C55 De-cat pipe

[Shude]

Actually it should have a positive effect. More torque....

More torque doesn't mean improved fuel economy although I'm sure there is a pile of maths that demonstrate more torque at lower revs will slightly improve the economy.

The ECu can't measure back pressure.

Even if it can't be measured the increased airflow through the exhaust may increase air intake (which is measured) and that will definitely cause the ecu to increase fuel injection to keep the mixture straight.

Anyway I need the fuel economy to improve because I'm building it into my portfolio of reasons why I need to remove the cats on my CLK55. I'll need strong evidence if I'm to get this past the missus...

 

[BlackC55]

More torque doesn't mean improved fuel economy although I'm sure there is a pile of maths that demonstrate more torque at lower revs will slightly improve the economy.

Even if it can't be measured the increased airflow through the exhaust may increase air intake (which is measured) and that will definitely cause the ecu to increase fuel injection to keep the mixture straight.

Anyway I need the fuel economy to improve because I'm building it into my portfolio of reasons why I need to remove the cats on my CLK55. I'll need strong evidence if I'm to get this past the missus...

A C180 and a C200 for example.

The C200 will often return better MPG. More torque?

 

[Shude]

How much louder is a 55 with cats and resonator removed? Just thinking resonator might be step too far, volume-wise.

A C180 and a C200 for example.

The C200 will often return better MPG. More torque?

With both engines on a bench in laboratory conditions I'm sure you could prove this

 

[BlackC55]

Its not too loud at all.

Come down and have a listen to mine ot Jacks

 

[Shude]

Its not too loud at all.

Come down and have a listen to mine ot Jacks

Tempting although it's a bit of a trek just to listen to a loud exhaust

 

[Sp!ke]

Actually it should have a positive effect. More torque....

The ECu can't measure back pressure.

You cant get more torque magically, something other than pixie dust must change for this to happen like stuffing more air/fuel mixture through the engine.

No, the ECU doesnt measure pressure but I would assume as in the motorcycle world, because of the reduced back pressure, unless the correct pressure wave is created via exhaust design or the valve overlap is somehow modified to suit, a more free flowing exhaust will allow a greater amount of the unburnt mixture to escape via the exhaust valves which the lamda sensor will pick up on and attempt to compensate for by instructing the ECU to richen things up a little and squirt a bit more fuel in via the injectors. On a carb fed bike, you'd need to do this manually by increasing the main jet size.

I only briefly touched on thermodynamics when I studied engineering but what I do know is that it is a particularly complicated area and farting around with exhausts will often lead to negative performance gains unless you know exactly what you are doing.

Whilst I have to agree that it sounds lovely, I think a more scientific approach as to what is going on exactly with the fueling should be considered before making performance assumptions.

It would be useful to see the lambda output before and after the modification and ideally get the car remapped to suit.

Whilst fuel use isnt such a great issue on most race cars, on a road car, back pressure and more importantly pressure waves should be given much consideration to ensure you're not wasting shed loads of precious fuel out of the exhaust valves. Flames out of the exhausts on the overun might look cool but its a sure sign that there's unburnt fuel post combustion chamber.

 

[Will]

a more free flowing exhaust will allow a greater amount of the unburnt mixture to escape via the exhaust valves which the lamda sensor will pick up on and attempt to compensate for by instructing the ECU to richen things up a little and squirt a bit more fuel in via the injectors.

If a greater amount of unburnt fuel is escaping into the exhaust system, surely the lambda probe will identify that the mixture is becoming richer and compensate by providing less fuel, not more?

Ignoring the flow characteristics, the original cats and exhaust section weigh a significant amount more than the replacement sections that we are seeing here - the weight saving would probably offer some improvement in MPG alone

 

[BlackC55]

The C43 cat and resonator must weigh 25KG. The decat pipe weighs about 2kg.

 

[Bobby Dazzler]

Anyway I need the fuel economy to improve because I'm building it into my portfolio of reasons why I need to remove the cats on my CLK55. I'll need strong evidence if I'm to get this past the missus...

Let's start a new thread which is absolutely rammed with "evidence" of why it's a good idea, which can easily be shown to SWMBO.

I can see a potential series of threads to justify things like:

Decat pipes reduce fuel consumption by 7.2% and harmful emissions by 11.4%, with payback period of 62 days based upon just 2 journeys of 10 miles per day

Sexy time 5 times a week can help extend your life by 12 years, marriage by 19 years, and on average consumes 780 calories and burns 19 grammes of fat

etc

See just don't make the claims wild.

PS If Mrs Shude reads this I happen to be Chair of the NATO Steering Commitee for Exhausts Saving Planets, and a leading advisor to the Chinese Government on Motor Vehicle Pollution. Not to mention my PHD in the Psychological and Physiological Effects of Human Engagement, and advisor to NASA.

 

[artyman]

I think you forgot to mention your Phd in Bull***t

 

[just240]

First impressions of my C55 with the De-catt

Hi everyone, I thought I would post my impressions of my car & notice in changes since picking it up from Olly's garage this afternoon & making the journey home to N. London.
Firstly, this was the first time I actually met Olly as when I dropped off my car last week he was not at the garage that day & I met & spoke with Jack who was really great & showed me his C43/55 engined conversion with the decatt. This time both Olly & Jack were there & they were very proud to show me the work that had been carried out on my exhaust and the new sound of my car.
I was very impressed with the quality of fabrication however, what amazed me the most was the reduction in weight!! Removing the secondary catts & resonator + steel pipework must have saved a minimum of 25kgs. It actual terms you probably would have struggled to pick up the previous catts & resonator alone but the replacement pipe you could handle in 1 hand as its only 2kg!
The sound is absolutely stunning & is exactly what I was after,,, on the cold start up it does sound very meaty however after about 1 minute when the engine warms & the over rev decreases the sound drops to a very low considered burble. The best way to describe it is that it sounds like a standard C63 now when stationary!
On the drive home I noticed the car does pick-up ever so slightly better, & the sound is fantastic when you put your foot down. However, it is completely non-intrusive & nothing like the slap-on big-bore back boxes that the Jap or Ford young guys stick on their cars. In fact on the motorway home I actually had to changed down a couple of times & push hard to appreciate the sound again. The C55 also has so much sound deadening that from inside the car on an open motorway/road you don’t notice it much at all.
Olly was great to deal with & he provided me with a wealth of knowledge concerning other mods however, what I was most impressed with was his complete honesty, & non-pushy sales speak. I found him to be a completely genuine guy compared to previous "performance garages" I have dealt with in the past who always want to sell you the most expensive, latest mod/gadget without issue.
Finally, anyone thinking of having this mod is very welcome to come and have a listen to mine in N. London (Barnet/Finchley Area) if they can’t quite make the trip down to Prestige. Believe me – you Won’t be disappointed!!

 

[mercedescl500]

After 20k miles here's my findings

Ok here's my 2pence worth of actual experience. I have run Long Tube Headers (including Kleemann remap via It's uk distributer *to address Lambda issues, open loop and closed loop parameters) on my CL for nearly 20k miles now and here's my findings;

Power/Torque = better off the line acceleration off the line WITH cats.*

Mid Range = much better without cats.*

Top end = much better without cats.*

I believe that a NA engine will accelerate off the line faster WITH catalysts *than the same car with NO catalysts if the engine was originally designed to use cats. *I do love the way it sounds but in my experience you could lose a little bit of power in the lower rev range. *But you will make more power (or at least feel like it is) from 30mph+ to 1 Lepton. HTH. *

Olly the fabrication looks A++ very nice indeed.*

 

[DRBC43AMG]

Just had Olly's secondary decat and resonator pipe installed here locally and HOLY SMOKE what a noise I LOVE it and have to say that the sound the C43 should have made in the first place. Discrete when potting around but when the pedal goes to the floor its like thunder. Installed also my Green filters and the combination makes it a n° 1 in the sound charts.
Will get a sound video during the week-end with a decent camera and microphone and I'll post it here when done

Despite the lousy weather during the weekend, I managed to do a short cold start of the C43 with Olly's decat and resonator pipe installed. Will do a short acceleration video when the weather is better. In the meantime, enjoy: YouTube - ‪C43 cold start after secondary cats + resonator delete.AVI‬‏

 

[Gaz74]

That does sound really rather nice! I'm interested to have this set up fitted to my C32, as it is just a bit subdued really and would like a bit more bark to go with the bite! Would you mind giving me an idea of cost and if you need the car there for more than a day?

Thanks!

 

[DRBC43AMG]

Get in contact directly with Olly (Blackc55 on here) or through his shop advertised also on here

 

[DRBC43AMG]

Get in contact directly with Olly (Blackc55 on here) or through his shop advertised also on here

Found the right tread with all the info: http://www.mbclub.co.uk/forums/engine/108647-c32-decat-resonator-delete-pipe.html

 

[DRBC43AMG]

Get in contact directly with Olly (Blackc55 on here) or through his shop advertised also on here

Found the right thread with all the info: http://www.mbclub.co.uk/forums/engine/108647-c32-decat-resonator-delete-pipe.html

Sorry posted twice by mistake

 

[just240]

C55 de-catt & Res delete update

Just a quick update to everyone following the de-catt & resonator delete that Olly did on my C55 last week.
On Saturday I took the car to Cadwell Park race track in Lincolnshire, (luckily the weather held out up north!).

In order to be allowed onto the track all cars had to have a noise (exhaust) test. As the C55 red lines at 6500-7000 RPM they asked me to put the car in neutral & rev the engine to 3500-4000 RPM while they measured the noise. The level they recorded was only 83 decibels!
For comparison a friend of mine who was also racing his E92 M3 (with the BMW standard 4 exit exhaust) had to rev to 4500 RPM & his car recorded 88 decibels. So I can totally confirm that the exhaust modifications are completely non-intrusive & fall very well within the legal tolerances required.

I am also very happy to say that 2 guys with TVR’s )Giffin & Sag) came over to me & were really impressed with the sound of the car, I also had 3 or 4 bikers who were there racing ask me about what had been modified as they had never heard a Mercedes sound so good & finally the official track day photographer commented that under full acceleration on the straight the car sounded the best vehicle all day by a long shot!

 

[JonMad]

Thanks, Olly showed me the vid of him revving the C55 and a question I had today was what did it do to noise for static and drive by tests.

Kind of handy the Mercs don't let you rev that high in neutral!

Sounds like it was enjoyed by a few people on the day

 

[BTB 500]

I'm sure that a partial decat won't be too much of a problem but you should be aware that the (fairly new) MOT noise check is subjective, and not based on a dB reading

Method of Inspection
assess subjectively the effectiveness of the silencer in reducing exhaust noise to a level considered to be average for the vehicle

Reason for rejection
a silencer in such a condition, or of such a type, that the noise emitted from the vehicle is clearly unreasonably above the level expected from a similar vehicle with a silencer in average condition