Rpms of ICE when accelerating

full acceleration is 4500 plus rpm--- lots of engine noise
moderate acceleration is about 3-3500
cruising at 70 is 1500-1600 on level surface.

engine noise starts to come in at about 3000 rpm for mine
if i rem correctly,, at 3/4 bar its about 2500 rpm
hope this give you some idea.

 

The RPM is probably going to change a lot as you hold the power constant and accelerate from a stop, but at high power demand, it is all coming from the ICE, either directly to the wheels or through MG1->MG2, the difference being only the 0.9 energy conversion of going through the MGs. The only reason the RPM will change is that the torque load will change as you hold the HSI at constant power as the vehicle accelerates.

The HSI is not an rpm meter. It is basically a power meter, although it isn't very linear. Measurements I've done are here:

http://priuschat.com/forums/gen-iii...ink-im-getting-hang-60-mpg-4.html#post1145624

Center of HSI = ~10 kW
Line dividing ECO from "Power" = ~25 kW
Right edge of "Power" area = ~45 kW

However since Power is proportional to RPM*Torque, you need to know the torque to back out the RPM from the HSI. i.e. the RPM at any position on the HSI will depend on vehicle speed (due to wind drag), and the grade of the road you are on.

Sorry its so complicated! If you really care about RPM you will need an OBDII scanner. If you want to operate the car at peak efficiency, keep the HSI equal to the right edge of the "ECO" label, that is about 1/4" from the HSI centerline. At that point the ICE is at 15 kW and at the peak of its efficiency curve.

Hobbit has a great explanation:

HSI

Normal/Power/or ECO mode shouldn't make any difference. The HSI is still a power meter and those modes just adjust how much go-pedal maps to how much power demand.

 

Oh, I'd guess you'll be around 1800 rpms, but that's just me. cobradb obviously has a different opinion.

 

On flat ground in ECO mode, 3/4ths is between 1,500 - 1,800 for me. I just now tried it. Obviously, speed and load will make this vary with the CVT.

 

Looks like my post from late last night didn't do a great job of answering the OP's question. I misread RPM range as RPM. Oh well, I'll leave the post there and maybe someone will find the info useful. Sorry!

 

There are gremlins in the hsi, that's why they made sure we wouldn't have a tach. Seriously, I would get a scangauge, but I don't like the display. Instruments that are needed are tach, net current (or power) going to the motors, temperature. Since the battery could be charging or discharging the rpm of the engine does not have to correspond to the power to the wheels. I'm in the process of writing an iphone app to show the missing instruments, but its during my spare time.

 

Pakitt,

There are folks around here who knows this better than I do, but I've been thinking about it for a while, I've been doing my own measurements and I have good tools. So I'll give it a go:

To start with you need to read and injest hobbits "sweet spot" article. I really like it and it is the 2nd post today where I'm referring to it:

Sweet spot refinement

If you look at the BSFC plot, you can see where on the Torque vs RPM chart the genIII engine operates at peak efficiency. Hobbit and Bob Wilson have both pointed out that the BSFC measurements are kind of contrived but it is probably pretty close. Now, If you look at the BSFC plot there is a heavy black line. That is the "basic operating line" for the genIII. The engine ECU tries very hard to operate the ICE on that line. Most cars that have fixed gear ratios, have a relationship between RPM and speed. On the Prius we can operate the ICE for whatever power demand we would like at any time, irrespective of speed. That gives us huge flexibility to operate the ICE where we want it. Again on the BSFC chart, the peak efficiency is the grey region in the center which extends from about 10kW to about 30 kW. Hobbit argues that, in the real world, the peak efficiency is towards the lower end of that range at about 15 kW. Thus if you want peak efficiency for the ICE you want to run it at 15kW and certainly no less than 10 kW, and probably no more than 25 kW or so. The isoclines (dashed lines) on the BSFC chart map ICE power. You can see that if you have some indication of the power, you can figure out exactly where you are on the basic operating line and know where you are inside the efficiency contours. A tach is really the wrong tool because you need torque as well to tell you where you are inside the efficiency contours, although the Engine ECU will try to keep you on the basic operating line. The tach is almost useless without a torque meter. What you really, really want is a power meter (power proportional to torque*rpm) which tells you everything you need to know.

Now comes the really cool part. The HSI, as I pointed out in my last post, is a power meter. It is exactly the right tool. Peak efficiency for the ICE is with the HSI green bar just even with the right edge of the "ECO" label (15 kW). However, the efficiency is actually pretty close to peak over the entire "ECO" range, funny that (Thanks Toyota!)... So, to drive at absolute peak efficiency, (ignoring hill climbing strategies, regen strategies, and other special cases) you want to run the ICE at 15 kW or turn it off, i.e. glide.

There are a couple things you really want to avoid. One is operating in the "power" region of the HSI unless you really have to. The power region on the HSI is from 25-45 kW and efficiency really suffers. The other is to run the ICE below 10kW. You know the ICE spins when you are above some magic speed ~47 mph (75 kph) even if you take your foot off the accelerator. However, it is unfueled and in a state that minimizes pumping loses. In this state it creates about 2 kW of "drag" so the car doesn't really glide well but decelerates. You need to counteract this with a little help from the traction battery and MG2. The tricky part is that slightly above the "chg" region of the HSI the ICE will kick on at ~5 kW, increasing to 10 kW at the center line. I don't know why it does this because according to the BSFC chart this is a very inefficient operating mode.

Thus the best operating strategy is to accelerate up to highway speeds from a stop with the ICE at least at 15 kW (too little and too much acceleration are both bad as the ICE operates at lower efficiency) but this will be a very slow acceleration so you probably have to accelerate harder. As long as you aren't getting run-over, try to keep the HSI below the power region. Once you are at highway, speeds oscillate the car between 15-20kW and zero to maintain speed. Accelerate a little, glide, etc... To glide you need to apply just enough accelerator to show a few mm of green bar on the HSI but not enough to kick on the ICE. You don't need a tach for this, and in fact a tach doesn't indicate this very well, but it is helpful to have some indication that the ICE is being fueled. I use an ICE torque parameter on my DashDaq (which is a very sophisticated scan gauge like tool) which shows clearly when the ICE is unfueled and fueled.

Hobbit has a great article on driving efficiently with the HSI. Highly recommended:

HSI

Bottom line is that Toyota has given us a great tool in the HSI. You don't really need an OBDII scanner. The scanners are great fun though, also highly recommended.

 

Pakitt,

Some of your questions don't (yet) have good answers. I think we are all trying to figure this stuff out in real time, and I'm one of those who are still catching up. Somehow I missed out on the Prius GenII, driving my Subaru to 500,000 km. I was just too cheap to replace it. Again, there are people here who know a lot more than I do but I'll try and answer anyway. Part of the problem is that the GenIII is very, very good at managing the hybrid system for minimum fuel consumption. We can just affect it in the margins. For example, if I race around with a lead foot, I still get 45 mpg. If I try really, really hard, and risk getting run over in traffic, I can get 65 mpg. That isn't really a big range. Certain things do have big effects: Braking hard (friction braking), keeps you from regenerating the kinetic energy in the car. Running in the "power" region of the HSI, and especially when the HSI is saturated is really inefficient. Also, not having a good strategy for hills such that you have to go heavily into the "power" region, can be really bad. So here are a few possibly useful answers:

Yeah, this is a problem. I don't know if there are good names for the regions of the HSI so I've made some up and I haven't really been consistent. Here is what I think I've been using (from left to right):

1. "Chg" region -- Provides some indication that you are mostly using regenerative rather than friction braking.
2. "Batt" region -- Below the line in the center of the HSI. Below ~47 mph the car is normally in stealth mode. Above 47 mph where the ICE is definitely spinning, this is a very inefficient region to be in.
3. "ECO" region -- Between the center of the HSI, and below the "Pwr" region. This is where the ICE runs close to peak efficiency and where the "ECO" indicator is lit.
4. "Pwr" region -- Farthest to the right. This is where the ICE starts to get really inefficient. The efficiency gets terrible as you saturate the "pwr" region.

Yes, well, you are right. You have to integrate your strategy with what you can actually do, i.e. you are, of course, constrained by your route and traffic flow. You do what you can and what you are comfortable with. At 65 km/h this should work much better than at highway speeds. Here the ICE isn't running so you can truly glide or even provide some extra boost from the battery, i.e. run with the indicator about 1/3 of the way up the batt region with occasional bursts of ICE to 15-20 kW. The optimization region can be pretty broad, i.e. if you run the at higher power say 25 kW and get 30 mpg with a 30% duty cycle, then you will actually be getting 90 mpg! However, this has to be interesting for you because playing with the optimization requires some concentration, and your speed won't necessarily be steady. If you just drive with power sufficient to maintain steady speed, irregardless of terrain, then most of these strategies won't work, but you will still get pretty excellent efficiency!

Not being a "real" hypermiler, I can only put words in their mouths (hopefully they will speak up), but, yes, this is the essence of one hypermiling technique: pulse-and-glide. The premise is that you run the ICE at as-close-as-possible to its peak efficiency (pulse) or you turn it off (glide). Since the ICE starts and stops in about 0.1 seconds you can play this game fairly easily in a Prius. It gets somewhat more difficult when the ICE spins unfueled above ~47 mph.

As you say, the ECO/Normal/Power buttons only affect the mapping between gas-pedal-position and throttle. I like the higher sensitivity of ECO, especially in trying to glide at highway speeds. If you drive normally it should make no difference in fuel economy, which button you select. Except for the AC throttling in ECO mode, but I suspect that is a minor effect.

I had thought that this was just marketing. I haven't played with it much. If the buttons are just playing with the linearity of the encoder, then I see no reason for the PWR button to affect the Prius'
internal strategy of running the ICE. Does it really do this? I'll have to give it a try... I have some experiments planned for my next tank that will give terrible fuel economy, I guess I'll do some playing with PWR mode as well...

My guess is this is a transient where the ICE is spun down. I've logged some of these and I don't believe they mean anything. The ICE takes about 100ms to spin down and lots of things read-out strangely during this time. I haven't looked at it closely yet. I noticed this last week when I was logging data to make "real world" BSFC (Brake specific fuel consumption) graphs (hopefully the subject of a soon to be written post).

If you use a strategy of staying outside of the PWR region (as much as you can), not saturating the CHG region (i.e. not friction braking (again as much as you can)), then you will be doing pretty well. One additional strategy that I would include, is that at highway speeds, if you aren't going to try gliding, then always keep the HSI above the center line (i.e. in the ECO region). Running in the "batt" region at highway speeds, unless you are really paying attention to gliding, runs the ICE in a very inefficient manner.

I hope this helps!

 

Forgive me to try to put in my 2 cents while I also try to learn from veteran hypermilers here in the forum.

I also have been trying to practise the pulse & glide techique and found that it was very difficult to apply in medium heavy city traffics. So I tried my own Pulse/CC/Neutral Glide technique I used in my 15 years of Honda Civic hypermiling experience (which produced marginally better FE from 8L/100km EPA to 7L/100km actual).

I'm now driving the GenIII with PWR pulse to speed of traffic, set it to Cruise control (with radar set to short distance) thus keeping the speed very constant. With radar cruise control keeping a minimum distance it helped a lot when the car in front slows down. I also "drive" the car constantly adjusting the CC set speed to comply with traffic conditions.

I found that as soon as I set it to CC and take my foot off the gas pedal, the instaneous FE gage immediately drops down a lot and yet the car stays at constant speed (mostly between 65-70 km/h). A lot of times the ICE even turned off with instantaneous FE bar disappearing meaning battery power only and no fuel consumption.

In slight uphill climbing the FE bar flutuates between 2 to 5 L/100km. When the uphill climb is steeper, the ICE roars to power and I manually tap the CC control down 1 km at a time trying to manage a lower fuel consumption. Other car drivers following you normally accepts a speed reduction on steep hill climbing so I don't think they'll be too displeased.

I try to look way ahead and anticipate for traffic stoppages such as red lights or traffic jams. At between 600-400 meters before the stoppage, I turn off CC (pulling level towards myself) and wait untill the FE bar disappears then I put the car in neutral (push the gear knob towards myself for 2 seconds), and the car glides in neutral untill close enough to red light (like 100-50 meters). I put the gear back to D and keep gliding with regen, apply brake pedal to engage more regen and eventually mechanical brake to full stop.

I also use this neutral glide for long and slight downhill slopes. I put it back to D if the gliding speed exceeds 75 km/h. I read somewhere that at higher speeds (like 90 km/h?) in neutral glide, the MG1 may overspeed and get damaged. I also put it back to D gliding or CC if I'm catching up to the car in front too fast. Don't want to make them feel I'm tailgating them.

I've been attaining between 4.1-4.3 L/100km consistantly. The best trip got 4.0 L/100km, and I've been really stepping on it for acceleration, right up to and beyond the red PWR zone.

I haven't been observing the HSI so that's what I'm going to do next. I think I'll try to limit my accelerations to not go over the red PWR zone too much, and adjust the CC speed setting to reallign the ICE to its most efficient range as displayed on the HSI when traffic conditions allows.

May be my fuel consumption will go down a bit more, but my main concern is still safety. If it means impeding traffic or causing road rages from drivers behind, I won't do it.

P.S. I've been using the A/c quite a bit too but I set it to 1/2 degree below outside temp. to make it work like a dehumidifier. Feels comfortable enough and does not seem to affect FE.

 

Hi Prius42 -

I understand exactly what you're saying. I have one question: How do I know if the ICE is on between 5-10 kW?

I've seen -sometimes- when I'm in that Batt portion of the HSI where the instantaneous MPG seems to indicate that the ICE is on (presumably between 5-10 kW - usually when the engine is warming up, I think). Other times, (when warm?) the Instantaneous MPG gage seems pegged at 100MPG regardless of where I am in the Batt portion (left of the middle line) of the HSI.

During the "other times" - when I'm pegged at 100MPG, and operating in the Batt portion - I'm presuming that I am NOT burning fuel, and only using battery. Am I mistaken?

Thanks,
Eric

 

Eric,

It is really hard to tell when the ICE is "on", i.e. burning fuel, when you are in the "batt" portion of the HSI above ~47 mph if you don't have extra instrumentation. I look at the ICE torque using my DashDAQ OBDII scanner. It shows positive ICE torque when the ICE is fueled. The built-in instantaneous fuel economy gauge is often still pegged at 100 mpg in this state. Thus you are still getting "great" fuel economy during this time but you are still essentially gliding. Unfortunately you are also burning fuel and very inefficiently. If you pay attention, you can feel the ICE start burning fuel as you slowly push the go-pedal. It gives a little "kick". The point where this happens varies, but is very close to where the HSI curves down near the "charge" region. It is easy to miss though. Without extra instrumentation, I would try to keep the HSI completely out of the "batt" region. Either run the ICE with the HSI about 1/4 of the way into the ECO region, or glide with the HSI exactly between the charge and batt regions, i.e. nothing showing on the HSI at all. I've never seen the ICE kick "on" in that state.

The HSI is really an amazing tool. If you keep the ICE running in the "ECO" region it really is operating at its most efficient state at around 230 mg of fuel/kWh. If you run in the "batt" region at speeds where stealth is not possible, or in the "power" region, then efficiency really suffers. How you "game" your trip knowing this information takes some guesswork and practice. I learn something new every trip, and I'm not always successful.