Controlling RPM - might be useful for long distance REXing

[tobiassej]

Once a week I do a trip from home to work 162 km (100 Mile). During cold winters here in Denmark thats the range of both battery and 9 liters petrol (high speed and 22C/72F). I can charge at work so this question is not a major problem to me.

I would prefer that I could somehow decrease the RPM (rounds pr minute) on long distances when I need the whole battery and whole gasoline tank.

It would make it more quiet - the REX engine makes some noise at 120-130 km/h (75-80 miles/h) - If I could start the engine once possible and have it working at lower RPM while the battery is also decreasing a bit at the same time. You can barely hear the engine when going 90-100 km/h (60-65 miles/h) probably due to lower RPM.

Is it somehow possible to do a hack and keep the RPM controlled lower. Both noise and fuel economy might even be better when the engine is working at lower RPM than maximum.

Best Tobias

 

[busaman]

it will be possible but where you would find it i have no idea it will be in the map of the DME but where god only knows there will be a torque request map vs battery depletion (only on hold soc) i think in some circumstances it might be more economical but BMW will have done their homework...

if anyone has an actual DME map i will have my tuners take a look

 

[jadnashuanh]

The load goes up radically as you speed increases, and if you want to try to maintain your SOC, the REx needs to run faster. Even then, it might not be able to keep up. Running it nearly continuously at a lower rpm would not be anywhere near as 'green' either as only running it as needed. Not the solution you're after, to keep it running slower, go slower!

 

[janner]

ReX operation:

• The ReX can be started and stopped manually at a SOC below 75% (except in the USA).

• At <6.5% SOC the ReX will be started automatically.

• Once started the ReX has a warm-up period (for the engine and catalytic converter) of about 6 minutes, depending on ambient temperature, when it runs at 2,200-2,400rpm (7kW) – this is the engine idle-speed. Stop/Start is inactive during the warm-up period.

• If SOC charge is <0.7% then the ReX runs at idle up to about 12mph (7kW) and then increases gradually to 4300rpm (23.3kW) at about 40mph.

• If SOC charge is <1.5% then the ReX runs at idle up to about 25mph and then increases gradually to 4300rpm at about 56mph.

• If SOC charge is <2.5% then the ReX runs at idle up to about 35mph and then increases gradually to 4300rpm at about 62mph.

• Between 1.9% and 3.5% stop/start will be deactivated.

• Below 1.9% power is restricted. Above this SOC the i3 behaves exactly the same whether on ReX or pure battery but has the capability to deliver an additional 21.6 kWHrs of energy from the 9 litres of petrol.

• Between 3.5% and 6.5% SOC the engine is stopped at speeds of less than 6mph. Above that it runs at idle between 6mph and 35mph when it increases gradually to 3600rpm (20kW) at 56mph and above.

• It is assumed that above SOC of 6.5% and below 75% SOC the ReX will operate at idle to 20mph, rising steadily to 3600rpm at 56mph delivering up to 20kW and will increase to 4,300rpm if additional power is necessary to hold the designated SOC. The ReX is a variable rpm machine; for Noise and Vibration N&V reasons it spends more time in specific operating rpm bands.

 

[psquare]

• It is assumed that above SOC of 6.5% and below 75% SOC the ReX will operate at idle to 20mph, rising steadily to 3600rpm at 56mph delivering up to 20kW and will increase to 4,300rpm if additional power is necessary to hold the designated SOC. The ReX is a variable rpm machine; for Noise and Vibration N&V reasons it spends more time in specific operating rpm bands.

I've noticed that mine goes off when dropping below 10 mph and >6.5% SOC. I use that when I'm in stop&go traffic, trying to maintain a steady speed of <10 mph, but obviously trying to drive safely.