Anyone running 9:1 or higher on the street? Options

[-JR-]

I'm still hashing over compression ratios. I've been reading online that these motors don't or won't run compressions as high as 9:1 without taking extra steps. Like aluminum cylinders or electronic fuel injection. Mainly just because of the heat involved.

Has anyone "got away" with running higher compressions like this on stock cylinders?

*** IF anyone has any feedback on what fuel grade they are running at their higher compression and if they are getting any knocks ect... I would also greatly appreciate that information too.

Thanks everyone!

James

[lapuwali]

QUOTE

CO gets better, but NOx goes up, way up, with flame front temp

Yes, but only HC and CO were being measured when the engine was being designed. NOx measurement didn't come into play until after 1980. The first catalytic convertors (so-called oxidizing or two-way convertors) only handled HC and CO emissions, too. The cats on the '75 and '76 914s, for example, were oxidizers. The later three-way or oxidizing/reduction catalysts handled HC, CO, and NOx.

The ironic thing is you can take an engine that, bare, spews out HC numbers of 300ppm, and similarly terrible CO and NOx numbers, just add a $75 three-way cat to the exhaust pipe, and your emission numbers will fall to 10% or less of the pre-cat numbers. However, if you really do nothing else, the cat will die in 10-20K miles and the emission numbers will climb back up again. The O2 sensor and the related electronics and mixture control are there primarily to control O2 levels to the point where the cat will continue to live for 50K miles or so.