On the original 90s-era Prius, wikipedia lists the Japanese engine as having 58hp and 13.5:1 compression. When the car was brought to the U.S. the horsepower was increased and compression changed to 13.0:1. Why the change in compression? ALSO: Was the original Japanese Prius more efficient than the U.S. modification?
it mostly has to do with the EPA. 13.5 is extremely high. the higher the compression the higher the gas TEMP the higher the NOx emissions out the tail pipe. Also you get engine Knock from low octane gas. Most cars in the USA range from 8.0 to 1 up to 9.5 to 1 on the high end.
Looks like you are talking about gen 0 Prius that was not available in USA. Apples to oranges (and wrong forum).
Possibly fuel standards? But I know power was increased to match US driving conditions. The US-spec Prius (which is the same Prius they sold in 2001) was basically the "midlife update" of the Gen 1 Prius and is more efficient because of better batteries. The NHW-10 (1997-2000) used D-Cell batteries. The NHW-11 (2001-2003) used NiMH batteries. It also had a more energy-dense battery. http://www.john1701a.com/prius/images/Prius-Generations.png
The compression ratio on the Prius is artificially high because of the Atkinson cycle function where the intake valve remains open during the first part of the compression stroke. So the compression ratios of Atkinson and Otto cycles are not comparable.
I don't see a G1 forum. I looked before posting but found nothing. The official designations were XW10 and XW11 respectively..... Japan and US were both the G1 models with just minor tweaks. (XW20 and XW30 were major changes to G2/G3.)
It is not clear why Danny has chosen to hide the Gen 1 forum, but it DOES exist. Generation 1 Prius Discussion | PriusChat
If it's hidden how will anybody Read my post & answer my question? I'm not wasting my time posting to the G1 forum if it's invisible.
It is not invisible, it is stuffed in the Gen 2 forums oddly, which makes it hard for new users to find. Gen 1 owners post there a lot, I suspect they Bookmark it. As any question, they show up in 'Whats New'.
The new Auris hybrid shares the same basic 1.5 ltr engine as the gen2 Prius, but the compression ratio has gone back up to 13.5/1 (theoretical). John (Britprius)
