Too hot to handle

Wow, that's nasty. Are your pipes now closer to the bumper since the exhaust work? Also, on my rear heat shield ("diaper") there are two fiber heat insulators that are mounted below the bumper mounts, to protect them from exhaust heat. Do you have those as well? I would think that the core problem is now exhaust tip proximity to the bumper. If they're closer, you may need to move the tips? Tips can get hotter than you might imagine....especially with a stationary car. I know that the tricked-up Honda kids run into a lot of melting back there, due to those soup-can mufflers being too close to the urethane.

 

Now I am curious. Can you post some pics?

 

Was this checked upstream of the cats with the air injection disabled? Not putting too much extra fuel into the exhaust stream is one reason to try to not exceed the factory CO spec by too much...

 

Are you sure on the air/fuel ratio? If a air pump is not working properly it can cause the O2 sensor to lean out the engine which could cause excess exhaust temps as well as possibly harm the engine. Just a thought. Keep us posted.

 

Did you reconnect the air pump? When I got my 308(carb) it had a disabled air pump and melted cats. I'm convinced that unless the air pump is there to seriously reduce the CO entering the cats they will be over loaded and over heat.

Just my theory, but it you engage and disengage an air pump while watching CO with an analyzer the difference is significant.

TomB

 

Can you please post a scan of this FSB or provide a link? I've never come across a tailpipe spec for the US i-2V cars -- TIA.

 

No O2's on the 2Vi cars. I would look at the goop as it looks more like a tar based underbody sealer. Look at the back side and see if the bumper has been repaired. I wouuld expect to see blistering at the tips before melting but weirder things have happened.

 

Here it is for a carb car- sorry for the bad pic- it says max 1% at tail pipe with air pump, 6% without
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Different beast -- both those values are much, much higher than for a CIS car.

 

Confirmed, that's a 1978 engine data plate.....

 

I agree- my point was the CO reading ratio between the pump working and not. Just trying to figure out why things got so hot back there.

 

Understood, but those US '78-'79 carb values are for "no air pump and no cats" (i.e., at the cylinder with airpump disabled) vs "with airpump and with cats" (i.e., at the tailpipe with the airpump working).

My interest is seeing if F is allowing sort of an unreasonable amount still at the tailpipes on a US 308i-2V (like maybe 0.5% CO maximum); whereas, on a well-working system, it should be more like 0.0% CO (i.e., unmeasureable).

 

The Car dose'nt seem to have a Heat Sheild,I looked at my Car and it looks as if I have one over the Muffler,I'll try and get a Picture,My Camera Took a Crap the other Day.

 

Yes, your car is missing small L-shaped metal heat shield that follows lower inside edge of bumper. Also, the diaper might help deflect/dissipate heat.

I can send you photos and dimensions if you need to make one.

 

My gtsi has one or more...can't remember.

 

Very interesting. Sorry to see your damage. I've got a cat-less Tubi on my 84 QV. My car runs cooler than it did with the cats on it. I would have to agree that the stoichiometric values might be off, meaning if the car is running too leanly, it will run VERY hot. If she is running rich, it would run cooler. Can anyone agree or chime in?

 

Only if you added them As MNE wrote, "No O2's on the 2Vi cars" (neither euro nor US).

This is true for the exhaust gas exiting the cylinder head, but not for the exhaust gas exiting the cat -- as significant futher combustion will take place inside the cat (especially on a model with continuous air injection).