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Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

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Old 12-28-2006, 09:23 PM   #1311
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Quote:
Originally Posted by diamondlarry
I'm not sure how lean it's running but I think that as long as I am very light on the throttle I should be ok. I read an article sometime ago that talks about combustion temps actually decrease when running lean, IE less fuel less heat. I'll see if i can dig that up because it kind of goes against everything I always heard.
Nice job on doubling your FE!

Have you seen this chart? I posted it in another thread. You can see that Exhaust Gas Temp peaks just above stoich, and cylinder head temp (CHT) peaks below stoich (around 13.5 A/F ratio). As you get leaner, temps go down.
http://www.gassavers.org/attachment....0&d=1167022596
I've noticed a loose relationship between CHT and knock, so going leaner than stoich has a counterintuitive effect.

I noticed that when I lean out my car too much the throttle response goes flat at higher throttle openings. It feels fine at light throttle, and I found I can lean it out quite a bit as long as the throttle/load stays light. Cruising on the freeway is fine when set very lean. But when I need more throttle to go up a slight rise, or to speed up a few mph, the car likes a slightly richer A/F ratio. As you can see by the chart in the link, there is a point of diminishing returns. Wish I knew exactly where it was , guess I'll have to find out through trial and error.

edit: let me know if you can't read the words, the resolution didn't come through so good.
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Old 12-28-2006, 11:10 PM   #1312
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I couldn't make out the words very well. I did notice that at one point while I was dialing in my pot setting that there was some significant knock with anything more than very light thottle. I think I have gotten past that for now.

Quote:
Have you seen this chart? I posted it in another thread. You can see that Exhaust Gas Temp peaks just above stoich, and cylinder head temp (CHT) peaks below stoich (around 13.5 A/F ratio). As you get leaner, temps go down.
I think this is pretty much what the article I was thinking of said. I will have to keep an eye on my coolant temp.
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Old 12-29-2006, 12:04 PM   #1313
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How am I supposed to keep up with you when I am buried in a snowdrift?

You are gettin' it on. CO
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Old 12-29-2006, 04:34 PM   #1314
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Quote:
Originally Posted by CO ZX2
How am I supposed to keep up with you when I am buried in a snowdrift?

You are gettin' it on. CO
Maybe you'll have to see what kind of numbers you can pull off with a snowmobile.
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Old 12-29-2006, 09:17 PM   #1315
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"I couldn't make out the words very well. "
Ack! OK so I tried making more copies hoping to make it legible, but nothing worked. So I'll just type it out.

The line at the top is labeled 'EGT' (exhaust gas temp), it has a scale on the right side that says,'Change From Max EGT' and it's labeled with a 0 at the top of the scale. Going down the scale the numbers are -100, -200, -300 degrees C.
The next line down is 'CHT' (cylinder head temp). It's scale is on the left which says,'Change From Max Power CHT, deg C. The numbers on the scale start with 10 at the top, going down is 0, -10, -20, -30.
Next is % Power. It's scale is on the right showing % Max Indicated Power. The numbers from top to bottom are; 100, 90, 80, 70%.
Reading down the chart there are some blurry words left of center that say 'Best Power Range'. Those words are in a light grey shaded area which corresponds to the peak of the 'max power' line.
Just right of center is another set of blurry words in a darker shaded area that say,'Best Economy Range'. There's an arrow pointing at the shaded area.
At the bottom of the chart are two lines that cross. Sorry, I can't tell which is which on the left side. It probably doesn't matter at that point anyway. The line that curves up and down is labeled,'Specific Fuel Consumption'. The line that continues downward is 'Fuel Consumption'.
At the very bottom of the chart is the general opinion that the left side of the chart is 'rich' and the right side is 'lean'. HTH

I just realised the info on the chart probably doesn't matter as much to you since you have a Scangage. Can't you just gradually lean it out while driving at a steady speed until the SG shows max mpg? That'd be too easy!
Ima hafta get me one a deez
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Old 12-29-2006, 11:15 PM   #1316
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Quote:
Originally Posted by DRW
I just realised the info on the chart probably doesn't matter as much to you since you have a Scangage. Can't you just gradually lean it out while driving at a steady speed until the SG shows max mpg? That'd be too easy!
Ima hafta get me one a deez
If I didn't have the pot jurry-rigged that would be pretty easy. It's basically just hanging in mid-air because I didn't want to start cutting until I knew it would work or not. If this tank looks better than usual at around 250 miles I may have to mount the pot permanently.
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Old 12-30-2006, 07:50 PM   #1317
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Quote:
Originally Posted by diamondlarry
If I didn't have the pot jurry-rigged that would be pretty easy. It's basically just hanging in mid-air because I didn't want to start cutting until I knew it would work or not. If this tank looks better than usual at around 250 miles I may have to mount the pot permanently.
I vote for a dash mounted pot. You'd have a dash mounted FE adjuster in your car!

As for me, my average mileage keeps creeping up little by little. I filled up this morning for a tank average of 38.76 mpg. This week I made some adjustments to the ecu so it wouldn't run so rich for the first couple of minutes after startup in the morning. I also added a pair of front wheel fairings and started shifting into 5th gear at slower speeds. On the downside, holiday traffic was less cooperative than my standard commute: sometimes there were heavy traffic jams, sometimes the roads were so empty there was no corridor effect. I guess it all works out in the end.
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Old 12-30-2006, 10:59 PM   #1318
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Just broke the $1,000.00 barrier with 61 total fillups for my Geo today. 295.367 gallons used to date.
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Old 01-03-2007, 05:22 PM   #1319
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Bad news

My MAP sensor experiment seems to be a bust. It seems that way at least for the way I was doing it anyway. I went 241.3 miles and used 4.842 gallons for 49.938 mpg. If anything, it looks like the mileage went down since the temps were basically the same as they were for the last tank.

The SG reported 4.0 gallons used instead of the 4.8+ gallons that I pumped. It was also reporting 61.2 mpg. Tank offset was the same as it was for the last tank. Back to the drawing board. I'm thinking about ordering a set of shop manuals and see if I can get a better idea of how the ECU works and see what I can come up with.

Here is a link to a thread at cleanmpg.com that tells how to get the average temperature for a tank of gas from start to finish. Very cool tool!
http://www.cleanmpg.com/forums/fuel-...tank-3182.html
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Old 01-04-2007, 04:18 PM   #1320
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On this last tank of gas, I only had to climb up the mountain into NC and drive the interstate to work for only one day. The rest of the tank was driving at mostly 50mph on rural SC roads. Temps ranged from 25F to 60F. Got 82mpg over 443 miles.

Got pulled over by a municipal cop last week. The reason he gave for stopping me was that my license plate was under a layer of plastic (legally the plate has to be totally uncovered, even a clear license plate cover or having it sitting inside your car's rear window is illegal). But the cop seemed to be more interested in my car, and the covered licence plate seemed to be just an excuse to pull me over to satisfy his curiousity. He didn't give me a ticket or warning, but was very interested in that I was getting 70mpg. I asked him if anything else about my car was technically illegal and he mentioned that there was some glare from the taillights and that if someone rear ended me, they could claim that they couldn't see my brake lights. He had no problems with my rear view mirrors. So I am in the process of installing some trailer tail lights at the back of the boattail (and also a backup light while I was at it). I also relocated my license plate outside of the boattail and mounted it just behind the muffler in the pocket of disturbed air behind the muffler (which I couldn't cover because of the heat), so it won't adversely affect my aerodynamics.
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