[420i vs 428i: what mechanical differences?
Sorry for the delay guys.
I put my 2 cents on the subject.
We have already had a good experience in Italy on these engines, even before we did in Germany and then we collaborate with several German and northern European colleagues with whom we can exchange useful information and some info we can have it every now and also from BMW DE.
Based on all this we came to the conclusion that for the Z4 the 20i and 28i engines are 100% identical, only the electronic limitation in the ECU of the 20i changes, so the two engines reach the same powers once mapped.
Instead on series 3 and 4 (if nothing else those that have passed under our hands and those of our colleagues, and they are not few) there are these differences in the pistons that you have already detected and there are also some differences also in software.
So for the Z4 you load the map of the 28th and then you map further, while for series 3 and 4, after checking the original software and compared with that of the 28th of the same software revision, if it differs as in these cases we found , the map is modified on the basis of the data of the 28th, removing the electronic limitations but not copying it entirely, and then further mapping.
Based on all this, the 20i series 3 and 4 mapped reach slightly lower power levels than those of the 28th mapped.
On the Z4, on the other hand, the results obtained are the same.
On your last argument I confirm that one of the methods often used to limit the powers in the control unit is to act on the% of the butterfly opening, a method used for example on the Mini .
And I confirm that by now they are becoming more and more identical engines with different power levels thanks to electronics, like for example also in Audi./quote]
Smartbear said:
Msport said:
Thanks Smartbear, I have read alot of your posts on this subject and that was what initially made me decide to look for a 20i instead of the 28i.
One thing I have wondered though, iif the UK Z4's are all the same, why do nearly all UK tuners map the 28i to more power than the 20i?
Have you also upgraded the brakes on your 20i to the Z4, and would that involve just larger discs and calipers? If so the extra £2k-£3k and less choice for the 28i make the 20i the better buy for me..
No one has satisfactorily explained why the 28i can make more power :?
My 20i stops better than my 3.0si ever did so I’ve not felt the need to upgrade the brakes, it’s possible but i think you need the caliper brackets & maybe the hubs as well?
Rob
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