New and looking to buy Z4 E89 20i or 28i

[Pbondar]

Thanks,

Celtic do three stages, which did you go for and does the stage three need additional mods (280bhp, but doesn't specify any additional modifications requirements).

Is this a safe level or should I go for the stage 2 241bhp, basically just mapping it to a 28i?

I see no benefit in opening up the box for anything but the stage 3 tune.

Don't know whether you are going for a manual or auto?

The Celtic torque figure stage 3 is within the ZF auto torque limits ( The 20i Evolve shown on their website is not)

The reality is you are not going to hold the engine at max throttle for but a few seconds based on UK road use.

So you can really treat it as an overboost in the real world anyway..

At 280BHP its within the thermodynamic limits of the engine, RPM limiter is still in effect..

So I would say go for the stage 3 tune..just bear in mind if you ran it unrestricted on a German autobahn at around 165-170 mph for several hours you MAY eventually have a problem!

Having said that the DME (ECU) has lots of self protection modes built in such as limiting power if oil /water gets too hot etc

[Msport]

Thanks,

Mine is the manual, is the torque over the limits for the manual box with the stage 3 tune?

Thanks,

Celtic do three stages, which did you go for and does the stage three need additional mods (280bhp, but doesn't specify any additional modifications requirements).

Is this a safe level or should I go for the stage 2 241bhp, basically just mapping it to a 28i?

I see no benefit in opening up the box for anything but the stage 3 tune.

Don't know whether you are going for a manual or auto?

The Celtic torque figure stage 3 is within the ZF auto torque limits ( The 20i Evolve shown on their website is not)

The reality is you are not going to hold the engine at max throttle for but a few seconds based on UK road use.

So you can really treat it as an overboost in the real world anyway..

At 280BHP its within the thermodynamic limits of the engine, RPM limiter is still in effect..

So I would say go for the stage 3 tune..just bear in mind if you ran it unrestricted on a German autobahn at around 165-170 mph for several hours you MAY eventually have a problem!

Having said that the DME (ECU) has lots of self protection modes built in such as limiting power if oil /water gets too hot etc

[Pbondar]

Thanks,

Mine is the manual, is the torque over the limits for the manual box with the stage 3 tune?

I don't know but doubt it..AFAIK the manual box is the same as used in the 30i 35i so doubt its an issue

Auto boxes are rather clever these days so they can be more problematic but again they self protect unless someone(Celtic or others) re-program them too!

You will just struggle to keep up with the speed it revs up compared to an auto box..

[warmasice]

You'll find that a well equipped 20i easier to find than a 28i. Then simply remap.. huge bhp increase and potentially way more torque if you find the right tuner. Go for it!

[Msport]

Got my new car, here she is next to my old car.. an E46 coupe. Both Sapphire Black

Will take more pictures when I valeted it properly over Easter..

[Msport]

My 20i is gettng tuned this week. Been doing a bit more research on the 20i vs 28i difference debate. Found a very interesting discussion here, its in Italian but used google translate. A tuner basically confirms what real OEM and yourself have always maintained, that even the pistons on the Z4 n20 engines are identical (but different on the 3 and 4 series) :
https://www.bmwpassion.com/forum/thread ... 253/page-4

[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]

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