I don't understand how hybrids without this technology get better mileage. If you aren't recapturing mechanical energy that would otherwise be lost as heat, then a hybrid w/o the regen capability is just getting the electrical energy from the engine. Because of the laws of thermodynamics, you can't get get more mechanical energy from the electricity that was derived from the mechanical engine in the first place. Are these hybrid just getting better mileage because it turns off while idling and because the have smaller combustion engines?
You have something mixed up. There are no hybrids without regen. We need more info to figure out the real functionality in question. .
But if you did have a hybrid without regen, then increased mileage would come from these factors: 1) Turning off the engine when not needed. 2) Being able to use a smaller and more efficient engine. 3) In the case of Toyota's HSD, elimination of the normal transmission with what amounts to an electrical CVT. Tom
Oh. I thought that toyota had a specifically unique "synergy" hybrid drive where when you break or coast w/o accelerating, you get electrical energy back. Is this true for all the american and honda hybrids? Also, is this true for most EV's also? Well, let's start with all the american hybrids.
Hybrid refers to something that is an offspring of two things (for instance). A hybrid drive would be one that produced the power from multiple sources, i.e., gas/electric. Whether that power was exclusively from petrol, or from regenerated power, has no real bearing on the word 'hybrid', in my opinion.
Hi Burritos, Its not only using a smaller engine, its not using the engine at a low efficiency load. There are at least two aerodynamic things that happen in engines that are key. At part throttle, the trottle is partly closed. But the engine is still sucking in air past that plate. Which causes extra air friction. Additionally, engines use what is called "scaveging", which works through valve overlap (the time when both valves are slightly open). This method helps to use the exhaust energy to pull in new air. It acts by the momentum of the existing exhaust creating a lower pressure than atmosphereic at the intake valve when it opens. This was invented by the Puegot brothers, and they came over to the US and won the Indy 500 with an engine that used valve overlap. Prior to that time the valves did not have overlap, and consequently were severly limited in maximum RPM. These engine aerodynamics issues conspire to cause a normal Otto cycle engine to have very poor partial throttle efficiency. The partial throttle part is obvious, more air drag over the throttle, but the scavenging being an aerodynamic process is very non-linear, and works best only at specific loads and rpm's. The tuning of the exhaust and intake passages greatly impacts scavenging, and ram-tuning. Early 500 CC British racing motorcycles made great use of this, and with only one cylinder dramatic increases in HP were attained when the ram tuning and scaveging, but were so non-linear the power was only available over a small range of RPM near max, which became the racing art for these machines. Its more difficult with multicylinder engines to get such gains, however. So, when an Otto engine car is tooling down the road at 35 mph, its engine efficiency is around 12%. Whereas a hybrid runs the engine, to push the car and charge the batteries during the 35 mph cruise. Which puts the engine at less partial throttle, because besides pushing the car, its charging the battery, and it is a smaller engine. When the battery is charged, the engine goes off and the battery pushes the car. The Prius goes even further and uses a new engine, which does not have the RPM range to work in normal cars. The Atkinson Cycle (Miller valve train) engine has very good part throttle efficiency. It was measured at Argonne Labs to have a 25 % efficiency, at 12 HP (or 1/6 th the max HP). Which is over twice that of a normal Otto engine. The RPM limitations of the Atkinson Cycle engine are overcome by the battery and motor of the Hybrid. This is one of the "synergies" that give HSD its name.
Well then that rules out the Prius and all models came with regenerative braking. The only way to turn it off is to shift in "N" when stopping. Now if we expand the list of hybrids to include all, to the best of my knowledge, they call claim to have regenerative braking. Do know of a make or model that does not? The only one I know of that does not have regenerative braking is the do-it-yourself one that you just drop a motor in the rear wheel shaft: http://www.go-ev.com/ Is that the one you want to discuss? As far as regeneration, it is proportional to the electric motor power rating. The Prius has one of the highest ratios of electric to total power. All other hybrids have lower ratios and thus less regenerative power. When you get to the mock hybrids of GM, typically less than 5 electric hp, there is effectively nothing, which is how much value they have. Bob Wilson
