Exhaust centre resonator box

[Kilmaine]

Does anyone have a 500 E exhaust system they could measure please?
My 1991 car which I have owned for 21 years requires a new centre silencer. I have just received a pattern one from Autodoc but the silencer output pipe is only 56mm internal diameter whilst the input to the rear section which it joins is 68mm ID. I don’t think this can be correct but would be grateful if someone could check an original system. Unfortunately I can’t check my old one as it appears to be a 129 part which must have been fitted decades ago! Any assistance gratefully received.

 

[gsxr]

The item in your photo appears to be for a 400E. The 500E unit is different, and yes it has a 129- part number. To mate with the 500E rear muffler, it needs a 3-bolt flange:

 

[Kilmaine]

Sorry that was a poor photo, the new Imasaf box does indeed have a triangular flange that will mate with the rear silencer. It was still wrapped up! However the outlet pipe from the Imasaf has an ID of only 56 mm whilst the old box has an outlet ID of 68mm as does the mating rear pipe. The rusty centre box currently fitted has a 129 no, viz 129 491 0301. This would appear to be an SL 500 box from what I can infer from the net. My point is that to fit a new centre box with an outlet 12 mm smaller than the existing must surely reduce the performance. My rear box actually has the number 124 491 6101 on the casing but was supplied as 124 490 7821 by a Mercedes specialist 14 years ago and is in good order.
So my question being does the new Imasaf box have an undersized outlet pipe or were they always like that?
I’m sure an erudite forum member will know!

 

[gsxr]

68-70mm is correct for the 500E muffler inlet. If your new box only has a 56mm outlet, something is wrong. Appears that someone fabricated that piece using a 400E resonator and attaching a 500E flange on the outlet? The proper 500E resonator / center box should look like my photo in post #2. Yours looks totally different, much more like the 400E/E420 unit.

The 500E center box may have a 129- part number stamped on it.

The 500E replacement muffler p/n you would order from a dealer is 124-490-78-21. This is NOT the same number stamped on the muffler itself. Mine has 124-491-60-01 stamped on it. The 124-491-61-01 muffler may be from a 400E/E420.

More pics here: Index of /images/M119/exhaust/400E_mufflers

 

[Kilmaine]

Thank you for your speedy response, that is what I wanted to know. The new Imasaf box is being sold as an E500 box. I approached another supplier in Germany today who is also offering the box and he kindly measured the outlet pipe and it was also 60 mm OD! See attached photos.

 

[gsxr]

Since the 500E resonator is NLA, it appears some vendors are getting creative with "custom" units.

I'd be sorely tempted to just have a Y-pipe installed instead. If you have catalysts, the Y-pipe sounds nice and weighs less.

 

[Kilmaine]

I was wondering about that. Yes I do have catalysts so maybe that’s an option. Does anybody in Europe offer a Y pipe as a ready to fit item? I was concerned that the noise might be obtrusive but see from other posts that the catalysts are efficient silencers. Is it noticeably noisier inside without the resonator box?

 

[gsxr]

There is very little difference with the Y-pipe replacing the resonator (which is a straight-through design anyway). Adds a tiny bit of rumble out the tips, but the difference inside with the windows up is small, IMO.

You are correct, the catalysts are efficient silencers. I tried a Y-pipe without cats and the low-rpm resonance was unbearable.

I'm not sure what European vendors offer a bolt-in Y-pipe though. @JC220?

 

[Kilmaine]

OK, thanks for your advice I shall look into that and if necessary get one made.
Didn’t understand @JC220?

 

[gerryvz]

Didn’t understand @JC220?

He's our resident Norn Ironer. Always faffin' around with his banjaxed Benzes!

 

[JC220]

There is very little difference with the Y-pipe replacing the resonator (which is a straight-through design anyway). Adds a tiny bit of rumble out the tips, but the difference inside with the windows up is small, IMO.

You are correct, the catalysts are efficient silencers. I tried a Y-pipe without cats and the low-rpm resonance was unbearable.

I'm not sure what European vendors offer a bolt-in Y-pipe though. @JC220?

I have checked this out a couple of years back and I am not aware of any European company currently offering a bolt on Y pipe for the w124 500E.

Yes the factory cats are very good at silencing. (Or restrictive depending on how you look at it!) I drove my 500E with only the factory cats just for giggles.

What I did was fit a new Fox Germany stainless Y Pipe and back box which is bolt on to the 500E and available. (They make them to order) I was very pleased with the quality. I did post lots of photos on the board please do search for Fox Exhaust and several threads will appear.

Note however that I do not think the Fox Y Pipe alone will fit a stock 500E backbox. I believe you need to buy the Fox Y Pipe AND Fox backbox for a bolt in system but the price is reasonable.

 

[gsxr]

Note however that I do not think the Fox Y Pipe alone will fit a stock 500E backbox. I believe you need to buy the Fox Y Pipe AND Fox backbox for a bolt in system but the price is reasonable.

This is correct. The factory muffler is flanged with a gasket, the Fox is a slip-fit with no gasket. Different designs; not interchangeable.

 

[TimL]

This is correct. The factory muffler is flanged with a gasket, the Fox is a slip-fit with no gasket. Different designs; not interchangeable.

@gsxr, Dave do you know what the PN is for the gasket between resonator and rear muffler?

 

[gsxr]

@gsxr, Dave do you know what the PN is for the gasket between resonator and rear muffler?

Yup! It is p/n 129-492-01-80, and this gasket can be re-used multiple times, until damaged. It's a steel-core gasket.