OM603 exhaust - PeachParts Mercedes-Benz Forum

martureo · #1 06-16-2020, 07:59 AM

I'm looking to finish the exhaust on my OM603 powered S123. I don't have a good reference for the stock exhaust diameter.

Looking on this forum I've found references to a 2.5" and a 3" exhaust.

I have a lead on a stock downpipe from an 87 300TD and it looks like it will fit. But I still need to have the rest of the exhaust fabricated.

I'm looking at having one of these resonators put in.

https://www.borla.com/products/universal-resonators/

tjts1 · #2 06-19-2020, 10:05 AM

Straight pipe it. Mufflers, resonators etc make no difference on the turbo om603.

bsmuwk · #3 06-19-2020, 02:45 PM

Quote:

Originally Posted by tjts1

Straight pipe it. Mufflers, resonators etc make no difference on the turbo om603.

straight pipes on 603's drone and sound terrible at anything under 3k rpm.

Mxfrank · #4 06-19-2020, 02:53 PM

I'm not sure what happened to the first version of this thread. The correct diameter is 60.5mm, roughly 2 3/8" ID.

awsrock · #5 06-19-2020, 05:44 PM

Quote:

Originally Posted by bsmuwk

straight pipes on 603's drone and sound terrible at anything under 3k rpm.

I agree. I have a thrush hush or something of that nature on a 3" exhaust and it's barely louder than stock. Without it, it sounds terrible. Also if you go custom make sure the mounts are good and nothing is touching the body because a w126 resonates EVERYTHING

martureo · #6 06-19-2020, 10:25 PM

Quote:

Originally Posted by awsrock

I agree. I have a thrush hush or something of that nature on a 3" exhaust and it's barely louder than stock. Without it, it sounds terrible. Also if you go custom make sure the mounts are good and nothing is touching the body because a w126 resonates EVERYTHING

I'll probably reuse the stock mounting point and the same style of rubber hangers.

tjts1 · #7 06-20-2020, 01:21 AM

Quote:

Originally Posted by bsmuwk

straight pipes on 603's drone and sound terrible at anything under 3k rpm.

Maybe in an NA engine but certainly not on an om603 turbo. I drove mine for a month with just a down pipe while I was still ironing out the .971 head and exhaust manifold swap. Didn't drone at all. T3 turbo does all the muffling you'll ever need. Eventually I had the exhaust reinstalled (.961 and .971 manifolds dump the exhaust at different angles requiring some welding) and there was no noise difference what so ever.

bsmuwk · #8 06-20-2020, 12:22 PM

Quote:

Originally Posted by tjts1

Maybe in an NA engine but certainly not on an om603 turbo. I drove mine for a month with just a down pipe while I was still ironing out the .971 head and exhaust manifold swap. Didn't drone at all. T3 turbo does all the muffling you'll ever need. Eventually I had the exhaust reinstalled (.961 and .971 manifolds dump the exhaust at different angles requiring some welding) and there was no noise difference what so ever.

Looks like every other individual posting with experience on the matter contradicted your own. Oh well.

awsrock · #9 06-20-2020, 03:27 PM

Quote:

Originally Posted by bsmuwk

Looks like every other individual posting with experience on the matter contradicted your own. Oh well.

I don't know if it matters but all of my muffler-less experience was with a 3" exhaust and Hx30 / S200/ TD05 but I don't think it really makes much difference. Maybe a t3 and stock exhaust provide more sound control. I still wouldn't take the chance, there's hardly any benefit performance wise as long as you have a good flowing muffler or resonator. My logic was a bigger pipe with a slight restriction still flows more than a stock pipe with no restriction. On my SDL some of the bends were as small as 2" on the stock pipe.

tjts1 · #10 06-20-2020, 09:03 PM

Quote:

Originally Posted by bsmuwk

Looks like every other individual posting with experience on the matter contradicted your own. Oh well.

I'd like to see who else drove an an OM603/T3 with just a downpipe for a month and 2000 miles. Even tested it with at various speeds with a DB meter. There's zero difference.

Anybody?

neumann · #11 10-08-2020, 01:49 PM

Quote:

Originally Posted by bsmuwk

Looks like every other individual posting with experience on the matter contradicted your own. Oh well.

Yes, it drones on...don't waste your time. Get an exhaust system with a true muffler.

martureo · #12 06-19-2020, 10:23 PM

Quote:

Originally Posted by tjts1

Straight pipe it. Mufflers, resonators etc make no difference on the turbo om603.

No. I'm not interested in a drone of any sort.

I removed the muffler on my 84 300D Daily because of rust and put a straight pipe in its place. It's not incredibly loud, but its got a drone at speeds that I'm not interested in replicating.

Diseasel300 · #13 06-19-2020, 12:52 PM

Measuring my spare exhaust from my old 300SDL, I get 60mm or 2.38". 2.5" is probably close enough.

martureo · #14 06-19-2020, 10:23 PM

Quote:

Originally Posted by Diseasel300

Measuring my spare exhaust from my old 300SDL, I get 60mm or 2.38". 2.5" is probably close enough.

Thank you.

bsmuwk · #15 06-20-2020, 12:25 PM

OP

Look into Aero Turbine mufflers/resonators, they're all straight through designs and the ceramic packing is excellent. I've not had one blow through with high EGT's.