Im looking to do the diode mod, but have heard horror stories about lean a/f ratios. I was told that an EGT gauge is better to use for proper a/f readings. Is this true? And if so how do i read the egt gauge in order to figure out a/f ratios?

 

if your going to be logging data, get a wideband a/f meter. if you just want to buy a $50 gauge and hook it up to your O2 sensor you arent going to get any worthwile data from that so dont waste your money.

if you want to monitor your tune in real time while driving (mostly for those with big turbos) an EGT gauge will tell you pretty quickly when you need to pull over and do some tweaking.

you cannot measure air/fuel ratio with an EGT gauge. same as you cant measure oil pressure with an coolant temp gauge it just doesnt work that way. you also need to do some of research and learn what the numbers of either gauge you choose actualy mean because without a reference point they are kinda useless.

if your egt reads 1370* is that good or bad? if your a/f reads 15.2 is that good or bad?

these numbers will all vary depending on engine load/boost/a number of other things. if all you want to do is make sure your not running lean from the diode, get a innovative motorsport LC-1 wideband sensor, and you will need vagcom or the software it comes with to actualy log your ratios. if you need a hand installing it in place of your stock O2 sensor without your CEL going on let me know and il take some pics for you.

 

Yeah thats one of the gauges i was taking a look at. Comes with the wideband 02 the sensor and bung to go into the exhaust, and the gauge for 290. If you could take some pics that would be great also.

 

you can use the bung they give you but you have to take your whole exhaust apart and get it welded in there, then put it all back together. or you can just remove your pre-cat sensor and put the wide band in its place. the LC1 has a narrow band simulator wire, so that you can connect this wire to the vehicles O2 signal wire and it will act like it has the stock sensor still installed.

you will however get a CEL for the "heater circuit" of the origional sensor not working because its not there anymore. to get rid of the CEL you need to figure out a way to keep the origional O2 sensor hooked up to the power wires so that the car thinks its still there. i just bent a piece of sheet metal in a U shape and drilled a hole for the sensor to go thru and mounted this on the firewall. il get some pics of this and i can tell you what wires to splice if you actualy end up buying it.

if you dont want to do all that messing around with factory wiring (only 3 wires, although if you do it the way i did, its completely removable, you would just need to buy a new OEM O2 sensor) then just have the bung welded in.

also be aware that you need to recalibrate the wideband sensor to open atmosphere levels of O2, meaning remove it from the car, every once in a while. you have to do this before you install it, then after like 500 miles, then after another 1000 miles, then every 5k miles or so once its 'broken in'.

 

Huh, didnt know it had to be recalibrated like that. Will definately still look into this. Probably wont do much with it till next summer. Im going to save as much as possible over the winter and hopefully buy everything i need before i go to college next fall. Once i go there im screwed... All my money will be going to expenses.

 

The calibration can be done while in the exhaust pipe. You can do it while the car is cold and has sat over night or you can do it while engine braking. Only time I do it with the 02 sensor out of the exhaust pipe is when I am installing a new sensor.

If you do have the bung welded into your exhaust make sure to put it no closer then 18" away from the back of the turbo.

 

even if you let it sit overnight tho i would still think there would be some sort of exhaust gas in there, i mean the sensor is at the far end of an 8 foot pipe and its got the cat between it and open air. there would be some sort of airflow just because gases like to mix, but it would take a loooong time. i know they say in the instructions you can do it with the sensor in the exhaust if you let it sit, but i think they said its better to do with it out of the pipe. thats my reasoning anyway. i just wouldnt want to risk skewing the baseline reading cause it would throw the whole ratio off.