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#1
10-22-2009, 12:00 PM
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Need Guidance: Should I remove OxyCat for straight Pipe
Wondering if I could get a general consensus from CA model owners as to whether I should get rid of the oxidation catalyst that was installed when the trap cat was replaced. I've looked around the forum and I've seen that some junked their oxycat for a fiited peice of pipe. What's the reasoning? Need Benz knowledge. I can never get enough.
Thanks 1985 300CD 
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#2
10-22-2009, 03:37 PM
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The reasoning is that a less restricted exhaust will provide more power and better economy. I have not heard a lot of good comparisons of mileage before and after of people changing over to a straight pipe. It is obvious that using the federal exhaust manifold and changing it basically over to a 84 300D would increase mileage. The 85's have a different rear end ratio too that helps keep the rpm's down on the highway. The straight pipe doesn't have the filter but still some efficiency is lost compared to the federal exhaust manifold which output goes directly into the turbo. I personally do not think it is worth the money at this point. I get 24-25 mpg consistently on mine but that is about 50% stop and go and the rest cruising at 75 mph on the highway. The last couple of years I have put very little money into maintaining it and it runs very well. I think the best improvement (few more mpg) was getting some rebuild injectors with new nozzles since mine were the originals with 300K.
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85 300D Turbo
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#3
10-22-2009, 03:39 PM
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Quote:
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'98 E300 turbodiesel
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#4
10-22-2009, 03:48 PM
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Let say the following are true:
26 mpg before straight pipe 28 mpg after straight pipe $3 a gallon for diesel 15,000 miles a year $200 for straight pipe You would roughly save about $120 on gas a year or it would take about 2 years to get your money back. But if diesel prices go up or you drive 30K a year then it makes more sense to get a straight pipe. I would like to hear some good averages of people on here of before and after they installed a straight pipe. Speak up... 
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85 300D Turbo Last edited by NoCalMer; 10-22-2009 at 06:25 PM.
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#5
10-22-2009, 04:24 PM
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Ok, I see. So it's a matter of slightly better fuel economy. About the injectors, I have 127,000 miles and no info as to when the the trap was replaced w/ the Oxycat (I could get in touch w/ the previous owner and get that info if he has it). Replacement of injectors would be in response to trying to eke out a few more mpg's? Thanks for the feedback fellas. I appreciate it.
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#7
10-22-2009, 10:46 PM
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I'm in the 23-25 mile range and that pleases me just fine. Any other nuances about the Cali. model you can fill me in on? I bought this car because I wanted a coupe. Really wanted a coupe. Without being aware it was a CA model I bought it. In fact, I didn't even know they existed until I got the car. I did see the pictures of the engine and noted the air filter, thought it peculiar, but to be honest I coveted the car so much I didn't do a lot of research. I love it. Runs great. Couldn't be happier.
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#8
10-23-2009, 12:22 AM
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I changed my 85 cali over to like a 83 is set up.
Changed the down pipe,intake/exhaust manifold, turbo to pre avr. (84 - 85 have it). get the manifolds off a 78, 79, early 80 w116 300SD, this is pre EGR, think the EGR was installed in late 80. then nothing to block off. use a air filter like the federal one, or modify the cali filter. the turbo will sit a little lower, so the turbo inlet and the outlet pipe on the filter housing are at the same level. might have to cut the pipe and fab up a hose for the inlet. the 85 doesn`t have oil drain from the air filter to the pan like the Fed set up. the 85 cali is A GOOFY set up the way the oil vapors connect to the housing. It "T`s" off to the filter and straight to the inlet just before the turbo. Just run it into the turbo inlet. when we changed it over it was a different car. especially at higher altitudes like 9000ft - 10,000ft elevation. before the change, it was a dog, after, ran like a raped ape. as far as milage, I don`t remember. the cali starter is about twice what a Fed starter is. and also the cali turbo costs more, as well as the down pipe. the best improvement, is when we pulled the automatic, and swapped in the 4-spd. incrase of 2 - 3+ mpg. 29 to 31.94mpg on the last tank. check with the dealer, they should have a record when the trap was changed the last time. Charlie
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there were three HP ratings on the OM616... 1) Not much power 2) Even less power 3) Not nearly enough power!! 240D w/auto Anyone that thinks a 240D is slow drives too fast. 80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works
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#9
10-23-2009, 11:19 AM
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Thanks Charlie. I have an 85 300D that I may use for parts. Yikes, tho. That's a project, but that's part of the thing about these cars that gets in blood. Working on them is half the fun. If it turns out right, that is.
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#10
10-23-2009, 12:05 PM
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It looks like a lot of work, all depends where you are coming from. I just look at what I want, don`t think about the work involved, and focus on the end result I want to achieve.
Start looking around the JY for parts you want. don`t have to do it all at once. when we changed this over, I didn`t know or think about Pick N Pull type yards. so went to specific MB yards. so cost a lot more. example for the Down Pipe, I found it on a 82 300CD. guy charged $100. but it was the only one I could find at the time. then 3 or 4 yrs later the flex part cracked, and had to buy a new one any way.  A couple yrs later I found some on line auto supply sites and discovered the pipe at that time was $127 new . live and learn.Wish I had stumbled on this Forum 10 yrs ago  .In the Resources tab above, there is a write up and pictorial of a 85 SD being changed over. when you get rid of the Trap, you can still use your cali starter. Iam not sure, but I think you can still use the Cali Turbo, just might have to clock the compressor side some to line uip with the air intake. You will also need the turbo oil supply line from a FED set up. Charlie
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there were three HP ratings on the OM616... 1) Not much power 2) Even less power 3) Not nearly enough power!! 240D w/auto Anyone that thinks a 240D is slow drives too fast. 80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works
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#11
10-23-2009, 12:06 PM
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Quote:
 Injector nozzles are a wear item. They wear out. 120k is a lot of miles to put on a wear item.
__________________
'98 E300 turbodiesel
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#12
10-23-2009, 03:42 PM
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Quote:
It is more important to look at your mileage, starting issues, idle, and exhaust smoke than some number. Sure if you have a lot of smoke and loud idle at 120K then change them. It also depends on the quality of fuel you get too. A good filter and water trap should really help the injectors last a lot longer than 120K.
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85 300D Turbo
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#13
10-23-2009, 03:44 PM
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I would pull them and have them tested at a minimum.
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#15
10-25-2009, 08:34 AM
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Quote:
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'85 300D Cal 280,000 miles '14 GLK 350 60000 miles
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