How much does removing the trap oxidizer improve performance? - PeachParts Mercedes-Benz Forum

RLNAMERCEDES100 · #1 08-15-2002, 06:14 PM

I have a 1987 300D turbo that needs the trap oxidizer removed because of a recall. I was wondering if anybody would know if this will improve the performance of my car? If so will it improve acceleration also? Thanx

psfred · #2 08-15-2002, 08:04 PM

You will get slightly better performance than when a functioning trap oxidizer is in place.

However, if you are getting the trap oxidizer replaced because it is plugged (and MB won't replace it otherwise!!), you will get a HUGE increase in performance -- you are just about dead in the water now! You also have a dead turbo, too, don't forget.

The only reason, apparently, that my brother's SDL was still running was that the seal ring on the trap had blown -- we were hearing a strange whistling noise (sort of like a quiet OTR truck turbo) -- thought it was the turbo, was in fact the exhaust sqealing on the way out!

Peter

mike riemann · #3 08-16-2002, 07:07 AM

Greetings Psfred et al,
Re teh "squealing " sound...my 85 300CD has such a noise...AND I have noticed that the acceleration is rather mushy until the tach reached 2500 - then it comes in nicely...did you brother's machine behave in such an unseemmly manner? If so, I guess I'll just have to locate this gizmo and see if I can figure out if it's stopped up or not...

Mike

jcyuhn · #4 08-16-2002, 09:45 AM

I got a huge increase in performance when mine was removed. With the trap-ox in place there was never any real surge when the turbo came online. It kind of gradually built boost from 2K RPMs to about 3K RPMs, but there was never a point where it really kicked in.

Had the trap removed. Now when the engine reaches 2K RPMs Bam! it kicks in and you're gone. Tons more midrange torque. Where it feld OK for a diesel before, now it feels pretty fast - noone ever thinks it's diesel powered.

Elripster · #5 08-16-2002, 11:51 AM

Is the trap oxidizer that big old thing in the exhaust line under the car towards the rear? If so, what is involved in removing it. IE, what diameter tubing is required? Does it need to be bent or is it simply a straight through-no-change-in-diameter mod. I can easily weld a new pipe in place but I don't have a tube bender.

Frank.

surfblau · #6 08-16-2002, 12:13 PM

Elrip,

The trap oxidizer is on the left of the engine (when you look at it), basically part of the exhaust manifold, sort of above the turbo. It is about the size of a 2# steel coffee can (4-5inch diameter). That is for a 603 engine.

It sounds like you are talking about the resonator (or some other part of the exhaust system that I really have never had to think about).

Elripster · #7 08-16-2002, 01:23 PM

Ooohh. My car has the 617. I don't recall a part like that on it there so maybe it doesn't apply to me. The part I was thinking of could be a resonator type thing.

Frank.

surfblau · #8 08-16-2002, 01:39 PM

617 cal 85 and later probably had it at one time, but I think most have been replaced by dealers...

RLNAMERCEDES100 · #9 08-16-2002, 02:43 PM

I'm taking my car in to have the trap oxidizer removed today. I hope it inproves my acceleration. If so I'll be set. I'll post back to let everyone know how it went............

psfred · #10 08-16-2002, 06:49 PM

You will be VERY pleasantly surprised!! If it was plugged, you were way down on hp!

Mike:

I suspect one of the two following problems -- if you do have a trap oxidizer, check the seal between the exhaust manifold and the oxidizer. If you have soot buildup there, the oxidizer is plugged and the seal blown. You will be able to hear the whistle and locate it to the seal, too.

If you do not have a trap oxidizer, I suspect you have a leaking or wornout turbo. Highly unlikely to leak (the noise is escaping air from the joint between the turbo and intake -- I think it is a "gasketless" joint, but not sure. If the bolts are broken or loose, the pressurized air is leaking out. Also check for a busted flex tube on the EGR and for other leaks in the intake -- some of them have a pressed in sheetmetal plug, and if that is loose, out comes the air. You will get power when the turbo manages to spin fast enough to overpower the leak. I don't think MB has a vent like the Volvo (which doesn't have an overboost swtichover valve).

It is possible for the turbo to make the noise, too -- we heard a strange whistle on the SDL (after a funeral, of all things), and found that it wasn't the brakes, but the air filter to turbo pipe off, allowing dirty air in and noise out when the air recirc valve opened.

Hopefully it isn't dead turbo bearings. You can check those by removing the intake line with the engine off and rotating the turbo by hand -- should spin freely with a little "sticktion" and require the same effort all the way round -- no sticky or rough spots. There will be a little sidways play, but should be no axial play (or is it the reverse, I can never remember) due to the floating sleeve type bearing -- it spins in a pressurized oil bath with more clearance than you would expect. At any rate, if it is stiff or jerky, it won't spin properly and you have a bad bearing set. You will also have exessive oil on it, and probably some blue smoke from leaking oil seals, too.

Peter

gsxr · #11 08-16-2002, 10:39 PM

As other said, if your trap is plugged, you're in for a shock when the car comes back from the dealer. If the trap is clear and just being removed as preventive maintenance, the increase is 5hp and 1-2mpg.

Mine was OK before but when removed, there was a noticeable power difference, and MPG increased too. I'd like to pull out the new catalyst (downstream in the new dealer-installed free exhaust) and see if there is a few more HP to be had. You just need to install the old front pipe, or ask the dealer to leave that one piece on the car (don't know if they will, though.)

BTW - easy power test is to clock the car 0-60 on flat road, should be 11 seconds (at sea level). If much slower, say over 13 seconds, something isn't right.

Good luck!

#12 08-19-2002, 11:10 AM

MY DEALER WILL NOT REPLACE MY TRAP OXIDIZER BECAUSE IT IS UNDER 30000 MILES, WILL IT DAMAGE MY CAR? I DO HERE SOME WHISTLE NOISE SOMETIMES, THANKS...

gsxr · #13 08-19-2002, 12:29 PM

If your car is a 1987 300D.... then your dealer is an idiot. The 30k intervals are gone, the NEW fix is to REMOVE it. Call MB USA if necessary, or go to a different dealer... not sure if the same applies to the 1985 CA models, which also had the trap.

#14 08-19-2002, 03:22 PM

Removeit totally and get 5 more horses and better throttle response in the mean time while potentially saving you turbo. Trap Oxidizer synonymous with breathing through a straw while running a mile.

psfred · #15 08-19-2002, 06:45 PM

MB will NOT replace the trap oxidizer unless it is plugged. If it isn't, leave it strickly alone. DO NOT remove it yourself, as doing so voids the warrenty on your turbo, and it pobably has damage from the trap. MB WILL NOT honor the replacement warrenty if ANYONE besides a dealer replaced the trap oxidizer. They have been know to run for 150000 miles or more with no trouble at all, so it isn't an absolute necessity anyway.

If you drive it, the trap will eventually fail, and then you will get the catalyst and a NEW TURBO (since the trap falls apart and eats the turbo). The total cost of doing this yourself is around $2500, surely a better deal than a few more horsepower.

Try another dealer, too -- they can be reluctant to replace it since they don't get much money for the work.

And check to make sure it is actually there - it is a large ovoid think a little larger than a football on the passenger side of the engine. If there is only a rectangular pipe a couple inches square covered in reflective insulation, you already have the catalyst in there and the issue is moot. There aren't very many trap oxidizers still installed.

Please note that the "recall" is NOT to replace the trap oxidizer reguardless of condition, it is a program to replace the trap when it fails, only.

Peter