I'm wondering about the accuracy of the trip computer function. Has anyone checked the tank average MPG against paper and pencil calculation?

I'm old school. Learned to figure my gas mileage with the old Ward's brand car expense books. I've been using a spreadsheet for a number of years. Enter in date, odometer, gallons bought, price, and let the spreadsheet calculate the MPG for that tank.

In my 02 Maxima, there is an avg MPG readout, but it's always optimistic. I usually show about 26mpg on the readout, but get 22 actual. Clearly, there's an error in the programming, and the program thinks it's using less fuel than it really is. Impossible to tell, though, whether the bug is in the calculation, or in the ECM report of fuel used. If the ECM would tell ScanGauge the REAL amount of fuel used, I might get one of these. Wonder if they can be returned? ;-)

 

I think it would difficult for any of them to be dead on accurate. There are so many variables to consider. However, the Scanguage is adjustable either manually or when you fill up and adjust the actual amount of fuel you pumped in the tank. If you maintain a similar driving style day after day and it becomes pretty accurate. If you drive easy one day and hard the next, it will not match what you calculate manually.

 

I have found that it is very, very accurate when you do a lot of highway cruising.

The tank I am on now is a lot of city, lots of short trips. I doubt it will be as accurate, but time will tell.

And I also keep a very detailed spreadsheet.

 

So, with a question from the Department of Redundancy Department, your spreadsheet values match the ScanGauge values? ;-)

 

Well I have filled the tank three times since getting the ScanGauge.

Fillup 1 was void since the ScanGauge had no clue how much gas I had actually used, only an idea what it thought I had used. I tell it that I filled up.

Fillup 2 is to calibrate the Scangauge. It thought I used (Don't remember, but it was about 22% off) so I had to tell it how much I had actually used.

Now that it is calibrated, Fillup 3 tells me that they are real close. I believe it was off <0.2 gallons, I did not think to check what the ScanGauge thought my mileage was for that tank, only the fuel used. Well I did think to check, but it was about 0.5 seconds after I told it I filled the tank.

When I fill up again in a couple weeks, I will report here.

 

Very cool, thanks! I also contacted ScanGauge asking them about the issue. If they reply, I'll post it.

 

As far as accurate mileage figures go, you also have to factor in that the odo's accuracy is off by some factor depending on the diameter of your tires. With the stock tires, I figure mine's short by a wee bit more than 4%.

 

The Scanguage has correction for that too.

 

I'll have to check that out - I mostly use the ScanGauge's mpg report as a rough guideline, and a reminder to go gently on the gas pedal. For "real" fuel efficiency, I just use the corrected odo number and however much fuel I've put in at my most recent fill-up. I do know that the ScanGauge's speedometer is more accurate than the dashboard, but haven't checked the SG's odo.

 

As I recall (and it's been a while since I checked), the odometers on all our cars are really close (even my son's Civic, with its 17" wheels). The speedos on the Civic, and the old Previa, were optimistic, though. My Maxima speedo is spot on (checked via GPS and a chronograph). Haven't checked the box speedo, though.

 

It's about 5% high.

 

Ok, I just bought one on eBay for $164.99 w/ free priority mail shipping. Sweet.

I want to install mine exactly like Chad's pictures above. However, I don't want to remove the dash if I don't have to. Does anyone know if I can just drill a hole big enough in the dash and be ok? Is there anything behind that long cubby that could get damaged if I choose to drill w/o removing the dash first?

Any help will be appreciated. Thanks!

 

you might drill into the air duct if you drill within 6" of the right hand side of that cubbie. I drilled mine into the very side of the cubby, and fished the wire through.

 

If you drill straight back, you should be ok. If you go up you could hit the air vent that runs right behind the part of dash above the cubby. In either event it's not easy to reach the cable up there.

I can't find the post but another XB owner put the Scanguage in the same location as mine but ran the cable down just above the steering wheel column so you only saw about an inch of it before disappearing.

 

Thanks for the advice guys. I figure I'll grab the mag light and try to look up under the dash from the driver foot well. If it looks like I can drill it, I might take the plunge. I'd just hate to mess it up and end up w/ a nasty hole in my dash! But if I get it right, it should look nice just like Chadfo's.

I'll let you all know which route I choose. The Scangauge should be here monday or tuesday.

 

The folks at ScanGauge wrote me, and said that the ScanGauge will 'learn' about true fuel consumption, and override what the sensors relay through the ECM.

ZanexGT, when you get yours, would you let us know the following?

Before you start using it, fill up your tank, and reset your trip meters, and/or note what your odometer reads. At the gas station, right after you fill up, startup the 'Tank Trip' meter.

The next time you fillup, calculate the old fashioned way
( ( new odo - old odo)/gallons used) and tell us that figure, and the MPG reported by ScanGauge for the tank.

Yeah, I know. I'm too picky. It's a character flaw. It goes back to my navigator days "A man with two chronometers doesn't know what time it is"

 

Has anyone with the new scangauge tried the function of downloading the information in realtime to a laptop. That was supposed to be avaliable in September. I think it involved a second cable that had a USB end for laptop hookup. That is the one I want.

 

No problem. I already track mileage 'the old fashion way' and I'm interested in how accurate the scangauge really is.

The scientific method, hard at work.

I'll also post some pics, etc.

 

So far that feature hasn't made its appearance, and I don't see any mention on the scanguage site.

 

Here is where I found out about the interface to the laptop.
It was supposed to come out in July, but keeps getting pushed back.

http://www.thinkgeek.com/gadgets/electronic/8426/