Any modificaiton to exceed 33/34 MPH EV limit?

Even in neutral? I do not know about you, but I've been able to go over 55mph downhill without the engine starting while in neutral. That said, I know of no other way to prevent the car starting the engine at speeds above 41mph in any of the other gears. (I don't use ev mode).

 

Ewert Energy Systems (ewertenergy.com) has the Hybrid Energy Manager (HEM) which is a modification that allows EV up to 70 MPH.

It's currently only available with the Plugin Conversions (PICC, Plug-In Home) system though. It can also operate in a "mixed" mode where it uses the full range of the electric motor and then uses the gasoline engine to provide whatever additional throttle is needed (probably the more practical mode for higher speed driving).

It's pretty nifty--but hey, people say I'm biased because I have it in my car .

I don't think you would see much benefit with an Enginer system anyway since the car draws a lot of power at higher speeds in EV mode due to increased wind resistance and tire resistance--it really needs the much more powerful battery of the total battery replacement conversion PICC system.

EDIT: There is a /hack/ that allow you to do "EV" up to 52 MPH--however that hack has numerous problems and associated risks with it. See my many other posts for more details (or PM me) and my rants.

Andrew

 

.....and having to stop the car in the middle of the road, shut it of and restart it in order to restore it's normal drivable operation.

 

yeah, I was including that as one of the major drawbacks to the 52 MPH hack...it's scary not having power (gasoline engine) when you need it. The hack basically convinces the Prius that the engine is broken and so it won't use it until you restart the car, regardless of how hard you press the pedal (thus if your battery is low you may not have any power at all).

The HEM in my car allows seamless transition between high speed EV mode and regular gasoline engine mode without setting any DTC codes or having to restart your car to get ICE power back (or any other sort of ritual-esk behavior)--but I'm getting ahead of myself =).

No, unless you're looking to upgrade your system to a more powerful system ($$$) then I think you're more or less stuck with the 34 MPH limit of EV mode for now.

Andrew

 

The HEM upgrade is now bundled with the PICC conversion kit at no additional cost--I think they were originally planning to sell it as an optional feature but found it so effective that they included it as part of the base system.

Anyway, if you just want EV for going down hill I suggest getting good at letting the car drop to ordinary stealth mode by backing off the pedal once the gasoline engine is warmed up (you may want a scangauge or equivalent to assist in that). If the Enginer system is charging the battery enough it should drop to stealth pretty easily when going down hill on its own...

Andrew

 

I have a Hymotion system. If I am in EV mode when I start going down a hill, all I have to do is shift into neutral BEFORE EXCEEDING 32 MPH and my engine will stay off. That's with a completely cold engine. Once I exceed 32, I won't be in EV mode anymore, but the car will go back into EV mode when I slow down below 30 or so.

One note: It is best to come to a complete stop before shifting back into Drive.

Another thing to keep in mind: If the state of charge of your regular Prius drive battery is too high or too low, that could cause the engine to come on when you leave EV mode.

Arthur

 

Do you still have your ewert sytem?

Posted via the PriusChat mobile app.

 

Shielding a byte of data transmitted by the HV controller (engine start command) allows unlimited electric power, but due to the maximum speed limit of the mg1, you can't accelerate indefinitely, because that may cause the MG1 to overspeed.

In addition, you need a larger battery, because the driving current is also very large.

 

What do you mean unlimited electrical power?
If you would do that with original battery you have only 40hp or so I believe?

 

The limit with the original battery is about that; it is about 30 amps maximum regen also. I have a WiFi OBD-II meter and have a phone that shows the horsepower (both charging and 'output'), HV current, engine RPM, and many other things (including voltage, SoC, delta). Basically, I can choose what I want to display, and I have got my mileage down from 4.4liters/100km to 3.5l/100km simply by having this realtime data available (still not 'the best' MPG that people have got, but I have high mileage, failure of the emissions system, a worn battery, and loads of failures across the car - I monitor it closely, but it is now a car that 'only I can drive', because constant vigilance is required, in case something fails, to prevent total destruction of the car. It is not as bad as my old 3 cylinder Bluebird non-turbo with a crack in one cylinder, which would pressurise the coolant, force it out of the expansion tank, and would have overheated and seized in minutes if not monitored. I drove it for a year like that. I still have that car

Anyway, the EV speed limit is deeply embedded in the code of one of the ECUs, as far as I am aware. I don't know of any really good ways to modify it. Yet. (However as a hobby I am developing a flexible V850 emulator, and plan to modify, eventually, all the ECUs). This could include fast EV mode among other things. I have a spare Nissan Leaf ECU that I am analysing, and plan to, at some stage, get a worn out Leaf battery, and replace the NiMH battery with it. I will confess that this is a grandiose idea as it requires reverse engineering Toyota and Nissan ECUs to a level that hasn't yet been done. But it is worth a try, especially as the charge current for the Leaf battery is higher than the max regen braking of the Prius, and the discharge current of the Leaf battery is about 100HP, so a modified Leaf battery (repackaged with fewer cells, likely using the Leaf BMS unit connected to the CAN bus and talking to the other Prius ECUs) would make the ultimate Prius PHEV.

In terms of driving current, I can say that about 11-12 horsepower is good for maintaining about 90km/h on the highway (100km/h speed limit, and not holding people up of course). This is the engine HP at that speed, and the HSD is actually a bit wasteful because it basically generates electricity from the engine and then sends it to the motor to drive the wheels. So, with a sufficiently powerful battery, 40HP would be plenty for maintaining any speed, with the ICE as a backup for acceleration and going uphill and so forth. The downside would be that the MG1 and MG2 would probably slowly overheat if used too much (in fact the early Prius test models tended to have catastrophic failures - of the inverter - because they focused on using the electric mode to the max, and the engine only when the electric mode was fully loaded - they fixed this with a better inverter and by using the electric components to assist the ICE).

Regarding the EV speed limit, my car has a max of 45km/h. Which is about 27mph or something. Town speed limits are 50km/h which is kind of annoying. To keep the engine off above 45km/h, going downhill, you put the car in EV mode, put it in neutral, and it coasts above 45km/h. It then keeps rolling / speeding up. The EV mode deactivates but the fact the car is in neutral means the engine 'cannot' start. This could be beneficial if there is long gentle down-hill run. However, if you need to apply the brakes a lot, you are wasting energy that could have gone into re-gen braking, so it depends on the particular commute. I have two commutes to work, and one is very nice, with the initial section allowing engine-off for about 4km, and a 'full' battery at the end, followed by a flat section to allow pulse and glide between 48 and 53km/h (so that nobody knows I am doing ti!). The other commute has a steep down-hill section. I have been known to go downhill at 25km/h, since that maxes out the regen, and any faster wastes energy on the friction brakes.

In my case, I have a steep driveway to drive up, so that if I have a 60% SOC, I end up with 50% no matter what I do. I reverse the car from my garage and line it up, start the engine, wait 5 seconds, then drive up, let the engine warm up, drop the SOC to 45%, then begin the long coast, engine up with 70-75% SoC and no use of engine over the next 4km.

In the Gen 2 Prius, one of the motors will over-speed if you go above 67 km/h with the engine not turning (which is why the engine spins above that speed, even if there is no fuel going into the engine). My personal limit is 75km/h, and up to 82km/h for very brief periods. I do this by going into neutral if coasting downhill at 65km/h, so that the car speeds up, then slows down going back uphill (I live in NZ hence the terrain is quite hilly with a combination of long up and downhill grades, as well as short sections of steep up and downhill sections).

It should be noted that, if going above 67km/h, and going into neutral at 65km/h to avoid engine braking, it is only worth doing this if you know you will slow back down to 67km/h soon. If you need to use your brakes at all when in neutral above 67km/h, it is better to be in 'drive', since the engine braking only uses about 2-3 horsepower, but regen is a lot more than that.

It is unlikely to happen, as I am not a genius by any means, but I would love to be able to modify the ECU code on the Gen 2 (and other) Prius. Having a high-speed EV mode, as well as having a way to prevent the prolonged engine warm-up cycle (and the annoying stage-3 cycle where the engine keeps running in town until you pull over and stop for a few seconds) would be good. I will keep this Prius long-term, and hope to eventually have a Leaf Battery, but also to have a 'standard' version of the 1.5 engine (Otto cycle), probably turbocharged, and a high-speed EV mode, and a warm-up cycle aimed at better fuel economy.. A high-compression turbo would mean the engine would be efficient, but would be more wasteful when the turbo is on boost (as the mixture would need to be richer). But it would be fun to leave even more cars at the lights, while being able to hypermile. All of this would be very illegal in California of course... However, environmentalists might argue that slightly higher NOx emissions could be a good trade-off for majorly reduced CO2 emissions. Maybe.

 

Edit - 29.9 HP is max regen, so about 100 Amps; will test max current draw up the hill after work!

 

The EV speed limit is a function of the variable gear ratio of the power split device. At 34MPH your MG1 motor is spinning very close to its redline RPM. If the engine starts turning, the ratio changes and MG1 can slow down a bit while the wheels go faster.

If you aren't going to cut a new set of planetary gears with a different ratio, the only other hack is to use larger wheels and tires. The speedo will read wrong, but the limit will go up.

 

I've just realised we are talking of two related but slightly different things; on my car, at 41mph, the engine spins up (even with no fuel), and runs at about 960rpm, to protect MG1. However, the actual EV mode button disengages at 28mph on my car; if the EV mode could be hacked to run faster (subject to, for example, certain power limits to prevent battery drain), it could allow the warm-up cycle of the engine to be done at a time more suited to good fuel economy. My commute doesn't actually need this mod, but what is annoying is when the engine stays running, wasting fuel for 'nothing', while driving downhill at 30mph; the EV mode button, if it was limited to say 31mph on my car, could let me shut down the engine down the hill and continue the warm up later!

 

Fair enough- and I think I have confused it further; apologies.

I shouldn't post so late at night!

I know the gear ratio changed with different generations. In the earlier ones it was quite close to the electrical speed limit. I guess they never upped that limit to follow the new gear ratio.

We tried the EV button in our car once to make sure it worked, but haven't otherwise found a use for it.

You've got me curious- how long is this hill? I would think that it would be fine to warm up the engine going downhill, since it would take quite a few minutes for the fuel-to-heat investment to be lost and wasted. If the downslope is less than 20 miles I probably wouldn't worry about it.

Back to the hack though- I've seen a post floating around this board where somebody very cleverly installed some carefully measured bits of wire as deliberate current leaks across the shunts on the inverter. This way there is always somewhat more power going to the motor than the computer thinks there is- it spoofs the controller. I don't know if there is an explicit speed-triggered cutout from the ECU, but that would be the next bit to tackle.