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Engine, Fuel System, Transmission, Hybrid Cars, Coupe, Convertible, Hatchback, Truck, Sedan, SUV
#1 of 206 Advanced Course in Hybrid Engineering
by Kirstie@Edmunds HOST
Nov 05, 2004 (1:04 pm)
Want to talk about the merits of various engine designs? Need to debate IMA vs. HSD? Have a penchant for performance statistics?
You've hit the right topic. Roll on!
Roving Host & Future Vehicles Host
Nov 12, 2004 (12:07 pm)
- As an engineer, one of the first things I consider is "What happens if a part fails?" I look at the Prius & I notice that if the electric motor #1 or motor #2 fails, the car will not move. The transmission will spin, but the car will go nowhere.
- In contrast, the Honda Hybrids don't rely on the motor. Even if the motor is dead, the car can still move forward on engine power alone. And you can drive it as a conventional car until end-of-life.
- Both the Prius & Civic Hybrid are approximately equal here (~50 mpg highway), but the Civic comes with a lean-burn engine. A careful Civic driver can watch the gauges, keep the engine in lean-burn, and routinely score 60 mpg highway.
#3 of 206 Series Hybrid because. . .
Jun 17, 2004 (2:01 am)
John 1701A observing that the two car companies active in the hybrid field have slightly different thrusts stated that :
Toyota is for reduced emissions
Honda is for increased efficiency
But I would suggest a third thrust might be taken given that there is room for improvement in the efficacy of coupling the ICE to the road wheels.
Consider the methods currently available:
I am not saying that I don't enjoy driving stick in an Echo, it has great Torque/Mass ratio, equivalent to an Acura TSX , however efficient as it is; the Stick method is too tricky to lend itself to computer automation.
So occasionally I drive the "relentless search for perfection" vehicle which comes with a transmission that is supposed to be computer friendly. And now I'll get the occasional tap in the rear while waiting at stoplights, the unexpected surge at low speed and finally when I egress the rolling backwards an inch or two. Sound familiar? So they can't get it right am I supposed to accept this as normal.
Now for the hybrids, I invite you to observe the images provided by usbSEAWOLF2000 #193 on the Hybrid Honda Accord 2005 board. The first image is that of a Honda Civic Hybrid engine and the CVT as you can see is situated on the right hand side. That is one large and complicated piece of mechanical engineering I have to say.
I find it incongruous with my experience in electronic drives that someone would come along and fit a mechanical variable speed device on shaft of this engine. This is probably the obvious
solution for a company heavily biased in mechanical engineering. But in the new millennium I would have suggested alternative ideas. Such as increasing the stack length of that generator to up the capability
to 80kw at 7000 rpm. Discard the CVT entirely. Select instead a 25hp (1800 rpm base speed )3-phase induction motor with rotor balanced for 12,000 rpm and a 30 second rating 75hp to be coupled into the trans axle with a 10:1 ratio.
Additionally two inverters on the HV bus would be needed. The first would be the starter for the ICE and would subsequently degrade to become a 3-phase rectifier. The second would be the traction inverter. I would also place a couple of transistors in series across the HVbus as an UP/DOWN converter for the main battery pack. That's for those who want some "Stealth" capability and braking regen.
I need to say something about the Prius. That planetary device with servo is way too complex IMHO for mechanics. Even on these boards there have been struggles to get a handle on the concept. Yeah a VCR/dvd player is complex but at least for $50 you can junk'em. But I gotta say I love that 200/500v bus idea. Constant v/f ratio would run out of headroom at 52mph otherwise.
And because current costs but voltage is free it complements the fact that although we crave horsepower we drive torque (hybrid v Diesel Idletask #6) This means the system is able to maintain constant current (read torque) and optimal slip for the induction motor as the vehicle accelerates. As frequency increases it gets harder to force current into an induction motor so the torque would start dropping, not desirable obviously.Having extra voltage via an up converter (Prius) or increasing excitation to the alternator (series hybrid).
I would carry over the technique to a series hybrid but go even further to as high as 800Vdc. Heck, European inverters hit 1000Vdc I'm told. If this doesn't sound too clear. Just trying to broach the idea of Power Envelopes. Hope this didn't appear preachy.
Why series hybrid........
The use of the traction inverter will insulate the driver from instantaneous power fluctuations from the ICE that the other systems are susceptible to. This was the original point I was trying to get over. But I got caught up in explaining how this would be done. After all you can talk the talk but how close is practicality is what I also wanted to demonstrate.
Hmm.. 5.00am it's really quiet on this board. Time for a Bark Off don't you think?
#4 of 206 Re: Series Hybrid because. . . [toyolla2]
Oct 20, 2004 (4:26 pm)
You really have delved deep and techno into this subject while I on the other hand have come to the Hybrid realm thru the world of railroading. Years ago in a galaxy far, far away there once was steam-powered locomotives but technology, as always, moved on and along came the diesel-powered engine that eventually became one of the first duel-powered vehicles of the 19th century when it was combined with traction-motors for the final power to the rails(kinda like the first hybrid).
One thing for sure these hybrid cars sure can scare us with all the gadgetry and techno stuff. I've noticed quite abit of hesitation on the general public to grasp the transition to it all and take the plunge or as we say on the railroad,"Get On Board!". Toyota sure has made it more comfortable with the eight yr/100K coverage on the hybrid drivetrain. I must say that Motor Trend bestowing "CAR of the YEAR" award said volumes about the in the know thinking of an establishment long known for their love and bias to conventional combustion cars. One last tidbit, as to all your technical info shared with us novices,one question popped up several times...Where were you when American car manufactures piddled with turbine and the other like power sources? (they cudda used you)
Culliganman (retired hogger)
#5 of 206 Re: Series Hybrid because. . . [railroadjames]
Oct 21, 2004 (1:13 pm)
"...that Motor Trend bestowing "CAR of the YEAR" award ..."
But you have to remember that Trend Micro has a very limited selection criteria, only brand new or substantially changed models
and they have made some big fopahs in the past --Like when they named "Renault Alliance" car of the year.
Me thinks the techno-gadgets and the current Hybrid-fad may have clouded their selection vision.
#6 of 206 Re: Cars of the years M/T (not a bad avg)
Oct 21, 2004 (7:57 pm)
Well, you touched on a tender spot when you pointed out the Renault. I once had the "Encore". It was quite inovative with its extended wheelbase and frontwheel drive. Price was very friendly not to mention decent MPG's. I think its downfall was a lack of quality control back then. Since I knew this car I can speak with some knowledge. Your point is fair to say that M/T could have made a better choice (IN HIND SIGHT). As to comparing the PRIUS to the Renault well, the jury's still out but do remember that Toyota has been into this hybrid game for the better part of 10 yrs not to mention R&D with over 300 of their own patents per Hybrid Techno. If you really think that Hybrid Technology is a fad you might might want to re-think that since half a dozen models are out now and more than another half dozen are on the way.
P.S. Maybe you think the HUMMER should have been "CAR OF THE YEAR" perhaps?
Culliganman (toot toot)
#7 of 206 Re: Series Hybrid because. . . [railroadjames]
Nov 04, 2004 (7:19 pm)
it is encouraging to get a positive response now and then. Your view that the public is slow to 'Get on board' with hybrids may be in part due to cost concerns regarding the repair of the hybrid powertrain. These costs can be the automotive equivalent of 'dropping it on the floor' if railroad parlance serves me right. Then there's the fact that there are some good non-hybrids available out there which have nearly the mileage but without the price premiums of the hybrid.
This is my thinking:-
What we have in the market is the result of but two design teams and their solutions, IMA and THS. I would judge the Honda solution to be 95% mechanical, the Toyota about 50/50 mechanical/electrical. But there is no 95% electrical solution which I take to be the series hybrid.
Reverse logic would imply that if the two methods presented so far were in fact la creme de la creme how is it that neither company dabbles in the other company's technology? Shouldn't competing technologies be about equal? Someone posted that Honda had limited resources to go further into the development of full hybrids. This I believed until the launch, recently, of their version of the Learjet. Or perhaps this was a different Honda
The Honda method is about reclaiming energy from braking and hill descents, I believe it does very little for performance. Considering the Honda IMA with Manual transmission if it were fitted with a tall gear in fifth (0.7). This would give it the superior mileage in longer hiway trips.
The Toyota method has to emulate the tall gear which is comparitively lossy to do, so it cannot compete against the Honda on long hiway trips. However when fluctuations in speed are required the THS, which is always in the 'right' gear, delivers superior acceleration performance because the ICE rpm will not be sawtoothing up and down as in the Honda M/T as the driver rows through the gears. Maintaining a constant high speed from the ICE means that the THS is able to provide a higher average continuous power to the road. 30-50 MPH times bear this out.
I ought to mention the Honda CVT (w/IMA)variant. Like the THS, not so good on long hiway trips compared to the Honda M/T(w/IMA). OTOH acceleration with the CVT should be very good as long as the system stays in top shape. The question is how long will they stand up to aggressive driving.
As I understand it the CVT in the Honda is some form of hydraulic computer gear-changing gizmo, very mechanical and prone to go wrong with wear. CVTs had been used industrially quite a lot until DC thyristor drives became popular - about 35 years ago. They were followed later with a transistor invertor /induction motor combination.
As Seinfeld would say, we know they've seen the fork, we've shown them the fork, so why are chopsticks still around. Do they think we haven't noticed?
My opinion is that less mechanics means increased reliability.
The series hybrid in my 95% electrical solution works on the acceptance that controlling mechanical power is difficult and gives lots of problems involving clutch /gearbox/CVTs/ICE stability over extended speed ranges.
The solution as I see it is not to control mechanically but to control electrically. In this regard it is necessary to convert mechanical power as early as possible into electrical power. The ICE being directly coupled to the generator. Then finally an invertor feeding an induction motor which drives a differential with a 10:1 ratio would complete the system.
The 100kw invertor/induction motor package would be similar to that used by GM's EV1. No risk there.
The ICE would be a 'CLEAN' engine meaning there would be no power takeoffs, at 15,000 RPM they would not be too reliable. Two pistons on the same crank would allow the use of just two main bearings. Balanced firing 360 degrees apart to each cylinder. The generator rotor containing Neodymium magnets could be fitted to one end of the crankshaft or divided in two and placed at each end if overhang is a problem. Valves would be magnetically actuated.
#8 of 206 Re: Series Hybrid because. . . [toyolla2]
Nov 12, 2004 (4:01 pm)
The 100kw invertor/induction motor package would be similar to that used by GM's EV1. No risk there.
I appreciate what you said that I was able to understand. I lean toward the series hybrid with the more efficient diesel engine. I felt the EV-1 was buried before it had a chance to mature. Batteries being the big Achilles heel. I like the idea of plugging the car in at night with the option of a genset when out and about when no AC is available.
#9 of 206 Re: Series Hybrid because. . . [toyolla2]
Nov 12, 2004 (9:03 pm)
Sorry for the delay getting back to the details and you. I had some extenuating things come up. I too have had some miss-givings about the highly technical systems involved with the Prius and it's intricate electrical sys. but then I got to thinking...My wall switches and outlets at home (all 24 of them) are 52 yrs old and not one of them have gone bad. I have a ceiling fan thats 29 yrs old and again she's running like the first day up. Well, what I'm getting at is obvious. Toyota has put high quality electrics into the Prius starting with the main battery and continuing thru to the CVT transmittion. Let me add that we all put trust in our vehicles every day. When we turn the steering wheel, step on the brake, turn on the lights, wipers and even the electric starter. We've come to expect our cars to deliver unfailingly. Some do it better than others. Toyota (I think) is one of a select few. I now have nearly 12K on my PRIUS. I've had my hybrid over 110MPH and felt the car sure footed. I've driven her hard and I've babied her to extract as much as 56 MPG's. The Prius has delivered on all of my demands.
People really fail to understand that to get a great car that delivers high mpg's (say over 45) and have roominess AND reasonable performance is almost unheard of until now. I'm convinced the PRIUS has filled the bill while others have only titillated the concept. Being an avid motorcyclist I have seen many a bike 2-4&;6 cylinders get a meager 34MPG's and even a few (Harley for one) get less while usually ridden hard. Bikes weigh in usually around 390 lbs while hybrids come in at around 2800 lbs There in lies the delimma. Alot of good milage is determined by one's own driving habits too. I simply find it satisfying that the hybrids have excelled at fuel efficiency and reduced pollutents to a very respectable and practacle low level.
Culliganman (Green like Kermit)
#10 of 206 Re: Series Hybrid because. . . [railroadjames]
Nov 13, 2004 (5:16 pm)
drove my sister's '05 prius today. it seems like a good real world vehicle. it drives normally and seems practicle for a family(4), plus attractively designed and well put together(interior). no faults with the exterior either. imo.
to me the biggest problem is with peoples attitudes. when i told them my focus was rated pzev, they didn't know what that meant.