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Originally Posted by bwilson4web
THANK YOU!!! This is what I needed to see:
My initial impression from what you've posted is they are discussing the loading " at 85 miles per hour", a very important qualification. It is not uncommon to find the efficiency of any system varies as a function of the load. In this case, 85 miles per hour is a speed that except for parts of Montana and the Atlanta beltway outside of rush-hour would result in a speeding ticket with reckless driving citation.
I'll do a little more research and independent confirmation. It so happens, I've got an NHW11 03 Prius with instrumentation. Knowing my lead-footed wife, I will take some measurements (between the occasional "Holy SH*T! Do you know what the speed limit is??")
BTW, I was a mechanical engineering student at Oklahoma State University before doing four years in the US Marine Corps (there used to be a draft.) This means I not only know how to figure it out but I also have unusual skills to defend my opinion. <GRINS>
Bob Wilson |
you're welcome! i definitely want to hear your take on the article and discussions. like i said, i'm trying to understand the interesting intricacies of hsd. i think it is an ingenious system and frankly i agree no system is going to be operating as its peak efficiency during all load conditions.
having said that, i'm still leaning toward saying that psd is a true cvt at lower speeds (under say 85mph) but acts less like a true cvt at higher speeds (say above 85mph) than would a belt and pulley cvt. i say that at speeds above 85mph, the fixed gear nature of psd begins to introduce non-significant losses (from the electric motor needing to be running and running more the higher the speed) and that the cvt-like behavior/benefit of the system begins to slip away as the ice revs higher and higher to make up for the inefficiencies of these losses. this behavior would not be present in a belt and pulley cvt as the gear ratios exist to allow the ice to operate in a comparably more efficient range. i say this without qualifying the need for traveling at such speeds and just purely looking at the question posed.
and as a final disclaimer, the prius is *excellent* at what it does and meets 95% of our needs here in the states. by understanding hsd better, we may shed light on how to improve the system for the last 5%.