MG4 Restricted speed - weird

[Tweed98]

Im going to illegally video myself driving mine the next time it decides to withhold power so people can see just how appalling the acceleration goes from 40% battery and how dangerous this is.
I also want proof for the MG dealer seeing as they CLAIM never to be able to repeat the same problem when they drive it

Try a cheap dash cam fixed inside so you don't have to remember to start the recording or mess about when your on the road.

 

[bowfer]

Try a cheap dash cam fixed inside so you don't have to remember to start the recording or mess about when your on the road.

It’s such a predictable fault in my car that I just used to take a passenger and drive a mile or two.

 

[robrymond]

I just collected mine and it capped out at 91mph.

 

[bowfer]

I just collected mine and it capped out at 91mph.

 

[Eber]

My MG-Guy called me today, telling me that there was some control unit update that might improve this behaviour. I'd also get the R16 update (I am on R13), which should improve iSmart App things.

Hemmerle?

 

[G48MG4]

No, Müller in the north of Munich

 

[stevegus]

Interesting, I presume it was a Trophy they were testing ? Maybe MG will loosen up the protection with sw updates once they become confident the system can take a little more 'abuse'.
Its possible that its mainly the motor / inverter they're being cautious with of course, that's the only coolant loop I've seen active on my car to date. The battery one has been dead other than when I activated battery heating out of interest.

I posted earlier in the thread the info on the motor from the manual.

The motor is not rated for 100% power. The constant power rating is about 60% of full whack.

This implies a car driven fast may eventually have an issue with motor overheating

 

[tsedge]

From the sounds of it there is an update out there that aims to fix at least some of this issue, be good to know if it has made any difference for anyone that has received it?

 

[Mars6394]

That's the first time I hear about a BMS update/fix for this. Can you find out whether it was just a reflash or an actual update?

I have the LFP, too, with the same problem on the Autobahn: 7 °C and sunny, after 120 km/h the car slooowly creeps to a maximum of ~144 km/h. It took 14 % SoC to drive about 14 km (37 % to 23 %).

PS: Hello friends, new MG4 Standard driver here.

Mine had 2 error codes I will dig out my paperwork tommorow.but my car was a total reflash of the BMS system not a update.dealer wouldn’t give me the paperwork for the actual fix they followed from mg but that’s what I was told a BMS flash not had the issue come back since I have done around 3000 miles since
When mine showed fault it was cold it battered my battery not throttle above 30mph battery went from 70% ish to 20% after doing around 4 miles

 

[Lucky5]

I posted earlier in the thread the info on the motor from the manual.

The motor is not rated for 100% power. The constant power rating is about 60% of full whack.

This implies a car driven fast may eventually have an issue with motor overheating

This is standard on all EVs, even Tesla have much lower continuous power rating versus what can be delivered for short bursts.

MG4 should still hit maximum speed at its continuous rating so I doubt if this explains the lack of top speed

 

[Ayoull]

This is standard on all EVs, even Tesla have much lower continuous power rating versus what can be delivered for short bursts.

MG4 should still hit maximum speed at its continuous rating so I doubt if this explains the lack of top speed

There's a difference between top speed on the flat vs top speed going up a hill, the motor is having to work significantly harder in the second scenario.

From the manual:

The electric drive transmission may become very hot in a high-temperature environment with frequent starting, frequent rapid acceleration and deceleration, long-term continuous steep climbing, and overload of the electric drive transmission. In order to prevent damage to the motor, the system will perform an overheating protection function, the warning message “EDU Coolant Overheating”displays. In this case, park your vehicle safely or, while keeping a lowload, continue to drive your vehicle at a constant speed to cool the motor. Only when the motor temperature has decreased, and the warning
message disappears, can the vehicle be driven normally.

I think the problem is either the car isn't reporting the warning correctly as bowfer appears to have it occur when on a hill accelerating, or the system is misreading the temperature and throttling back to its constant rating as a result.

 

[tsedge]

There's a difference between top speed on the flat vs top speed going up a hill, the motor is having to work significantly harder in the second scenario.

From the manual:

The electric drive transmission may become very hot in a high-temperature environment with frequent starting, frequent rapid acceleration and deceleration, long-term continuous steep climbing, and overload of the electric drive transmission. In order to prevent damage to the motor, the system will perform an overheating protection function, the warning message “EDU Coolant Overheating”displays. In this case, park your vehicle safely or, while keeping a lowload, continue to drive your vehicle at a constant speed to cool the motor. Only when the motor temperature has decreased, and the warning
message disappears, can the vehicle be driven normally.

I think the problem is either the car isn't reporting the warning correctly as bowfer appears to have it occur when on a hill accelerating, or the system is misreading the temperature and throttling back to its constant rating as a result.

Bowfer has reported it happens early in his short journeys so highly unlikely to be overheating. The strange restriction of the top speed points to a bug or the motor trying to limit rotation perhaps due to a sensor issue.

 

[Deleted member 10041]

I would say they is definitely an MG4 issue here, it's not just an EV thing.

The link I posted from the Top Gear Magazine kind of backs that up.
The three EVs in the group test were an id3, Megane and long range MG4, in their words they were "Pasting them down twisty roads for several miles"

The other 2 performed without issue and as stated the MG4 trimmed power and started showing thermal warnings.

This fault/issue certainly looks like an overheating issue but it could be all connected some way

 

[tsedge]

I would say they is definitely an MG4 issue here, it's not just an EV thing.

The link I posted from the Top Gear Magazine kind of backs that up.
The three EVs in the group test were an id3, Megane and long range MG4, in their words they were "Pasting them down twisty roads for several miles"

The other 2 performed without issue and as stated the MG4 trimmed power and started showing thermal warnings.

This fault/issue certainly looks like an overheating issue but it could be all connected some way

Yes, I am not saying it doesn't overheat, just that this doesn't seem to be bowfer's issue: limiting power is different from a hard stop on top speed.

 

[Lucky5]

Well the OPs car does it downhill so nowt to do with power limit slowing it uphill.

Continuous Power rating being lower than peak is an EV (motor) thing but it does not usually impact anyone day to day even if pushing on.

 

[Deleted member 10041]

Well the OPs car does it downhill so nowt to do with power limit slowing it uphill.

Continuous Power rating being lower than peak is an EV (motor) thing but it does not usually impact anyone day to day even if pushing on.

Exactly the point the article in the magazine made they said the trimming of power and thermal warnings was only normally something they have seen from EV's on heavy track testing in hot weather

 

[tsedge]

It is entirely possible that MG has a lower cooling capacity than the competition and that they've trimmed this to keep costs down on the basis that most people won't drive the car in a way that shows up an overheating problem.

The lower price has to come from somewhere, so this could be a real differentiator, although clearly not publicised! I am not saying (if true) that it is the right call and I can understand it being a deal breaker for enthusiastic drivers.

 

[Deleted member 10041]

It is entirely possible that MG has a lower cooling capacity than the competition and that they've trimmed this to keep costs down on the basis that most people won't drive the car in a way that shows up an overheating problem.

The lower price has to come from somewhere, so this could be a real differentiator, although clearly not publicised! I am not saying (if true) that it is the right call and I can understand it being a deal breaker for enthusiastic drivers.

Could be, as you say that doesn't sound like Bowfer's main issue but the two together could maybe manifest into it.

Most drivers potentially won't notice it, interesting it was a LR car in the test so motor issue rather than battery??

 

[tsedge]

Could be, as you say that doesn't sound like Bowfer's main issue but the two together could maybe manifest into it.

Most drivers potentially won't notice it, interesting it was a LR car in the test so motor issue rather than battery??

The battery and motors are different between SR and LR but may have the same overall design and manufacturer I suppose.

 

[Macadoodle]

There's a difference between top speed on the flat vs top speed going up a hill, the motor is having to work significantly harder in the second scenario.

From the manual:

The electric drive transmission may become very hot in a high-temperature environment with frequent starting, frequent rapid acceleration and deceleration, long-term continuous steep climbing, and overload of the electric drive transmission. In order to prevent damage to the motor, the system will perform an overheating protection function, the warning message “EDU Coolant Overheating”displays. In this case, park your vehicle safely or, while keeping a lowload, continue to drive your vehicle at a constant speed to cool the motor. Only when the motor temperature has decreased, and the warning
message disappears, can the vehicle be driven normally.

I think the problem is either the car isn't reporting the warning correctly as bowfer appears to have it occur when on a hill accelerating, or the system is misreading the temperature and throttling back to its constant rating as a result.

A frisky hill climb at 30% SOC is was the first time in 3 months that my SE throttled the power.
It came in quickly and disappeared quickly.
The motor will have an NTC sensor or whatever buried in the windings I would presume, something's reacting very quickly to thermal load for sure.
The fact that the dealer replaced bowfer's motor and he saw no difference would suggest it's the system's reading of the temp that's going wonky on some cars.