Cat question for those in the know?
Thread Starter
Melting Slicks
Joined: Mar 2003
Posts: 2,512
Likes: 49
From: Franklin IN
Cat question for those in the know?
I have an 87. I'd like to run cats. I'd like to not have to run an air pump with all it's hoses and junk. Can it be done and get the cats to light off?
Race Director
Joined: Nov 2003
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
I thought I understood the cycle back when I removed my AIR setup but it's obvious air is pumped both the manifoldl and to the convertors for at least some period of time...and not at the same time either.
In both cases, I'm assuming it speeds up the operation of the converters. Without the AIR system, I don't believe I've seen documentation on how much delay is present but I'm convinced the converters still work within a reasonably short delay after the stock config. (I could see what the FSM says about operation if you're really curious.)
Another possibility presented by this forum is the AIR pump "dilutes" emissions by increasing the percentage of air to carbon. And, as Dave pointed out in a recent thread on E15, that's NOT a realistic way of reducing emissions. It's a cheap parlor trick.
Thread Starter
Melting Slicks
Joined: Mar 2003
Posts: 2,512
Likes: 49
From: Franklin IN
Thanks for the reply. But my issue is the main Cat. I never had precats since I owned the car. I fear the main is not lighting off. When ever I had somone behind me they siad the fumes we enough to knock them out. I was hoping to be able to eliminate the air pup and the line running to it by running a different type of cat. I know much has changed since this car was designed and I do want to be green (and legal).
87Bob
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Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Hi Vader,
Thanks for the reply. But my issue is the main Cat. I never had precats since I owned the car. I fear the main is not lighting off. When ever I had somone behind me they siad the fumes we enough to knock them out. I was hoping to be able to eliminate the air pup and the line running to it by running a different type of cat. I know much has changed since this car was designed and I do want to be green (and legal).
87Bob
Thanks for the reply. But my issue is the main Cat. I never had precats since I owned the car. I fear the main is not lighting off. When ever I had somone behind me they siad the fumes we enough to knock them out. I was hoping to be able to eliminate the air pup and the line running to it by running a different type of cat. I know much has changed since this car was designed and I do want to be green (and legal).
87Bob
There is a possibility your car has another issue. Mine started to smell bad when one/two injectors lost their integrity. When injectors "fail", they can throw the O2 sensor off. When at least one injector is weak on the O2 side (driver's side), all the other injectors will be instructed (by the ECM) to add more fuel. By adding more fuel, the ECM thinks it's correcting a lean condition for all cylinders (vs a lean condition on just one cylinder).
If this happens, you'd actually be running rich. If two (or more) injectors are bad on your DS bank, the result could smell awful. That's because the PS bank will be very, very rich.
FWIW: The only evidence I've seen on the main cat's ability to "light off" w/o an add'l air supply is based on anecdotal evidence saying someone passed emissions w/o that tube. IMO, that doesn't mean the cat doesn't perform better with it. I'm fairly certain emissions are based on a percentage compliance based on the year of the vehicle. That means the older the vehicle, the more it can pollute and still pass.
Thread Starter
Melting Slicks
Joined: Mar 2003
Posts: 2,512
Likes: 49
From: Franklin IN
You're afraid the main cat is not "lighting off" even with your AIR tube still attached?
There is a possibility your car has another issue. Mine started to smell bad when one/two injectors lost their integrity. When injectors "fail", they can throw the O2 sensor off. When at least one injector is weak on the O2 side (driver's side), all the other injectors will be instructed (by the ECM) to add more fuel. By adding more fuel, the ECM thinks it's correcting a lean condition for all cylinders (vs a lean condition on just one cylinder).
If this happens, you'd actually be running rich. If two (or more) injectors are bad on your DS bank, the result could smell awful. That's because the PS bank will be very, very rich.
FWIW: The only evidence I've seen on the main cat's ability to "light off" w/o an add'l air supply is based on anecdotal evidence saying someone passed emissions w/o that tube. IMO, that doesn't mean the cat doesn't perform better with it. I'm fairly certain emissions are based on a percentage compliance based on the year of the vehicle. That means the older the vehicle, the more it can pollute and still pass.
There is a possibility your car has another issue. Mine started to smell bad when one/two injectors lost their integrity. When injectors "fail", they can throw the O2 sensor off. When at least one injector is weak on the O2 side (driver's side), all the other injectors will be instructed (by the ECM) to add more fuel. By adding more fuel, the ECM thinks it's correcting a lean condition for all cylinders (vs a lean condition on just one cylinder).
If this happens, you'd actually be running rich. If two (or more) injectors are bad on your DS bank, the result could smell awful. That's because the PS bank will be very, very rich.
FWIW: The only evidence I've seen on the main cat's ability to "light off" w/o an add'l air supply is based on anecdotal evidence saying someone passed emissions w/o that tube. IMO, that doesn't mean the cat doesn't perform better with it. I'm fairly certain emissions are based on a percentage compliance based on the year of the vehicle. That means the older the vehicle, the more it can pollute and still pass.