when i heard people saying theyre running their cars lean...what does that exactly mean? and how do you do it? i have 91 NA.

 

Lean - Ratio of air-to-fuel is higher than 14.7:1
Rich - Ratio of air-to-fuel is less than 14.7:1

To make adjustments to the A/F ratio you need a standalone engine management system or some other way to fool the stock ECU. Since n/a FCs run very rich stock, power gains can be had by leaning out the A/F ratio. You need a wideband O2 sensor to tell you what the A/F ratio is and a dyno to see the result of your adjustments. This is something that should be left to experienced tuners, since running too lean can cause detonation, which kills motors.

 

Why would you want to do something if you don't know what it is?

Running the car lean refers to running on the upper side of stoich. That is, the optimal air fuel ratio is 14.7:1. Run 15:1, and that's lean.

Running a bit lean during cruise can save on fuel. But as mentioned, to do this you will need a piggyback (or full standalone) to adjust the fuel curve. And if you don't know what you are doing, your next investment will be a new engine.

Additionally, the 2nd gen runs pretty rich under wide open throttle from the factory. Pulling out a little bit of fuel will result in a power increase.

 

i have 2 questions on this line.

1> how much power is there to be had in teh high end, as well as how much mpg savings is there? (is it worth it?)

2> what is the device of choice to control the air/fuel ratio? i know standalone is preferred, but would like to know a few options of each type.

 

S5 NA w/ Rtek 2.0: http://www.digitaltuning.com/index.p...age=2&ecu=S5NA

Click on "Show Dyno Graphs". AFRs were adjusted from mid 10s stock to mid 13s.

 

thanks for the info, and the link. i guess it is not really worth it for my use. just wanting to make the car a bit more fun and get better mpg.

power seems to be more up top.