ScanGauge and Fuel Efficiency

[JimboK]

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!

[hobbit]

[replied over in cleanmpg.]
.
_H*

[hdrygas]

I used the ScanGage for 6 months until I got a CanView. One of the advantages of the Scan Gage is that the MFD and the ScanGage can be used together. I looked at fuel flow, coolant temp, as primary indicators on the ScanGage. Both of those can be helpful, day to day. You need to know coolant temps to know when you are in S4, or can get into S4. That is the most important thing the ScanGage can do for you. The rest will help but are of lessor importance and you can get the other information from the MFD. ScanGage is good as a help tool but for understanding the process of the HSG the CAN View is better. For those of you with the 06 and greater say tuned Norm is on the job.

[JimboK]

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.

[tomdeimos]

<div class='quotetop'>QUOTE(JimboK @ Sep 29 2006, 08:04 AM) [snapback]325492[/snapback]</div>

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.
[/b]

I try to get to s4 when temps get over 163 degrees. It seems to vary a bit and happen early sometimes or late, esp. when I have had a fast warm up.

[Frank Hudon]

if your trying to see how to get the best mileage at road speed you might consider the following.
1) throttle position
2) calculated load
3) RPM
the reason for the first two is you want the throttle position to be at it's lowest % for the Calculated load. The RPM you have little control over but if you see it rising you will probably find that the road isn't flat. One thing that I found is that the HV computer tends to hold the RPM steady and apply fuel injector on time as the load increases on slight grades instead of releasing the RPM to increase the MG1 speed to provide more current and voltage for MG2.

[JimboK]

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

I try to get to s4 when temps get over 163 degrees.
[/b]

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!

[Frank Hudon]

<div class='quotetop'>QUOTE(JimboK @ Sep 29 2006, 09:44 AM) [snapback]325629[/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.
[/b]

My observations on the 2k4 is 63-70C with the inverse of BSOC 60%-70% so at 70%BSOC 63C will give you S4 but it still needs to go over 72Km per hour or a full stop for 6 seconds.

[tomdeimos]

<div class='quotetop'>QUOTE(JimboK @ Sep 29 2006, 12:44 PM) [snapback]325629[/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!
[/b]

I don't recall all the original description, but after my code updates my car doesn't exactly switch the same as before when the write up was done.

The 163 deg is adequate for S4 or S3. In fact I can stay in S4 down to maybe 140 after the warm up.
You need to stop and let the idle calibrate and then shut off the engine normally to go to S4. Till then you stay in S3. I think the car requires some minimum catalyst temperature too that leads to a delay in this sometimes. Battery charge level may be a factor too.

I have also seen S4 without stopping but it is rare and I don't know how it happens. Sometimes I get to stealth more than once before coming to a stop, preventing the idle cal and switch to stage 4. So I have to stop again. I am learning to just make sure the engine is running just before a stop at a light when I need it to switch.

I think I get to S2 at a bit higher temp than 104. Maybe more like 120. Again this changed with the code update.

Once warm I can get good stealth switching down to 143 deg most days, once battery is warm. And I adjust my winterizing so temps stay below 195 deg.

[theorist]

<div class='quotetop'>QUOTE(Frank Hudon @ Sep 29 2006, 11:22 AM) [snapback]325586[/snapback]</div>

the reason for the first two is you want the throttle position to be at it's lowest % for the Calculated load.
[/b]

Interesting. Can you say why that is?

Is calculated load expressed as an estimate of delivered torque as a % of the maximum for that RPM, as the torque as a % of the maximum torque for any RPM, or an estimate of of the delivered horsepower as a percentage of the maximum horsepower for any RPM? I assume this would be engine (ICE) torque or power as opposed to net HSD torque or power.

I thought the rate of fuel flow in gallons per hour might be very useful. I trust that the engine will produce the maximum amount of horsepower for a given amount of fuel supplied or equivalently use the minumum amount of fuel for anf amount of power demanded. It really shouldn't matter then which we look at, unless we wan't to have a sense of minimizing total or average consumption over a trip where we choose how to vary power deliver over time. In that case, I'd prefer seeing fuel consumption in gallons per hour. If only I could see the ratio of fuel rate and power produced or better yet fuel_loss = {fuel_rate - R * power} where R = min( fuel_rate / power ). Anyone want to discuss applications of dynamic progamming to finding really good state values or scores to display and optimize while driving? We could include kinetic energy, electrical energy, and perhaps even potential energy as well as fuel energy consumed all into a single score. Optimizing this summary score in the short run could better minimize fuel consumption in the long run.