Hulk

Wow, that's pretty much stock bro

E55Greasemonkey

The big restriction stock is the manifolds, and more importantly the manifold outlet/cat inlet, I measured something like 1.8" diameter. Crazy.

Hulk

Manis and collector and all those bends lol

GT-ER

Get back to is when you go to the track but I insist there is at least 20whp to be gained by doing your exhaust properly.

E55Greasemonkey

First time at the track today, with this car...

1st 2 runs were my best, I'd call this real world testing..Drove 1 1/2 hours to the track, pulled in, registered, dropped the drag radials to 20 PSI and went..

12.02@ 116 1.77 60ft
12.03@ 116 1.79 60ft
First 2 runs only 35 minutes apart, left side slip is earliest

I am picking up another stock midsection and will have the headers connected properly, and get the tune cleaned up. The weather was mild to hot today.

cij911

Not bad, but I would have thought better with your setup. Interesting that your results are almost identical, but your mph is lower than what I would have thought.

I'd be willing to bet $$ that you are running crazy rich. My box tune started off at 10.5:1....Unless you logged and tweaked the tune, I am sure that is why you are so down on power.

E55Greasemonkey

I was expecting high 11's with the mods I have. I think you are right. The car feels rich to me,it has since the tune. I have a bucking/hesitation when taking off too. And the amount of black soot I saw in the pipes that the muffler shop had off last visit leads me to believe it too. The tips got black and there was black soot all over the rear bumper/trunk last week. I am going to have it dyno tuned on Dec 1st. I have a wideband bung installed but no wideband yet...

GT-ER

I still insist that your exhaust is holding you back. You may be rich and leaning it will make it quicker but your exhaust has power left to unlock.

E55Greasemonkey

I am planning on taking it to the muffler shop on Monday, to have the aftermarket resonators removed and the proper Kleemann downpipes installed. Not as easy as it sounds...I've been to 3 different shops and none of them have done, or understood, what I wanted to do.

I will try shop #4 on Monday.

lowprofile

^ I'm with you, I want my exhaust quiet. IMO, your exhaust looks fine, barring a clogged cat or such. Look elsewhere for your power loss. Are you datalogging? This is where you need to invest your $$$/time.
Those resonators are pretty long, are they Yonakas?

Jakpro1

Wish we could get a look at your boost numbers somehow. Be interesting to see how much psi/bar over stock the smaller pulley is giving you.

E55Greasemonkey

Am I really losing power though? Look at Berti's numbers from today...

https://mbworld.org/forums/w211-amg/...-lots-fun.html

He's trapping the exact same @ 116 MPH and we have the same mods, except his exhaust is even more radical.. Does this show that the exhaust/cats really aren't that restrictive?

Yes those are the 22" long Yonakas, but in 2 1/2"...The 3" were too big. I figured the longer, the quieter. I still have a bad drone at 2k, the yonakas didn't fix that, they made the fun sounding part of the exhaust quieter, but not the resonance. Friends suspect some of the resonance are the 2 1/2" custom downpipes from the headers causing a venturi effect and speeding up the exhaust gases...Interestingly, when it's cold out, or the cooler the exhaust, such as a short trip, the resonance is not bad..the hotter the exhaust, the worse it is, the faster the flow when it's hot.

I am contemplating some side branch resonators to cancel the drone, but every muffler shop I've been to locks up when they see the 2 3/4" factory pipes, side branch resonators would be like going to the moon

I have the TORQUE APP for my phone but it's logging capabilities are limited. Can't drive 120 at the track and stare at my phone ya know

Again, these runs today were hot, some back to back, etc. On the way home at night as the air cooled, the car felt better of course. And interestingly, a friend I raced on the way with a Turbo'd VW pulled a car or two on me, but on the way home we were dead even.

With todays heat I bet my IAT's were up there towards the end of the 1/4

E55Greasemonkey

My Torque app has a pressure sensor reading but it never seems to read correctly.

GT-ER

Just in case, but map sensors read in absolute pressure so whatever number it gives you you must subtract 14.5.

With nearly the same mods and a better exhaust setup I ran 11.8@119mph ( all of the runs trapped high 119's, one of them being 119.8 ) on a high 80*/low 90* day with HUGE humidity ( over 60% ) and dumping fuel in 2nd and 3rd gear from my box tune ( low 10's in 2nd and high 9's in 3rd ). The only difference to our mods was that I had a 178mm pulley but no supercharger pulley and my exhaust was free from cats and straight through. I didn't have injectors nor throttle at the time.

I'm sure your temps are a lot cooler and less humid than mine and the pulley difference between us is marginal ( maybe 20whp ) but if you add the exhaust difference ( which I believe could be another 20whp ) you get the 40whp you are missing ( I put down 507whp so it's more like 58whp difference but I'm just messing with numbers ).

Check and maybe fix your A/F ratio and test again, but I still think it's mostly your exhaust.

lowprofile

I should have worded that differently. I read through your thread late last night and thought you already concluded that you were low on power. My point though still stands, your exhaust is not hurting you imo.
Berti_00's similar track numbers with same mods does support your case.

DVC

It seems that there are some exaggerated expectations of this blower pulley.

cij911

Not at all....It is similar to a 172mm, but the REAL issue is in the box tune. He is running crazy rich and probably down on power by as much as 30whp (my guess).

Anyone modding their cars should start with a good OBD2 datalogger and wideband IMHO. Otherwise, you are just guessing what your car is doing and playing with fire....

DVC

Trying to work this out..

Have you seen the same boost with the blower pulley as the 172mm crank pulley?

A 172mm is supposed to make around 3.5 PSI over stock. I don't see how the smaller blower pulley can make more than maybe 1 to 1.5 PSI (it's not that much smaller than the stock diameter). At 14hp per 1 PSI, the pulley shouldn't be worth much more than 20hp, whereas the 172mm around 50hp.

Seems like the blower pulley is a great way to get a new clutch with a little more power.

Great point about the wideband! From what's been posted I'd be afraid to run a canned tune without one.

cij911

I am basing my comment from memory...If you search posts from Shardul you can get the boost and corresponding crank pulley size (maybe it was 168mm). Regardless, I can guarantee you the issue is the car is running too rich and the issue has nothing to do with the OP's exhaust setup.

berti_00

man i cant wait for december 1st to get our real dyno tunes dialed in and than see how we do at the track

E55Greasemonkey

Had my exhaust "redone" today, made an interesting discovery or two. Looks like the resonators came apart inside from the heat. I'm guessing they weren't designed to be installed so close to the headers.

My second concern is where all the stainless packing went..it mostly appears to have blown backwards and compacted in the undamaged section. I will have to boroscope my factory secondary cats next week to make sure they are not partially clogged.

On another note, when the muffler guy convinces you that going from 2.75" to 2.5" is no big deal, keep in mind that 2.5" crush bent ends up being 2.25" or less

I purchased several sections of 2.75" mandrel bent stainless pipe, months ago. The last muffler guy didn't want to use it.

At the new shop today, I caught the guy starting to crush bend 2.5" pipe again, and stopped him and explained what I wanted, and he let me under the car to show him. He used my mandrel pipes and sectioned it in place. It's not real pretty but certainly a big improvement, and no more restrictions. It will have to do for now, I wanted to get it done before the dyno day/retune Dec 1st.

GT-ER

My exhaust is 2.5 mandrel bent. No crushing for me.

Good find...told you it was the exhaust ( even if it was for other reasons...lol ).

E55Greasemonkey

Good call! Thanks

DVC

Way to get those crush bends out of there. Some theories state a crushed 2.5" is worse than 2.25" due to flow. Who knows.

Why not throw a new I/C pump on there for ****s and gigs?

Looking forward to your dyno tune results.

E55Greasemonkey

My car seems to be down on power since the exhaust downpipes were redone, both off the line and on the highway. Yesterday was about 70F out, just didn't seem to have the torque off the line like before, and on the highway from 70-100 wasn't as thrilling as it was before. I unplugged the engine control unit hoping to reset the adaptations, and will drive it later today. Tomorrow I will reset all the adaptations with STAR. Weird, but I am thinking the crush bends and the added backpressure really brought my torque curve down low which "felt" a lot more powerful.