Hi folks, I’m new to posting here, although I’ve been reading the forum ever since I bought the car — almost 7 years ago, with about 200k km driven during that time. Recently, I drove another Gen 2 Prius and noticed a clear difference in performance, so I started investigating mine. (Gen 2, 2007, currently at 390k km) Initially, I measured 11 seconds for 80–120 km/h acceleration, which was disappointing compared to two other Prius 2s that could do it in under 9 seconds quite easily. At first, I noticed that the HV battery, despite showing no fault codes, was running a bit warm and dropping below 6.5V per blade under heavy acceleration. Fair enough — it’s 19 years old. I replaced it with a newer healthy pack from 2020. Now the battery readings look fine, but the symptom remains: During an 80–120 km/h pull, the car starts accelerating well, then the ICE revs up to around 5000 rpm, and at that point the acceleration actually DECREASES. It feels like the ICE is missing 10–15 hp somewhere. What I found so far: MAF reaches a maximum of 56 g/s — isn’t that a bit low? LTFT is between 3–4% MG1/MG2 and inverter temperatures are normal Cat converter temp sensor 1 reads 600–800°C, while sensor 2 is 100–200°C lower. Could this indicate something suspicious? (The cat is aftermarket, about 150k km old. I previously had a P0420 efficiency code, which I “solved” using a spacer.) Thanks for any thoughts or ideas!
Could be the fact your engine is worn out after all those miles, maybe previous owner didn't change oil often? Could also be you bought the wrong type of tires and low tire pressure. Can you explain the servicing you've done? When were the spark plugs replaced? What kind of oil and how often do you relace it. Throttle body and MAF cleaning? What's your MPG / KMPL? Also, have you considered that if you're driving up to 5000rpm you're pushing the car way beyond its limits and over the course of 200,000 Kilometers with that type of driving style you've damaged your engine? I've driven more than 300K kilometers in my Prius and can count on one hand the amount of times I've spun it up past 5000rpm. I mean you say you're over revving your engine and noticing a loss in power (obviously) and because of that abuse it sounds like it's time for a new Prius or new engine that you don't abuse... As in the slow driving old lady Priuses I take care of never have these problems when I drive them agressively.
Acceleration is a safety feature in my opinion, hence I'm keen on getting it at factory level. Maf, throttle body cleaned. Engine oil changed after every 12-13k km (200hrs). Burns 1.5 dl oil on every 1000km.30k on the spark plugs.
Do a fuel system cleanup/ throttle body/ air filter replacement. Does it feel like cutting out at high rpm? Any oil burning? Also just like PriusCamper suggested, plugs are good? Since you already replaced the cat converter, it can't be. There is no code also right?
How much oil does your car burn? My guess is a bad cat. It may be partially blocked. Disconnect the front of the cat and take it for a drive to see how it responds. There was a recent thread created by another forum member who found out that he had a clogged cat. If interested, look at the thread https://priuschat.com/index.php?posts/3606706
My 2006 reads 56g/sec @ 5000 with the accelerator pedal on the floor going 75mph. Fuel trims are 0 to +5%. About the same as yours (you might compare those readings to one of the other "faster" cars). Then see what amperage is going out of the battery during hard accel, and compare to the other cars as well. Posted via the PriusChat mobile app.
Thanks very much for the info. So mine takes breath normally. I also wanted to check the misfire counters but I couldn't find such a PID in Torque pro. (I forgot to mention that I feel a slight vibration from the ICE) I'll have one another car to test and compare tomorrow. Will keep you updated..
The spark plugs were replaced 30,000 km ago. At high RPM it doesn’t feel like it’s misfiring or cutting out, it just seems less powerful than it should be. It uses about 0.15–0.2 liters of oil per 1,000 km. The catalytic converter was replaced 150,000 km ago with a cheap aftermarket unit, which started throwing a code after about 70,000 km. I installed an O2 sensor spacer at that time to suppress the code, so the catalytic converter is still on my suspect list.
If the pack SOC indicator is down in the purple bars the car will accelerate poorly, shifting energy from the ICE into charging the pack rather than into accelerating the car. It is markedly slower in that state, and the ICE also goes to higher RPM. (This is if one tries to make it go faster, not just drive along on a flat road at a steady speed.)
Yesterday, I had access to another car which did 11+ seconds on the first run, then 9.1s on the second. (The owner had previously measured 8.x seconds, but those runs were measured against the speedometer, not by Torque Pro.) Later, I managed to experiment on a longer trip with mine and concluded the following: Scenario A: When it is floored, it goes into open-loop at 5000 rpm, retards the ignition, and runs rich (I saw a lambda of 0.82; I suspect this is the lower display limit). Scenario B: If I try to keep it in closed-loop around 4000–4400 rpm, the ignition timing remains around 20 degrees, and the lambda stays between 0.99 and 1. I could confirm this feeling, as it did the 80–120 km/h sprint several times in less than 10 seconds in Scenario B (once I even achieved 7.8s, but I'd disregard that extreme result). AI is trying to convince me that this is how it should work at WOT, but I still think it's nonsense that the highest performance is not achieved at 100% pedal.
