interesting observation using CANVIEW

Sounds like the car was doing what you wanted...

 

Were you in Cruise Control? I thought the goal was to maintain 103 Kph. The car did that. Your goal may have been to maintain fixed fuel consumption, but how would the car know?

 

Frank itis pioneers like you and your CANview that make this forum's reverse-engineers able to enlighten the rest of us non-engineers! Thanks. Too bad a Toyota engineer won't/can't enlighten us.

 

CANview? Help Me

I'm a new member; what's the CANview and what does it do? I feel naked driving without a tach and the fuel flow meter sounds great; how do we get one?

 

It takes more power to climb a hill than to drive on the flats so it is inevitable that the fuel flow would have to go up (unless the extra power needed was drawn from the battery). The car's computer already has a few options for delivering the power required by balancing ICE and MG power input; it's interesting if it can also juggle the power of the ICE at fixed RPM.

 

i would think that more fuel would be necessary for additional power to maintain RPMs while gaining altitude. would it also be possible that more power is sent to the EV also? that would increase fuel consumption also.

 

It is entirely possible that it required twice as much power to go up a small incline than it takes to cruise on the level, so the increase from 0.2 to 0.4 l/hr is resonable. Cruising on level ground requires very little power. Accelleration and/or climbing hills requires much more power.

I can't explain why the engine RPM did not change. Perhaps the engineers at Toyota who calibrate the hybrid system can, perhaps they can't. As I understand it, the system tries to run the ICE near wide open throttle, but not necessarily at WOT. It may be that it was running at 80% and was able to meet the torque requirements by opening the throttle a little, changing spark and/or valve timing.

I have been involved in the calibration of standard ICE, the hybrid system is twice as complicated. Usually the control system is broken up into several subsystems, each of which is calibrated somewhat independantly, then there is an arbitration algorithm when there is a conflict. Then you run everything through a whole lot of testing to make sure none of the control loops fight each other and cause problems. There are a lot of adjustments and tweaks to the system over many months to get everything working. It is rarely as simple as "I did A so the car should do B."

There are several inputs to the hybrid system (pedal position, vehicle speed, battery state of charge, temperature etc.) there are also several outputs that the system controls (motor/generator torque, engine speed, engine throttle position). Add in such things as regulatory requirements (emmission, OBD), driveability requirements, efficiency demands, diagnostics and liability concerns and it gets very complicated.

Keep testing and keep us informed. I am interested in something like the CANView.

Best regards,
Steve Turner

 

I believe, the simple answer is no. In the same situation in a conventional car, the added load on the engine from the slight incline would be overcome by added fuel & air (throttle) and the rpm would not change (constant speed, direct gearing). The Prius seems to be doing exactly the same thing in your example.

However, your Prius effiency is higher than you would see on a 1.5L conventional car due to the Atinson cycle and lower rpm resulting in a more optimal higher power loading (even though, highway-cruise is not hsd's forte) From my Scanguage, it appears that hsd tries to keep the power between 45-65% of that available.

If you were to run the same experiment again with a slightly steeper incline, I would expect to see the resultant higher rpm (still less than typical 1.5L) as the hsd algorith increased it to keep the output power in the desired efficiency band.

 

MY conventional vehicle does not add rpm to hold speed; only power.

 

Frank, what is the duration of your test run? Your fuel consumption seems too low. At 0.2L/103 km is about 1211 MPG!

I think this can only happen during warp stealth and the car is mostly powered by the Bty to MG2. Without knowing the SOC at that moment, it is hard to tell if the increase is due to the Atkinson Cycle.

Vincent

 

Frank,
I have had similar experience using the Scan Gage. I was not sure what to make of it. I see this more at lower speeds (20-35mph) than at higher speeds (35-50). I have not had the Scan Gage out on the freeway yet. I have also have not seen the ICE RPM up with out gas usage being 0 gal/hr. My understanding is that I should see this during start up and shut off but so far have not observed this. This observation is clouded by the fact that I do have to keep my eye on the road and there are sampling rate issues on the CAN bus. Having this device has only made me want to learn more and have a better tools to learn how this car works.