exhaust pressure not equal... thoughts?

All,

just picked up my 86 mondial 3.2 and I noticed that one side of the exhaust is flowing fine, while the other side (drivers) is only flowing about 20% of the right side. any thoughts on cause?

thanks

D

 

Bad Cat

 

The stock mufflers are asymmetric internally so this is normal behavior for those. If you have a symmetric aftermarket muffler (e.g., Tubi) then that is a problem. Is it running poorly at high RPM?

Here's an example of a euro 328 muffler cutaway (where the "loud" side is put on the left because the Driver sits on the right):

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(US 3.2 Mondial have a shared, single cat so that can't be the trouble -- unless the OP has a US-converted euro where they used 2 cats.)

 

I thought there was a slight imbalance (you can see it on cold mornings)..

But not 80/20?

 

+1

 

thanks all. I was thinking bad cat or clogged injectors. I'll check if there is 1 or 2 cats on the car tonight when I get back.

If only 1 cat, could that still be an indication if one side is flowing less than the other?

 

One side flows more than the other by design. Don't know ratio. I've put 12,000 miles on my 87 in this condition this year. Runs great.

 

It sounds normal.

How were you able to make a 20% vs 80% comparison; just by feel?

 

100% agree if car is running well. My 308 is similar when cold but evens out a little after warming up.
Brent

 

If it is a stock exhaust, it is normal.

 

That is a great picture. I've always wondered, now I know.

 

I think it starts evening out when you get on road in which case you can't see, feel or easily measure it. One exhaust seems to be the primary and is much stronger than the other during idle. It has been explained to me but I can't remember the details but from everything I have been told, it is normal, provided there is only one CAT.

Cheers
Dave

 

I just ran my car in 28 degree weather. The exhaust on the passenger side was twice the volume on the drivers side. Its been like that since new.

 

Since there is no crossover or mixing of exhaust gasses to provide balance,


I wonder how that uneveness effects performance and / or wear.

 

excellent, thanks all.

One item I thought I had to fix is now crossed off the list. On to the next one!!

 

+1 normal

 

Thanks guys. I was just wondering about this too.

 

My 86 328 is unbalanced also. I've never tried to measure the differential, but one side is definitely stronger than the other, and understood that that was normal. I noticed it on my 308 as well, though it had a Tubi exhaust and the difference was not as noticeable as on the 328 with stock muffler.

 

Don't fret! I have an 88 1/2 Mondial 3.2, and its exhaust does basically the same thing. Maybe not 80/20, but nowhere near 50/50. BTW, it did this both in its original exhaust configuration and AFTER I took off the cat and installed a Stebro free flow exhaust. It is not the exhaust or cat IMHO.