Catalytic converter suggestions

[pgrindstaff]

Since something always has to be wrong in the e34 world I find myself in need of new catalytic converters. First there was the exhaust smell indicating there was either a problem with the cats or O2 sensors. Having access to a rubber mallet this afternoon I went out to do some 'testing'. A little rapping on the driver's side (left) cat gave me a 'tink tink' hollow sound. The right side cat gave me a 'thunk thunk' solid sound.

I am now in search of replacement cats and need your suggestions. From what I have read, magnaflow cats don't pass ga emissions. Do any of you have experience with D.E.C cats from BMA or bavauto? I am not exactly interested in OEM cats as those are outlandishly expensive. The cats from both bma and bavauto are more reasonably priced but I am open to your experience and suggestuons.

Thanks, Patrick

[Tiger]

Manaflow cats on ebay... cut old one out and weld new one in. Save old cats so you can sell them for about $120 a piece.

[attack eagle]

decs don't pass either. Shrike tried those after the magnaflows.

When I get a round tuit, I will order the 5 speed exhaust bracket and sundries and go get my catco welded in and try to pass TX ep county smog. 2 speed idle test, no rollers.

I'll let you know how it goes.

[Tiger]

Wait a minute... if you can't pass with a new cat, you got problem in engine... not the cat. The cat can only burn off so much. You probably got a leaky fuel injector or bad MAF.

[pgrindstaff]

Just to be clear, the cat that sounds hollow is the bad one correct? It probably isn't necessary but I would most likely replace both cats at the same time regardless of which cat is bad. I figure I might as well replace the O2 sensors while I am under there.

[Tiger]

The one that rattles is the bad one... meaning it is broken inside.

[pgrindstaff]

Strangely enough, neither car actually rattles. Since it is somewhat hard to describe the sound each cat makes with words I have recorded the sound each one make when I tap them with the rubber handle of a hammer.

Left cat (http://grindstaffp.googlepages.com/leftcat.wav)
Right cat (http://grindstaffp.googlepages.com/rightcat.wav)

Hopefully these clips help identify a problem, or lack thereof. I find it strange that the two cats make completely different sounds, but it is definitely possible that my sulfur-ish smell is due to the O2 sensors.

[Tiger]

Wierd... both sounds okay to me. I would not blame it on the O2 sensor... it is too easy to blame it.

If you have engine problem... you will notice something from the exhaust... lots of white smoke is unburned fuel.. sulfur rotten egg smell is also too much fuel.

What I would do in your case is, clean the MAF with MAF cleaner... not carburator cleaner. Make sure the air filter is clean.... Make sure the duct that goes from air filter to engine intake is not torn nor ripped (mine was).

Then I would check the spark plugs... make sure there is no unusual colors on the white insulation... at the same time, I would inspect to make sure there is no excessive oil around the plugs.

Lastly, I would change all spark plug coil boots... there is new updated version that will solve all the old problems with misfiring (kinda hard to tell of misfiring on V8).

I did all of the above and no unusual smell anymore nor smokes.

[pgrindstaff]

Thanks Tiger. I had planned on at least checking the plugs but your list is very helpful and will guide me in the right direction.

[bubba966]

A cat doesn't have to rattle to be bad. Yes, one that rattles is broken up inside. But if they get too hot they can melt down/burn up the innards. Making them pretty much hollow.

And I just listened to you sound clips. The left one does sound like it's hollow. The right one sounds fine to me. A good cat is heavy & solid.


Wait a minute... if you can't pass with a new cat, you got problem in engine... not the cat. The cat can only burn off so much. You probably got a leaky fuel injector or bad MAF.

A new cat can certainly fail emissions if it's not big enough to do the job properly. And that's what people are running into when they slap Magnaflows in that are smaller than the OE cats. Not only are smaller cats not burning off as much as they need to, but the smaller cats restrict the exhaust resulting in the engine not running as well as it should. So the engine doesn't run as well as it should giving the cats more to do. But as they can't do the job well enough in the first place adding more emissions to deal with just makes the problem worse.

Ask the people that've had both the ceramic cats and the metal cats (less restrictive than the ceramic cats) in their E34 M5's which cat makes their S38 run better.

And my truck used to pass emissions better catless than with cats. Not that it gets tested for emissions anymore as it's too old (it's now 30 years old) for emissions tests. Makes me wonder how a more modern engine would act with & without a cat. I'd love to get track pipes made for my M-Sport and see how that did vs. how it does with the stock cats.

[Tiger]

Mmm... I know the newer cats are smaller than factory units... Can't we put a larger Manaflow unit in than the one they recommended as long it can physically fit in the location? What would you recommends?

[Ferret]

Wierd... both sounds okay to me. I would not blame it on the O2 sensor... it is too easy to blame it.

If you have engine problem... you will notice something from the exhaust... lots of white smoke is unburned fuel.. sulfur rotten egg smell is also too much fuel.

What I would do in your case is, clean the MAF with MAF cleaner... not carburator cleaner. Make sure the air filter is clean.... Make sure the duct that goes from air filter to engine intake is not torn nor ripped (mine was).

Then I would check the spark plugs... make sure there is no unusual colors on the white insulation... at the same time, I would inspect to make sure there is no excessive oil around the plugs.

Lastly, I would change all spark plug coil boots... there is new updated version that will solve all the old problems with misfiring (kinda hard to tell of misfiring on V8).

I did all of the above and no unusual smell anymore nor smokes.

Best way to tell what's going on with the v8s is the gearstick - if it's wobbling around a tiny amount, the car's running fine - the v8s naturally move a little on their mountings. If it's shaking around a lot, you've got a misfire on one or more cylender.

Your exhaust at idle when the cats are up to temp should be almost totally odourless. I had problems with the plug leads on mine and it used to stink of fuel at tickover - after replacing all 8, the exhaust went back to almost totally odourless.

[pgrindstaff]

At idle the stick only shakes slightly and has never caused concern. Tomorrow I plan on checking the temperature of the exhaust, before, on, and after the cats. I will also pull a couple of the plugs to check the condition of both the plugs and the boots and replace if necessary.

I would really like the problem to be caused by something other than the cat but I am not holding my breath. I can't imagine it is good to have two cats make two distinct sounds. They should be the same or something must be wrong in my opinion. I would like to ask however that if someone has a moment, tap on your cats and compare the sound to mine. I suspect they should both sound like my right cat but it never hurts to ask/check right?

Thanks for everyone's help

[attack eagle]

yes they should sound dead/solid and identical.

[bubba966]

Mmm... I know the newer cats are smaller than factory units... Can't we put a larger Manaflow unit in than the one they recommended as long it can physically fit in the location? What would you recommends?

Larger Magnaflows should fix that problem if you can get ones that fit. That's really the only problem with them is that they're not big enough.

Anybody know the flow rate of the stock cats to compare it to the various Magnaflow models?

[Tiger]

I took a look at the specs... They recommended the 94005 for 540i... and it is 16" length, the cat itself is 12" length and 6.5" width. Outlet is 2.25".

The largest one they have is the 95505 with the same outlet size... is 21" long and the cat is 15.5" length and 7" wide. This is the biggest cat Manaflow makes and is probably the biggest we will ever see on the aftermarket cats.

Now, I need someone to get underneath their 540 or 530i and measure if that can fit.

[pgrindstaff]

Without getting too involved in measuring the cat (reaching under the car with a tape measure) the total length of the cat plus outlet is 20"-21". The outlet is in the ballpark of 2" and the cat itself is 18". I could not get a good measurement on the width of the cat but think it is in the 5"-6" range.

On an unrelated note, I have found a source for an OEM cat at close to 50% off dealer price. That still means $750 but it is not as crazy as almost $1600 per cat.

[Tiger]

So it looks like the 95505 will fit... About $162 a piece... and pay someone to weld them in for about $300 or so for both side... and keep your old cats because you can sell them for $120 a piece... so your new cats cost $42 each.

Yeah, I know... dealer new cats is way way too expensive.... even $750 is alot of money.

[pgrindstaff]

Got my IR Thermometer today and took some readings immediately after turning off the car. I took the measurements directly before, dead center, and directly after the cat. Temps will be listed in that order.

Left: 350/210-215/300+
Right:350/350+/350

The number was bouncing around and I didn't have a pen with me so these are approximately what the temps were. Doesn't look good for the left side cat.

[genphreak]

Interesting check! Perhaps also measure the temp of the heads and manifolds as well as the converters (after it has run under load a while).

I bet if you have a restricted cat, the manifold and at least the head on that side will be hotter too.

[Paul in NZ]

So it looks like the 95505 will fit... About $162 a piece... and pay someone to weld them in for about $300 or so for both side... and keep your old cats because you can sell them for $120 a piece... so your new cats cost $42 each.

Yeah, I know... dealer new cats is way way too expensive.... even $750 is alot of money.
but surely worth it if it is the solution to a cat problem where the aftermarket ones arent?

[pgrindstaff]

As suggested I checked the spark plugs and boots (only two cylinders). There was minimal oil on the plugs, probably from when they were replaced last. The plug boots looked brand new, and the only oil around the plugs had dried up suggesting it had been there a while. The valve cover gaskets look to be new as well. Since I don't have any documentation with the car I do not know when what was done so the best I can do is guess.

I have attached some images of the two plugs I pulled:
http://grindstaffp.googlepages.com/P1000997.JPGhttp://grindstaffp.googlepages.com/P1000999.JPGhttp://grindstaffp.googlepages.com/P1010001.JPG

[Tiger]

That brown ring around the base of the plug tells me that your coil boots are no good. Called brown ring of death... search it up in the forum... lots of discussion about this.

[whiskychaser]

That brown ring around the base of the plug tells me that your coil boots are no good. Called brown ring of death... search it up in the forum... lots of discussion about this.
I've seen that on plugs for donkeys years with no adverse affects. Hate to buck the trend:D

[Tiger]

I am just saying... BillR was the one to report that to us... it has no adverse effect, but it tells you that your spark plugs are not getting the full power as it should... which is why egg smell... lots of white smokes... and killing cat converters...

I am serious, my car does not smell anymore. It used to smell and smoke like crazy.

[mclark1983]

At idle the stick only shakes slightly and has never caused concern. Tomorrow I plan on checking the temperature of the exhaust, before, on, and after the cats. I will also pull a couple of the plugs to check the condition of both the plugs and the boots and replace if necessary.

I would really like the problem to be caused by something other than the cat but I am not holding my breath. I can't imagine it is good to have two cats make two distinct sounds. They should be the same or something must be wrong in my opinion. I would like to ask however that if someone has a moment, tap on your cats and compare the sound to mine. I suspect they should both sound like my right cat but it never hurts to ask/check right?

Thanks for everyone's help

I tapped the cats on mine and they both sound nice and solid.

[Ferret]

I am just saying... BillR was the one to report that to us... it has no adverse effect, but it tells you that your spark plugs are not getting the full power as it should... which is why egg smell... lots of white smokes... and killing cat converters...

I am serious, my car does not smell anymore. It used to smell and smoke like crazy.

I agree with Tiger on this one - the brown ring spells ignition trouble for the V8s, they're highly sensitive to HT leakages.

Think it's time for some new plug boots on that car!

[pgrindstaff]

I agree with Tiger on this one - the brown ring spells ignition trouble for the V8s, they're highly sensitive to HT leakages.

Think it's time for some new plug boots on that car!

Ordered them last night. Hopefully I will have them by Wednesday but we'll see, can't ever count on UPS.