I was wondering what the life expectancy of the stock o2's is? I hear that octane boost and fuel addatives can plug them up and I dont know what the guy before me ran so I was considering replaceing them. Also When I put my car on the dyno their AFR readings were different then my defi gauge readings. Could that be the reason why?

 

As long as you dont run leaded fuel a lot the stock sensor should last at least 60k miles. Leaded fuel does shorten the life a lot, typically the way you know it is if your AFR's bounce around a lot at idle or cruising it will not affect your WOT. Your Defi gauge is probably a narrow band gauge which honestly is not worth crapping on unless you like looks and needles bouncing around.

 

The needle is bouncing at idle and its reading a lot richer then its actually running at wot. What would be a decent gauge fora reasonable price?

 

Also is their stuff decent quality? Its like 60-70% cheaper then napa and mitsu
http://www.automedicsupply.com/catal...2.0L+Evolution

 

You have to get a wideband gauge/sensor, there is no doubt that everyone who is modding should have one. Im not sure how much gauges are these days, i've had my AEM for almost 2 years and it was around $300 when i bought it.

 

Lead is a serious life shortener. 60,000 miles + becomes 100-200 hours.

With add-ons, a serious killer is heat. Many vendors simply republish the max EGT rating for whatever sensor they are using, but there is typically a more restrictive max bung temperature for a sensor as well. For example, with the Bosch sensor we use max EGT is spec'ed at 850C, but the max bung temperature is spec'ed at 530C.

We monitor both temps and report an error if either is exceeded, but most controllers don't. Bung temp is actually fairly tricky to monitor, but, surprisingly, is the most common problem. Short term, the heat shows up as distorted measurements, but long term it dramatically shortens the sensor life.

Please note that the above refers principally to wideband measurements. Narrow band sensors/controllers are also effected by heat, but short of gapping cracks in the ceramic, generally can find stoich fairly well regardless of age.

-jjf

 

Good info^. Typically a wideband gauge starts reading super lean or reads some sort of a Error when the sensor is fried. As far as narrow band, I doubt that his is shot unless he has been running tanks upon tanks of leaded fuel.....like myself

 

Then whats up with the needle bouncing around at idle? Just a crap gauge?

 

Your not going to get a good reading with any narrow band gauge.

 

If you are running closed loop and looking at a narrow band sensor the reading will inherently oscillate. The ECU is typically looking for the stoichiometric ratio (not that this is the best place to run an engine, but it is best for emissions control).

But the narrow band sensor does not really have a 'stoich' reading. It only gives two readings Rich of stoich (ROP) and Lean of stoich (LOP). So, if the ECU is trying to keep the engine at the point in between, it is only natural for the readings to bounce back and forth.

With a wideband meter, which is trying to measure lambda, oscillation can mean different things. There often is some legitimate oscillation in the actual exhaust stream (fuel distribution is not perfectly balanced between cyls, etc). So if a controller is fast enough and sensitive enough to see this, a little bobbling, especially if the display is in lambda - which is typically a finer scale than AFR, is normal.

On the other hand, oscillation can mean a faulty sensor or an air leak around the bung. These would be my first suspician on a wideband controller based on some designs. It isn't really a fault with the designs, it is just that they originated in static dyno tuning, and often have fairly long settle times. If a measurement is twitching a couple of times a second, then the sensor is actually seeing fast, large swings - almost certainly a crack or leak.

With a design geared towards street tuning and/or inertial dynos, there is typically more emphasis on measurement speed. So oscillations are more likely to be legitimate readings. Air leaks tend to show up as much bigger spikes and swings. Sensor failure is still a possibility, but as the measurement speeds go up, there are other things that the controller can monitor about the sensor to detect common types of failure.

But, again, the hardest to detect sensor failures often begin with out of spec temps.

Good Luck,
-jjf

 

Yeah I have no idea what your talking about, but thanks for the effort.

 

Sorry. "Stoichiometric Ratio" is chemically optimum combustion in terms of an air/fuel mix. Nominally 14.7:1 with gasoline.

That is why EGT (our exhaust temp) peaks here. It is not a great point for economy (optimum about 70 degrees lean of peak) or power (optimum about 150 degrees rich of peak), but it is great for keeping emissions down.

So, the ECU often tries to keep the car exactly at that point. Often using a narrow band sensor. A narrow band sensor can tell if we are rich of the point or lean of the point, it just doesn't know how much. It also can't indicate when we are exactly on the point. So the ECU does a balancing act and the sensor reading swings back and forth.

Is that any clearer?

-jjf

 

yeah kinda. Basicly I need to get a wideband gauge