Marcus Frost

France,

Without getting extremely technical, you have nothing to worry about. What you read is more theoretical and does apply in certain applications but not in yours. PM me if you want to go into more detail.

FWIW, I have the Eisenmann on my car, and it sounds absolutely fantastic. I think you'd really enjoy them on your car, even if they are a bit pricey.

-m

vraa

MF - If he PMs you can you just post it in public? I want to know as well.

france2112

Marcus,
Your car looks amazing. Thanks for the reply.

I went up to Renntech today and got a detailed explanation from Hartmut (the owner). He told me essentially what you did, that it shouldn't really matter but he did say it is possible to lose a small amount of horsepower (almost un-noticable). Something about resonance, length of tubing, and resistance. He was a real gentleman and spent a lot of time just showing me around.
Renntech is in the process of making a tuned exhaust system for the 55's, 65's, and 600's. It shouldn't be too much longer so I'll just wait for their product. I have a new respect for how detailed they are at Renntech after spending a few hours with them today and I'm sure their exhaust will be very high quality.

It actually may be a mute point for me because I have the bug for a CL65 and may get rid of mine for one.

jimabbott74

Would love to hear one before I do mine.

Marcus Frost

After having the Eisenmann on my former 600, I will be going with straight pipes on the 65. Even with the Eisenmann the car was only as loud as my current 65 is stock. I really liked the Eisenmann but it's still a bit too quiet. This may be a point of contention with others, but I want my 65 to have (please pardon the language) like IT HAS A PAIR. The truth is I cannot imagine the car getting too loud for my tastes - however if some of you guys want to stay conservative with your cars, then maybe this won't be the route.

Personally, while I like my car being somewhat of a sleeper, at the same time I don't want to fall asleep in it

I will post before and after videos/sound clips for you all. I will be having my MB tuner do the fab work (they installed my old Eisenmann system) so I'm sure it'll look great - although like it's been said we're not talking about anything too complicated.

-m

V12Godspeed

So wil you just be eliminating mufflers and replacing with pipes? Seems very simple. I am planning on doing this for the 65 but I want to go all the way 3 inch from H pipe to the back. I think some performace gains are to be found in doing this. Please keep me updated with what you find. Thanks!

DoctorV8

The factory pipes are well designed, but the passenger side pipe flattens out into an oval shape just before the differential to clear the driveshaft. That's gonna be a difficult area to modify. I assume the AMG engineers have shaped that area to minimize restriction, but I agree, there are probably some gains to be made there. Do keep us posted.

V12Godspeed

Your CL is stock putting out 560RWHP? That is a monster...lol! very good numbers

I know exactly what you are talking about, it is somewhat like a sandwich...I will see what can be made. This is a nice restriction, not to mention the mufflers as well.

Murtaza

Straight pipe the mufflers

It still won't be too loud, I've heard an SL600 straight piped and I'd say it was on par with an Eisenmann E55 if not a bit more quiet. The turbos really absorb a lot of volume.

It will also cost a fraction of what Eisenmann would, 120bucks vs 3000.

V12Godspeed

I might try this very soon. Can't compete with the prices, lol!

Marcus Frost

That is correct. I'm not saying I don't appreciate the craftsmanship of these expensive mufflers, however I think in our particular application they may not really be warranted. I do not think straight pipes will make much power, but the sound will be great and you can't argue about the bang-per-buck...

-m

Vadim @ FD

I tried straight pipes on my S600 and it was too loud. Sounded great under WOT, but in everyday trafiic, just too much.

I ended up cutting out resonators and leaving stock mufflers alone. Just perfect.

Murtaza

What have you done to your S600 so far Vadim...

contigo

do you have a sound clip?

Bukwild

kinda scary with all the people that claim that have knowledge of boosted cars, no one has mentioned this.

When you remove mufflers and pre-mufflers you remove the resistance of your exhaust flow which will increase your boost. This raises HP but lowers TQ numbers. Your turbos will no longer have problems breathing and you will get more performance.

Downside. Is boost creep and tuning issues. Now that you have a less restrictive system you should have your car re-tuned. If the stock ecu sees your boost go above preset levels it will compensate by dumping more gas in. This fouls plugs and worse can cause "pings" if its running to lean. Pings are baddddddd.
I am new to these car engines but have destroyed several rotary motors in my rx7 from exactly what I have described above. It also has me wondering at what point these cars would require larger fuel injectors to safely run this type of power levels boosted. I also wonder who will be the first to run a alky injection systems to really cool the intake temps and make pump 93 basically race gas?

Marcus Frost

I am somewhat interpreting this as a comment towards me. You come from an RX7 background and let me tell you that these cars are nothing like RX7s. We do not have boost creep and we definitely will not have tuning issues from not having mufflers. Our ECUs do not let our cars run lean from the factory, and are far more sophisticated than the ones you may be used to.

Appreciate the "lesson" in thermodynamics but the M275/M285 V12 Biturbo and your 13b rotary engine have almost nothing in common. As I mentioned above, you are not making a big enough difference in these cars specifically to warrant the gloom and doom you posted about - not to mention the way your ECU deals with certain situations is very different from ours. I believe some guys (600 or 55) have messed with alchohol injection but it's not as straightforward as you seem to imply - personally I do not like running any auxiliary fluids or gasses on my cars (meth, alky, nitrous...)

For what it's worth - my car, without mufflers, ran a 11.5 @ 121mph on 20" wheels, stock.

Bukwild

comments were not pointed at anyone, they were general.

I do would however like to know how mercedes solved the ageold boost creep problem going up through the gears that every boosted vehicle in the world experiences. Does the stock ecu have a boost cut feature after the ecu sees x amount of boost? because there is only 2 ways to deal with it. 1 dump fuel in, which causes u to run rich, fouls plugs and you actually loose HP/TQ or holds the wastegate wide open until factory levels are back to normal which makes the car feel like it fell flat on its face.

What do these ecu's run for AFR's? What duty cycle are the injectors running at under full boost? these are all questions that I personally would like to know the answer to. I bet alot of other people who are risking there $30k engine would like to know as well.

Bukwild

"Our ECUs do not let our cars run lean from the factory, and are far more sophisticated than the ones you may be used to." My rx7 has a fully programable haltech e6x. Does'nt get a whole lot more complicated than that.

Marcus when it comes to tunning the rotary engine, our tuners have to build the most complex fuel injection maps there are. That's why there are so few in the world. Not compairing the 2 engines just merely stating that FI tuning principles are universal and when ever you are already above stock boost levels (ecu flash) and you remove resistance from the exhaust system which will make your boost levels higher you should have your AFR's checked on a dyno.

Thericker

You should stick to Rx7 forums, your statements/posts on V12TT's w/out mufflers are completely false. I've had my SL600 Dyno'd (mods in Sig below) a few times AFR's are normal @ 12.5 & boost/PSI have dropped to 11.5-12.0 from stk 14.5 PSI

Removing back pressure on these MB's equates into boost drop, not increase

Average SL600/65 AFR sits stock @ 12.2-12.5

Thericker

These V12TT engines cost a lot more than $30k & cutting off mufflers has ZERO effect on their future health. you really need to better inform yourself before posting this drivel...

Marcus Frost

Actually, it does. While most standalone ECUs give you great in-depth control, the amount of tuning you do on the dyno is a drop in the bucket compared to what OEMs do to get cars to run 100k miles in all weather conditions, fuel types, altitudes, etc. The manual for the Bosch ME2.8 is roughly 4000 pages, all in highly-technical German. We have pressure sensors in our airboxes for christ's sake. Yes, in our airboxes, so our ECU knows that the amount of vacuum generated for each bank of cylinders is uniform and therefore it will not overspin one turbo or the other to compensate for a lack of airflow in one of the intakes.

No disrespect Bukwild, but I've owned 6 90s era Japanese TT cars, including one that made over 1000hp @ 31psi. You are assuming a level of stupidity amongst V12 owners here that is unwarranted. I've had my SL on the dyno a dozen times or more (and if you did a search you could see some of my charts) and I can assure you it does not suffer from insufficient fuel, excessive boost creep, or a loss of torque. Our problems are quite different than what you RX7 owners have, although obviously, there are shared principles when talking about forced induction.

I suggest you do a bit more reading on here and about the community before you assume we are doing mods to our cars with no comprehension for the basic fundamentals of thermodynamics and forced induction. I can assure you, we have some very intelligent and experienced people on this forum who put a lot of effort into the development for the aftermarket and performance of these platforms.

-m