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Advanced Course in Hybrid Engineering



  • i842wingsi842wings Posts: 1
    I just have a question about the use of internal combustion for hybrids and you guys sound like you know what your talking about. Why not use an external combustion (steam) power source to generate the electricity needed for a hybrid car. Aren't they much more efficient. Any know what happened to the Enginion steam cell?
  • toyolla2toyolla2 Posts: 158
    Not to put a damper on your suggestion but steam is only useful in the mega scale. I think others who pass here and have been familiar with enthalpy-entropy charts and the 1939 Callendar Steam Tables will concur with that also.

    Solutions to electric vehicle propulsion have always been subject to wacky ideas. Even car companies like Mercedes Benz which was looking to fit thermoelectric generators on hot exhaust pipes ! Well I guess there was a government tax credit attached so why not let some guys play around ? As long as the outcome is unlikely to change the status quo.

    All that is really needed is good applications of existing technology. For example when Toyota introduced liquid cooled heatsinks in the Prius I remember thinking that that in itself was fairly exotic technology to employ for a 50KW inverter. The largest single electronic drive I ever commissioned was 300KW (400Hp) and the SCR stack was forced air cooled, so from my standpoint I couldn't see why Toyota would ignore this more bulky but time proven method. In the event liquid cooling has shown that this is the way to go for automobile systems, their failure rate is a thousand times better than I would have predicted they would have received with an equivalent version that would have been air cooled.

    The idea I proposed earlier, using a single cylinder 450cc engine has received no comments yet but it is a good suggestion for reducing the cost of hybrids. When the engine is fully decoupled from the wheels as in a series hybrid it provides a lot more options in the prime mover. Generally you want high speed because that reduces frame sizes for the same power, but exotic devices like gas turbines have to be precluded because they require expensive high temperature materials and don't perform efficiently at part load. A modern single cylinder design on the contrary may net you 60HP in a small light package and avoid all that, so the resulting hybrid vehicle could actually be lighter than one with a conventional four cylinder with clutch and manual transmission. Not forgetting that with this hybrid you can redline the engine at max torque from a very low speed until you reach your target roadspeed - can't do that with a stepped transmission manual or the auto kind nor can the Prius either until it reaches 50mph. So this 60Hp may behave more like it was 100HP in practice.

  • dhanleydhanley Posts: 1,531
    "Why not use an external combustion (steam) power source to generate the electricity needed for a hybrid car. "

    That *might* be possible. The biggest problem with steam is that it takes awhile to get going, so to speak, and if you stop suddenly, a lot of heat might gp to waste. In the case if a hybrid, the electriv motor could move you at first when the steam was being accumulated, and after parked, the leftover steam could top off the batteries.

    I've had much the same thought in regards to a stirling cycle engine, which is more efficient than steam.

    BMW is developing a small steam engine driven by the heat of the exhaust, which then assists in driving the car. Supposedly, this increases both power and fuel economy by 15%.
  • tpetpe Posts: 2,342
    but exotic devices like gas turbines have to be precluded because they require expensive high temperature materials and don't perform efficiently at part load.

    You are talking about a series hybrid, right? Why would the gas turbine ever have to operate at part load?
  • toyolla2toyolla2 Posts: 158
    TPE, as I stated in my post #186 : -

    My model does not require an HV battery as either a major storage element or as an element able to deliver major power. In the model I propose, a conventional sized lead acid 12v battery could deliver 900W of power to the HV bus which would suffice for starting and for the type of limited low speed mobility in forward and reverse most often required.

    Our series hybrid models are quite different. You seem to be a battery storage type guy and I'm not. That means therefore my choice of prime mover will be operating at part load all the time except on steep inclines or when extreme acceleration is required.
  • tpetpe Posts: 2,342
    You seem to be a battery storage type guy and I'm not.

    Not really. I do like performance and the beauty of EVs is that you can have both performace and efficiency. There's no way a 60 hp engine can deliver the type of performance that I'd be interested in unless it was able to charge a more powerful battery pack. I'm not talking about a huge battery, <100 kg would suffice if it was the new type of fast charge/discharge offered by Altairnano or A123 Systems. Yes carrying around this extra weight would detract somewhat from efficiency but if you can more effectively take advantage of regenerative braking then the extra you spent to accelerate the greater mass would be largely recovered. Also, unlike in your system, the engine that was charging this battery would only operate at its peak efficiency, which would further offset the hit taken by the added weight.

    Interesting concept.
  • toyolla2toyolla2 Posts: 158
    tpe, the thing is not to sacrifice yourself on the Altar of High Efficiency. A BEV needs regen since the battery is the equivalent of a gallon of gas. Else regeneration on a hybrid is way too much trouble to save a cup of gas - you would be doing a heck of a lot of regenning to even do that.
    And who pays for the energy lugging that battery round the streets ? And who wants to pay for the battery also ? I've been into that before on this forum, let's not go there.

    Load levelling for peak efficiency. Talk of peak efficiency always raises a red flag with me. Like a product in a supermart with the word Gourmet on it. Expect to pay double. It's usually the same thing in a fancier box.

    So now you've got me turning off my engine while I drain my battery to 10% SOC at which point my engine comes on at full bore ( for peak efficiency of course) to recharge it. I see you bought into this one.

    Let me ask you some questions. Are you aware of the losses involved churning energy through a battery ? And are you oblivious to the problems of poor mileage experienced by HCH owners when temperatures drop to five degrees C ?
    Sure the battery is in the cabin, but the car might be outdoors 24/7. Your 40 minute commute is not going to be long enough to thaw it out.

    But its not all bad news. Here's a creed I can go with. It was in your EVWORLD article : -
    The overriding design strategy for Velozzi is weight-savings and has its origins in high performance auto racing. He pointed out that the lighter the vehicle, the less energy it takes to move it.

    Exactly ! So no 100kg battery for me. When you've unloaded a 4-cyl together with its clutch and transmission from the engine bay a genuine 60HP with a throttle response second to none won't seem so bad.

    My whole thrust nowadays is to look for ways that hybrid costs may be reduced. Replacing the HV battery with a 'virtual battery', the elimination of the stepped transmission or mechanical CVT of questionable durability and the adoption of single cylinder 450cc engine technology are definitely on that path. They won't please everybody
    but they will be an answer to the rather expensive, bloated HSD system now out there.
  • tpetpe Posts: 2,342
    I guess the main difference between your philosophy and mine is that I view hybrids and plug-in hybrids as an evolutionary step towards pure EVs, powered by batteries, ultra-capacitors, hydrogen, or some yet to be discovered storage device. Your path does not lead in that direction.
  • toyolla2toyolla2 Posts: 158
    Could it at least be said we are both of the opinion that electric power is the most efficacious way to drive the wheels ?
    We just differ on the source of that power.

    My suggestion is about proven technology, successful application should be quick, simple and relatively inexpensive.
    It's the now.
    Energy storage systems of which you speak are not yet proven technology, development will be slow, difficult and expensive.
    It's the then.

    I will agree that there can be penetration of Battery Electric Vehicles into the market if they come suitably equipped with tunes, A/C and at a reasonable cost, this is not the 'Operation Hairshirt' crowd, I know that. But I question whether any car company has the will to do that today. And it is not encouraging when even advocates like yourself insist on raising the bar as you did somewhat when you preferenced in terms of 60+ HP versions. For that particular upmarket, I can't see vehicles to be available in the short term and they will be expensive unless, as they say, the alchemist shows up and soon.
    Case in point, Ballard Power Systems with its fuel cell design, been in existence seems like forever and still not ready for primetime with consumers. Battery technology indeed is difficult.

    Meanwhile I, on the other hand, propose a back to basics rethink.

    Here's the amount of electric power we need - say 45KW (60 HP).
    Here's the best way (small, lightweight, simple and lowest cost) to generate it - a brushless alternator at 10K+rpm.
    And since the alternator is going to need a mechanical drive.
    Here's one of the better ways (small, lightweight, simple and lower cost) to drive it - the 450cc big bore short stroke liquid cooled 4 valve single cylinder engine.

    This is the horse I am betting on. Thanks, nice discussion
  • tpetpe Posts: 2,342
    I'd be surprised if a 450cc engine could generate 60 HP at less than 8,000 RPM. What would that do to longevity, and it might be a little loud.

    You mention that people won't adopt EVs if they don't have the ammenities they've become accustomed to. I agree. But a 60 HP engine cannot provide the power that people have become accustomed to if this is your "prime mover" as you put it.

    I used to live in San Diego and probably 4-6 times a year I'd make a road trip to Las Vegas with 2-3 friends. This involved about a 25 mile stretch of highway where you climb 4,000 feet in elevation where traffic is running around 75 mph. The 60 HP engine just wouldn't cut it. Granted this driving situation only took place a handful of times a year but its enough to make the vehicle less marketable. A larger battery pack could have supplemented the power on these occasions. Yeah the bulk of the time you'd be taking a mpg hit by carrying this weight around but you also take a mpg hit by carrying around the extra weight of an AC and even more of a hit when you use it. It comes down to what would be more marketable.
  • "I'd be surprised if a 450cc engine could generate 60 HP at less than 8,000 RPM "

    I wrote 'consider the 2006 Honda CRF450R engine which weighs in at 28.9Kg, its oversquare 96mm x 62mm single could probably put out around 60Hp @ 9000rpm for those short bursts of vehicular acceleration.' -citation needed.

    I don't have dyno figures for this engine - morons ripped the pages out my library copy of Cycleworld. So for now let's extrapolate from the Honda CBR600RR which yields 118Hp from an inline 4cyl. Each of its 75mm pistons should develop 29.5Hp. At similar piston speed and piston dia. (squared) CF450R should be capable of 48.3Hp on paper. The cooling efficiency of a single is way better than a four so it may very well be capable of 60Hp. I'll do further research on this and get back later.

    Notice another benefit of the series hybrid idea that could make this engine even lighter. Honda describes this particular engine having a dual sump design in order to separate clutch/gearbox contamination circulating into the engine lubrication. A crankshaft mounted alternator would of course not need this consideration. It has a 12:1 compression moving it towards diesel effcy also.

    The piston speed limitation I would place at 18m/sec or 9000rpm with the 62mm stroke. Yes, I gun for speeds higher than 8000rpm because this reduces the size of the alternator needed for an equivalent power.

    Re longevity, I agree no engine will survive 9 - 10 thousand RPMs for extended periods, but if we are looking at 8 seconds to 60mph a theoretical distance of only 117 yards will be covered before the engine will be returned to speeds of 3000 rpm or less for cruising.
  • toyolla2toyolla2 Posts: 158
    On February 6th 2008 The 1/X Concept Prius was displayed at the Chicago Auto show.
    This vehicle said to have around the same internal dimensions as the Prius and intended to seat 4 rather than 5 passengers has a curb weight of 926lbs against 2,890lbs of the Prius. It achieves this by the extensive use of carbon fiber reinforced plastic. The 500cc flex fuel engine is part of a plug-in hybrid powertrain that weighs only one quarter of the equivalent system in a Prius using a lithium ion battery. The result is a vehicle with the possibility of traveling over 600 miles on a small four-gallon tank of fuel and achieving the acceleration performance that is equivalent to the Prius.
    They don't explicitly announce this is a series hybrid and no photographs of the powertrain have been put up. Furthermore I don't know whether this is a single cylinder engine either and that is rather important for cost reduction.

    If we can sidebar on this for a moment - intuition would tell us that a 850cc inline four engine, for example, probably involves as many components and machining operations as a 2.7L inline four. It is therefore reasonable to expect that the price delta between these engines in mass production may be quite small. It is a fact that Tuner shops notice a similar situation in the costing of crated V8 engines between 302 cu. inch and 454 cu. inch that are produced specifically for the aftermarket.

    On the production line it's the reduction in number of cylinders that would seem to bring about significant cost savings. This might be the reason Toyota is about to replace the 2.4L inline four on the Camry with a new 2.7L engine. It occurred to me that this engine may come so close to 200Hp to discourage the 20% of buyers that have usually accepted the large price delta for the upgrade to the 3.5L V6. That they would have to move up to the Avalon to get the V6 would then make more sense. It further begs the question that in the horsepower race, just when is enough enough ?

    For those growing numbers more interested in fuel economy, however, when a 150mpg vehicle arrives with 0 to 60 in ten seconds I think there are going to be plenty of takers. In case there are still those who will equate this car with the 3-cyl 67Hp Insight it is well to consider that mated to a stepped transmission, albeit even with IMA assist, is a poor way to extract power from an engine. When available maximum power is limited to 67Hp, then when you need it, you must have that 67Hp right away and it must maintain continuously. It is not an acceptable system that allows vehicle acceleration only while the engine is struggling from the middle to the top of its power curve and then at which point you are forced to changeup and cause the the engine revs to sink back down to a lower power point to repeat the process all over again in the new gear. It is just poor efficacy to do this. That is what I have always been against.
    Earlier posts #186, 188 and 195 have outlined different aspects of my design and it is encouraging to see that as far as engine capacity goes finally someone at Toyota 'gets it'.
  • toyolla2toyolla2 Posts: 158
    This article by Mike Allen over at Popular Mechanics seems to echo what I have been proposing in the preceding posts regarding smaller engines. He questions the choice of today's engine sizes, and in this particular case the size of the motor generator set being fitted to GM's PHEV, the VOLT. Do we in fact need an engine that all by itself could generate enough electrical power to probably chirp the tires off the line? He proposes a more modest 10Hp, and goes on to say, in effect, that a vehicle that would cover the 95 percentile of commutes might be more efficacious to economical design. The 53kw gen on the VOLT will provide 45kw continuous power which is more than enough to cruise at 100mph - but why ?

    link title
  • tpetpe Posts: 2,342
    Maintaining highway speeds (~70mph) requires more than 10 hp even for the most aerodynamic vehicles. If you're going up hills, into a headwind, have several passengers I'm guessing a minimum of 25-30 hp would be required. Sure the heat put off by the ICE powered generator would solve some of the mentioned problems in cold weather but only after you had depleted the batteries to the point where this generator kicked in. Isn't this the situation you're trying to avoid? For my 9 mile commute this wouldn't do me any good at all. For that matter a traditional heating system is pretty worthless for the first two-thirds of my trip. And what about running the air conditioner in hot weather? Again, 10 hp isn't going to cut it. Besides, it was my understanding that battery packs put off heat. Why can't this be used to help heat the cabin? I suspect that it will be.

    One of the nice things about electric motors is that increased power does not equate to a reduction in efficiency. In fact small electric motors are typically less efficient than larger ones. The electric motor on the Tesla Roadster weighs about 70 lbs. So I don't think weight is much of an issue. Certainly driving 100 mph is going to use more energy than driving 70 mph. But for the person who chooses to drive 70 the fact that he has a more powerful motor than he needs will not result in an efficiency penalty. So you can have a confuration that appeals to the performance enthusiast as well as the person trying to use as little energy as possible.
  • Kirstie_HKirstie_H Posts: 11,025
    A reporter hopes to speak with anyone who purchased or considered a hybrid vehicle in 2007. If this describes you and you care to share your story with a reporter, please respond to with your daytime contact information and a few words about your experience no later than Friday, April 18, 2008.


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  • peraltaperalta Posts: 94

    Is there a site that provides simulation for RX 400H? I kmow there are a number of simulation for Prius hybrid in which you can see the relationship between road speed, engine speed, MG1 speed and MG2 speed.

    I am particularly interested on the engine speed at 60 MPH if the MG1 is frozen to zero speed. In the prius simulation, the engine speed is 2500 RPM. I want to know the engine speed of RX 400H in the same situation.


  • toyolla2toyolla2 Posts: 158
    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.

  • kdhspyderkdhspyder Posts: 7,160
    ...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
  • grandtotalgrandtotal Posts: 1,207
    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.
  • toyolla2toyolla2 Posts: 158
    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'.
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