Custom exhaust options? (Merc Cosworth)

[JOEPRO]

My new to me old 1989 Mercedes 2.5-16 Cosworth has a fairly rotton exhaust system. The original downpipes has specific clearances stamped into them and I don't want to mess with that so the custom exhaust place will pick up from them backwards.

There are currently 3no mufflers total. I plan to omit / delete the first / front most muffler.

Old system layout:



I am unsure what is best regarding dual or single pipes performance wise? Eg options I see off hand -



Would a Y connector between the downpipes be important? Ill ask the stainless custom exhaust place too of course but id like an idea of what I want when getting into this detail

 

[Blobber]

On a straight engine the connection between the downpipes isn't needed, it will be done in the 1st box anyway, see how much space you have underneath as you may struggle to get a large single pipe into the 1st box?
The manifolds and downpipes together give you a 4 into 2 into 1 type "manifold" which helps with torque I believe so thats probably worth thinking about?

 

[JOEPRO]

She has factory headers. Looking at it closer I think the 1st original muffler had 2 pipes simply for space / packaging.

So best to go with this option A:

 

[dave h 2]

The first box may be a resonator to correct the tuned length of the system.
Option B removes half of the tri-Y design which will likely kill the mid range torque as Blobber suggests above, so far so good.
Hopefully your 'Custom Exhaust Place' knows what day it is and will notice the design effort put into the manifold and expect similar went into the rest of the system and advise you accordingly.

 

[bricol]

I'm not convinced yer average "custom exhaust place" quite has the test and development budget of such as Mercedes . . .

 

[JOEPRO]

I'm not convinced yer average "custom exhaust place" quite has the test and development budget of such as Mercedes . . .

Given all parts are obsolete for this car, something has to be done at the same time.

 

[Blobber]

I would keep the 1st two pipes of your down pipe the same length before merging into one as these are effectively the secondary pipes which as said above will affect the driveability, after that I dont think its going to matter too much but as also mentioned that 1st box may be a resonator rather than a silencer
Ok not the same engine but similar power and front pipe design is the Carlton at 217hp, the 1st pipes (secondaries) are 50mm OD merging into 60mm OD then splitting again into 50mm which may give you a starting point

The system is then dual 50mm pipes to the end, take no notice of the little link pipe as this was originally a V8 System

 

[JOEPRO]

I would keep the 1st two pipes of your down pipe the same length before merging into one as these are effectively the secondary pipes which as said above will affect the driveability, after that I dont think its going to matter too much but as also mentioned that 1st box may be a resonator rather than a silencer
Ok not the same engine but similar power and front pipe design is the Carlton at 217hp, the 1st pipes (secondaries) are 50mm OD merging into 60mm OD then splitting again into 50mm which may give you a starting point
View attachment 513748
The system is then dual 50mm pipes to the end, take no notice of the little link pipe as this was originally a V8 System
View attachment 513749

Thank you for pointing out the resonator element.

The main issue with this exhaust system is from the output of the 1st muffler/ resonator. Its been welded up before and badly. But in theory I could patch the 1st muffler and go double pipes from its outlet to the 2nd muffler like factory spec.

Is there an easy way to tell the physical difference between a resonator or muffler? If I cut the old middle box off and put an inspection camera into the 1st box would I be able to tell which it is?

 

[Blobber]

If it's a resonator there won't be much in it as its function is to alter frequencies, if it's a silencer it will probably have perforated tubes/baffles and wadding, that's my understanding anyhow!

 

[JOEPRO]

If it's a resonator there won't be much in it as its function is to alter frequencies, if it's a silencer it will probably have perforated tubes/baffles and wadding, that's my understanding anyhow!

The old outlet side double pipes are knackered on it anyway so ill go ahead and cut them later when I get home and take a look inside

 

[Turbo]

Cosworth spend a lot of time and money developing this car for Mercedes and that would include optimising the exhaust for performance without it being crazy loud.

So I would try to replicate the original system as much as possible. I should think any future owners of this rare car will want originality.

Surely there is a forum or group out for this car there who can steer you toward an aftermarket replacement system.

 

[Pigeon_Droppings2]

On my old mr2 I took out a resonator box as I figured that was where the cat went on some market models so bit useless!

It made the exhaust sound very annoying and I ended up retrofitting a resonator back in as I preferred the OEM sound track.

As above I'd stick with something close to the OEM design.

 

[minimutly]

The classic 4 cylinder (which is what the Cosworth Merc is?) needs 4 into 2 into 1 to make mid range torque. High end torque requires long 4 into 1.
So your manifold does the 4 into 2, and I would expect the 1st box is there to make the "into 1". As mentioned it's also likely to act as a resonator, which will reduce noise (mostly), but also likely to boost power at a specific (low) rpm. I would try to replicate it, do not give your exhaust place free reign, they just make pipes.

 

[JOEPRO]

Cosworth spend a lot of time and money developing this car for Mercedes and that would include optimising the exhaust for performance without it being crazy loud.

So I would try to replicate the original system as much as possible. I should think any future owners of this rare car will want originality.

Surely there is a forum or group out for this car there who can steer you toward an aftermarket replacement system.

The only aftermarket systems available are "cat back" style. The car has no cat but you know what I mean.

The rusty bad outlet pipes on my 1st section are too far gone to be able to bolt up an aftermarket solution. So some element of custom rework is required to repair that bad section.

 

[roofman]

my old S500 i straight piped the rear boxes...sounded wonderful and miss that car so much.

 

[MetalMonkey]

As turbo suggests - a lot of work goes into developing exhausts systems, especially on NASP engines where they can be "tuned" for specific properties.
If you want optimum, its probably best to replicate what is there unless you have the benefit of test data from dyno runs to qualify other designs - or you are just not that bothered in optimising it (nothing wrong with that either).

 

[JOEPRO]

Another option is this -

2.5 16v Cosworth Cat Back Stainless Steel Exhaust for Mercedes 190 (W201)

Stainless steel cat back exhaust system for the Mercedes 190 (W201) 2.5 16v Cosworth. Made entirely from T304 stainless steel so will not rust or corrode and should last the lifetime of the car. Lifetime guarantee. Made from OEM pattern so fit's straight on to the car with no modifications...

www.190parts.co.uk

So a new purpose made stainless "cat back" system and I make good the bad pipe section on the output of the old 1st muffler / resonator and patch it up as the 1st part also has at least one rust hole in it.

 

[Blobber]

You dont get much for £750 these days!

 

[Munkul]

Cosworth spend a lot of time and money developing this car for Mercedes and that would include optimising the exhaust for performance without it being crazy loud.

I always think this thought is hilarious no offence meant, I'll justify my reasoning -
sure, the intention is there, but the reality with mass produced cars is, they get something that gives "enough" power whilst being a. Quiet, b. Cheap, and c. Not spending time and money on development.

If you think the Cosworth badge means they spent loads on development, you'd be mistaken. There's just an ounce more of thought gone into it than would have otherwise.
Great cars, great engines, don't get me wrong, but the exhaust is absolutely utterly NEVER going to be a perfectly optimised part. It's the easiest part to cheap out on.

 

[JOEPRO]

I always think this thought is hilarious no offence meant, I'll justify my reasoning -
sure, the intention is there, but the reality with mass produced cars is, they get something that gives "enough" power whilst being a. Quiet, b. Cheap, and c. Not spending time and money on development.

If you think the Cosworth badge means they spent loads on development, you'd be mistaken. There's just an ounce more of thought gone into it than would have otherwise.
Great cars, great engines, don't get me wrong, but the exhaust is absolutely utterly NEVER going to be a perfectly optimised part. It's the easiest part to cheap out on.

The Merc Cosworth development is more complex than that! Note there were full blown DTM 190E race cars back in the day. These were 400hp roughly from memory with the same engine.

Then as part of the DTM racing rules, Mercedes had to produce road going versions. They were given the standard KE jetronic injection and the head ports reduced slightly to detune them down to circa 200hp for the 2.5L.

The race car likely had a totally different exhuast granted but this is what the "Introduction to service" manuals say regarding the exhaust on the road going Cosworths:





The headers are obviously very different to the other models that had a cast iron item.

It also says the mufflers and pipe diameters are larger.