View Full Version : What is my Ultragauge telling me?

02-18-2013, 02:50 AM
So I got an Ultragauge a little while ago, primarily for monitoring mpg, but also to get better feedback on how my van is running overall. Most readings seem normal, but I have noticed one effect that I did not expect:
When I am at highway speeds, going downhill, and back off of the throttle completely, I notice that the mpgs (instantaneous) actually go down a bit from when I have the throttle slightly depressed. % load readings seem normal, and drop to 0 when coasting downhill, but I've noticed that boost pressure increases slightly to 2-4 PSI, up from <1 when I have very light % load, say 15%. My expectation would be that inst. mpg would go way up, and boost pressure would drop to 0.
So, any ideas on what's happening? Is this possibly normal? I believe I remember reading that the OM 612 turbo is vacuum controlled, vs. electronic on the 647, so wonder if it has something to do with vacuum pressure? And, I'm assuming that the ECM is reacting to the bump in turbo pressure by using more fuel, hence the drop in mpgs?

Thanks for any input!

Also, if people are interested, I will start a thread for typical values to expect with a T1N for the various gauges available on the Scangauge/Ultragauge- I know these have been covered in other threads but a condensed list might be helpful.

02-18-2013, 02:57 AM
I've never figured out how to properly config the ultra to take into account coasting. There is programming series to recognize "injector cutoff" but it doesn't seem to work right. Coasting down a long mountain pass, knowing I am not burning ANY fuel, and yet the ultra shows poorer mileage than normal road driving is frustrating, and it does reflect in the mpg averages. For me it is a bit of an irritant since we do lots of moutain driving, but that said on a number of coast to coast trips the mpg numbers are, in the net, very close to spot on.


02-18-2013, 04:31 AM
A. Hayes...icarus,
Might consider that the % engine LOD (Load) and the fuel flow (GPH) are the more important OBD-II PID's than the miles per gallon.
The MPG (whether on the UG EM or SG II) is a calcuated PID value, and while you could fool around with your mileage percentage offset
factors and dial that in a bit, it sounds like the net value you are getting is pretty close to what you calculate when you fill the tank (MPG= miles traveled/gallons used).
Watching the % engine LOAD and GPH values/PIDs is far better information about what changes/decisions the ECM is making for you, and keeping the % LOD and
GPH as low as possile (by manually downshifting/altering speed (or both) is what I have found is the key to getting the best mileage.
If you % engine load is > 70% you can easily see that the GPH has increased as well.
Downshift to reduce the % LOD and the GPH will drop as well.
You can see this on your Ultragauge EM when you are coasting..... the % engine LOD will be 0.00.... the GPH will drop to 0.00.
The MAP (PSIA)/Boost (PSIG) are set by the ECM via the turbo vane controller, so there's nothing you can do about that.... it's programmed
into the ECM and it is what it is!

02-18-2013, 05:46 AM

I hear you about watching the lode numbers for best fuel economy. The condition I describe (and I believe the OP is describing is coasting, lode is showing 0%, and fuel mileage is showing say 18 mpg, whenif I put my foot into it a tiny bit, the load might go to 10%, and the mpg goes to say 39 mpg. It just seems to a quirk in the ultra. I should take the ScanGauge out of another vehicle and see if it does the same thing.


02-18-2013, 05:54 AM
When you're coasting, the ScanGauge reads 9999 MPG, 0 LOD and 0 GPH.
Since there's still air being pumped through the engine (energy input from the coasting wheels), the turbo can be producing a few pounds of boost.


02-18-2013, 06:01 AM
My scan gauge does that other vehicles, but the Ultra in the Sprinter has the "bug" described, and I can't figure out how to change it.


02-18-2013, 10:04 PM
Thanks everyone for the replies. What Icarus describes is exactly what I am seeing. Interesting (and a bit frustrating) to hear that this is an Ultragauge glitch.

You can see this on your Ultragauge EM when you are coasting..... the % engine LOD will be 0.00.... the GPH will drop to 0.00.


I did a bit more testing today, and watched GPH and boost pressure relative to % load. What I see is actually a bump up in GPH when I go from very light throttle (around 15% load) to coasting, even though % load goes to 0. GPH goes from 3.5-4 or so to 4.5-4.75. Boost pressures also show as going UP 2-3 PSI.

So are any other Ultragauge users NOT seeing this effect when coasting down a hill at highway speeds? Just want to make sure it's not my van/ECM doing something wrong.

02-18-2013, 10:50 PM
I don't think there is anything wrong with the van. The problem with too much information is it causes us to question the information if it is contrary to either our intuition or a actuall experince. Then you begin to question all the info, making most of it worthless. I just accept the fact that it is a bug, and I don't worry about it.


02-18-2013, 11:26 PM
My Ultra Gauge behaves the same as you describe with yours. It baffled me, but I didn't pursue it. I get suspiciously low mpg numbers in lower gears too. Still really useful instrument.

02-19-2013, 12:55 AM
I think this is a serious issue with Ultragauge. I was tempted to buy one recently after being happy with the old Scangauge for a long time. I decided instead to upgrade to the new Scangauge mainly because I did not like the buttons in the back of the Ultragauge; had I known this issue I would have never considered it. The makers of Ultragauge need to be made aware of this problem as there are many people buying it that don't know this problem. My Scangauge has no such issues with what it displays... Al

02-19-2013, 03:22 AM
Thanks for the responses everyone. Maybe I should have coughed up that extra $80-100 for the Scangauge... Hopefully this thread will be helpful for those still shopping and comparing the two.

02-19-2013, 05:54 AM
I have both and actually prefer the Ultra even with the little bug. Not really such a big deal.


02-19-2013, 02:56 PM
I only have the Ultra, but I agree, not a big deal at all.

02-19-2013, 05:22 PM
My driving pattern has changed due to the Ultragauge as when I go up hill it says I am getting better mpg by leaving it and NOT downshifting. Are scangauge owners experiencing the opposite?


02-19-2013, 06:33 PM
Are scangauge owners experiencing the opposite?
I think so (at least for me).
There were a few hills that i took consistently on the way to work, so i was able to "play" with various approaches at in-city speeds.
There are portions of the I-5 trip between Portland and Seattle that offer opportunities for testing at speed.
I also fiddle during long boring (or exciting) parts of road trips, too.. so i've tested it up to 70mph.

I monitor MPG, GPH, LOD and MPH. There are times i'll flip in RPM (looking for consistency)
In pretty much every case i tried, doing the shift-down-above-70%-LOD showed improvment (i.e. less) in GPH at constant speeds
(i'm usually in Cruise Control, and the only thing i touch is the shifter)
There will be a momentary bobble at the instant of shifting (as the engine brings the RPM to the desired road speed), but then the improvement appears.
It can be as much as a 20% improvement, but it's usually less (such as 15 or 16 MPG improving to 19 MPG).
The improvement also depends upon when in the LOD range i do the downshift... if i'm already up to 99% LOD, the "win" is less.
The GPH and MPG track themselves, so i'm not seeing an apparent inconsistency due to a calculation error.

Overall, the only times i've seen a downshift appear to get worse MPG is in the already-99% situations.

As noted, i use cruise control... if i were to take a more active "speed up on the downhills, coast up", the experience (and overall trip mpg) might be different. But i try to stay at the legal speed, not go +/- 5mph around it.

p.s. i have a truly ancient ScanGauge "I"