While in the process of replacing the gas cap on my '92 318 vert, I noticed that there are both vented and unvented gas caps available. I know the difference between the two, but was curious about which is required for a stock E30 with M42 engine. I had always assumed that vented was preferred until I discovered all the unvented versions available. Ideas?
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Pretty sure you should select non-vented.
Pressurized vapors are supposed to be vented through the expansion tank in your right rear fender, then collected in the evaporative emissions (charcoal) canister under the hood. From there, they are pulled into the throttle body through the evaporative canister purge valve.
A vented cap would defeat this.Jon (OO=[][]=OO)
1992 325ic white, stock with a 5-speed swap
Palm Beach County -
Other parts of the world had less restrictive emissions when the e30 was made. They had the vented caps. We got the expansion tank / charcoal canister etc with the closed system.Comment
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OK, thanks for the info. Strangely, my car came with a vented cap when I bought it from the second owner, and I haven't had any issues for over 25 years. I thought that was a little strange then and now, but I guess I'll switch to non-vented since I need to buy a new one anyway.Comment
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