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Dan
05-25-2007, 06:57 AM
Anyone care to share their calibration settings for their SGII on a Prius? Here's what my records turn up.

In the default setting, the values are off by the following.

SGII-vs-FCD:
Miles = reads 1.5% lower than odometer readings.
Gal = reads 4.6% higher than FCD readings.
MPG = reads 6.5% lower than FCD readings.

And just for completeness, here's what my FCD -vs- physical readings yield.

FCD-vs-Physical:
Miles = spot dead on (have no way to calibrate, so I assume it's accurate).
Gal = reads 3.5% higher than physical readings.
MPG = reads 3.4% lower than physical readings.

So I calibrated SGII to FCD (these are the readings now stored in SGII for calibration of speed/fuel):
Speed (distance) = 0% (left this alone)
Gal = -5.9% (exactally 1/17th)
MPG = 0.53% (so now SGII should read 0.53% lower than FCD readings.. A 60.0 on SGII should show a 60.3 on FCD).

Also... What number do you report, FCD, SGII or Physical (MPGf, MPGs, MPGp).

11011011

locutus
05-25-2007, 10:30 AM
SG vs MFD MPG: within error bounds for virtually all individual trips, haven't bothered with TANK measurement

SG vs ODO miles: within 1%

MFD vs physical MPG: MFD reads 2.3% higher over 18,000 miles of readings

For the mileage log I report physical because I fill in miles driven and gallons filled. I note MFD in the comments for each tank.

Right Lane Cruiser
05-25-2007, 10:38 AM
Hi, Dan.

I'm not sure how much I can adjust all those on the SG1 -- I've only seen the gallons adjustment under the Fill menu. Perhaps there is somewhere else I can check? I haven't seen where I can adjust the speed or distance... :confused:

Mine is currently showing 16% offset. I'm pretty sure that is high because I'm having a hard time getting it over 40mpg now. I'm pretty sure that can't be completely correct because before applying all the harder driving tricks I was able to score a 39mpg tank.

The speed appears to be about right. The miles are drifting though with the SG reporting lower than it should. Right now the ODO is reading 34.3mi and the SG thinks I've gone 34.1mi. Before adjustment the mpg seem to have been reading roughly 16% high (49.7/43 = 1.1558 or about 16%).

Do you know if there is a way to tweak the percentages at a time other than fill? I don't really want to "start over" on the tank to get the settings tuned in...

I've been reporting the segments based on what the SG tells me, but the tank data I enter into the gas logs is just physical (gallons at the pump, ODO reading subtracted from previous fill ODO reading) I'd love to be able to trust what the SG is showing, though. Especially to gauge how much fuel I have left!

PaleMelanesian
05-25-2007, 11:03 AM
More -> Setup -> Speed
Adjusts MPH and distance traveled readings.

Don't know about adjusting the gallons mid-tank. I wish you could. I filled up yesterday, and adjusted the WRONG WAY. I redid it after 20 miles by doing a new fillup. I'll just have to track the combined in Excel separately.

For what it's worth, in my non-Prius, here's my setup:
Odo miles = Scangauge miles = 5% below GPS miles (my base-model Civic has smaller tires than the EX)
Tank gallons = SG gallons + 5%

Dan
05-25-2007, 02:32 PM
Do you know if there is a way to tweak the percentages at a time other than fill? I don't really want to "start over" on the tank to get the settings tuned in...Yeah, I was thinking of you when I posted.

For you it's easy... you simply unadjust the fuel. Do this by restoring defaults (then go back and set engine size and tank size and fuel type). That should remove all calibration and restore you to defaults. Taking off the +16% fuel calibration will give you a +16% fuel differential.. but if your interested in the math behind it for calibration....

OK... if your really interested, get your math hat on... it gets thick.

Speed first... that one is easy.

I've talked to the SG guy and he said that speed calibration and distance calibration are the same. The clock is gonna be pretty acurate, so +1% speed == +1% distance. So, you mentioned that you have 34.3 vs 34.1. So 1 - (34.3/34.1) = -0.58 %. So you probably don't want to change speed since since adding or subtracting 1 from .5 still leaves you off by about the same amount.

Now for the fuel calibration.

The way this calibration works is by adding or removing tenths from your gallons consumed. So if SG read 5.0 gallons consumed and you hit the left arrow on the fill up, you just adjusted it to 4.9, which was a 2% reduction (-2%).

<edit>
Don't know about adjusting the gallons mid-tank. I wish you could. I filled up yesterday, and adjusted the WRONG WAY. I redid it after 20 miles by doing a new fillup. I'll just have to track the combined in Excel separately.
If you want to move this number mid tank, just pretend to fill up. The more gas into the tank you are, the smaller the swing a tenth is. If you try it 2.0 gallons in, then each tenth represents a 5.0% adjustment. If you keep the tank (never hit the fillup button) for 50.0 gallons, then each tenth moves it 0.2%.
</edit>


MPG

So if your at +16% on fuel and you want your MPG to be adjusted 16% up, here's how it works. If x = unadjusted SG mile reading and y = unadjusted fuel reading, what you have reported now (since you haven't adjusted speed) is:

x * (1+0.0) / y * (1+0.16) =
x/y * 1/1.16 =
x/y * 86.20% ... So your adjusting the measured MPG down by 13.79%... so if you want it 16% up from the current reading... here are the calculations...

0.8620 * (1+0.16) = .8620 * 1.16 = .99 (actually equals 1)...

proof...
0.8620 = 1/1.16
0.8620 * (1+0.16) = 1/1.16 * 1.16 = 1.

The simple formula is this... SG adjusts your MPG based speed adjust (S) and fuel adjustment (F) in the following manner.

adjustedMPG = unadjustedMPG * (1+S)/(1+F). Remember F or S can be negative.

OK... Dan's getting back in his rocker ;)

11011011



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