ScanGauge and Fuel Efficiency

I’ve become quite focused (addicted, some might say) to maximizing fuel efficiency. I have pulse and glide down pretty well: I easily manage 99.9 MPG segments if road and traffic conditions allow. My MFD shows 61.9 MPG for the current tank as of a while ago, and fillups have been well into the 50s throughout the summer.

Now I’m working on maximizing high speed FE. I’ve read and re-read Hobbit’s article about a higher speed potential “sweet spot†as determined by a vacuum gauge:

http://techno-fandom.org/~hobbit/cars/sweet/

I say “re-read†because, though I have geek tendencies, I don’t have a geek’s technical or mechanical education. So if something like this is not written on a “see Spot run†level, it takes me a few tries.

But the take home lesson seems to be simple enough: At higher speeds use “warp stealth†when conditions allow, and when they don’t, in the Prius with no added instrumentation, keep the instantaneous MPG between 35 & 75. I’ve been doing both whenever possible.

I now have more instrumentation available: I just bought a used ScanGauge I. (Thanks DarellDD!) Hobbit suggests using RPM as another indicator of the sweet spot, so I’ve set the ScanGauge to display that.

The question to those familiar with his article (Hobbit, are you listening?): Assuming his theory to hold true, which of the other parameters available from the ScanGauge would be best to monitor in order to achieve and maintain this sweet spot, and what numbers should I aim for? Frankly, this mechanically uneducated brain doesn’t understand what some of these things are.

For those not familiar with the ScanGauge, I tried to attach a PDF excerpt from the manual that lists what it can display, but the attachment didn't take. Not sure if its because of this week's crash or a normal setting. I can list its various functions in the body of a follow-up message if needed.

For those with a ScanGauge and who are not familiar with the article: Which ScanGauge parameters do you monitor, and where do you try to maintain them to maximize FE at higher speeds?

Thanks in advance!

 

Thanks, hdrygas. I considered the CanView, but I have to pace myself with mods and accessories and watch what I spend. That's why I jumped on the used SGI when DarellDD offered it for $90. My ex expects her support payments!

Please bear with me as I pose some follow-up questions:

I've been watching coolant temps after re-reading the PC article on the four stages this week -- before the site crash. Now I can't find it. (Crash-related?) Anyway, my read earlier in the week was fairly quick, but I made some notes of temperatures to expect for each stage. But I couldn't find one to indicate the S3/S4 threshold. I've learned already from the SG that temp plateaus in the 180s, so I've used (somewhat arbitrarily) 180 as a presumed threshold. Is that about it?

By "fuel flow" are you referring to MPG, gallons per hour, or something else?

Do you ever look at engine loading? Hobbit's response on CleanMPG, and others over there as well, suggest keeping LOD at 50% or less.

Finally, I'm not getting a MAP reading; I'm guessing because it's not available. Can you verify?

Thanks again.

 

<div class='quotetop'>QUOTE(tomdeimos @ Sep 29 2006, 11:13 AM) [snapback]325581[/snapback]</div>

My notes say S3 is from 163 to...? Maybe I wrote down the wrong thing in my haste. Anyway, here is what I have in my notes, so maybe you or others familiar with it can verify or correct me:

• S1: <104
• S2: 104-163
• S3: 164-?
• S4: >?

And how do you "try to get" to S4 (the exact threshold aside)? I thought the temperature is what defines the 4 stages, and it has to warm up at its own pace.

Not second-guessing you, just trying to learn as much as possible via the SG -- and from the great wealth of knowledge here -- about what's happening under the hood of this remarkable car.

And Frank, thanks for the info. I've watched the throttle position and load at different times, but not together. I'll see what the combination gives me.

Thanks!

 

I no longer use ScanGauge; I got CAN-View a little over a year ago.

CV has many parameters available to monitor but can display only a few at a time, so I'm frequently switching among them depending on conditions. In descending order of frequency (roughly), this is what I watch and why:

• RPM: to avoid inefficiently high or low ranges.
• Battery state of charge: Of course the car displays SOC, but only in relative terms. Six blue bars actually can vary from ~55% to ~65%, so it's helpful to know the exact percentage to see incremental changes as they occur.
• Current into or out of the battery: to help maximize regeneration and minimize drain.
• ICE temperature: to know when the car can transition from one warmup stage to the next and when the car is fully warmed.
• Instantaneous MPG: same as the factory display.
• Trip MPG: to check results for a trip or a portion of it.
• Throttle position: This is a bit of a misnomer, I think, in that it is not tracking the position of the actual engine throttle, but instead the accelerator position. I use it to get a sense of where the pedal needs to be for maximum fuel economy at various combinations of engine and vehicle speed.
• Ignition timing: A lengthy discussion on CleanMPG suggests this allows identification of a mid-range (45-55 MPH) "highway" sweet spot of 14 degrees BTDC. ("Highway" is in quotes because that's really too slow for most freeway driving.) As I suggest in that thread, it seems that that timing level just happens to coincide with low RPM under load, so between that and limitations of the CV display, I just spot check it from time to time.
• Fuel injector timing: On my most recent highway trip, I used this to try to find some other highway sweet spot to use.
• Inverter temperatures: Mainly to assure they don't overheat when I have a grille block in place in something other than winter temperatures.

Two others mentioned in this thread -- engine loading and a true engine throttle position (which is what SG reports) -- unfortunately are unavailable in CV.

The ScanGauge I was using is the original model. The latest model has a feature called XGauge which allows programming of many of the parameters available from CV. There are one or two threads on the subject. Search for "XGauge" if you want to find out more.

EDIT (9/17/08):

I recently bought a splitter to allow both CAN-View and ScanGauge to be plugged in simultaneously. I mainly wanted to take advantage of the ScanGauge's superior trip mileage capabilities, but I also use it to watch IGN during my warmup to know exactly when S1 ends. (I couldn't continuously monitor IGN on CV the way I had the CV display configured.) So now for the list above I'll bump IGN up to between iMPG and trip MPG.

In addition, I have coolant temp and RPM showing on SG to allow continuous monitoring of those parameters while I fiddle with the MFD for the Energy or Consumption displays, climate control, audio, etc.

For the fourth displayable gauge I mostly have alternated between LOD and TPS, though I'm not sure whether either has any value for me, given what's available on CV.

 

Glad it's of some help.

You might know this, but the car tries to maintain an optimal SOC of ~60%. Much above that, then the higher it gets, the more car tries to use it. When I know I have some surplus that the car will try to use up anyway, I try to use it on my terms. For example, I might begin an ICE-off glide sooner than usual, knowing I can extend it a brief distance with a little bit of EV mode without dropping SOC below 60%.

At the other extreme, when it gets close to 50% (3-4 blue bars), I know I've got very little room to play with; my EV switch won't work below 50%. And the car diverts more ICE power to charge the battery, so I know I'll have to accept less and plan either to accelerate more slowly during my pulses or to have to push RPM higher than usual.

One nice thing about the CV display is that SOC is the one parameter that is always displayed. It's all the others I have to pick and choose from.

I'll try to help. Almost two years ago now, I thought I had started a thread there like I did here. I searched all threads I started (there aren't that many), but it didn't show up. So that leads me to believe it was a post in someone else's, most likely one of Hobbit's. This could be it, but I'm not sure. (The content is relevant to this PC thread, regardless.) I'll see if I can search some more of his threads later when I have some more time.