I've been cruising around the Interwebs for the past couple days and haven't been able to determine the A/F for my '98 Eclipse GST. Even a decent estimate or what it should have been as it came out of the factory would be acceptable. Thank you!

It is either 8.8:1 or 9:1 cant really remember.

during normal driving conditions there is no way to tell without a wideband O2 sensor and some sort of device to translate the signal (gauge, diagnostic unit). Your short band O2 from factory will cycle all over the place to get the mixture "somewhat right"

Generally speaking though, under load it should be rich. 9:1 - 10:1. it's possible to get it 12:1 - 13:1 but you better be running some high octance fuel or methanol injection

Since you have a turboed car you will want your AFR to be as low as possible.

Not always true. and not AS LOW as possible. about the best you can do under a load is 10:1. Like pwee said... anything higher, you'd better be running high octane.

Also, 14.7:1 is considered stoich.

Yeah 14.7 / 1 is what you're ecm is trying to get at all the time. It is the optimal combination where the fuel is atomized perfectly to combust with the most effeciency. Effeciency=Power

its the perfect combustion when using high octane fuel :thumbsup: