3
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Originally Posted by bockwho View Post
i have noticed that acceleration in a gear too high is bad for fe is this correct?
I think this is an example of how focusing too much on instantaneous mpg (as reported via something like the SG) can be misleading.

If you're accelerating efficiently (which means low rpm and heavy throttle), your instantaneous mpg could be low, even though you're doing the right thing. What's going on is the SG is not taking into account the value of the acceleration, which means the value of the kinetic energy that's being added to the vehicle (and potential energy, if you're climbing a grade).

This energy will pay you back a few moments later, when you're gliding. And then the SG will report very high mpg.

What you're trying to do is operate the engine efficiently. Sometimes this means using extra fuel now, in order to save fuel later. The SG can help you do this, but you'll be misled if you overly focus on instantaneous readings, which tend to swing all over the map.
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Old 05-21-2008, 07:52 AM   #4
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Originally Posted by PaleMelanesian View Post
Yes, that is fuel cut you're seeing. My civic holds fuel cut down to about 1200 rpm.
I wonder if it might even be lower. I know the spec on the VX is 850 rpm, and that's consistent with what I observe when I monitor the injectors with a DMM.

Quote:
Note that the scangauge will be inaccurate for the time it's running in lean burn. It reads air flow and calculates fuel used from that, assuming a standard fuel-air ratio. Lean burn changes this ratio, but doesn't tell the SG about it.
When I monitor AFR on my VX (using that DMM), I notice that readings close to stoich are rare. Depending on throttle position, mix is either lean or rich. And at heavy throttle (say, anything over 50%), the mix is quite rich.

So I suspect that on a wideband-sensor car (e.g., VX or HX), the SG will be inaccurate on both sides (lean and rich), not just on the lean side. But maybe the two errors tend to cancel out!

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You'll get the best mileage by accelerating at low-ish rpm and high load/throttle. Not quite to full throttle - there are diminishing returns above about 3/4.
I've seen you and others say this (avoid WOT), and as far as I can tell it seems to be based on a desire to avoid open-loop. But it seems to me that wideband-sensor cars generally avoid open-loop, even at WOT. So I'm questioning the assumption that 75% beats 100%, if open-loop is not a factor.

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Then, when you're at speed, you can cruise gently and use lean-burn.
But wouldn't he do better with P&G, instead of a steady cruise?
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Old 05-21-2008, 08:27 AM   #5
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I would P&G, but I haven't had the chance to explore what a lean-burn HX will do.

I tested my fuel-cut just last week. I monitored the SG open/closed loop, and there was a simultaneous "surge" from the engine when it started feeding fuel again. It's consistent at 1200 rpm. Yours may be different, though.

You may be right about WOT in your case. I don't know. But there's not much to be gained between 75% and 100% either. Try it and see.
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Old 05-21-2008, 08:47 AM   #6
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You may be right about WOT in your case. I don't know. But there's not much to be gained between 75% and 100% either.
My working assumption is that the difference between 75% and 100% is small, but positive.

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Try it and see.
I did run a test that I described here: http://www.gassavers.org/showpost.ph...93&postcount=7. Any test with only one trial has limited value, so I'm always interested in information from other sources. Overall I don't put on a lot of miles, so running lots of different tests takes a long time.

Sorting out the results is further complicated by the fact that the car is changing in various ways. For example, I've switched from CA to Federal (ECU and O2), adjusted the valves, and taken care of various tuneup items. Those all happened at different times, so it's hard to disentangle the various factors.
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Old 05-21-2008, 09:05 AM   #7
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Ah, I hadn't see that test you did. It looks pretty conclusive for choosing P&G over lean-burn. Thanks for testing that.
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Old 05-21-2008, 09:06 AM   #8
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Quote:
Originally Posted by monroe74 View Post
I wonder if it might even be lower. I know the spec on the VX is 850 rpm, and that's consistent with what I observe when I monitor the injectors with a DMM.
Yes, you're right. The factory tachometer moves very slow and doesn't report the RPM accurately when moving. The spec for a D16Y5 5 speed DFCO is 850 and 920 for the CVT.

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When I monitor AFR on my VX (using that DMM), I notice that readings close to stoich are rare. Depending on throttle position, mix is either lean or rich.
That's odd. I thought the O2 target for the VX calibration was all 14.7 except for the lean burn portion of the map. Was that with the CA ECU or the 49-state?

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And at heavy throttle (say, anything over 50%), the mix is quite rich.
That's normal.

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I've seen you and others say this (avoid WOT), and as far as I can tell it seems to be based on a desire to avoid open-loop. But it seems to me that wideband-sensor cars generally avoid open-loop, even at WOT. So I'm questioning the assumption that 75% beats 100%, if open-loop is not a factor.
How do you know whether it's in open or closed loop?

Even so, closed loop alone doesn't give you an indication of what AFR the ECU is running. The O2 target could very well be 12:1 for everything above a load that coincides with 75% throttle. That would be in line with every other car on the road.

It would be extremely valuable to see the factory calibration of the CA P07, federal P07, and the HX ECU. I'd pay good money to see the calibration on the P2J in it's entirety.
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Old 05-21-2008, 09:44 AM   #9
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Originally Posted by PaleMelanesian View Post
It looks pretty conclusive for choosing P&G over lean-burn.
It looks that way, because it was the same route, and I was being very meticulous with my driving technique. But it's unfortunate that it was two different pumps. I really don't trust those nozzles, even when it's the same pump.

Anyway, I'm going to try to devise some instrumentation to do a better job of calculating fuel use. I find it very frustrating that I have to wait until the next fill, in order to get feedback. I don't drive that many miles, so I have to wait a long time.

One consequence is that I usually fill when the tank reaches half, instead of waiting longer. But this means I'm dragging a lot of extra fuel around, on average. I recall your statistics, on this factor.
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Old 05-21-2008, 09:45 AM   #10
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That's odd. I thought the O2 target for the VX calibration was all 14.7 except for the lean burn portion of the map. Was that with the CA ECU or the 49-state?
I'm very interested in this subject, so I appreciate any insights you can share.

I didn't start monitoring AFR until after I did the CA-to-Federal conversion (I swapped O2 sensor and ECU). I have no idea what the meter would have shown, prior to that.

When I use a DMM to monitor AFR, I see readings from roughly -0.8v to +0.8v. The amount of time it spends close to zero is very low. I think I would have a hard to time keeping it there, if I decided to try (for whatever reason).

When you ask for moderate acceleration, it swings to roughly -0.3v. It will move smoothly to even more richness, as you open the throttle further. If you back off to a light setting and let it cruise, it swings the other way, to +0.3, or higher, if the throttle is very light.

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How do you know whether it's in open or closed loop?
Good question. I don't know for sure. I'm just making certain assumptions. I think when most people report that they are seeing a transition to open loop, they're reading a device like an SG that's getting the data from OBD2. Obviously I don't have that.

But my naive understanding of open loop is that I would see a fairly abrupt transition to a much richer mixture, as I approached WOT. But this is definitely not what I see. I see a very smooth increase in richness, generally proportional to throttle setting.

Also, I discussed this issue over at ecomodder, and a commenter who seemed very knowledgeable was quite sure that a wideband-sensor system generally avoids open loop. Except when cold, or when there's some kind of a sensor failure.

Quote:
Even so, closed loop alone doesn't give you an indication of what AFR the ECU is running. The O2 target could very well be 12:1 for everything above a load that coincides with 75% throttle. That would be in line with every other car on the road.
But I have a hunch that what you're saying only applies to a car with a regular O2 sensor (most cars, in other words). When I move from 75% to WOT, I see a steady increase in richness, from roughly -0.5v to -0.8v. I don't know how to accurately translate that into ratios, but I figure that the maximum richness does indeed go beyond 12:1, as I approach WOT.
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