Originally Posted by Pumpkinate

I'm dubious about the claim that turbo-back downpipes don't make much difference. Both Weistec and Kleemann sent me dyno graphs of tune vs tune plus downpipes and there was definitely a significant difference on their claimed results.

Originally Posted by BerndV

As I stated earlier, the only way to assess the performance gain of the turbo back pipe vs downpipe alone is to install the downpipe, dyno, then install the turbo back portion and dyno again on the exact same dyno with atmospherics standardized for both runs. Unless someone is willing to go to this much trouble, the benefit of the turbo back pipe cannot be objectively evaluated.

Originally Posted by Zod

But you clearly state other wise here

''5) Catless down pipes that retain the factory crossmember. Contrary to what most aftermarket exhaust sales pitches would have you believe, the factory exhaust breathes extremely well. With factory turbos, most of the improvement with aftermarket down pipes comes from weight reduction. Don't even think about a turbo back pipe if you are retaining the factory turbos unless you enjoy throwing your money away. ''

You make it sound as you either have tested, or have proof

Originally Posted by BerndV

As I stated earlier, the only way to assess the performance gain of the turbo back pipe vs downpipe alone is to install the downpipe, dyno, then install the turbo back portion and dyno again on the exact same dyno with atmospherics standardized for both runs. Unless someone is willing to go to this much trouble, the benefit of the turbo back pipe cannot be objectively evaluated.

Originally Posted by gaspam

http://forums.mercedesclub.org.uk/sh...d.php?t=140875

^here's e63s corrected run on same dyno before and after (stock vs weistec tune/turbo back dps) .... looks to me like it putting out about ~30whp/ 70ft-lbs trq more than typical tune only results which are usually around 600whp/700wtrq

now if that doesnt work for you then here is the owner's car with just the original MSL box tune box where you can see in graph below it made corrected 553 whp/ 564 wtrq w/o the turbo back pipes... in the graph above you can see with the addition or the turbo back pipes to just the MSL tune box it made corrected 597whp / 595 wtrq... a gain of 44 whp / 31 wtrq just by adding turbo back downpipes and not retuning for it



http://forums.mercedesclub.org.uk/sh...d.php?t=133726

Originally Posted by BerndV

The above data is also very interesting because we can see that even in 4th gear, the TCU is being more intrusive than in 5th gear.

Originally Posted by BerndV

One can infer from the speed portion of the graph that the stock, MSL box, and green Weistech runs were all made in 4th gear. Therefore, the comparisons of stock and MSL box vs Weistech tune and exhaust are only valid for the 4th gear portion of the graph. Thus, the addition of the Weistech tune and full turbo back exhaust over just the MSL box yields roughly 17.5 HP and 117 ft lbs of torque. The Weistech tune with turbo back exhaust over stock yields 92 HP and 200 ft lbs of torque. This is pretty much exactly where all the tuners claim to be with a tune and catless downpipes, again depending on how hard they are pushing on the ECU tune and the fuel quality to which the tune is matched.

Originally Posted by BerndV

The question still remains, what is the HP and torque difference between just catless DP's and a turbo back DP.

Originally Posted by BerndV

Thus we are back to one of the original points I made at the beginning of this thread; the TCU is the primary limiting factor when we discuss maximum performance in the lower gears i.e. 0-60 and quarter mile..

Originally Posted by gaspam

nope, there is a reason people dyno in the gear that is closest to 1:1 ratio (5th on our gearbox), because its a straight passthru while 4th is underdriven gear on our cars..Under driven gear will lose more torque to inertial loss (as you are accelerating the mass of the engine/driveline quicker) ..

Originally Posted by gaspam

well we know non-turbo back catless dp's make around +10 whp , so the gain of turbo dp vs non-turbo dps is around 20-30whp depending on if you are still accepting tuner's (weistec) claims

Originally Posted by gaspam

lol so your point is that we shouldnt get a tune or downpipes because our 1/4 mile times will be same as a stock car since TCU will interfere... ok oh wait, doesnt a tune/dp car trap about 6-10 mph than a stock car? weird, i guess that those performance modifications actually did do something

Originally Posted by gaspam

you keep wanting to argue that turbo back dp's dont do much of anything but every member that has them says that it does.... but what do they know, they only have them on their cars and you dont, so you know more than they do about it... sounds logical

Originally Posted by BerndV

Gaspam, I spent 15 minutes on the phone yesterday evening with a technical rep from Dynojet regarding the dyno graph in dispute. I emailed a copy of it to him so that we were both looking at the same thing. The guy laughed when I read your quote

Originally Posted by BerndV

The ONLY reason for the HP and torque difference between 4th gear and 5th gear is ECU/TCU intrusion in the lower gear.

Originally Posted by BerndV

Have you ever taken a university level physics course?

Originally Posted by BerndV

It has ZERO to do with "inertial loss" as you put it. The guy laughed when I read your quote. As an aside, do you have any clue as to the relatively massive difference in inertial force of the combination of rotating dyno drums and rotating drive wheels relative to the rotating inertia of the engine internals and the gearset in the lower gears? Have you ever taken a university level physics course? The reason cars are dyno tested in the gear closest to 1:1 is because this is the gear least likely to be intruded upon by EMS protection systems and/or torque converter lockup effects

Originally Posted by BerndV

I hate having to be repetitive with posters that either have poor reading comprehension or simply have not read the entire thread. The difference between turbo back downpipes and downpipes alone can only be objectively evaluated by dyno testing with the downpipe alone, and then adding the turbo back portion and dyno testing again with no other changes. This must all be done on the same properly calibrated dyno with atmospherics standardized. IMO, the turbo back pipe with stock turbos is worth about 10 WHP

Originally Posted by BerndV

An improvement of 15 WHP (Weistech claims 10-20 so let's split the difference) .

Originally Posted by gaspam

that's weird because my old 1980 jeep CJ7 put down different whp/ trq in different gears and it doesnt even have a TCU to intrude! wonder what caused that

you do realize cars have been dyno'ing well before EMS?ECU systems existed on cars right? lol... here;s a good explanation from LS1tech, since you dont get what i am saying, of why different gear ratios affect dyno numbers:

"Higher ratio gears will give you lower chassis dyno numbers for a strange, but logical reason. In essence, the DynoJet calculates hp based on the time it takes to spin up the 2800lb roller assembly. It's basically work divided by time and rpm. Think about this: If you car is at idle in neutral and you stab the throttle, it will take time to accelerate to...let's say 1.1 seconds. Now let's say it takes 8.2 seconds for your car to accelerate the DynoJet from low speed to top speed with 3.23 gears and 7.3 seconds with 3.73 gears. Dyno printout says 355 rwhp with 3.23 gears and 346 rwhp with 3.73 gears...why?

Think aabout this: In the 8.2 seconds it takes to spin the rollers with 3.23 gears, it would still take the motor about 1.1 seconds to overcome its own inertia (idle to redline). There's about 13.4% of the work used just to accelerate the motor itself. With 3.73 gears, the time to reach redline decreases to 7.3 seconds. Divide the 1.1 seconds into the 7.3 seconds and you will see that overcoming the inertia costs 15.1% of the work with 3.73 gears. There is less hp available during this time period to spin the rollers so the DynoJet will read a slightly lower hp figure. Make sense, or did I lose you?"

Originally Posted by gaspam

now there you go again straight up LYING... where does wesitec claim 10-20 hp for their dp's? actually if you go to their site you will see they post claimed dyno numbers of 608 whp/660wtrq for ecu only and 645/724 for ecu/ dps... do the math, no wait, i dont trust you since you are a proven liar... so difference is +37 whp/ +64 wtrq... here are graphs for your viewing pleasure.... and you can see under the curve the gains are even bigger... look at 4K rpm and you will see about a 60-70whp diff and about 75 wtrq difference... but to you thats probably not that much

Originally Posted by BerndV

According to the quote above, the dyno will report "355 rwhp with 3.23 gears" and "346 rwhp with 3.73 gears". Therefore, the lower the gearing (higher gear ratio number), the more HP the dyno indicates. This is making the exact opposite argument that you are claiming! According to this logic, the HP and torque numbers from the Dynojet graph in question should be lower in 5th gear than in 4th. However, the opposite is the case. If it has nothing to do with the ECU/TCU intrusion, then I await your explanation for these results since you claim such impressive mathematical literacy.

Originally Posted by BerndV

Of course your old Jeep put down different numbers in different gears. Nobody has claimed that dyno numbers in different gears will not generate different numbers.

Originally Posted by BerndV

The ONLY reason for the HP and torque difference between 4th gear and 5th gear is ECU/TCU intrusion in the lower gear.

Originally Posted by BerndV

the benefit of the turbo back pipe cannot be objectively evaluated.

Originally Posted by BerndV

Whether you manipulate the rear end ratios or the transmission ratios is irrelevant. The example that you gave to school me demonstrates that lower gearing and thus higher gear ratios generates more indicated HP on a dyno.

Originally Posted by BerndV

I am simply bored and out of patience with our exchanges, so feel free to post away on this thread. My responses at this point will only be to other members who have something logical, well reasoned, well informed, and relevant to contribute.

Originally Posted by BerndV

the benefit of the turbo back pipe cannot be objectively evaluated.

Originally Posted by gaspam

and alas, i repeat myself , the fact remains that the dyno for the MSL tune box only vs the MSL tune box + wesitec DP's was done in the same gear, so the other gear run is a moot point.... that the owner gained of 44 whp / 31 wtrq with just the addition of turbo-back downpipes.... I say again, what part of that dont you get ??? So back to the original point that brought all of this up, turbo-back DP's do provide good gains and have been objectively evaluated

Originally Posted by BerndV

the benefit of the turbo back pipe cannot be objectively evaluated.

Originally Posted by BerndV

the ECU/TCU in the E63/CLS63 is completely different and represents a significant bottle-neck in getting HP and torque to the ground. That was my entire point in starting this thread.

Originally Posted by BerndV

I stand by my statement. Most of the improvement with downpipes and stock turbos is from weight reduction.

Originally Posted by BerndV

This thread pertains primarily to the car I own and in which I am thus most interested, the AWD E63S. Differences in WHP and WTQ are greatly impacted by which gear you select in ways that had no bearing on your old Jeep. Therefore, my commentary is directed at this vehicle only. Gear vs dyno results for other cars are irrelevant

Originally Posted by BerndV

the benefit of the turbo back pipe cannot be objectively evaluated.

Originally Posted by BerndV

With that said, I am asking you politely how we can accurately parse the difference in HP and torque gains between a well designed catless downpipe alone vs Weistech's full turbo back exhaust system. I have made the assertion that the only way to do so would be to install the well designed catless downpipe, dyno, add a turbo back pipe, then dyno again.
If you think my assertion is somehow faulty, then please explain why.

Personally, I am a big fan of the classical definition of "the scientific method" as it was drilled into my head as a college freshman. One goes from an observation to a hypothesis to a theory and then, rarely, to a law. First and third party attempts to disprove the hypothesis are made over and over. If the hypothesis cannot be falsified, then we have a theory. It may or may not ever become a law. Therefore, I am always sceptical of all claims in every intellectual and cognitive realm. Add in the potential for profit or monetary gain, and my scepticism is piqued.

Originally Posted by BerndV

If I grant you a full 20 WHP gain for the best designed turbo back exhaust (Weistech) vs catless DP, the question then becomes subjective; is it worth the extra parts and labor expense? Even on a RWD E63, installing that midpipe without lowering the engine would be a frustrating cuss fest. I don't know what the cost is for installing a midpipe on a RWD E63, but as someone who does most of the wrenching on all my vehicles, I would not even contemplate doing it. Perhaps Kponti can chime in here. On an AWD, we are looking at $8000 installed. A salesman at Weistec named Zack told me flat out that it would be a waste of money to add their turbo back system without installing better turbos in the AWD models. A full 20 WHP improvement on this car equates to a theoretical 0.12 second improvement in quarter mile elapsed time (http://www.nitrousexpress.com/oldweb...alculators.htm) That assumes all of the additional power is put to the ground without any type of TCU interference in the lower gears. So my original point at the beginning of this thread was that the price/performance ratio of a midpipe on this car with stock turbos seems unjustified unless you have the ability to get around the TCU. BTW, the same improvement in theoretical quarter mile time can be had by dropping just over 100 lbs from the car. Swap the two batteries for lithium ions (super easy DIY) and you are more than half way there. The added benefit to weight reduction is better handling and fuel economy (not that I personally care about fuel economy).

Originally Posted by BerndV

A TCU tune doesn't exist that will fix this problem. Nobody, and I mean nobody, has been able to crack the Bosch encryption for the TCU. These intermittent "lag" problems all originate from the TCU limiting the fun in the first three gears. These turbo engines produce so much torque relative to any NA cars from the past that something had to be done to protect the drive train from endless warranty claims and the resulting customer dissatisfaction. The faster that wet clutch locks up relative to mashing the pedal in lower gears, the greater the shock that is transmitted to the drive train. The torque multiplication in gears 1-3 is therefore limited by the algorithm in the TCU that monitors dozens of variables.

The car I owned previous to my current 2016 E63 was a 2014 E550 4MATIC. The E550 produces less HP and torque and has a torque converter. The combination of less torque and a torque converter (which delivers torque with greater smoothness and less shock) means that the TCU in the E550 can come equipped from the factory with a much less aggressive algorithm for drive train protection. Therefore, as I experienced when transitioning from the E550 to the E63, certain driving conditions resulted in more pronounced lag or delay when flooring the throttle pedal.

The solution for this problem with the turbo AMG cars is a standalone ECU. Speedriven has been developing this very product in conjunction with an ECU manufacturer in Europe for close to two years now. It is now available for M279 powered AMG's and will be alpha-tested this coming winter in the M157. However, you will lose your cruise control, so there is a compromise that comes with the standalone ECU. Also, be prepared to spend $$$ to strengthen the transmission at a minimum, and you will need strengthening of everything else between the transmission and the wheels if you start adding bigger turbos.

This TCU "problem" is the reason the AMS Alpha 9 is only 0.1 seconds quicker in the quarter than the Alpha 7. It is also the reason the Alpha 9 is also slower than the Alpha 7 from 0-60. Without a standalone ECU or a complete bypass of the factory EMS, you can install bigger turbos, stronger rods and pistons, and all the ancillary performance modifications you care to throw at this car and will only gain an edge in roll-on half mile or one mile passes, which is a pretty useless improvement outside of the realm of YouTube video hits and ego inflation.

If you choose not to go the standalone ECU route when it becomes available, the best mods for this car in descending order of importance are:

1) ECU Tune; pick your poison, Renntech, Alpha, and Speedriven are probably the top choices. Tunes are not rocket science, HP and torque improvements are contingent on how much the tuner wants to push the numbers. The "lesser" tunes will often result in more daily driver satisfaction because they don't push the TCU as much.

2) Improved intake volumetric efficiency i.e. AMS carbon intake system, Renntech carbon intake system (IMO the AMS is a better design).

3) Improved intercooler performance i.e. full AMS turbo cooler system. This is especially important if you track the car, make repeated 1/4 mile passes, or operate daily in a hot climate. The resultant heat soak kills performance in turbo cars.

5) Replacement transmission pan that improves fluid capacity and cooling. High transmission fluid temps are one of the variables that the TCU algorithm monitors. My preference is the Speedriven billet pan because the Weistech is cast aluminum. One crack from a rock and your MCT is toast.

5) Catless down pipes that retain the factory crossmember. Contrary to what most aftermarket exhaust sales pitches would have you believe, the factory exhaust breathes extremely well. With factory turbos, most of the improvement with aftermarket down pipes comes from weight reduction. Don't even think about a turbo back pipe if you are retaining the factory turbos unless you enjoy throwing your money away.

6) Replacing the exhaust resonator with an H pipe configuration along with lighter and better breathing mufflers. Almost zero HP difference here with factory turbos but you get more weight reduction and a properly designed H pipe will prevent drone. Again, the AMS exhaust with either their mufflers or the Renntech's would be good depending on your aural preferences.

After that, it is all about weight reduction. Lithium Ion batteries are an easy weight reducer i.e. Braille lithium Ions. This and exhaust are the first mods amateur motorcycle road racers like myself make for relatively dramatic weight reduction on liter bikes that start at over five hundred pounds dry. After replacing the two batteries with lithium ions, be prepared to start dropping big money for bespoke carbon, magnesium, aluminum, and titanium parts.