Does running the air pump heat up the cats?

Correct.

Cats need heat though to work more effectively/efficiently.

 

+1

 

Are you running an average A/F ratio that is towards the rich side? Is the injection system still K-Jet without Lambda, or has that been changed too?

 

"with Lambda" = it has an O2 sensor and runs closed-loop (the A/F ratio is held to a value near stoichometric so not a lot of unburned fuel goes into the exhaust stream when things are working right = cats runs normally).

"without Lambda" but has cats = what you have = no O2 sensor = important that the A/F ratio is not set too rich (and IC engines run great set a little rich) as this increases the heat generated in the cats. With the continuously-operating air pump, you could probably overheat the cats even if things are set right and working right (because when you are really on it, it adds extra richness), but something to check IMO if your real problem is that the cats seem to be running too hot.

Do you still have the stock camshafts, or were they also "upgraded"?

 

This may be contributing to the increased cat temperature if the overlap between exhaust ending -to- intake starting has been increased (that allows more of the unburned intake charge to "leak" directly into the exhaust system). They had to reduce the historically-used exhaust-to-intake overlap amount used on non-cat models when the cat models came out for this reason. If the cats still overheat when the idle A/F ratio is in the stock ballpark (which is about as lean as possible and still have decent driveability), you may be able to fiddle a little with the cam timing to reduce this overlap (but not a bunch). Do you have the lift & duration values for your cams to compare to the stock values (and how they were set)?

I'd say that it would be worth checking to confirm/deny if it is contributing to the problem. It may be OK, and you may just now have a mechanical configuration that (unfortunately) can't use cats without overheating them.

Yes, that's not the best -- you'll probably just ruin the cats more quickly (they, or the coachwork , may not burn up without the airpump working, but the cats might get fouled from the lack of extra oxygen). I applaud your effort to keep your modified engine quasi-US legal so hope you'll get it working.

 

Mark
Wasn't your engine recently rebuilt down at sea level? Your photo thread of your new engine suggests it was dyno'd during the rebuild. That makes me think it was set properly for wherever the dyno was, which was not in Denver, correct?

If the car doesn't have an oxygen sensor, could it be running rich up here at 5280 ft altitude?

Maybe the car is dialed a little rich bc of the altitude change, which is causing the cat temps to be a bit high?

I would think you could sniff the car and adjust the air/fuel of the KJet to be proper for up here, and that would hopefully solve the cat temps.

Jonathan
Denver, CO
the FiatRN

 

Do you mean that BOTH slowdown lights flickered on together, or do you only have one slowdown light in the dash? If you have two and it's just one of the slow down lights showing a problem, perhaps you should first swap the warning light ecus to see if the problem stays on the same bank (probably is real) or moves to the other bank (showing it's probably the warning light ECU that is flaky).

Can you back up some and describe better what you have. Since you say that you have a 308QV with a belt-driven air pump, that would usually mean a 1983 US version 308QV --is that what you have, or something else (e.g., a euro 308QV that was imported to the US and "federalized")?

 

Yes, under the passenger footrest plate -- swap the two warning light ECUs (all connections) and see if the light behavior changes sides or not. Is the self-test working perfectly and always on both sides?

Your model (1981 US version 308i) would only have the two thermocouple sensors in the cat exit areas. It did orginally have an EGR system -- so would have some extra tubing/plumbing in the exhaust system, but no "third sensor". Check the EGR system figure on page 76 in your 216/81 OM and see if any of that might be what you are seeing.

 

EGR = Exhaust Gas Recirculation (some exhaust gas is rerouted back into the intake system under certain conditions).

Yes, that's exactly as it should (always) be. If the light doesn't come "on" at all, that is a failure -- but sometimes people don't notice (whereas, it always gets noticed if a warning light wrongly stays "on" more than the second or two).

 

Not sure that's what it is -- just a suggested possibility. Can you post a photo?

 

Sounds like Steve pretty much has you covered.

I agree that running the cats w/o an air pump may "poison" the cats. They definitely do not run as hot as when the air pump is running. The added O2 assist in further combustion of unburned gases in the exhaust. I don't know how long the cats can last w/o the air pump connected. Hypothetically speaking, I could have been running them for 10 years w/o the air pump running...except for regularly every 2 years for a short stint

I have found an electric air pump that is pretty much a direct replacement for the pulley driven one. I don't want to hijack your thread, unless you want me to post it here. I did this because hypothetically speaking, if I were to install early/euro cams, there is not a drive for the pulley on the end of the exhaust cam.

Like what you've done so far.

Henry

 

I bought one and was playing with the idea of using an electric pump. Beware, they draw serious electricity.

 

The one I installed does draw some, but not huge current. It is right around 10 amps. It blew a 7.5, but the 10 amp fuse is holding fine.

The air pump I used is from a late 90's Camaro. It was also used on late 90's Jags. On the Camaro it was for the 5.7 liter V8. Here's a link to Cardone (remanufacturer)...

Product Detail

This mounted on my existing brackets and looked stock. I just passed CA smog testing with this a couple weeks ago. I'll try and post some pix later today.

 

Here's the install...
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I am seriously thinking of removing the entire airpump system from my 83QV. I have already disconnected the drive belt ( fearing that if the airpump bearing seized... it would lock up the drive off the cam and take my entire engine valve train with it... not sure if that fear is even correct -- but having that old gm airpump connected to my cam looked worriesome)

So... I have been driving around with the added weight and congestion in the engine bay for no purpose and the system always seems to get in the way of any repairs ( you need every mm of space in there to work..

I search but this seemed the thread to ask about airpump removal from usa -non CA - spec cars..