How to identify what engine is in my Z3...

[djheadphoneskid]

Hello Everybody!

I just picked up a 2001 BMW Z3, that from the factory had the 2.5l engine. But supposedly, the person I bought it from had swapped in an M54B30 engine (had no paperwork...), and I was wondering how I could tell if it had the 2.5l engine or the 3.0l M54? I'd prefer not to have to tear anything apart to find out, if possible.

Thanks for any and all help!!!

[Terry F.]

How about a photo of the engine bay?

[328 Power 04]

The back of the head/block near firewall should have the VIN or identifier data on the engine. A bit hard to see with some of the harness holders in place.
Other signs can be a larger intake manifold and DISA valve, but if you have something to compare it to. Also if they actually put those items with engine (they should have).

Injectors on the 3.0 are purple, while the 2.5 ones are black. Those should have been changed too, it's not ideal to run the black ones on a 3.0.

[Mystikal]

Easiest way for me is looking at the MAF. 3" 2.5, 3.5" 3.0. A tape measure strewn across should answer your question quickly, even with an untrained eye.

[BimmerBreaker]

At BDC just fill up the cylinder with liquid and measure how much came out once you hit TDC and multiply by 6

Is that not the way everyone does it?

[328 Power 04]

Easiest way for me is looking at the MAF. 3" 2.5, 3.5" 3.0. A tape measure strewn across should answer your question quickly, even with an untrained eye.

If they bothered to put the m54b30 maf or other accessories... and then the tune mismatches; I've seen some weird configurations and owners claim 'it works perfect' except adaptations are at the limits and engine runs but is limping along.

[ProductUser]

At BDC just fill up the cylinder with liquid and measure how much came out once you hit TDC and multiply by 6

Is that not the way everyone does it?

I like the way you think

[LannVouivre]

If they bothered to put the m54b30 maf or other accessories... and then the tune mismatches; I've seen some weird configurations and owners claim 'it works perfect' except adaptations are at the limits and engine runs but is limping along.

How am I supposed to sleep tonight after reading this? Those poor engines!

[Mr Bingley]

Isn't the 3.0 block aluminum and the 2.5 iron? I would think a magnet will tell all.

[rf900rkw]

No, the only cast iron Z3 blocks have M badges.


I would remove a plug, and drop a long rod down to the piston. Turn the engine slowly by hand. Mark the lowest point. Mark the highest point. Measure the difference. 75mm is 2.5, `90mm is 3.0.

[JesterMX6]

does it feel like it has power? then its a 3.0

[LannVouivre]

If the injectors weren't swapped, it may lack power regardless. If the person came from something like a base corolla, basically anything else would feel powerful.

[gmushial]

In the VIN, digits 4-7 will tell you: CN33 = 2.5; CN53 = 3.0L ... though all the other suggest methods might be fun... ;-)

[rf900rkw]

But supposedly, the person I bought it from had swapped in an M54B30 engine (had no paperwork...

I have a tough time believing the PO would change the VIN to match his illicit engine swap.

[gmushial]

I have a tough time believing the PO would change the VIN to match his illicit engine swap.

I would too... will have to read more carefully in the future :-(

[rf900rkw]

It's not often I get to bust you.

[gmushial]

It's not often I get to bust you.

All's good amongst friends :-) good catch ...

likewise I would suggest measuring the stroke is the most reliable, fail-safe method.

[JesterMX6]

i was gonna give you the benefit of the doubt and assumed you meant the vin on the block lol

[LannVouivre]

I assumed he meant VIN on the block as well. Was wondering where the busting was and how getting where being able to clearly read the block marking would be easier than sticking things into the cylinders to measure.

I mean, anything on the rear of the head or block is going to be a PITA to look at. Still not as bad as a longitudinal ecoboost, thank God.

[Terry F.]

OP, still here?

[djheadphoneskid]

Yeah, still here.

Here's an image of the engine bay, sorry it's so big:

[z3forlife]

That's a 2.5 I do believe. Looks like my 99 2.3 did. If taken care of it's a great motor sold mine at 197000 miles and still ran like a top and didn't use/leak any oil. Very little service ever needed

[gmushial]

That looks a lot like my m52tub25... I guess the big change externally was from m52 to m52tub (single VANOS to dual VANOS)? .. but if that were a m54b30: how would it look different... anyone got a 3.0 pic they can post?

Of note: when I go to google and look for images of 3.0 Z3's... I can't see an obvious difference btwn them and the 2.5... are there give aways? Or is that the real meat of the thread, ie, casually, externally, they're difficult to get apart?

[328 Power 04]

They will look nearly identical from that angle.
A little bit more in depth investigation is needed.

[gmushial]

They will look nearly identical from that angle.
A little bit more in depth investigation is needed.

I think Randy's: measure the stroke is the most straightforward and sure-fire method... and it only takes a few minutes at most.