Loss of power due to empty battery / uphill driving / acceleration / overtaking

[firewall76]

hello, my father purchased a MG ZS+ in February 2025. He got some problems: Loss of power due to empty battery. He went to the car seller, but he was told everything is ok and no update is required. Some flash drives don't work correctly (the songs stop, the system crash and reboot),other have no problems. Sometimes the steering wheel, just after star the engine , moves: my father was told it's depending on the wheels if parked straight no movement otherwise the car tries to make the wheels stay. But it is not like this. Someone could help me? Thank you

 

[Corvo]

Hi, I also have an MG ZS Hybrid+ that I bought a month ago. The power loss problem when going uphill is likely due to the HCU and ECU software not being updated, which was released in March 2025. Since your father's car was purchased in February, I assume it hasn't been done. However, it's easy to check even without going to the shop. Set the "energy flow" display and keep it there. If the battery never drops below two bars, it means you already have the latest update. Otherwise, go to the shop. Since you're from Pesaro, I recommend Arauto in Villa Fastiggi. I've had good experiences with them. As for the car in motion, when you put the gearshift in Drive, press the brake and release it and you'll see that the car won't move anymore. It will remain stationary until you press the accelerator pedal. Don't worry, it never does this uphill or downhill, at least mine. If yours behaves differently, go to the shop. Hello and happy driving.

 

[Emanuel]

Regarding this very “issue” (which is actually quite common in all hybrid cars, not just MG), I’ve been following an interesting YouTube channel (unfortunately for you, only in Italian) called “Pedalsprint.” It’s an Italian company that designs and sells a control unit that plugs into the accelerator pedal connector and remaps the signal sent to the ECU. It’s a very simple operation.

It can be activated/deactivated and adjusted as desired in the following modes: Eco2, Eco, Comfort, Sport, and Race. Many reviews speak positively about it, saying that it almost completely solves the issue of high engine revs during long uphill drives and provides a much more responsive throttle (even in Comfort mode).

Moreover, according to them, it should not void the warranty, since it does not directly modify the ECU (the engine control unit).

Here are the links:

 

[Emanuel]

I’m not completely convinced yet, but I’m continuing to follow reviews for more examples before buying it and testing it myself.

 

[Emanuel]

Many mention that the engine revs, which previously went well beyond 4000, now reach a maximum of around 3500. In addition, some show that the battery can even charge while going uphill, which I have never seen happen.

 

[Corvo]

Many mention that the engine revs, which previously went well beyond 4000, now reach a maximum of around 3500. In addition, some show that the battery can even charge while going uphill, which I have never seen happen.

Yes, I'm familiar with Pedal Sprint, and I've seen a lot of videos about it. It's simple to use; it improves the sensitivity of the accelerator pedal, but although I haven't tried it, I doubt it actually reduces engine rpm. RPM is reduced if we modulate the car's acceleration better with our feet, and it definitely helps. For now, however, I have no intention of using it.

 

[Emanuel]

I think we’re basically on the same page. Pedal Sprint (or similar throttle controllers) only changes the accelerator pedal response curve, it doesn’t actually modify the engine mapping, gearbox logic, or hybrid management of the mg zs hybrid.
So if some people are seeing lower RPMs (e.g. max ~3500 instead of 4000+), it’s likely because the more responsive pedal makes it easier to modulate acceleration, rather than the system itself reducing engine speed.
As for the battery charging uphill, that’s more related to how the hybrid system decides to manage power between the engine and electric motor. In certain conditions (light throttle, steady load), it can happen, but Pedal Sprint shouldn’t directly influence that logic.
So in my opinion, any differences people notice are probably indirect, due to driving style changes rather than actual changes in how the car operates.

 

[mick78]

I did come across the videos of Pedal Sprint as well, but I agree, it really mostly seems to (and really, looking at the installation diagram, its basically a box going in-between the pedal connector and thus can't more than) mostly play around with the pedal input signal; And it makes sense. To a degree, I know that you learn to modulate the pedal resp. you can with slight variations force the engine to lower RPM to a degree, and I assume this pretty much does that; The question is how it gets the signals for RPM and battery load (after all, you don't want to overcorrect PD052 and run out of battery). But the fundamentals of the MG's system remain the same.

An ECU remap of the engine (or the classic "chip"), apart from being way less effective in a NA engine compared to a turbo, would probably send the whole Hybrid into limp mode as the power curve of the ICE input would suddenly be different (I remember a Toyota technician once telling me how complex it would be to get more power out of a Toyota Hybrid system, saying a more powerful petrol would either use less Power in % of the ICE in the planetary gearbox, or produce limp mode, as there the real power figure is combined and controlled not though the ICE engine); And whilst in theory probably on the top speed end of the 3rd gear, where electric assist is limited or barely there (I think the 3 speeds are really more serial- parallel - petrol than classic gears), its again down to so many components (ECU, gear box controller, battery management, combined Hybrid control unit) that I doubt that you could really modify and improve the actual hybrid system "by some boys in a shed". We can already see by the number of updates that MG has thrown out since release that it is a complex task.

So if the Pedal Sprint box really makes the pedal much more sensitive and thus easier to modulate, I guess the 220ish EUR is quite cheap for anyone to try. I however have doubts (and honestly, in the videos the car behaves pretty much like mine does in the same situation), so I'll definitely wait if some people actually buy and report back before I spend any money.....

 

[mick78]

Many mention that the engine revs, which previously went well beyond 4000, now reach a maximum of around 3500. In addition, some show that the battery can even charge while going uphill, which I have never seen happen.

It can charge uphill, but that happens with high RPM; This is the main reason why people complain after PD052, before that the car would mostly use the battery assist and low RPM uphill, which seemed more relaxed (note how very few early reviews mentioned the higher RPM), but at the cost of eventually getting to a very low battery load and running out of power (or relying, depending on speed, either the 40kw the generator can provide below 50ish km/h or the 70ish kw of the petrol engine above that where the ICE engine can directly drive the wheels, both a significant downgrade from the claimed combined figure). Now, charging starts almost instantly as an incline is detected, again leading to higher RPM, especailly in serial mode.