Compression Ratio Differences between Cat and Non-Cat Engines??

[Lemon98]

Hi all,

I have read online from specification websites that the M20B20 came in a variety of different compression ratios and that for the later model cars, there is quite a large difference between those that were specced with a catalyst from factory and those that were optioned with the catalyst deleted.

Does anyone know anything about this or can advise on where the engine number is located on the block so that I can find mine and try and confirm which compression ratio my engine is?

Thanks in advance

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References: https://www.engine-specs.net/bmw/m20b20.html it states three different ratios: 9.2, 9.9 and 8.8:1

[BenHar]

https://www.e30zone.net/e30wiki/index.php?title=Engines

Ben

[Lemon98]

https://www.e30zone.net/e30wiki/index.php?title=Engines

Ben

Yeah cheers Ben, unfortunately that doesn't mention anything about compression ratios and I have checked the wiki pages before.

Will

[flybynite]

Hi all,
I have read online from specification websites that the M20B20 came in a variety of different compression ratios and that for the later model cars, there is quite a large difference between those that were specced with a catalyst from factory and those that were optioned with the catalyst deleted.
Does anyone know anything about this or can advise on where the engine number is located on the block so that I can find mine and try and confirm which compression ratio my engine is?
References: https://www.engine-specs.net/bmw/m20b20.html it states three different ratios: 9.2, 9.9 and 8.8:1

Try here:
https://www.e30zone.net/e30wiki/index.php?title=Engines
Click the link " find the number on the engine itself."
List of engine codes, you can use them to x reference pistons on realoem.

The list you linked to is for e21 as well. FWIW the only compression ratio for the e30 320i I have listed is 9.8 (9.2 for E21 UK) and there are not many piston variations listed for the 1990 320 although there is a "low compression" piston listed which I would assume is the 8.8 one.

[BenHar]

https://www.e30zone.net/e30wiki/index.php?title=Engines

Ben

Yeah cheers Ben, unfortunately that doesn't mention anything about compression ratios and I have checked the wiki pages before.

Will

It has a link to where to find the engine number.

Ben