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

[Msport]

Hi,

I'm new around here. Signed up as I am selling my BMW E46 and buying a E89 Z4.

I am attracted to the N20 engine, whether that be in 18i, 20i or 28i form.

I have read alot about this engine, including many, many posts on here. Alot of the posts say that the engines are identical apart from mapping. But the engine is also used in the 2 series, 3 series and 4 series and alot of information I have read suggests the pistons and compression ratios are different between the 20i and 28i, hence why the 28i can be mapped to higher power.

I want 28i power, but they are alot more than the 20i and there are about ten times as many 18i or 20i on the market, and given the engines are supposedly identical I have been toying with the idea of buying a 18i or 20i and mapping it to 28i power.. but will the engine really handle this well, despite what real oem says alot of posts suggest the pistons are different including this (which is about the 3 series but same engine):

https://www.bimmerfest.com/forums/showthread.php?t=670647

 

[Smartbear]

Hi,

I'm new around here. Signed up as I am selling my BMW E46 and buying a E89 Z4.

I am attracted to the N20 engine, whether that be in 18i, 20i or 28i form.

I have read alot about this engine, including many, many posts on here. Alot of the posts say that the engines are identical apart from mapping. But the engine is also used in the 2 series, 3 series and 4 series and alot of information I have read suggests the pistons and compression ratios are different between the 20i and 28i, hence why the 28i can be mapped to higher power.

I want 28i power, but they are alot more than the 20i and there are about ten times as many 18i or 20i on the market, and given the engines are supposedly identical I have been toying with the idea of buying a 18i or 20i and mapping it to 28i power.. but will the engine really handle this well, despite what real oem says alot of posts suggest the pistons are different including this (which is about the 3 series but same engine):

https://www.bimmerfest.com/forums/showthread.php?t=670647

Hi, that’s a primarily American site & their cars may be different to uk versions, all uk e89 z4’s with the n20 engine are the same & all run a 10:1 compression ratio with the same turbo/intercooler etc etc
Rob

 

[Msport]

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, if 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 28i, 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..

Hi, that’s a primarily American site & their cars may be different to uk versions, all uk e89 z4’s with the n20 engine are the same & all run a 10:1 compression ratio with the same turbo/intercooler etc etc
Rob

 

[Smartbear]

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..

Hi, that’s a primarily American site & their cars may be different to uk versions, all uk e89 z4’s with the n20 engine are the same & all run a 10:1 compression ratio with the same turbo/intercooler etc etc
Rob

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

 

[Anonymous]

[/quote]

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
[/quote]

Simplification and generalisation warning!

For those tuners who used their own software AND were doing re-map then it makes no difference which N20 engine you use.

For those 'hacking' a frig on the existing DME AND all those doing an add on box then it does matter what the starting point was.

I fitted 28i front discs to mine, its a caliper and caliper brackets change..

The brakes are more powerful but it wasn't that the 20i was underbraked..

 

[Smartbear]

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
[/quote]

Simplification and generalisation warning!

For those tuners who used their own software AND were doing re-map then it makes no difference which N20 engine you use.

For those 'hacking' a frig on the existing DME AND all those doing an add on box then it does matter what the starting point was.

I fitted 28i front discs to mine, its a caliper and caliper brackets change..

The brakes are more powerful but it wasn't that the 20i was underbraked..
[/quote]

Yep, that’s what i meant to say
Rob

 

[buzyg]

Welcome to the forum OP.

 

[Mr Tidy]

Yes, Hi and welcome OP - good luck with your search.

And don't forget the photos once you've got one!

 

[Msport]

Thanks guys,

I am picking up a black 2012 Z4 20i on Saturday, I will post pictures then

Which remap company comes most recommended? I want something that will unlock the power of the engine whilst maintaining its reliability, it 260bhp really within reliable parameters?

From what I've read evolve and Celtic tuning are my top choices, is one better than the other? Celtic tuning are cheaper and nearer but I would travel to evolve if it's better? I could even get it remapped on the way back from picking it up

 

[Jim S]

Not so long ago, when the E89 was new, how on earth was BMW able to justify the huge extra cost for the 28i over the 20i ???

 

[Smartbear]

Thanks guys,

I am picking up a black 2012 Z4 20i on Saturday, I will post pictures then

Which remap company comes most recommended? I want something that will unlock the power of the engine whilst maintaining its reliability, it 260bhp really within reliable parameters?

From what I've read evolve and Celtic tuning are my top choices, is one better than the other? Celtic tuning are cheaper and nearer but I would travel to evolve if it's better? I could even get it remapped on the way back from picking it up

Considering the 28i makes around 245bhp with reliability and has the same engine as the 18i/20i, mapping them to 260/280bhp isn’t going to push it over the edge
Rob

 

[Smartbear]

Thanks guys,

I am picking up a black 2012 Z4 20i on Saturday, I will post pictures then

Which remap company comes most recommended? I want something that will unlock the power of the engine whilst maintaining its reliability, it 260bhp really within reliable parameters?

From what I've read evolve and Celtic tuning are my top choices, is one better than the other? Celtic tuning are cheaper and nearer but I would travel to evolve if it's better? I could even get it remapped on the way back from picking it up

You’re not going to go wrong with either of those, just avoid the backstreet tuners that no one’s heard of!
Rob

 

[Anonymous]

Thanks guys,

I am picking up a black 2012 Z4 20i on Saturday, I will post pictures then

Which remap company comes most recommended? I want something that will unlock the power of the engine whilst maintaining its reliability, it 260bhp really within reliable parameters?

From what I've read evolve and Celtic tuning are my top choices, is one better than the other? Celtic tuning are cheaper and nearer but I would travel to evolve if it's better? I could even get it remapped on the way back from picking it up

Well on the balance of issues..

I would go for Celtic...

Cheaper

Token warranties...but Evolve explicitly avoid any commitment to warranties...

The Evolve graphs look slightly strange which I’m not quite sure how you explain the torque bump on the 20i version..strangely the 18i version looks more normal...and in line with others...

Of course I’m biased but I have had a fault free positive experience on 3 cars through 3 different dealers..

 

[Msport]

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?

Thanks guys,

I am picking up a black 2012 Z4 20i on Saturday, I will post pictures then

Which remap company comes most recommended? I want something that will unlock the power of the engine whilst maintaining its reliability, it 260bhp really within reliable parameters?

From what I've read evolve and Celtic tuning are my top choices, is one better than the other? Celtic tuning are cheaper and nearer but I would travel to evolve if it's better? I could even get it remapped on the way back from picking it up

Well on the balance of issues..

I would go for Celtic...

Cheaper

Token warranties...but Evolve explicitly avoid any commitment to warranties...

The Evolve graphs look slightly strange which I’m not quite sure how you explain the torque bump on the 20i version..strangely the 18i version looks more normal...and in line with others...

Of course I’m biased but I have had a fault free positive experience on 3 cars through 3 different dealers..

 

[Msport]

Thanks,

Sorry missed this post when posting on my mobile earlier! I take it you'd go for the stage 3 tune if I went with Celtic then, 280bhp instead of 241bhp from the stage 2? Stage 1 seems pointless at 215bhp

Thanks guys,

I am picking up a black 2012 Z4 20i on Saturday, I will post pictures then

Which remap company comes most recommended? I want something that will unlock the power of the engine whilst maintaining its reliability, it 260bhp really within reliable parameters?

From what I've read evolve and Celtic tuning are my top choices, is one better than the other? Celtic tuning are cheaper and nearer but I would travel to evolve if it's better? I could even get it remapped on the way back from picking it up

Considering the 28i makes around 245bhp with reliability and has the same engine as the 18i/20i, mapping them to 260/280bhp isn’t going to push it over the edge
Rob

 

[Anonymous]

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

 

[Anonymous]

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..