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Old 06-12-2009, 07:24 PM   #6 (permalink)
Matt Herring
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Join Date: Jun 2008
Location: North Andover, MA
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Bone's 2010 Prius - '10 Toyota Prius Black
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This is interesting but given the design of the MG1 and MG2 in the Prius engine it leaves alot to be discussed before deeming it "safe" for the Prius...it looks like fun but it may not be in the long run. When I first started getting into the Prius engineering (shortly after I bought it) I immediately was told "no neutral coast near or over 60 mph (and most people told me to avoid it all together). I still use it but no where near 60 mph.

The software that Ewert has created (and the upgraded battery pack they install with it) is still operating with the original Prius engine. Because of this the "gears" that simultaneously operate in the car ICE are still in play. The MG1 in that engine is built to sustain up to about 10,000 rpm (in the 62 mph range). In essence, the MG1 continues to spin when in EV mode to protect the engine and at 70+ mph it is clearly reaching it's limits before "overspinning" and doing harm to the engine (a poster on here showed me the math in my Prius thread if you want to reference it). This is something I am very aware of when doing any neutral coasting in my Prius (I don't do it anywhere near 60+ mph).

The software Ewart has created is basically a "hack" for the Prius engine system...it tricks the engine into thinking the SOC is high enough to use EV mode (thus allowing it to stay in EV at that high of speed...usually only available below 42 mph) and keeps it EV mode beyond the 41 mph limit. This is a problem in my mind because while EV mode is built into the car it is not built into the car at 42+ mph...really only up to 60ish mph where the MG1 is nearing "overspin."

Another area to consider is inverter temps at this high of speed and length of time while pulling higher amps to stay in EV mode using their system. Not only are you overflexing the Prius capabilities in terms of the inverter you are also spinning the MG1 at a ridiculously high rate. I'm no expert on the MG1 and MG2 in the Prius but I know that the MG1 spinning in neutral or EV mode over 60 mph is a no-no.

I'd like to see more in regards to what rpm's the MG1 is at while they are at the 65-70 mph speeds.
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