Last post on Jun 17, 2008 at 4:30 AM
You are in the Toyota Sienna
What is this discussion about?
Toyota Sienna, Hybrid Cars, Van
#15 of 44 Re: 2008 Sienna Hybrid - Do you want 4 cylinders or 6? [timothyh]
Jul 11, 2007 (5:36 am)
Actually, you're probably right.
The hybrid Accord (V6+electric) did not sell very well because they emphasized power over economy.
I just wonder if the 2.4l will really be adequate, and also if they can tune it better like the did the 2GR engines.
Maybe if they add Direct Injection technology to the 2.4l, it could achieve a better balance of power/economy.
#16 of 44 Re: 2008 Sienna Hybrid - Do you want 4 cylinders or 6? [jim314]
Dec 15, 2007 (6:41 pm)
The results are about right, although the efficiency factor could be higher in certain cases. No matter what, 40hp is enough for a loaded Sienna cruising 65mph at level ground, unless it has under-flated tires or it's towing sth heavy.
The steepest freeway uphill grade in the US is <7% (actually the design rule says 6%). To run up 7% grade at 65mph, the power needed for a 6000lb Sienna(1600lbs for passengers and all loads) can be calculated as 0.07*6000lb*4.45(converting pounds into Newton)*65mph*0.444(converting mph into m/s)=54KW=72hp. Adds to the 40hp at level ground, that's just 112hp.
#17 of 44 Re: 2008 Sienna Hybrid - Do you want 4 cylinders or 6? [ateixeira]
Dec 23, 2007 (8:04 am)
Around here, when gas prices are hitting around 4 bucks per gallon, 4 cylinders, with hybrid system would be nice, but that is to underpowered for a 4000 + pound vehicle. V6 is my choice(I don't want to be stranded in the middle of a hill, that the passing BMW's could climb)
#18 of 44 Re: 2008 Sienna Hybrid - Do you want 4 cylinders or 6? [crh3]
Dec 23, 2007 (8:07 am)
You have a point. But with all those V8's here, you can be wishing for more power , right? ( We are getting spoiled with all this 300, 400, 500, 600, 700, 800), or even more horsepower in some cars!!)
#19 of 44 I vote for the I4 hybrid but with a SuperCharger.
Dec 24, 2007 (11:19 am)
Using the battery for "virtual" HP boost, "Supercharging" in city stop-n-go traffic when the battery can usually be recharged via regenerative braking is perfectly reasonable. But using that method in highway cruising, distance travel, is clearly not advisable since the primary resource for subsequently recharging the hybrid battery is typically the ICE itself during periods when "boost" is not required.
Very "lossy" path, that.
What is needed is a variable speed supercharger that provides no "boost", only atmospheric pressure, in city stop and go traffic as long as the battery sustains a reasonable charge level via regenerative braking.
On the highway the driver would activate the "cruise" mode, maybe via the simple engagement of cruise control, and now the supercharger would be used to boost engine HP for acceleration or climbing instead of the hybrid battery being depleted.
The SC would be ICE belt driven but via an E-CVT. The opposite E-CVT input would be an low HP (3..??) AC permanent magnet synchronous motor using a(nother) variable frequency A/C solid state drive. The E-CVT would be used to control the speed relationship between the ICE and the SC, thereby having complete and total control of the SC's boost level independent of ICE RPM.
It seems even possible that the throttle itself might be replaced via the SC's E-CVT intake airflow control.
#20 of 44 Re: I vote for the I4 hybrid but with a SuperCharger. [wwest]
Dec 26, 2007 (12:14 pm)
Sounds interesting, but very expensive.
IMHO the 3.5l is well more than enough, so perhaps a smaller V6 would work? Something around 3.0 liters?
#21 of 44 Re: I vote for the I4 hybrid but with a SuperCharger. [ateixeira]
Dec 26, 2007 (3:58 pm)
Not nearly as expensive as all the $3.00/gallon fuel you will be buying for that V6 just to overcome the extra friction and pumping losses over an I4/SC combination throughout the useful life of the vehicle.
For how much can you purchase, wholesale, an electrically driven Prius/HH/RXh A/C compressor. That would constitute the major components, a variable frequency AC drive, and AC motor, and a compressor.
Manufacturing costs would be what, twice that..?
Light weight carbon fiber positive displacement SC?
#22 of 44 Re: 2008 Sienna Hybrid - Do you want 4 cylinders or 6? [tpulak]
Dec 27, 2007 (6:34 am)
You've consistently voted for the 6 cylinder-hybrid combination since your first post in June. Most of the engineers who have replied have had various formulas that conclude that even 200hp is more power than is really needed, even for climbing hills.
Remember that the hybrid engine WILL work simultaneously with the ICE. A hybrid does have two engines, pretty redundant if the electric engine could work full time. If you do need the power, the electric engine will kick in while climbing a hill and provide extra boost. In my opinion, it's a shame not to use that feature in order to downsize the ICE.
Your comments do speak to reality, however. There are some people who remember the sluggishness of the 4-cylinder minivans sold in the 1980s and 1990s. Convincing those consumers, and you, that a 4-cylinder ICE plus an electric engine is NOT equivalent to the old 4-cylinder minivans is probably a lost cause. No amount of information, either technical or advertising, is going to change your mind.
By the way, Bob Lutz, Vice-Chairman at GM, said that the Chevy Volt is likely to come out with a 1-liter, 3-cylinder ICE in addition to its electric engine. I have no idea what HP that converts to, but its not a lot. Yes, the Volt won't be a 2-ton minivan with another ton of passengers or payload, but it does speak to the over powering that we have gotten used to. The Volt is said to have 0-60 times of 8 seconds, which is enough for passing and merging into traffic. Yes, it won't beat the BMW 535 up a hill. But you also won't be able to buy today's version of the 535 in 2020 when CAFE requirement go to 35mpg.
In my opinion, I hope that Toyota comes out with a Sienna that maxes out its fuel economy potential. It may not suit every consumer's need, but it might be the best choice for consumers looking for fuel efficiency.
#23 of 44 Re: I vote for the I4 hybrid but with a SuperCharger. [wwest]
Dec 28, 2007 (8:23 am)
In practice, the supercharged I4 in the Previa minivan was very, very inefficient.
The 2GR 3.5l V6 blows it away in terms of fuel economy. No contest. It's also much quicker.
I don't see a reason to go back to a supercharged I-4.
#24 of 44 Re: I vote for the I4 hybrid but with a SuperCharger. [ateixeira]
Dec 28, 2007 (8:50 am)
Yes, absent the variable speed capability an SC only means PERFORMANCE, not efficiency. With the variable speed, INFINITELY variable boost capability, the SC would only be used on the hwy where the hybrid capability is less efficient. The hybrid capability would be reserved for city stop and go traffic where its efficiency is STELLAR.
Keep in mind that this would not be a LARGE high capacity SC, just enough HP boost to bring the ICE up to "snuff" for light acceleration or uphill travel. Passing acceleration would still require the hybrid "boost" aid.