Hi, im using the a/f monitor from my apexi turbo timer for now... When I was stock it was reading 14.3...14.6...14.8 and when I was pulling the gaz it reach 18..19 and sometimes over 20. When my turbo will be running (hahn s16g, stock injector, fmu, smic, egt,boost,fp gauge.) what i expect to see for normal number ? is 20 mean rich or lean ? I just want to make all the info before start it and break something.

thanks !!!

20 is VERY lean, you want to be in the mid to high 11's for the afr. you want to shoot for .93-.94 volts I think under boost. Either way using the narrow band o2 for tuning is a joke.

EDIT: Oh yea, SEARCH this has been asked hundreds of times.

Originally posted by CarbonFiberRST
using the narrow band o2 for tuning is a joke.

Ok, so that number I was seeing without boost (14.6...18-19) was not correct? because 19 for a non turbo car is weird... the best way should be to buy a wideband like zeitronix that will replace my o2 sensor and the result will be accurate ?

First off I'm having trouble understanding what you type. by "pulling the gaz" do you mean you were not pushing the gas and slowing down in gear? if so then 20 or leaner is perfectly fine, my megasquirt cuts the fuel all together under that condition. While cruising, maintaining constant speed your afr should be in the high 14's or 15's under boost low 12's or high to mid 11's.

Sorry, im in quebec so I speak french and its a little hard to speak english. For my a/f when im crusing its in the 14-15. You said it will be 11-12 under boost... I was thinking more lean than usual cause so moch more fuel ill need... the fmu will ajust it under rich condition right? and a last newb question...

Also, I was worry about the fuel in the tank. A little less then 1/4 tank left and its 87 octane. If I just start the car with the turbo and dont wot the car... just let it drive normal to the nearest gaz station and fill with 91 octane... is it ok ? Or its dangerous to run 10min with that gaz?

thanks a lot!

Originally posted by ChloRure
Sorry, im in quebec so I speak french and its a little hard to speak english. For my a/f when im crusing its in the 14-15. You said it will be 11-12 under boost... I was thinking more lean than usual cause so moch more fuel ill need... the fmu will ajust it under rich condition right? and a last newb question... Also, I was worry about the fuel in the tank. A little less then 1/4 tank left and its 87 octane. If I just start the car with the turbo and dont wot the car... just let it drive normal to the nearest gaz station and fill with 91 octane... is it ok ? Or its dangerous to run 10min with that gaz? thanks a lot!

The octane rating is the resistance to knock. The higher the rating, the higher the resistance. If you drive like normal (little to no boost) it will be like you aren't even turbo'd, and so you won't have to worry about knock. The higher octane is needed for when you are running a good amount of boost pressure (i.e. more than 2-3).

Also, you really should not even pay attention to what your TT says the A/F is at. It is not accurate and should not be taken too seriously. And you would rather be rich rather than lean if you are not sure what you're actual A/F ratio is. My suggestion is to get a real wide band.

Originally posted by ChloRure
Sorry, im in quebec so I speak french and its a little hard to speak english. For my a/f when im crusing its in the 14-15. You said it will be 11-12 under boost... I was thinking more lean than usual cause so moch more fuel ill need... the fmu will ajust it under rich condition right? and a last newb question... Also, I was worry about the fuel in the tank. A little less then 1/4 tank left and its 87 octane. If I just start the car with the turbo and dont wot the car... just let it drive normal to the nearest gaz station and fill with 91 octane... is it ok ? Or its dangerous to run 10min with that gaz? thanks a lot!

Cruising, light throttle, light load, 14-15 afr is ok.
Underload, doesn't have to be boost, 11-13.
Heavy load, boost - 11-12.

Get a wideband, end of story.

As for 87 octane, as long as no hills, no heavy throttle, u can make it to gas station.