Trap cat test pipe finished - 1985 300D (CA) W123/OM617
 

The machine shop finally finished building me a test pipe with which I can temporarily replace the trap catalyst on my 1985 300D-T (California version) for testing purposes only. The car has been torn apart for three weeks waiting for the test pipe to be finished; I'm looking forward to putting things back together this weekend and seeing the results.

To begin with, I'll admit that the "swap in a complete Federal exhaust system" proponents were right. The machine shop billed me for four hours of work -- making a jig based on the trap cat, machine work to clean up the cut-off ends of the junkyard trap cat, welding and grinding, etc. One could surely buy a complete Federal exhaust system including the turbo for less than that. Then one would be able to share in the joy of dealing with collapsed air-cleaner mounts as many forum members have bemoaned.

The pictures I have attached show my original trap cat and the finished test pipe side by side. The test pipe weighs 3.5 pounds (1.6 kg) compared to 14.5 pounds (6.6 kg) for the trap cat. The labeling on the side of the trap cat is shown in the second picture. Some folks were asking about that. The part number is 126 490 34 14.

When I took the car apart, I discovered that there was no gasket between the exhaust manifold and the trap cat (three-bolt junction). This is strange. The EPC doesn't show one either. Then again, it doesn't show one between the trap cat and the turbo, even though I found one when I took the car apart (four-bolt junction). Anyone know if there's suppose to be a gasket between the manifold and the trap? Does the Federal car have a gasket between the exhaust manifold and the turbo? The EPC doesn't show any gaskets except for the long manifold-to-head gasket.

I'll report on results once I have the car back together. By the way, machine shops in my neck of the woods now get $100/hour, almost as much as my dentist. :eek:

Jeremy

very nice...
When I changed mine to fed. the gaskets were the same congiguration as yous. No gasket on the manifold, metal plate gasket at the turbo.

Well you could have them make more and sell them. A muffler shop would have charged less. :o

A muffler shop might not have been able to hold the tight tolerances necessary. The pipe has to fit in between the exhaust manifold and the turbo and there isn't a lot of room for error.

I don't think a regular muffler shop would have been able to make the plate with the studs and I don't think they would have made a jig to assemble it either; a custom car shop maybe.
Would it have been possible to cut open the original trap cat and remove whatever is inside and reweld it?

I know from trying that the local muffler shops will not touch it. They are scared of the gov. and the modification of an emmission system rules.

Ditto. Many will not even make a custom exhaust unless they include a muffler.

Risky surgery
 

Yes, I think so. Some people have reported on this forum that they simply drilled a big hole through the trap material. Given the right-angle bends in the attaching flanges, they must have cut one end off, done the surgery, and welded it back up. However, that still leaves a big "expansion chamber" right where you don't want one (before the turbo). You would also have to be very careful not to leave any "dangling chads" that would get sucked into the turbo and possibly damage it.

Another advantage of making a replacement test pipe is that it leaves me with a complete trap cat to put on the shelf. In case I ever need to put the engine back to stock, I have it and all of the EGR stuff put away.

An additional advantage to removing the trap cat is that you can install a factory block heater. With the trap cat in place, access is impossible. (I have one of DieselGiant's radiator hose heaters so I will stay with that.)

Forced and Black are right on the money as regards muffler shops' reluctance to sell anything to do with smog devices. After over a year of my searching, SirNik from this forum found a complete trap cat for me at 'Pick and Pull' in Sacramento but they refused to sell it to him. After some discussion, they allowed him to hacksaw off the flanges. These flanges, some 2 inch exhaust pipe, and my trap cat as a 'model' were what my machinist had to work with.

Jeremy

No. Being pre-turbo trying to hollow it out would have a very high risk of damaging the turbo.

Anybody comment on how the engine runs after the test pipe is installed?

"I'm better now" (Stan Laurel)
 

Engine runs same as before, no noticeable difference in starting, idling, or running on the road. It is more responsive, the turbo spools up quicker. See post #14 in this thread for more details.

Clearly, I will have to run the car with the test pipe for awhile (at least as many miles as the car has on it now) before I can be sure of the difference. :D

Jeremy

Does it support the weight of the turbo? If not, how about a simple elbow at each flange and a flexible section between?

Sixto
87 300D

Supporting my Mercedes in its old age
 

Good question, Sixto. There is a brace at both ends of the test pipe, one from the four-bolt flange (at the turbo exhaust inlet) to the engine block and another at the three-bolt flange (at the exhaust manifold junction) to the block. So I think it is well braced. The turbo is also attached to the intake manifold with two bolts and an L-bracket.

The trap cat has a brace on the underside and some test pipe builders have included one but I chose not to. I think the braces at either end of the test pipe will be sufficient and there are 11 pounds less weight to support with the trap cat gone. If necessary, I could cobble something together from a length of heavy strap iron and a couple of hose clamps around the test pipe.

Take a look at the pictures, see if you don't agree it's enough bracing.

Jeremy

I could easily make that and sell them for the right price if anyone is interested.
Let me know and send me some drawings.
jon@monstercraftsman.com

dieselkid
 

How much would you want for one of those??? I have a 85 300SD that needs one.
-Stephen