Toyota RAV4 Forums banner

1 - 3 of 3 Posts

·
Registered
Joined
·
236 Posts
Discussion Starter #1
Hi folks... I'm new to the forums and haven't had my RAV4 long, but I appreciate the wealth of information here! I have a ScanGauge II and I wanted to see if these observations sounded consistent with what other people may have noted.

Engine / Gearing
Based on MG1 and MG2 speeds, it would appear that when the eCVT is at a 1:1 ratio with the MG2 (MG1 shows 0 RPM / MG2 speed is fixed to the wheel speed at all times / ICE is turning at some speed other than 0), the ICE ratio appears to be 1000 RPM per 32 MPH. This seems to imply that the eCVT is in an "overdrive" condition when the engine speed is below that ratio (vehicle is going more than 32 MPH per 1000 RPM) and vice versa. I'm not sure I'm describing this well... I have noticed that from about 45mph and up, the ICE is more willing to run in "overdrive" - a condition in which MG1 spins backwards and the ICE is able to turn more slowly than if it were permanently fixed to MG2. Naturally, like a non-hybrid, "overdrive" tends to be more efficient.

Assuming the battery SOC is not too low, the ICE seems to really like running at about 1500 RPM when under light to light-moderate acceleration conditions (up to the ECO / Power divide in ECO mode). I'm guessing this is a particularly efficient RPM? One of the things I've noticed is that when running at lower speeds (under 40mph) and not in EV operation, the ICE will STILL try to run at about 1500 RPM. From my observations about the eCVT ratio, it would appear that the vehicle is often in a "lower gear" when the ICE is running at these speeds (arguably not all that much different from a non-hybrid vehicle).

But to maximize the engine's efficiency and let it run in an "overdrive" condition, it seems like the minimum optimal speed for running with the ICE is around 48 MPH (1.5 x 32). This actually coincides well with the maximum allowed EV speed anyway. Even at 55 MPH, the ICE still likes to spin at 1500 RPM. It does tend to run faster with more speed, however - likely because of the additional power demands as the air resistance ramps up.

Anecdotally (I haven't done any formal testing), I seem to get my best mileage running between 40-45 and gliding as much as possible when not on the freeway (speed limit permitting) and running between 55 and 60 on the freeway. I'm guessing 45 to 50 is the ideal for a nice country road, but in suburban conditions it tends to be too fast and on the freeway it's a bit too slow...

Mandatory charging
When the hybrid battery hits 40% SOC, the ICE will turn on regardless of the driving conditions and continues run until the battery is charged back up to 50%. I have found it to be better to try to get some charge into the battery when it's in the low 40's (force the ICE to run by accelerating and then not let it shut off for an EV glide by keeping the throttle engaged to the extend possible). If it hits that 40% threshold it can really drag down MPG number if the ICE keeps running while stopped or in stop-and-go traffic. That said, depending on traffic conditions, it's sometimes just unavoidable.

ECO vs NORMAL modes
In terms of ECO vs NORMAL modes (I haven't played with SPORT mode at all), I will agree with most posts that generally speaking it is just a re-mapping of the electronic throttle. However, there do seem to be some other benefits besides feeling like someone tossed a boat anchor out of the tailgate door. Notably, under heavy throttle conditions that are short of full throttle (say, 7/8 on the power scale), the ICE will rev up to about 4400 RPM and stay there. This is key because it is approximately at the torque peak for the engine. Not to get into a big discussion about the difference between HP and torque or the effects of gearing, suffice it to say that it's likely a bit more efficient to run the engine at this speed when demanding more power than at the HP peak which is around 5500 RPM. When running in NORMAL mode, the ICE is far more willing to spin up past 5000 RPM even under moderately heavy, but not full throttle applications.

Additionally, in ECO mode, the battery seems to add power more regularly when the ICE is in use (such as on the freeway) when small amounts of additional power are requested (such as going up a light grade, or gentle acceleration) - at least for a short time. In NORMAL mode, it appears that the ICE is much more apt to just spin up to add the additional power and I don't see the battery / MG2 chipping in as much. I should qualify my statement by saying that I am basing these observations by watching MG2's torque and the SOC. I have not yet figured out the X-code to directly observe the hybrid battery amperage. In ECO mode under the light power demand condition, MG2 torque ramps up and the SOC tends to fall, whereas in NORMAL mode, MG2 torque tends to remain stable and the ICE RPMS rise, but SOC stays pretty steady.

Grill blocking - engine temps
And lastly... I mentioned this in a reply to one of the other posts, but I'll put my observation here as well... I have about 85% of my lower grill blocked. I only left an opening in the grill space immediately in front of the ambient air sensor and an identical space symmetrically on the other side. My upper grill is WIDE OPEN. The lower block does appear to provide slightly better fuel economy, but I haven't specifically quantified it. (Don't have a lot of spare time to actually go out and do any formal A-B-A testing and what not...) I know there are concerns with overheating, but I ran with the grill block in 90 degree temps for about 3 days (during a recent heat wave) and the engine temperature never varied from what I saw prior to blocking it. Temps all generally below 180 with a couple minor jumps during hard hill climbs - but even then, only to about 185 and the radiator fan never kicked on. I think it's safe to say that the vehicle has a suitably robust cooling system.

If anyone else has made any observations on these issues, I'd love to hear them. I could totally be misinterpreting the data I'm seeing since my observation period has been relatively short...
 

·
Registered
Joined
·
236 Posts
Discussion Starter #2
Other random observations now that I have more X-Gauge data to play with...

My observed maximum instantaneous discharge of the HV battery seems to be right around 145A at about 260V (~ 37KW) which squares pretty well with a linear progression of the battery data published from a study by the Department of Energy regarding the Gen II Prius. 37KW is approximately 50HP, so that also seems to match up well with Toyota's claim of a combined 192HP. Granted this is not a continuous output, but their peak.

My observed maximum charge of the HV battery was around 80A at 320V (~ 25KW).

Anyone else have different observations (either with a ScanGauge or Hybrid Assistant)?
 
1 - 3 of 3 Posts
Top