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Old 06-23-2008, 02:22 PM   #1
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P&G not helpful in Saturn SL2

I'll be filling up my gas tank tomorrow afternoon and calculating my MPG as well as resetting my ScanGauge II for it's first break in full tank.

Just wanted to say, for me anyway, P&G (usually done from 55mph to 40mph) has yielded what looks to be ZERO benefit. I'm at 279 miles this tank, generally fill up at 300 miles, I'm bearing down on the "E" mark on the fuel gauge which will put me right at 300 once I hit it.

Looks to be another 30 mpg tank, but I'm thinking P&G did next to nothing for helping the mileage. I also fabbed a HAI halfway through this gas tank and it too appears to not be much help. I guess I need to finish that heat shield and fab that grill block. I'm seeing 150*F IAT at operating temp from the HAI, but I'm still wondering why my new thermostat is opening at 170*F when it was a stock replacement from Napa, supposed to be 192*F.

Just venting I guess, seems I've been trying super hard this tank and its not looking like it will have paid off at all.
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Old 06-23-2008, 02:36 PM   #2
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Possibly been trying "too" hard on a DOHC motor that doesn't get into it's power band until 4000 RPM or so. Also bear in mind that paying too much attention to the instantaneous MPG readout will screw you.
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Old 06-23-2008, 02:48 PM   #3
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Originally Posted by RoadWarrior View Post
Possibly been trying "too" hard on a DOHC motor that doesn't get into it's power band until 4000 RPM or so. Also bear in mind that paying too much attention to the instantaneous MPG readout will screw you.
How do you try too hard? The car hasn't seen 4k rpm in over a year probably. If I steadily increase throttle it shifts on its own around 3500. What I've been doing is what everyone on here suggests, P&G w/ heavy throttle at low RPM, which according to the instantaneous MPG readout, as you mentioned, shows the best FE I've seen yet. Driving w/ the "egg under the pedal" like I used to, so far, has showed me that it was just taking too long to get into the next gear, and those light throttle low RPM, low gear, situations were only showing 15-20mpg, heavy throttle 35% or less, got me through the gears quicker and into 4th where I steadily putted along at <10% throttle and usually over 40mpg.

I'm just feeling annoyed.

If you have suggestions, I'm all ears! Thanks.
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Old 06-23-2008, 03:08 PM   #4
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How do you try too hard? The car hasn't seen 4k rpm in over a year probably. If I steadily increase throttle it shifts on its own around 3500. What I've been doing is what everyone on here suggests, P&G w/ heavy throttle at low RPM, which according to the instantaneous MPG readout, as you mentioned, shows the best FE I've seen yet. Driving w/ the "egg under the pedal" like I used to, so far, has showed me that it was just taking too long to get into the next gear, and those light throttle low RPM, low gear, situations were only showing 15-20mpg, heavy throttle 35% or less, got me through the gears quicker and into 4th where I steadily putted along at <10% throttle and usually over 40mpg.

I'm just feeling annoyed.

If you have suggestions, I'm all ears! Thanks.
Learn to work the auto trans more better. I have noticed in my Camry (with auto trans) that the shift points are a function of speed and throttle angle. I can induce an upshift by lifting, as well as induce a downshift by "standing" on the gas.

I don't have a SG and have seen improvements up to 34 mpg by being light on the throttle at low speed, religiously P&G at highway speed, and just generally coasting as much as possible.

Is your driving mostly city or highway?

Have you pumped up the pressure of your tires?

Is your fuel filling technique consistent?
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Old 06-23-2008, 03:31 PM   #5
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It IS possible to try too hard. I was trying too hard at first, until I realized that it's okay to not P&G even if that's my current strategy.

Start just by taking only really good opportunities to P&G, and revert to "egg under the pedal" driving the rest of the time. As you get practice, you'll phase in more P&G at less opportune times.

It is pretty hard to P&G effectively with an automatic, though your Saturn probably can do it better than my GMC.

Also, it helps to separate your experiments so you know the effect each one has. It can be hard to tell if P&G and HAI are canceling eachother out, for example.
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Old 06-23-2008, 04:28 PM   #6
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Tire pressure is 48 front/rear, I know when to let the throttle out so it will shift to 3rd and 4th by itself, and just how hard and at what speed it will downshift, I've learned this transmission well over the last few years. My driving is generally about 70 to 80% city, and although I don't use the same pump, I use the same station and the same slow setting on the gas pump each time.

I know I should've seperated my experiments, but the whole reason I wanted the ScanGauge was to monitor IAT w/ a HAI, it just so happened that I started P&G when I first filled this tank and my ScanGauge showed up a few days later so I constructed the HAI and continuied the P&G.... although I doubt they would cancel each other out.

For this Saturn anyway, the only benefit I see from P&G w/ neutral vs. just leaving it in gear and doing a P&G, is the GPH go from roughly 0.50 in gear vs. 0.40 in neutral, and obviously, in neutral you glide further than you do in gear.

I'm not sure of other Saturn owners w/ auto trans experimenting w/ P&G, but I'm thinking my results would probably be consistant w/ other's in the same car. It just doesn't seem beneficial.

We shall see though, I've got another 26 miles until I hit 300 on this tank, maybe I'll try to squeeze more out of it and go 320 for my all-time new high?

The math on my 12.1 gallon fuel tank works out to be 364 miles per tank @ 30 MPG. Maybe I'll go to 330 or 340? Risky!!
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Old 06-23-2008, 06:01 PM   #7
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Quote:
Originally Posted by Project84 View Post
I'll be filling up my gas tank tomorrow afternoon and calculating my MPG as well as resetting my ScanGauge II for it's first break in full tank.


I'm seeing 150*F IAT at operating temp from the HAI, but I'm still wondering why my new thermostat is opening at 170*F when it was a stock replacement from Napa, supposed to be 192*F.

Just venting I guess, seems I've been trying super hard this tank and its not looking like it will have paid off at all.
Greetings,

When I first got my scangauge last December the first thing I noticed was the temp at 160-170F. I replaced the thermostat with a oem. Temp now climbs to 195F and stays there. That low temp of yours is hurting mileage.
I have a 99 and 97 SW2. The 99 is a automatic and gets 32-34MPG 75% highway at 65-70MPH. The 97 is a 5 speed, just recently purchased and averaging 3 tankfulls it gets 38MPG. My IAT is at outside air temp, no hot air intake. Did you check your ECT sensor? BTW I dirve at a constant speed, use cruise control and take it easy off highway. Tire pressure at 35 F & 33R. Also I don't use the scanguage to calculate mileage. I use the same pump to fill and calculate amount used by mileage driven.

Steve
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Old 06-24-2008, 03:38 AM   #8
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Driving Marvin, "trying too hard" is keeping the revs under 2K rpm and grannying it away from intersections... gets 18-20mpg like that. All the gases "ooomph" goes bye-bye in the the tranny fluid. I'd imagine that staring at an instantaneous MPG gauge would tell you, you're doing quite well.... would probably say 22 mpg.... so you strain it up to speed over 5 or 6 blocks at 22mpg then get 25mpg for one block before the next stop. OTOH, if you are somewhat spirited with the gas pedal without flooring it, staying between 2K RPM and 3K RPM when accelerating, you get maybe 15mpg for 80ft and and 25mpg for 6 3/4 blocks, and if you're not staring at the MPG gauge, you can probably spot that you can glide the last block or two.

With a DOHC and an automatic, you've got a less than ideal combo, I mentioned 4K RPM because I think that's about where your torque peak is, and your lowest BSFC will be somewhere around there. I'm attempting to accelerate between 2K and 3K all the time because my tq pk is at 2800, I'm thinking you should be aiming for 3-4K
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Old 06-24-2008, 05:28 AM   #9
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So would you suggest I go to the dealer for the thermostat? Sucks, the Napa one I put in was $17 w/ my discount!
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Old 06-24-2008, 09:03 AM   #10
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My driving is generally about 70 to 80% city, and although I don't use the same pump, I use the same station and the same slow setting on the gas pump each time.
There's the problem. I've noted only marginal improvements in city driving, with substantial improvements for highway driving.
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