# Has anyone cracked gen2 Prius computer for pure EV drive?



## T1 Terry (Jan 29, 2011)

I have a Gen 2 Prius with a PHEV battery pack in the spare wheel well. With the ICS Kill applied (basically the fuel pump disabled) it can reach 85km/h (roughly 50mph) when the battery is fully charged.
I understand this limit is to avoid over speeding the planetary set. 
My query is, can the ICE motor be removed to allow the MG1 to drive through the sun gears to provide added power and another electric motor added in place of the ICE that can be allowed to spin freely when required to avoid over speed of the planetary set, yet powered when even more output power was required? 
Is there a hack for the motor control that could achieve this?
The idea I'm looking at is:
The sun gear carrier is driven by the additional electric motor, MG1 is driven as well as MG2. This would allow a constant variable ratio from direct drive out of the planetary set.
All driving at the same speed so effectively locked would produce maximum torque yet any of the 3 units can be spun at a different speed to reduce the total torque applied by reducing the current sent to that particular motor set or alternately, any 2 units spun at the same speed as the 3 unit to allow all the drive to be provided by any one of the 3 units, which ever is most economical at that speed. 


Am I looking for the Holy Gail or unobtainium? :lol:


T1 Terry


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## electro wrks (Mar 5, 2012)

Damian Maguire has done some work on this path to repurposed OEM parts madness: https://www.youtube.com/watch?v=mTkw31wrkLg


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## T1 Terry (Jan 29, 2011)

Thanks for the You Tube video, at least that's a start. Kinda worry about taking advice from someone who tore down a drive unit and has 2 parts left he doesn't know where they came from :lol:
I'll watch his next video tomorrow to see what he used to power the locked MG1 & MG2 motor set up.


T1 Terry


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## brian_ (Feb 7, 2017)

T1 Terry said:


> My query is, can the ICE motor be removed to allow the MG1 to drive through the sun gears to provide added power and another electric motor added in place of the ICE that can be allowed to spin freely when required to avoid over speed of the planetary set, yet powered when even more output power was required?
> Is there a hack for the motor control that could achieve this?
> The idea I'm looking at is:
> The sun gear carrier is driven by the additional electric motor, MG1 is driven as well as MG2. This would allow a constant variable ratio from direct drive out of the planetary set.
> All driving at the same speed so effectively locked would produce maximum torque yet any of the 3 units can be spun at a different speed to reduce the total torque applied by reducing the current sent to that particular motor set or alternately, any 2 units spun at the same speed as the 3 unit to allow all the drive to be provided by any one of the 3 units, which ever is most economical at that speed.


That seems like a lot of complication. Why not just remove the engine, mechanically lock the power split planetary (so that sun, planet carrier, and ring gear all rotate together), and simply drive it in the existing EV mode? With any luck, the 85 km/h speed limit is based on MG1 speed, not output speed; MG1 wouldn't be spinning fast so the limit wouldn't trigger.


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## Emyr (Oct 27, 2016)

brian_ said:


> That seems like a lot of complication. Why not just remove the engine, mechanically lock the power split planetary (so that sun, planet carrier, and ring gear all rotate together), and simply drive it in the existing EV mode? With any luck, the 85 km/h speed limit is based on MG1 speed, not output speed; MG1 wouldn't be spinning fast so the limit wouldn't trigger.


Depends how the oil supply works. I think the Lexus GS hybrid gearbox uses a separate oil pump but the Prius drives its oil pump from the ICE input shaft (iirc, don't have a reference to hand).


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## MattsAwesomeStuff (Aug 10, 2017)

brian_ said:


> That seems like a lot of complication. Why not just remove the engine, mechanically lock the power split planetary (so that sun, planet carrier, and ring gear all rotate together), and simply drive it in the existing EV mode?


So, that's what Damien has done.

In other news, Damien is teaching classes about one weekend a month in Ireland at Kevin Sharpe's shop. (1000euro/weekend). About half are introductory, and half are specialized intermediary.

As a result of these classes, there are supposedly soon to be some shops fabricating Gen2 and Gen3 adapter plates for the input shaft that you just bolt on, no need to own a welder. At first I thought this was a weird solution since anyone building an EV is almost certainly going to need a welder and the ability to weld... but now I see Kevin is pushing a much bigger picture of seeing the 10,000,000 dead hybrids out there that could be de-hybridized and had larger packs put in and be back on the road. Him and Damien just bought a Lexus hybrid in what appears to be amazing shape, for $500, because it has a dead hybrid battery.

So, mechanically, you either weld it up or eventually buy one of these adapters and it's a solved problem.

Control-wise, the Gen2 inverters are in a bit of a purgatory. Last year Damien tried (and succeeded) in pursuing a low-cost, semi-stripped down OpenInverter hardware based on the low-cost and through-hole-solderable BluePill microcontroller (another open source project, a part you buy). The idea was that tiny SMT components aren't easy for DIYers to build, and pre-populated SMT boards were too expensive.

Development of the BluePill solution was focused on the also-low-cost Prius Gen2 converters. So development of those got ahead of the Gen3s.

... However...

Soon after those got made, Damien switched to a new PCB supplier that is so massively cheaper for pre-populated boards that Damien went and redesigned almost every board he has to use their (limited) parts inventory. And, other people in the community had Gen3s and were making decent progress on them, so Damien had help (which is encouraging).

So, available for purchase, right now today, are Gen3 control board replacements that even fit the same form factor as the OEM control board you'll rip out of the inverter housing. You just bolt the new one right back into where the old one was and connect it with the same connectors. It even has the hardware to support one of the inverters to be repurposed for use as a high-capacity battery charger (software still in development).

With all that, and Damien's 30-item long to-do list including like, 5 actual vehicles... the Gen2 doesn't have one of the pre-populated boards made yet. And I'm half-trying to talk him out of it, since it's extra work for what is essentially something that already exists (in the Gen3 form).

Far as I know, I'm the only one actually using (or attempting to use) the Gen2 BluePill-based control board. And if a new Gen2 board comes out, I'll probably toss the BluePill one aside and just go with the new one.

I think he's even attempting build-in Wifi on the next batch of boards instead of using the Olimex ones (or the D1 Minis like some of us are).

Now...

That works just fine as a Prius Gen2 transaxle stolen for use in a different vehicle. How well does it emulate the original control board if you want to keep it inside a running Prius Gen2? Uhm... I dunno. You've cut off the vehicle's access to the motor, so you can make the motor do whatever you want, but whether the rest of the ECU is pleased with that decision or not, I couldn't tell you.

So, there you go. That's my summary of Prius control boards in the current state of affairs.


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## T1 Terry (Jan 29, 2011)

MattsAwesomeStuff said:


> So, that's what Damien has done.
> 
> In other news, Damien is teaching classes about one weekend a month in Ireland at Kevin Sharpe's shop. (1000euro/weekend). About half are introductory, and half are specialized intermediary.
> 
> ...



Wow, thank you for all that information. No point in trying to reinvent the wheel.
So, if I understand this correctly, if I get a Gen3 inverter there is a control board ready to drop in as an OEM replacement ... have I got that part correct?
Next question, what model Prius has a Gen3 inverter and will it work in with a Gen2 transaxle? 
If that is the case, does the transaxle now spin the drive shafts fast enough to exceed this self imposed limit the Gen2 has on pure electric drive? In other words, can I get better than 85km/h (50mph) driving with the gen2 transaxle only?


T1 Terry


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## T1 Terry (Jan 29, 2011)

Looking at the drive flow chart here https://priuschat.com/threads/introduction-to-prius-power-flow.29352/ it shows the ICE drives the planetary gear set, MG1 drives the sun gear in the centre and MG2 drives the ring gear that also drives the output shaft via the chain to the reduction gears etc.
This means, by holding the planetary gear cage locked to the case, MG1 would drive through the planetary gears to the ring gear providing maximum reduction, the sun gear (MG1) will spin a lot faster than the ring gear (MG2). This is basically what happens when the ICE motor is stationary. This means the sun gear (MG1) would over speed past 85km/h (50mph) and that is what the on board computer is avoiding by limiting the maximum speed.
If the planetary cage was to spin at the same speed as the outer ring gear, basically what the plate added by Damien in the first video, the gearset would be locked as suggests, there for both MG1 and MG2 would be part of the drive and both spin at the same speed. I can't see locking the planetary carrier to the case being a suitable fix unless a high torque reduced output speed was the aim.


Hopefully I've misunderstood just how this plate that bolts onto the bell housing works and that it isn't designed to hold the ICE driven member.


T1 Terry


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## electro wrks (Mar 5, 2012)

Something else to think about with the Gen 3 (~2010-2014) Prius inverters, and possibly with other Toyota models, is an overheating and failure problem: https://www.latimes.com/local/california/la-fi-prius-overheat-inverter-defect-20190414-story.html
It might be from something as basic as a loss of coolant leak or a bad circulating pump or, more troubling, some bad components in the inverter. It might also be the reason why the inverters are so inexpensive on the used market.


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## MattsAwesomeStuff (Aug 10, 2017)

T1 Terry said:


> So, if I understand this correctly, if I get a Gen3 inverter there is a control board ready to drop in as an OEM replacement ... have I got that part correct?


Yes. I think so. See first post:

https://openinverter.org/forum/viewtopic.php?f=14&t=488

History, including older attempts and older boards: https://openinverter.org/forum/viewtopic.php?f=14&t=51



> Next question, what model Prius has a Gen3 inverter and will it work in with a Gen2 transaxle?


Gen3 is just the 3rd generation of Prius. 2010-2015 model years.

Gen2 is just the 2nd generation of Prius. 2004-2009 model years.

Far as I understand, the transaxle has 3 power inputs, one for each of the 3 phases. Or rather, probably 6 since there's MG1 and MG2 in there. Maybe some temp sensors, the encoder/resolver, etc. But no brains. It's agnostic as to where that power comes from. The brains are all in the inverter.

So, I think that is fine, yes. But I haven't seen one and I'm not entirely sure so, maybe ask someone more knowledgeable.



> If that is the case, does the transaxle now spin the drive shafts fast enough to exceed this self imposed limit the Gen2 has on pure electric drive? In other words, can I get better than 85km/h (50mph) driving with the gen2 transaxle only?


I'm not sure all what goes on, since I don't have any transaxles (I'm using an ACIM from a forklift). You are the first person I recall who's pointed out this limit before, but I might've missed something.



> Hopefully I've misunderstood just how this plate that bolts onto the bell housing works and that it isn't designed to hold the ICE driven member.


Hmm. Driveline in question:










So, if the planet carrier (engine output) is locked to the case and can't spin, and the gears are 1:1 between the MG1 output (sun) and MG1 planet, then they have to spin at 4x the speed of MG2, or whatever they're geared to. And you're contending this might be too fast for them to handle, because in Prius use, it's too fast to handle?

Interesting. I have no idea.

So, I've seen two things happen, one on the Prius, the other on the Lexus. They're slightly different. 

Here's the Lexus: https://www.youtube.com/watch?v=Lb6TKI2GIWM

Someone asked: "Would doing the same on a prius gearbox avoid having to weld the power split device?"
And someone replied: "Yes but the oil pump is driven off the engine, so the gearbox would receive and lubrication. Also mg1 would have a high ratio to mg2, so mg1 could over speed. Welding the gears would turn the oil pump. Lexus has an external oil pump, so this isn’t an issue as such."

... so I think the Prius process is a bit different than in the above video, and, as it avoids the oil pump issue, perhaps it also avoids the overspeed issue of MG1?




electro wrks said:


> Something else to think about with the Gen 3 (~2010-2014) Prius inverters, and possibly with other Toyota models, is an overheating and failure problem
> It might be from something as basic as a loss of coolant leak or a bad circulating pump o


On Gen1's at least, there was no sensor for when the coolant pump failed. Only an overtemp sensor on the inverter. So, if the coolant ran out and pump ran dry and died? Or if the pump overheated and died? Or if the pump electrical died? You would never find out until or unless the inverter overheated.

And the inverter almost can't overheat, even without coolant, in hybrid use. So, tons of them drive around with broken pumps and no coolant and never find out unless they really push their motors.

I imagine it must be something similar with the Gen3. How else are they overheating, unless coolant issues? Or maybe coolant control issues (pump isn't on all the time?). Sounds like something you can fix manually.


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## MattsAwesomeStuff (Aug 10, 2017)

T1 Terry said:


> Next question, what model Prius has a Gen3 inverter and will it work in with a Gen2 transaxle?


"Prius Gen2 Transaxle With Gen3 Inverter": https://www.youtube.com/watch?v=2I9eUHb-zf8

It appears... yes. 

Even when you don't put all the parts back in.


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## electro wrks (Mar 5, 2012)

Here's a news feed that talks about the Gen3 inverter problem: https://www.youtube.com/watch?v=k3tJd8b_8LE


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## T1 Terry (Jan 29, 2011)

Thank you all for your relies, very informative. Looking through the Gen3 inverter report it appears I'd need to be very careful not to get a crook one when hunting through the salvage yards (wreckers) for one at the right price.
The replacement board that needs to be fitted to these Gen 3 inverters, would that solve the gen3 inverter problems or do I need to start with a known good late model inverter?
Must be still a lot of You Tube videos to watch because at the moment they only seem to be plugging into MC2, or have I got that bit wrong?
It still loks as though I could incorporate a third electric motor to couple in where the ICE did originally to add to the torque and possibly the speed as I'm unsure if MC2 still drives at the higher RPM required for higher road speeds or if that is all produced by the ICE and the MC2 simply spins at the same speed to create a planetary gearset lock up. If the planetary set is already locked via welding or a machined lock plate or similar, then the third electric motor would either freewheel or add drive or regen as required.
I think I'll have to get a Gen2 transaxle to dismantle and look at the possibilities. I wonder how much weight one of these transaxles could drive? They would make a great unit for the repowering of my '74 VW Kombi so I could do away with the gearbox as well as the motor. Would the Prius electronic gear selector still work?


T1 Terry


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## rmay635703 (Oct 23, 2008)

https://priuschat.com/threads/converting-prius-g3-to-all-electric-removing-ice.211099/

This guy could help

Cheap Gen III donor cars are cheap and common given the constant head gasket failures.


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## Boulder Hybrids (Jan 30, 2013)

OrionBMS.com used to sell a BMS and spoofing box (Hybrid Energy Manager) that would allow the g2 Prius to run without gas up to 60mph and not generate any fault codes, i.e. they intercepted the canbus messages and fooled the car. 

Their product only worked on 04-09 Prius. We installed quite a few back in the day in North America, not sure if they would work in a RHD Prius.

When in EV mode you had wimpy acceleration, but if you had a big enough battery pack (10-14kwh) you get up to 30-50 miles of EV range. If you punched the gas pedal , the engine would come on if you needed it. While in EV mode it wasn't bad for "around town" driving.

I don't believe they sell the HEM product anymore. We have some used old stock HEMs and BMSs we can sell but we are not in a position to provide technical support on these products. Used Orion BMS with HEM is $600 + shipping. You will need to provide batteries, battery box, wiring harnesses, and a charger so not a very plug and play setup. Pmail me if you are interested. -Paul


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## T1 Terry (Jan 29, 2011)

Thank you Paul. We already have a PHEV set up in the Prius with a 10kWh battery pack and it gives us around 80km range at 80km/h (50 mile per hr) but it doesn't have the pedal to the metal ICE start up and that would be handy some times.
I'll keep your offer in mind and I have had other people locally ask about where they could get such a kit. I'll drop you a private message in a few days when I get a bit of free time, work is really backing up at the moment. Seems suddenly everyone wants a lithium battery, solar and inverter set up in their RV yesterday and figure the quote they asked for 12 mth ago gives them priority in the booking schedule 


T1 Terry


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## Tom (Mar 26, 2008)

Hi Paul,
Can you share any information on the Orion Gen 2 Prius controls? We are a Prius dealer in Maine that rebuilds hybrid batteries and Comb. meters and generally keep things affordable for Prius owners.
I don't need more projects, but modifying to a Prius EV is too much fun to pass up.
We also sell lithium batteries that we get through a friend in the recycling business, to EV converters.
Best regards,
Tom Gocze
www.prius.store


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## Boulder Hybrids (Jan 30, 2013)

Years ago, we installed quite a few systems based on OrionBMS. The Orion stuff worked great, but the crappy Chinese batteries and Elcon chargers made it risky. All the systems failed and became a support nightmare.

If you were to do it, I suggest you do it on your own car, use quality batteries like Nissan Leaf modules and a good charger. Don't offer the solution to customers unless they know the risks. Tell customers if they want a PHEV to buy a "factory built" Chevy Volt or Prius Prime etc.


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## T1 Terry (Jan 29, 2011)

Does anyone know the maximum voltage to the inverter without causing damage? I was just thinking about my 80km/h (50mph) limit in electric only mode and wondered if an increase in voltage would improve the top speed and maybe the hill climbing performance from a standing start.


T1 Terry


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## T1 Terry (Jan 29, 2011)

Boulder Hybrids said:


> Years ago, we installed quite a few systems based on OrionBMS. The Orion stuff worked great, but the crappy Chinese batteries and Elcon chargers made it risky. All the systems failed and became a support nightmare.
> 
> If you were to do it, I suggest you do it on your own car, use quality batteries like Nissan Leaf modules and a good charger. Don't offer the solution to customers unless they know the risks. Tell customers if they want a PHEV to buy a "factory built" Chevy Volt or Prius Prime etc.


The Elcon charger is a real hit and miss item that's for sure. When mine throws a wobbly I have to disconnect all leads to it, wait an hr, then plug it back in starting with the battery plug, then the BMS interface, then the fans and last plug in the mains power.
As far as the crappy Chinese batteries, this Prius has the GBS 40Ah cells that were fitted by the previous owner. They constantly leak electrolyte so the smell first thing in the morning is fairly intense requiring the rear windows down and the air con on fresh air mod. It's probably heat related, it does get fairly warm over here, even when the place isn't on fire. 
The next battery I'm looking at using LTO cells. Their voltage is lower so I'll need more cells, but their ability to accept and release high current yet still get a long cycle life I'm hoping will offset any issues with energy density and a slight increase in weight. If I can do away with the ICE engine and all the hang-on bits, that will give me a bit of freedom for a bit more battery weight.


T1 Terry


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## MattsAwesomeStuff (Aug 10, 2017)

T1 Terry said:


> Does anyone know the maximum voltage to the inverter without causing damage?


~500v I think. 550v maybe?



> wondered if an increase in voltage would improve the top speed and maybe the hill climbing performance from a standing start.


I don't think so.

There was some discussion on that this week. The reason for the max 80km/h top speed in electric only mode on the Gen 2 Prius is in fact because you will overspeed MG1, which is at a 2.61x ratio to MG2. In the Gen 2 it's rated for 10,000rpm (versus 6500 for Gen1, 13,500 for Gen3, and 17,000 for Gen4).

In order to not overspeed MG1 (which actually turns counter-rotationally to MG2), the sun on the planetary gearset needs to turn, and the sun is the engine.

The Gen3 has a double set of planetary gears (one on MG2 as well) so you can get away with this, but the Gen2 only has a single set.

I believe if you remove the engine and weld the planet gears to the planetary carrier (not lock the sun shaft), you lock MG1 and MG2 to the same speed (and direction, but now the engine shaft will spin backwards). So I think that's your trick.


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## T1 Terry (Jan 29, 2011)

First thing to find out, can MG1 be spun backwards? If it can then locking the planetary set will have all components spinning at the same speed and direction as MG2.
If I allow the ICE shaft that is splined to the planetary to spin freely and drive MG1 and MG2 in the same direction, MG1 should not over speed, but how is MG1 speed determined? Does it have an encoder that signals the computer as to the rpm, or does it determine the max rpm for MG1 by road speed?


How does the Prius transaxle create a reverse drive? The ICE is still spinning in the original direction, does MG1 spin very fast in the reverse direction to cause the planetary gears to drive MC2's ring gear backwards, or does MG2 just spin backwards driving the ring gear and therefore the chain in the reverse direction?


T1 Terry


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## T1 Terry (Jan 29, 2011)

I found this that explains a lot on how the power divider part of the Prius Gen 2 planetary set works and it is very clever indeed http://eahart.com/prius/psd/


From this site many of my questions have been answered and it offers an interactive section of the planetary set in action that has given me a number of ideas on just how I can get this to work.
It seems if I hold the ICE input shaft stationary I can have up to 40mph just using MG1 and MG2, then if I spin the ICE input shaft at 1,000rpm I can have up to 60mph. If I increase the ICE input to 1500rpm I can get up to 75mph but still be able to reduce speed down to 0mph by running MG1 backwards at around 5.500rpm. Not that I'd intentionally do that, but in an emergency stop situation where I couldn't stop the electric motor that was driving the ICE input shaft, I could still stop.
Ideally the electric motor would spin up in 500rpm increments related to road speed, or if I got clever enough, the ICE input would be spun to keep the MG1 rpm within a safe range. Another alternative is holding the ICE shaft at 0rpm below 40mph and then spinning it at 1,000 rpm.


Maybe I could trick the original computer to use the throttle position to control the electric motor replacing the ICE and the spark and fuel cut to operate the power supply to the motor speed controller so it would free spin up to 1,000rpm the same as it does with the ICE motor and decide if it wants to power the ICE motor replacement or not, the same way as it does with the ICE spark and fuel.


Seems I need to get a Gen2 transaxle and tart playing.


T1 Terry


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## imwoody36 (Sep 25, 2011)

the open inverter project is exciting, and the toyota inverter is an amazing compact device

some years ago the solution you are asking about for greater speeds than 52mph for the gen two prius were resolved by ewert energy with the hybrid energy Manager or HEM.

essentially it plugged into the toyota harness behind the glovebox and would spin the combustion engine with very little fuel... this leveraged the top speed above 52mph to around 69mph.
I used this for phev conversions on the gen2. remember you need a capable pack.

nowdays I build prius rat rods... see youtube if you are curious.

now I am building a LEaf powered 1939 chris craft


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## dfgsd (Mar 6, 2017)

Huh, any luck? You can do it .Of course, the electric motor in the Toyota Prius is designed to help the main gasoline engine and to "jerk" in traffic jams, where a large average fuel consumption is formed. This is not to say that the Prius always runs on an electric motor at low speeds - the internal combustion engine is often turned on to recharge the main battery. After all, in addition to simply driving a 1.5-ton car, energy is spent on "daylight", music, navigation, stove fan operation ... Contrary to expectations, the internal combustion engine starts very accentuated, and not silently, as one might expect. Just as clearly audible and how it is muffled.


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## rmay635703 (Oct 23, 2008)

dfgsd said:


> For me, the best hybrid cars is the Lexus. This is a reliable, comfortable and high-quality machine that never fails. I recently bought an RX and I am very pleased. This is the best purchase of my life. Very nice car. It is comfortable to drive long distances, this car consumes a little fuel.


So you drive the 35mph Lexis HS?
Which is also the same body used for the Toyota Mirai?


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