Ordered mine on 4/27, to arrive in August.<br><br>With considerable difficulty, the dealer was finally able to confirm that the gas engine had an interference valve arrangement, regrettable but at least it is driven by a chain rather than a belt.<br><br>I believe the spec sheets tout "variable valve timing" or something like that. Anyone know how this is accomplished ? ...

There's a good explanation of the Prius specific valve timing the the Prius New Car Features manual. Ordering instructions were given in the eGroups toyota prius group. See:<br><br><a href=http://groups.yahoo.com/group/toyota-prius/message/1253 target=new>http://groups.yahoo.com/group/toyota-prius/message/1253</a><br><br>fo\ r ordering info.<br><br>It's similar VVT-i to the Echo, but with a different range ("authority") for the valve timing. Oil pressure is used to advance/retard the cam with respect to the chain drive. The range is physically limited to safe positions (as long as the chain holds out).<br><br>Don't most cars with reasonable compression have the possibility of valve/piston damage if the timing chain/belt breaks? I thought that's why you have to replace the belts religously. I think the chains have a much smaller risk of failure. That's what I've heard anyway.<br><br>By the way, the engine never exceeds 4500 RPM, so the timing chain and other engine parts get far less stress than traditional engines. The oil doesn't even get very dirty before it's time to change.<br><br>Robert Snyder<br>NJ-PIKACHU

<a href=http://motorshow.toyota-europe.com/m/m01.html target=new>http://motorshow.toyota-europe.com/m/m01.html</a><br>check out the engine and tech. section. The direct injection would have been a great engine for the prius, maybe the next one.<br>Charlie Fosdick

Many thanks for the info. Actually many engines including some other Toyota engines are of the non-interference design. I consider that a must with belt driven cams. In some engines, especially hemi-head designs, the intake and exhaust valve have the potential of clashing with each other as well as the piston.

Another good description <a href=http://www.onthenet.com.au/~billzila/vvtvtec.htm target=new>http://www.onthenet.com.au/~billzila/vvtvtec.htm</a>

Plus camshaft turns at 1/2 of engine RPM.<br><br>What other car has 4 valves/chamber on an engine limited to 4500 RRRR's?<br><br>Remember, 8 extra valves/lifters/springs increase<br>frictional demands, 4500 rpm limit allows "low tension" rings and valve springs, which DECREASE overall resistance.<br><br>It all doesn't add up, yielding a 45+ mpg SULEV!<br><br>Jeff (just throw out the book--or rewrite it)