What grade of gas is best?

100, 200k before seals go using E10 - no problem there.E30 has seals lasting 30 - 50k at best,then new seals are in order, unless one doesn't care about leaks, degraded engine performance.

DBCassidy

 

Really? Degraded engine performance? How? Does that E stuff leave more carbon deposits or clog up intake valves?

Mike

 

The Prius actually works the opposite to what you have described to provide high-efficiency.

The throttle is not used very much to control output power instead the engine RPM is varied. The valve timing will be used to adjust the charge allowed to enter the cylinder during the intake stroke.

At high power outputs the inlet valve is closed early to give maximum charge in the cylinder, the physical combustion chamber volume means that the cylinder cannot be filled more than ~70% full giving the 10:1 compression ratio and 13:1 expansion ratio.

At low output powers the inlet valve is closed later to allow some of the inlet charge to be expelled into the inlet manifold. The throttle remains fairly open for both scenarios so the inlet manifold pressure does not drop to the levels seen on a conventional engine - this minimizes pumping loss.

The Prius does not operate the engine at high RPM low throttle setting under normal conditions.

kevin

 

CAREFULLY, reread post.

DBCassidy

 

A leaky seal would drop your MPG for sure.

 

13-1 is the compression ratio. The VVT system adjusts the intake and exhaust timing optimize the overlap at various engine speeds. The ignition system has a built in knock sensor to retard the spark if the octane (compressibility) is insufficient. One good question, Toyota says 87 or higher. Has anyone tried running higher octane and seen an increase in economy? Can the ignition system provide more advance?

 

Some swear by 89 octane while some run the lowest cost gas they can put in there Some even run real high octane stuff I never run low octane gas in any of my vehicles.

Mike

SGH-I717

 

Bob Wilson did tests and got a minor power increase with Premium going uphill, but no MPG gain.

13 to 1 is the expansion ratio, and so is the mechanical compression ratio, but that is not the useful ratio.

Listening to this guy, recall that the Prius intake has a minimum closing degree of 72, and can close at 105 degrees maximum.