Wideband O2 Sensor ?
Thread Starter
Racer
Joined: Jan 2002
Posts: 341
Likes: 1
From: Cave Creek AZ
Wideband O2 Sensor ?
When I had my car dynoed I went for the wideband O2 sensor option ($15). Thought it would be nice to see the mixture at WOT.
I had never seen this used before so I don't know what the correct procedure should be. The guys at the shop merely clipped the sensor to one of the tail pipes. Since the gases have already gone through the cats is this method going to provide an accurate reading???? This setup indicated I was running a little rich. So I dropped fuel pressure about a pound.
Any thoughts would be appreciated. I don't want to be making changes based on bogus data. :)
I had never seen this used before so I don't know what the correct procedure should be. The guys at the shop merely clipped the sensor to one of the tail pipes. Since the gases have already gone through the cats is this method going to provide an accurate reading???? This setup indicated I was running a little rich. So I dropped fuel pressure about a pound.
Any thoughts would be appreciated. I don't want to be making changes based on bogus data. :)
Burning Brakes
Joined: May 1999
Posts: 999
Likes: 1
From: Gardner KS
Cruise-In II Veteran
Re: Wideband O2 Sensor ? (lead_foot)
You know, I've often wondered about that too but it seems like every dyno session I've seen or seen pics of has the WO in the tailpipe just like you described. I've always wondered if that's because it's the easiest place to put it and "close-enough" or if it really makes no difference.
Another thought is that you would think a cat would make the exhaust even leaner once it passes though it so if you're still reading rich then does that mean it was even richer before the cat? Just a thought. -Jeff
Another thought is that you would think a cat would make the exhaust even leaner once it passes though it so if you're still reading rich then does that mean it was even richer before the cat? Just a thought. -Jeff
Burning Brakes
Joined: Nov 2001
Posts: 1,241
Likes: 9
From: Houston TX
Re: Wideband O2 Sensor ? (lead_foot)
you can't trust the reading if the car has catalytic converters. on cars with converters, the only way to get a good reading is to use a screw-in sensor before any cats.
with totally stock (LT1) vette exhausts, this is near impossible. you can't weld a bung onto the stock manifolds, and there's hardly room in between flanges and cats.
with longtubes it's easy. just weld a bung into one of the collectors, at an angle where it's even possible to screw in the sensor without jacking up the car. i did this on mine, works great.
with totally stock (LT1) vette exhausts, this is near impossible. you can't weld a bung onto the stock manifolds, and there's hardly room in between flanges and cats.
with longtubes it's easy. just weld a bung into one of the collectors, at an angle where it's even possible to screw in the sensor without jacking up the car. i did this on mine, works great.
Burning Brakes
Joined: Nov 2001
Posts: 1,241
Likes: 9
From: Houston TX
Re: Wideband O2 Sensor ? (ELEVENS)
on LT1s (dunno about earlier vettes, never looked), the AIR pump goes into the manfifold very close to the cylinder head. therefore, it would affect the reading regardless.
no AIR injection at WOT, i think, which is why that's not an issue. i think the AIR pump stops so many seconds after startup, before it goes into closed loop, anyhow. after all, how could the stock ecu work in closed loop if the exhaust had the air injection going?
no AIR injection at WOT, i think, which is why that's not an issue. i think the AIR pump stops so many seconds after startup, before it goes into closed loop, anyhow. after all, how could the stock ecu work in closed loop if the exhaust had the air injection going?
Le Mans Master
Joined: Dec 1999
Posts: 8,540
Likes: 1
From: And on the fifth day, subpoenas were served to Obama senior staff
Re: Wideband O2 Sensor ? (MSR)
Seems that the LT1 cats do not use the AIR pump to add O2 to the system. On my 89 the AIR pump is diverted to the second section of the cat to provide O2 to facilitate reduction of HC an CO. During warm-up the AIR pump sends outside air to the exhaust manifolds to burn-off excess HC from the rich start-up mixture, and aid in speeding the heating of the O2 sensor and cats.
Regardless, I find it bad practice to place a sensor after the cat. There is very little O2 left after proper combustion, but I fear that what is present at the tail pipe is very different than before it enters the cat.
If your AIR pump feeds the cat, it is certainly not accurate - at all. Even if it doesn't, I don't see how it can be accurate after all the heat and processes going on in the cat.
Pete
Regardless, I find it bad practice to place a sensor after the cat. There is very little O2 left after proper combustion, but I fear that what is present at the tail pipe is very different than before it enters the cat.
If your AIR pump feeds the cat, it is certainly not accurate - at all. Even if it doesn't, I don't see how it can be accurate after all the heat and processes going on in the cat.
Pete
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski