Scanguage says 53.6mpg TANK, actual was 45.9??

[whatmaycome14]

Ok, so this is my first tank using the SG II. Something is obviously not right. The only thing that comes to mind is that I changed the way I was driving and used a LOT of P&G. I noticed that when I do this, the SG goes to 9999 instant mpg when I'm coasting in gear. I'm assuming that this is because the fuel injectors turn off? At least that's what I've read.

Why in the world would there be almost a 10mpg difference in what the SG is reading and actual mpg's? Do I need to change some settings? Help!!

[California98Civic]

You need to calibrate the SG unit. I have an ultragauge, but I'm sure it is simple. Someone with an SG will chime in. It's just a matter of calibration. Yes, the 9999 is an indicator of deceleration fuel cutoff mode kicking in.

[Occasionally6]

Yep. When you fill up "more" - "fill" (I think; I just do it without thinking too much about it now) you will get to a screen that says the amount used for that tank. If you press the buttons for "<" or ">" you can adjust the amount to that which you actually used/put in the tank. It will also display a percentage for the correction.

It won't be exactly the same each time but if you record it a few times you can get an average to use as the correction value (mine is something like 27%).

Yes, in gear coast will trigger the DFCO. Likewise, if you coast in neutral, 9999 mpg may display, even though you would be still be using fuel. The SCII interprets open loop plus speed indication as injector shut off, even though open loop may occur at idle. Open loop can also mean lean operation, rather than no fuel. Again, that's open loop plus speed indication and error in fuel consumption.

[UltArc]

I would refer to the instructions, which will show how to set it up. It will not be accurate if it is not set up. My roommate gets 40+ mpg in her Escape until she gets to the fuel pump- yet never calibrates. It's frustrating for everyone.

This may also help: calibrate - Google Search

Give a man an answer, he learns for a day. Teach a man to search, he learns for a lifetime.

It's most definitely because it is not set up. Mine is always off in the Mustang because I EOC, but it is LESS than right. I often check it, knowing I will get better than that. There are settings for it, but I like to see how far I EOC. The easiest advice is to set it up correctly, and then keep correcting it at each fill up.

[whatmaycome14]

So is it just a matter of filling up a few times and letting the gauge get used to the car??

[whatmaycome14]

Originally Posted by UltArc

I would refer to the instructions, which will show how to set it up. It will not be accurate if it is not set up. My roommate gets 40+ mpg in her Escape until she gets to the fuel pump- yet never calibrates. It's frustrating for everyone.

This may also help: calibrate - Google Search

Give a man an answer, he learns for a day. Teach a man to search, he learns for a lifetime.

It's most definitely because it is not set up. Mine is always off in the Mustang because I EOC, but it is LESS than right. I often check it, knowing I will get better than that. There are settings for it, but I like to see how far I EOC. The easiest advice is to set it up correctly, and then keep correcting it at each fill up.

I set the SG up exactly the way the instructions (that came with it) suggested.

[Occasionally6]

Yes, there is a baseline set up, which includes things like fuel type and engine size. It sounds like you have already done that, so that's OK.

The SCII won't self learn the correction required. You do have to make the final correction based on what fuel consumption you actually get. Once it's done though, with an average value programmed in, you can leave it at that.

One more thing: once you've found the average correction value, I suggest writing it down somewhere. Should you disconnect the SCII from power for any reason, the value will be lost and you have to reset it. That is easier if you can just program in your known value rather than have to figure it out again from scratch.

[UltArc]

I notice mine is pretty correct for the most part, sometimes on longer trips (600+ miles) it can be off by a bit, never more than 5%.

[MetroMPG]

A lot of pulse and glide will cause the SG to be off by more vs. if you calibrated it on a previous tank where you didn't use P&G. That's been my experience, anyway, and a few others I've read about.

[101Volts]

Originally Posted by UltArc

Give a man an answer, he learns for a day. Teach a man to search, he learns for a lifetime.

Yes, If he heeds the advice.