i3 Technical Documents

[mids]

A set of documents containing a lot of technical information about the i3

http://www.bimmerfest.com/forums/showthread.php?t=...

[Fish]

You read some of that and think wow...how complicated modern vehicles are... Don't want that out of warranty!

[anonymous-user]

Electronically & Network complicated, but mechanically quite simple (well, the pure EV version anyway......)

[AER]

Wow - what a pointless engine choice for a range extender! A small-capacity twin-cam engine revving to 5000rpm with a crap bore-stroke ratio, four more valves than necessary and no balance advantages over a single.

Now I understand why the i3 has such a shockingly poor RE range.

edit - I see it doesn't even have an even firing configuration. Makes Pierburg's V-twin RE more sensible.

edit 2 - Oh look! It even has balance shafts to polish the turd a little more! What an amazingly shït engine

Edited by AER on Wednesday 6th August 01:57

Edited by AER on Wednesday 6th August 01:57

[JonnyVTEC]

I was looking at that engine document just to see how much the thing weighed, any ideas?

The Insight engine 1.0 is a spritley 56kg and negaes balancer shafts on the triple 3 by using the IMA motors to assist and regen. Suprised they couldn't do something similar on this. I guess its a crate engine though, the engine code prefix even says 'third party'.

Guess next gen could be a more specific Range Extender... or even a Toyota fuel cell now BMW a& Toyota are getting cosy.

[anonymous-user]

AER said:

Wow - what a pointless engine choice for a range extender! A small-capacity twin-cam engine revving to 5000rpm with a crap bore-stroke ratio, four more valves than necessary and no balance advantages over a single.

Now I understand why the i3 has such a shockingly poor RE range.

edit - I see it doesn't even have an even firing configuration. Makes Pierburg's V-twin RE more sensible.

edit 2 - Oh look! It even has balance shafts to polish the turd a little more! What an amazingly shït engine

You're not wrong!

BUT!

No way would the project have flown if BMW had either to of developed a "new" RE ICE, or brought an expensive one from someone else! I think they are being pretty smart actually. The point of the i3 is that it is an ELECTRIC car, not a hybrid. And, especially as batteries slowly improve, and owners overcome "range anxiety" and "learn" to use their cars as EVs, i think less and less people will buy/use the REX. So, spending millions on a superduper engine is not sensible (it's also a route taken by the Volt/Ampera, using an off-the-shelf ICE to keep costs down) and the money was much better spent on the EV stuff and the new architecture (CF bodyshell etc)

ETA: Of the 18 i3s listed in the PH owners wiki, there is an exact 50:50 split between REX and EV! Which considering how new and alien EVs are to current car owners just goes to show how things will go i think ;-)

Edited by anonymous-user on Wednesday 6th August 11:12

[AER]

Where did they get it from?

There's at least two better alternatives hanging about looking for customers. Was it a second-hand BMW motorcycle engine?

[JonnyVTEC]

It looks like the i3's range extender is a modified version of the 650cc Kymco engine used in the BMW C650 GT scooter.

Interestingly the air cleaner forms part of the intake duct and isnt considered as a servicable item!?

[amstrange1]

AER said:

edit - I see it doesn't even have an even firing configuration. Makes Pierburg's V-twin RE more sensible.

Mahle's Range Extender twin deliberately has an uneven firing order to deliver primary balance, and eliminate the need for balancer shafts. Clever control of the generator deals with the in-cycle speed fluctuations that result. There's an excerpt of a journal article about it here:
http://link.springer.com/article/10.1007%2Fs38313-...

There are plenty of technically more optimal solutions for a range-extender/APU than BMW have chosen, but I think they've gone down a sensible route using something proven; available and relatively cheap given it's based on something already in volume production. BOM cost is an issue for any xEV, so crippling the business case further with an expensive low-volume engine doesn't help.