Premium Fuel?

[buickanddeere]

Just to conclude this thread.... I now have my i3 and carried out my own test of RON95 vs RON99 (Shell Vpower) and there was no detectable difference in range at all.....

Only way to really tell is to use instrumentation and measure the volts and amps from the Rx unit generator on tractor gas and premium.
I would assume the ICE is oversized so it operates at 85-90% of max rated when the generator is at full output?
Does anybody know what the generator end of the Rx unit consists of ? If I had to guess the engineers may have went with a flywheel AC 3 phase alternator and rectifier?
Would have been great to tap 120/240VAC from the Rx during utility outages to power the fridge and sump pump in the house.

 

[ultraturtle]

Would have been great to tap 120/240VAC from the Rx during utility outages to power the fridge and sump pump in the house.

Pretty easy to do, and a bunch of PiP owners are already doing it: http://www.converdant.biz/plug-out/

We just need to wait a bit for Converdant and other vendors to work out the tap points and interface.

 

[fdl1409]

That is not possible with a REx, as it does not work if the car is standing.

Frank
Germany
expecting i3 REx tomorrow ;-)))

 

[BrianStanier]

Isn't there a service mode for operating the Rex while stationary?

 

[ultraturtle]

That is not possible with a REx, as it does not work if the car is standing.

It really does not matter, but the REx will operate while the car is standing if needed to maintain the ~6% minimum charge state.

What folks may not understand about this system is that it is far more sophisticated and capable than a simple generator/inverter. It replaces a high-end battery backup, auto generator controlling system that typically costs over $20,000 for a system with a fraction of the battery capacity of the i3 (or any other plug-in for that matter). Go ahead and price out a SMA Sunny Island, Autoformer, batteries, enclosure, and a generator capable of being controlled by the system, and you'll begin to get a feel for what I am talking about.

In use, the system outperforms a simple gen-set for many reasons:

• - It runs silently most of the time. 18.8 kWh minus 6% of battery capacity is plenty of energy to power critical loads for many hours with the automobile engine off. When the automobile engine engages, it simultaneously charges the batteries and powers the loads, allowing it to operate at its most efficient while running (under significant load), then cycling off to power the loads from the battery pack.
  - It engages the engine only when the battery capacity has reduced to its trigger level of 6% capacity
  - It provides far greater surge capacity than a gen-set
  - It provides cleaner power than a gen-set
  - The automobile engine is quieter in operation than a gen-set
  - The automobile engine emits a fraction of the pollutants of a gen-set
  - The automobile engine - inverter system is roughly double the efficiency of a gen-set, i.e. twice as many kWh per gallon

 

[buickanddeere]

The inverters will be lighter, cheaper and simpler . When converting 370DC or what ever it is to 120/240VAC. No front end in the inverter require to chop 12,24 or 48VDC into pulsed DC and transform the voltage up.
Just a control board, over current protection, heat sinks and set of triacs.

 

[ecoangel]

Aero engines used in GA aircraft are mostly very low compression, unstressed large capacity piston designs that date back to the 1940s. Most of them run on 100LL. Generally however, engines have to be tuned to use a higher Octane in the fuel through ignition advance with higher compression engines. The extra octane is of no benefit if the engine is tuned for standard fuel. In anycase, the trouble with fuel additives is they tend to evaporate if you don't use them so I'd expect the i3 REX to be better with a standard UK UL fuel. Some Super UL fuels use Methanol to boost Octane ratings.

Ethanol has a higher octane rating than regular petrol but less energy per gallon/litre of fuel.

Article of E10 v UL here:

http://www.carsguide.com.au/news-and-re ... rison_test

The lower MPG from ethanol based fuels is another argument against potentially unsustainable biofuel models where corn is used more for fuel instead of food. Other biofuels can be produced from waste or in non monoculture agriculture where for example trees for bio diesel are grown in semi arid conditions or used to retain soil nutrients for food crops planted alongside.

Companies like Aldon Automotive make a superb Octane booster but it has to be collected in person - no postage allowed!

 

[user 1096]

As the use of the rex is limited, I don't think that there are any benefits for the i3.

I am waiting for the announcement from my electric supplier that they will supply premium current

Here in California the electricity providers have already found a way to play this game: you can pay extra if you want to get "clean" electricity (that has been generated through wind, soar, and thermal) instead of "dirty" electricity (generated from coal or gas burning).

I'm not sure how it is possible for them to send dirty and clean electricity out over the same wires and then separate them off at individual homes to those who are buying clean or dirty

LOL; Check with your Public Service/Utilities Commission--or maybe even CARB--I'm sure they have a reg for that.

 

[kevinb61]

Just to conclude this thread.... I now have my i3 and carried out my own test of RON95 vs RON99 (Shell Vpower) and there was no detectable difference in range at all.....

Unless the range extender was "knocking" (pre-ignition) with regular (the system would have to dial back a little timing), there would be no difference. As the energy potential between the two fuels are the same. Octane values only measure the ability of the fuel to resist pre-ignition.

 

[jadnashuanh]

Anything above the RON specified for any motor is pretty much a waste unless you can change it's programming (this is mostly true on turbo engines, where more octane can allow higher boost). Don't remember the minimum specified on the REx, but most BMW's call for a minimum of RON92. On the REx, it apparently can run at different speeds, depending on the load and other factors, so you might not notice any difference if your driving never caused it to try to use max RPM's allowed.

 

[RJBarry]

A friend of mine that owns a Volt says he fills it with premium fuel because he thinks it lasts longer sitting in the tank before it goes bad.

Any thoughts on that?

 

[i3Alan]

A friend of mine that owns a Volt says he fills it with premium fuel because he thinks it lasts longer sitting in the tank before it goes bad.

Any thoughts on that?

Didn't we all buy EVs because gas is bad? If it all starts out bad, how could one go bad sooner than another? :lol:

 

[kevinb61]

A friend of mine that owns a Volt says he fills it with premium fuel because he thinks it lasts longer sitting in the tank before it goes bad.

Any thoughts on that?

I don't believe anti-knock compounds (all the octane number is, is the ability for the fuel to resist pre-ignition) do anything for fuel longevity.

 

[Chrisn]

I think the answer is more complicated, and depends on BMW's ECU programing / tuning. First of all, octane ratings are fuzzy to begin with and the gas at the gas station probably exceeds the minimum test requirements. Secondly, the occurrence of knocking will depend on ambient temperature, elevation, humidity, etc. Thirdly, it will only knock under certain higher load scenarios. Fourthly, the car's sensitivity and reaction to knocking depends on the ECU programming and not any theoretical analysis.

In some cases, the car's strategy to deal with knocking will be to shift to a much less aggressive set of tuning parameters that will reduce maximum output significantly (perhaps 5-10%) to give it a wide margin of safety.

The above is based on my experience tuning high-performance cars and not REX-specific.

Given the small size of tank, I think buying premium fuel is cheap insurance, although I agree that is probably won't matter.

 

[kevinb61]

I think the answer is more complicated, and depends on BMW's ECU programing / tuning. First of all, octane ratings are fuzzy to begin with and the gas at the gas station probably exceeds the minimum test requirements. Secondly, the occurrence of knocking will depend on ambient temperature, elevation, humidity, etc. Thirdly, it will only knock under certain higher load scenarios. Fourthly, the car's sensitivity and reaction to knocking depends on the ECU programming and not any theoretical analysis.

In some cases, the car's strategy to deal with knocking will be to shift to a much less aggressive set of tuning parameters that will reduce maximum output significantly (perhaps 5-10%) to give it a wide margin of safety.

The above is based on my experience tuning high-performance cars and not REX-specific.

Given the small size of tank, I think buying premium fuel is cheap insurance, although I agree that is probably won't matter.

I see in the manual that recommended is 91 (premium), and minimum is 89. In that case, you may get some benefit (depending how aggressive they have to de-tune (mixture/timing for regular) for the premium gas. I have a BEV so I hadn't looked, but recommended being Premium, that's all I would probably run.

 

[jadnashuanh]

Most modern vehicle gasoline motors have knock sensors...so that you can use all of the available power (should you need it), you should run the preferred octane (more is a waste unless you can change the programming). Unlike a normal ICE where you control the throttle and thus determine the load on the engine, the computer is trying to provide enough generator output to keep you going, and you only have indirect control...for it to do its job, it needs the right fuel to do its best.

The vehicle programming will turn it on, even it if doesn't need to power the vehicle, mostly to lubricate the internal components, and possible to help drive off any moisture that may have accumulated. If your normal usage never actually used the REx as part of your needed range, you might want to talk to BMW about maybe using a little gasoline stabilizer like you might use in your lawn mower or garden tractor if you were not going to run it dry over the winter.

 

[ultraturtle]

A friend of mine that owns a Volt says he fills it with premium fuel because he thinks it lasts longer sitting in the tank before it goes bad.

Any thoughts on that?

Ironically, he may be getting the opposite result. One of the cheapest ways to boost octane without specific anti-knock additives is simply to increase the percentage of alcohol. That high ethanol percentage mix goes bad quickly - E10 (10% mix) goes bad in only 3 months!

 

[ecoangel]

Absolutely right about not using over or under octane fuel cf recommended.

Good info here about shelf life of petrol:

http://www.autocar.co.uk/forum/any-other-business/petrol-shelf-life