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Engine, Fuel System, Transmission, Hybrid Cars, Coupe, Convertible, Hatchback, Truck, Sedan, SUV
#203 of 206 2ZR-FE for 2010 Prius ?
Jul 17, 2008 (11:29 am)
Wasn't the 2010 Prius rumoured to be subject to cost reductions ? Although so far I've not heard any details following those CEO prognostications, some say the engine will be moving to a version of the 1.8L 2ZR-FE double VVt-i. The adoption of the "R" family engine is to be across the whole range according to Kdhspyder, our resident 'mole' if he doesn't mind me saying.
I see also that Chrysler, not to be outdone, has gone this route of providing the wider camming authority of double VVt in the 4 cylinder engines of their current offerings of Caliber,Jeep Patriot, Compass, Sebring, Avenger and Journey.
At Toyota we know that the Corolla has already gotten the 1.8L 2ZR-FE. Wiki shows a third member, the 2.0L 3ZR-FE at 140 Hp, which could be a base engine for the Camry line as gas enters $5 territory. The Hybrid Camry could then become the power version for Camry replacing the V6. That would clarify the Avalon role to be the sole choice for a V6 sedan at the dealership.
It appears that all three engines share the same bore of 80.5mm which is up from the previous 75mm for the Prius. Normally piston bore is a good indicator of power for a given piston speed. In this case power varies between the three engines because of increasingly longer strokes while leaving red line max rpm almost the same for all three engines at 6000, 6000 and 5600rpm resp. , with power ranging from 124Hp to 140Hp. Since they have the same bore it is clear that Toyota gets the power via higher and higher piston speeds across the range afforded purely by increasingly longer strokes.
There must be cost savings in having the same bore size over a range of engines. Makes you wonder though how critical bore/stroke ratio can be in the final analysis ! That does prompt the question regarding a business plan that builds three engines which differ overall by only 16 Hp. Perhaps someone out there could enlighten us ?
The 1.8L 2ZR-FE double VVt-i is as mentioned the current Corolla engine and I can't see them using this in the Prius when the smaller 1.6L 1ZR-FE engine at the bottom of the "R" range is available. This smaller engine still outperforms the 1.5L 1NZ-FE by 20Hp. A 40Hp increase by the Corolla engine seems excessive even when reduced by Atkinson camming.
I have to assume they are going with the 1.6L 1ZR-FE. They may also slow it down to 5000rpm. The following estimations show the effect. This junior member of the "R" family has a much reduced stroke of 78.5mm compared to 87.4mm previously The Prius piston speed will now be 90% that of the previous engine because of the new shorter stroke. When you factor that in along with the larger bore you would expect a 3.5% increase in power with the 1.6L but you would be wrong. In this case double VVt- i appears to deliver almost 20Hp or 20% more power which is hard to understand.
On the torque side we would expect Atkinsonizing to cause a drop off of 25lbs-ft of torque so we might expect 90lbs-ft to come through this time instead of 82lbs-ft. It will be interesting to see how MG1 handles this. Either the PSD ratio will be increased speeding MG1 beyond 10000rpm or MG1 will be beefed up to handle the new torque.
#204 of 206 A question to Toyolla2..
Aug 21, 2008 (5:58 am)
...that I have not been able to find an answer anywhere on the net.
In the HSD system - at startup - at a standstill - there is a 10 sec delay designed into the running of the drive system. This I believe is called phase 0 in some discussions. The vehicle is READY if the driver chooses to drive immediately but if the vehicle remains stationary then nothing happens until the ICE kicks in - giving a boost to the traction battery.
My admittedly non-technical hypothesis is that MG1 draws some juice from the traction battery to get the ICE pumping and spinning without actually injecting any fuel into the cylinders. This to make the ICE ready to jump into action in an efficient state. If the vehicle doesn't actual go into drive mode then the ICE starts to pump fuel and generate power which goes to 'pay back' the juice borrowed initially.
After the ICE has paid back its debt it shuts down until needed.
How much of this is accurate? Thanks
#205 of 206 Re: A question to Toyolla2.. [kdhspyder]
Aug 21, 2008 (6:14 am)
I believe the HSD system waits about 7 seconds after ready before starting the ICE, if necessary. MG1 will spin the ICE only if it intends to start it and spins it up to about 1000 RPM without fuel or sparks until oil pressure is established. Once oil pressure is established fuel and sparks are added and you have a running ICE.
#206 of 206 Re: A question to Toyolla2.. [kdhspyder]
Aug 25, 2008 (12:05 am)
I am not saying this is the answer.... but my understanding is that whenever the engine starts up it must continue until it has brought the Oxygen sensor up to temperature.I seriously doubt that one start cycle alone is a significant battery draw to require a recharge.
The 10 second delay on the Prius system engine startup may be the coolant temperature bypass valve allowing hot fluid stored in the thermos reservoir to be circulated through the engine. When that has been accomplished it enables starting of the engine to proceed.
Why is it programmed to do this ? I can only guess that the assumption is that if the car is not going to be moved in electric mode after a reasonable time delay, all bets can be covered if the engine is pre-emptively 'prepped'.