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I'm checking on internet to find what kind of valve seats the 320is has.

The head is in aluminum.

The fact is that i've found an article on a portuguese automotive magazine that reports unspecified 'problems' for the 320is, M3 using unleaded fuel.
i'd like to know if this problem is only knocking-related or wearing-tearing of the valve seats related.

i've always used unleaded without knocking problems, but can't obviously tell for tearing.

thanks

...only cast iron heads have the valves wearing problems, cause the unleaded fuel is aggressive for cast iron, and the valve seats are in cast iron too, not inserted.

The 320is has an aluminum head so the valve seats are inserted and should be made of stainless steel.

any comments?

Hello mr Fransesco.You use unleaded?With how many ron?The valve drivers if i remember well from mine is from copper and the seats from aluminium but im not sure for the second.Maybe it was from steinless but i will ask the man who fixed my car

unleaded RON (normal) is from 91 to 95, but i'm not worried about knocking cause i've never had it in my engine, and never heard its sound.

I was more worried about the chemical aggression of the unleaded fuel to the cast iron valve seats, that is not present only if you've got stainless steel seats (so the head must be in aluminum)

waiting for you mechanic answer and thank you.

So the ecu you post me was measured with unleaded?What you think about lpg?I work mine with premium gasoline.I didnt find my mecanik because he is ill.I will call tomorrow and i will let you know
Ciao

My mecanic told me that it is from stainles steel.

Hello,

I have used for a while 95, but then chenged to 98 or 100 Ron, and the engine runs bit more silent... as you know the 320is has a high compression ration so the higher the octane the better!
Regards
Frederico

you can run unleaded fuel without fear that your valve seats take damage. The M3 with catalytic converter has exactly the same cylidner head and valve seats and uses unleaded fuel ONLY.

most 320is will be run with 95 the last couple of years since 98 or higher RON octane has not been available in Italy since they took leaded fuels off the market. Only since shell started 100 octane V power you can get >95 octane petrol again.

The 320is has been developed for the use of 98 ron fuel, so running lower octane could give you problems regarding knocking/pinging/pre-ignition and whatever you want to call it.

By the way the valve seats are steel, not stainless steel: they can rust...

oh my god!