Something curious about the Prius computer algorithm... Most of the time, when I go downhill and release the gas pedal, the gas engine stops running. I can see that on the fuel economy gauge - it goes down to zero L/100 km. But then, almost every time, somewhere in the middle of the hill, the engine starts again. But just for 1 or 2 seconds. Then it stops again for the rest of the hill. Anyone experienced that? Does anyone know why it does that? What would be the purpose of starting the engine for 2 seconds in the middle of a regen?
It seems to do it independently of engine temperature. It does it when it is cold, and also when it is warm.
Would it be the same observation I made here? In my case, I noticed that the ICE comes in just around 68-69 km/h (42 mph) and turns back off just after.
Interesting. Your description is indeed similar to mine. You make me realize now that the event does not only occur during regen, but also during gliding. I'll check this weekend at what speed it occurs, and post my results here.
When you go downhill initially, ICE would not consume gas. MG1 would keep it idle under 1,000 RPM. When you get below ~44 mph, ICE is shutdown to 0 RPM. My guess is that HSD need to use gas to park the ICE for easy restart.
By "park", you mean to properly align the crankshaft to allow a seamless restart? My question would then be: why do you need to run the ICE to achieve this goal? MG1 should be easily able to do this at any time?
Might be good to combine this thread with the other one. http://priuschat.com/forums/gen-iii...peed-stop-ice-comes-in-between-43-41-mph.html
How long the downhill run in miles or period? I suspect you have a very long downhill 5-10miles, the ICE kicks in to warm up catalytic converter.
I tried it several times today on level ground with everything completely warmed up, it does the same trick, dip in the MPG indicator, every time the ICE shuts down at 41 or 42 MPH. I was able to reproduce this glitch (for lack of a better word) about 10 times in a row before I realized I wasn't going to get anything useful from the Scan Gauge.
Yes. My guess is the MG1 does not have enough torque in motor role. It would be spinning around 2,900 RPM and it would need to jump to 6,500 RPM in split second as ICE goes from 1,000 to 0 RPM.
Philosophe... It seems to me you found a bug in the system, unless there is something I dont understand. I drove for 4 hours in a hilly region this weekend. I have tested several things. Result? Every time I have crossed the speed of about 68-69 km/h and the ICE was not running, it started for a short while (e.g. 2-3 seconds) then shut down again. I have found that to be true in the following situations: The ICE is not running and: Gliding, crossing 68 km/h by slowing down Regenerating, crossing 68 km/h by slowing down Slight propulsion (electric only), crossing 68 km/h by slowing down Gliding, crossing 68 km/h by accelerating downhill Unless there is something I dont quite understand in the hybrid system, that seems to be a bug in the Prius control program. Opinions?
The reason I ask is because 70km/h is the new stealth threshold (previously it was 65km/h. If you drive a Gen 2, it'll occur at 65km/h). IIRC, above that speed, the engine needs to spin to control the speed of one of the MGs so it basically fires up for a split second then just pumps without fuel. It does the same to stop itself when you go below 70km/h. This is the reason why we P&G below that number to minimise pumping losses.
Ken, Patrick Wong, Hobbit etc can help you with the details. My first instinct was to direct you to this page. Maybe you can find the answer there Graham's Toyota Prius
Ken has mentioned before that the ICE consume some gas whenever it is stopped in gen2. It doesn't have to be at around stealth boundary. It also applies when you stop the ICE with the EV button.
