Are O2's Useless? Tuning

[V8killR4U]

Ok Ive been trying to tune my car with the scan master, and need less to say my o2's are all over at WOT sometimes 750-820. I was considering getting DS so i can record my runs, and look and see where im rich or lean. Besides KR and boost what other numbers do you guys look at. Ive heard alot of people say tuning by O'2s is useless they say tune by EGT. Where do i get an EGT guauge? IS TUNING WITH O2'S USELESS THOUGH. mY GN ISNT RUNNING VERY GOOD AND IM TRYING TO FIX IT

 

[b4black]

Get a digital thermometer and a probe. Try searching EGT and you find all you need.

 

[OKTurbo]

I wouldn't say that tuning by the stock O2 is ~worthless~, but it certainly won't be very accurate. The stock sensor is a narrow-band....or switching style o2 sensor. The stock computer uses it for nothing more than a rich/lean indicator. It is not very good at reading an actual A/F ratio.

The rule of thumb is to tune WOT for .780-.800 Volts. Your WOT O2's should be fairly steady....but may drop as you get going faster down the quarter mile.

At anything other than WOT the O2 readings ARE worthless since the computer is in closed loop and constantly changing the injector pulse widths to maintain the "perfect" ratio. The ideal ratio is 14.7:1. That is "perfect" for effeciency, but not for making the best power.....best power happens richer at around 12-12.5:1.

Your options are to get a wide band O2 that will actually read an accurate A/F ratio. There is a relatively inexpensive one you can build yourself.... www.diy-wb.com
This is what I'm doing....just haven't gathered up all the parts yet.

As a point of reference....a commercial WB O2 will set you back $1500-$2000. The DIY will cost about $250-$300

Or call Steve at SMC (www.smcenterprises.com) and order one of his EGT set-ups. You can also just buy and EGT gauge from Jeg's or Summit.

Your ScanMaster will give you lots of clues if your can is running bad. Check your BLMs and INTs...make sure they are in range. How are the O2 cross counts? Is your O2 dead or Lazy?

John

 

[jastrckl]

well sheisse, I had this little writeup below and you guys beat me since I had to actually work for a change. anyway if the other helpful fellows haven't clinched it for ya maybe this will help:


I can't remember which way it works but EGT temps 'shift' o2's... so your o2 is a measurement of both oxygen in the exhaust AND EGT, to a degree. I think it was the hotter EGT got, the leaner the o2 sensor would read. You can tune to o2s if it's something you get used to, you just need to find a fast sensor, something like a heated sensor or MUCH better if you can afford it, a wideband. Those don't require as much 'guestimation', but guessing can get you there if you're meticulous and keep good logs. Keep in mind also that EGT itself is a measure of more than just lean/rich, spark advance also affects EGT, since the ammount of fuel burning in exhaust changes based on spark timing. This of course also screws up the o2 sensor to a degree.

 

[Roger]

http://www.syclone.freeserve.co.uk/spagauges.htm

 

[SPEEDSTAR]

www.digatron.cc

 

[Steve Y]

V8,

With what you have look for about 1650 degrees or more egt with straight C-16.

An 800 02 reading at 1400 degrees might be 13/1, 805 at 1300 degrees might be 12/1......off the cuff.

Like was said earlier, anything but a wideband is useless, at least in my expirience.
There are some guys that have their cars figured out that can somewhat rely on the stock 02.

Steve

 

[bruce]

Originally posted by V8killR4U


I was considering getting DS so i can record my runs, and look and see where im rich or lean.

Besides KR and boost what other numbers do you guys look at.

Ive heard alot of people say tuning by O'2s is useless they say tune by EGT. IS TUNING WITH O2'S USELESS THOUGH.

Ds is a tuning tool.
A WB is a tuning tool.
EGT is a tuning tool.

The more tools you have and that you know how to use will make your tuning much easier, and less expensive.

Using ANY one tool can be misleading.

The idea is to gather as much data as possible and find out what your engine likes most.

An oem O2 is useless as a tuning aid. It can be an excellent diagnostic aid, once you know your cars sweet spot you can relate that to a specifc O2 voltage. But people have tuned that around into some silly notion that they can tune to a give number cause it worked for someone else.