I would say no because you can only draw 12A and you need about 50A at 50MPH on level ground and thats with a light foot. To really do 70MPG EV only you would have to be drawing 100A. Technically you could do it but you would drain the stock battery WAY before you reached 70MPH. I have the same problem but I could actually sustain the EV mode a little longer at those speeds since the Hymotion battery will give me about 30A.
I have the 52 MPH HSS and will be using it with the Enginer kit. The problem is that the Enginer kit does not provide enough power to maintain 52 MPH for long. It is mainly designed to provide motor assist to the ICE. Pure EV mode is limited unless you parallel several converters. I will be doing just that (paralleling two converters) this weekend to see if it works as promised.
Not to trivialize the thread, but YES... just run out of gas. Once you enter fuel starve you can spin MG2 as high as you want. I've heard reports of people out of gas making up to speeds of 60+. Heck all you probably need is to somehow inject the "out of gas" DTC then you've unlocked everything... Is this what the HSS mod does? Amps will be a problem though as others have stated. 11011011
Yes, HSS mod sends the "out of gas" signal. You get the DTC and then clear it with the SG. Then you are limited to 52MPH by the "out of gas" programming. At 52 MPH, the MG2 is at it's RPM limit. With the 70 MPH mod, the ICE is spinning, but not using fuel. Lots of wasted energy, in addition to the aero drag.
It's more complicated than that. Driving the Prius above 42 MPH with just MG2 (that is, Forced-Stealth-Mode, or High-Speed-Stealth-Mode: basically anything that causes the forcible termination of the gasoline engine with either a communication DTC or out-of-gas signal) risks over-revving the motor (Yes, it's true. Argonne National Labs has verified it). Additionally, when you use forced stealth mode by causing a DTC, all of the recorded diagnostic trouble codes for your vehicle are cleared. This includes legally required emissions data from your vehicle--which means if you plan on having your vehicle checked for emissions, don't plan on using forced stealth mode for several weeks in advance (depending on the state you live). When you hear about people going above 42 MPH (or heaven forbid, over 52 MPH) with just MG2 using the methods above, you have to understand that they are likely damaging their vehicle. Just because Toyota allows it doesn't mean it's good for the car. It's designed to be a limp-home mode and only to be used in an absolute emergency (you run out of gas or there was a serious problem with the engine). It's not designed to be used long-term by any means. The Hybrid Energy Manager modification from Ewertenergy.com (70 MPH in EV-mode you may know it as) gets around this problem by utilizing both MG1 and MG2 so the powertrain isn't over revved and remains within Toyota specs--though this modification is available exclusively with the PluginConversions.com 25 mile package. TheForce is also correct when he says that the Enginer system (and subsequently the Himotion system) cannot push forced stealth mode (MG2-only electric mode) for very long because the current transfer between the aux pack and OEM pack is so low (around 20 and 30 amps respectively). To sustain yourself at highway speeds we're talking about 70 to 80 amps just to maintain speed due to wind resistance. Even traditional low-speed EV-mode pulls around 110 amps during acceleration. Granted, at low speeds you won't accelerate for very long, but you likely will run out of battery power during a long coast if you aren't careful. Keep in mind that as your battery SOC drops, so does your sitting voltage. As your sitting voltage drops, so does the amount of power the electric motors can deliver (power = voltage * current). If you're looking to maximize your EV-only range and speed, I would suggest a more powerful conversion like the one from Plugin Conversions.
