MHardy

Hi. I have a 2003 SL55 with 61k miles but it seems like most people hang out in the E forum, so hoping to reach more people here.

I am having a very strange problem after modifying my car. The mods that I have are a full exhaust system including headers, 85mm TB, 72mm clutched pulley, 550 injectors, TCU tune, ECU tune, belt wrap kit for supercharger, and cooling upgrades.

I've attached 2 charts and 2 data logs here. One shows the car with stock ECU tune, stock supercharger pulley, and stock injectors (SESSION 46 CHART). The other shows the car with all of the above modifications (SESSION 51 CHART). I've made over 40 pulls and all of the logs look very similar to the 2 posted here for reference.

My problem is with acceleration under a hard pull. For example... I'm driving on the highway or test track and prepare to make a pull for logging purposes. I put the transmission into Manual and shift into 3rd gear. I start the pull at 2000 RPMs and in between 2500-4300 RPMs, I get a big drop in power at random spots in that specific RPM range. It's usually closer to 3500 or so but happens once or twice in that range. It's more of a lumpy acceleration pattern instead of a nice smooth/progressive power buildup. It's worth noting the the car makes good overall power on the dyno (upwards of 550whp) but has a big dip of 100whp or so in the specified RPM range when all the timing gets pulled out.

When this power drop happens, I can see on my logging device in real time that timing gets pulled from -7 to +3 for example. This can last up to 1,000 RPMs before timing advances again to start following the programmed timing curve. You can audibly hear and feel the drop in power as up to 10 degrees of timing is significant.

This happens every time that I make a pull and is not related to engine coolant temperature, intake air temperature, throttle position, or map/boost pressure. It makes a healthy 15 psi of the top of 3rd gear so it's building boost just fine. I have had this happen at intake temps of only 45-60 degrees so it's not related to cooling.

I've been down the rabbit hole trying to diagnose this problem and here's what I've changed:
- MAP sensor
- Crank position sensor
- Camshaft position sensor
- IAT sensor
- Fuel filter
- Knock sensors (torqued properly)
- Engine mounts
- Transmission mount
- Spark plugs (tried a heat range colder with gaps set at both 028 and 022 with zero difference)
- Mixing fuel to 100 octane blend to rule out detonation (zero change or effect from this)
- Tried adding more fuel or making it richer within the tune in the specified problematic RPM range to cool cylinder temps with no change
- Tried decreasing timing in the specified RPM range within the tune with no change
- Searched around the engine for loose or rattling pieces that may result in false knock
- Tightened up exhaust system to rule out false knock

Here's what I've tested:
- Measured spark plug wire resistance and all were from 1900-2100 OHM and spec is at 2k
- Tried smooth running idle test in Mercedes STAR (Watched and recorded values for 5 minutes with engine hot/warm (Cylinder count exceeding parameters during 5 minutes: #1-15, #2-0, #3-12, #4-2, #5-2, #6-3, #7-1, #8-1)
- Tried stock ECU tune, stock fuel injectors, and stock supercharger pulley (car runs perfect and timing curve is flat/progressive)
- Tried stock ECU tune, stock fuel injectors, and 72mm pulley (car has timing/power drops in referenced RPM range)
- Tried swapping TCU tune for stock TCU with no change noticed
- Measured fuel pressure at idle (75-77 psi)
- Measured fuel pressure during WOT (68-71 psi)
- Tried starting the pull/run higher at 3,000 RPM with no change

I must've made over 40 pulls now and I check for codes with STAR after each test. There are never any stored/pending codes related to this issue and never any Check Engine Lights which makes this is more frustrating.

The strange this is that the car runs perfect with the stock ECU tune, stock injectors, and stock supercharger pulley. As soon as I change out the stock supercharger pulley for the smaller 72mm clutched pulley, the timing/power drop events happen immediately after. This happens on both the stock ECU tune (safe as bypass is still active and bleeds excess boost) and the custom ECU tune. The pulley is gapped to spec at 045.

It doesn't seem like anything mechanically wrong with the pulley as it's building boost correctly throughout the powerband with no noticeable belt slip as seen in the logs. It seems maybe more like the added stress on components with the addition of 5 lbs of additional boost, maybe ignition related?

During the Smooth Running Engine test in STAR, I can hear that the engine doesn't sound perfectly even or smooth if that makes sense. While it's idling, you can feel little shakes or exhaust tone changes even though the idle RPM is damn near rock steady. This is when the counter shows a cylinder outside of parameters in the test. I think that I can rule out the fuel side of things as fuel pressure is good and it happens with both the 550cc and stock injectors. The power dips don't correlate with boost pressure or fuel. There are no lean/rich spikes when the power drops occur and Air Fuel ratio rides along at 11.5.12 through the run.

So if you made it this far, congrats! I'm really out of idea here on what could be causing this. I could throw another $600-$700 at it and replace the coils and wires but without any codes for misfires, it doesn't seem like it would be caused by this.

Any comments/thoughts/suggestions would be greatly appreciated and maybe I'll throw some cash to anyone that helps to diagnose the issue!

nemiro

I don't have an answer for you, but I am curious what you are using for logging?

E55Greasemonkey

One thing about the stock Bosch ignition cables...which hopefully you are using... The resistance test is not valid. I've replaced many sets of these for specific cylinder misfires or general rough idle problems over the last 20 years on 112 and 113 engines. They always tested good with a multimeter, so after a while I stopped testing them. I've also seen problems with anything other than the Bosch cables. Beru is not good. So, how old are your ignition cables? They seem to be good for about 100k miles or 7 years, give or take. I don't know exactly how this would affect your timing though, unless the ECU pulls timing for minor misfires below the shutoff threshold. The Bosch cables used to be around $170/set years ago on eBay, then went up to around $250 and were getting hard to find. Or you can buy them from the dealer for $1600..lol!

MHardy

Hello, I use an Innovate LM-2 unit for logging.

MHardy

Thanks for responding. To my knowledge, the wires and coil packs were original to the car with 61k miles. Interesting to hear about your experience with cables.

I have read about people having problems with the Magnacore cables before. Last night I replaced all eight coil packs, ignition wires, spark plugs (again), and engine oil. I used Denso wires as I actually had a spare set on hand and stock plugs with resistors (NGK 3588). Engine oil looked fine and plugs showed no abnormal signs of wear or DET.

The idle definitely did smooth out some but this could've just been due to the switch from 1 heat range colder plugs that were gapped tight at 022 to stock plugs gapped at factory spec. Or possibly some of the wires were faulty.

Unfortunately though, the timing dropout still persists. I was able to make 2 short 3rd gear pulls from 2100-5200 RPM and 2000-6100 RPM with no problem. Prior to switching the coils/wires, I usually could make one full pull with no timing issue. Each subsequent pull got worse in regard to the timing drops.

It seems like it's maybe related to heat? Not speaking to engine coolant temps or intake air temps but heat from electrical buildup or resistance or greater demand from the 5 extra pounds of boost? The fact that I cant make 7 back to pack pulls with all the mods listed in the first post but with the stock supercharger pulley and have zero issues or timing dropouts intriguing. I then switch to the smaller 72mm pulley with zero other changes made and I get the persistent timing dropout after being able to make one good pull.

I did redo the Smooth Engine Running test in DAS/STAR again when I returned for the same test period if 5 minutes. Here are the results below this time after swapping plugs, coils, wires. The error count did decrease a fair amount but with cylinder # 1 still showing the most errors. Keep in mind that I've never had a code for misfires and still do not.
#1 - 9, #2 - 0, #3 - 3, #4 - 4, #5 - 0, #6 - 0, #7 - 0, #8 - 1
COMPARED TO PRIOR TEST RUN
#1 - 15, #2 - 0, #3 - 12, #4 - 2, #5 - 2, #6 - 3, #7 - 1, #8 - 1

Really taking a shot in the dark here. The valve covers have a substantial thick layer of powdercoat on them (primer for magnesium, color, clear). Whenever I removed the old coil packs, the area on the valve cover of which the pack sits on somewhat melted the powdercoat slightly. On the back of the coil pack, there is a metal strap in the middle. One of the functions of this strap is act as a heatsink of sorts to dissipate heat. Could the thick powdercoat be acting as an insulator of sorts and not allow the coil pack to cool down and with each subsequent run, the pack gets hotter? You'd think if this was happening though, there would be a lot of other people complaining about this happening. I know that the metal strap isn't a ground as each pack has it's own ground wire.

MHardy

Here's the info from this mornings datalogging. As you can see, the first two runs look good. Then each subsequent run after gets worse.

GinDistiller

The one thing I didn't see in your notes of combinations tried is whether the 85mm TB was on for all of your testing. I spent a lot of time chasing odd timing pulls and did a lot of the things you did (knock sensors, IAT, MAP etc). At the end of the day, the problem never went away until I switched back to a stock TB. For some reason these ECUs are REALLY sensitive to airflow on the TBs and their relationship to the bypass throttle body inside the supercharger among other things. Every change I made to airflow (moving from stock to shorty headers, now long tubes, 82mm TB, 80mm TB etc) made an impact, but now back on my stock TB the car suddenly has an even timing curve and is happy at all RPMs. I still have a 77mm fixed pulley and LTH, the larger TB made more power with those but I couldn't stand the inconsistency.

If you haven't, I'd try putting your stock TB back on, leave the other mods installed, and see what happens. Not sure if you're running an adapter, if you swapped the rear housing then it will obviously be a pain to change back but that is the next step I'd take if it were my car.

Fountain35

So the Bosch are good what about BREMI?
May just order a set so I have them around in case.

Thanks!

MHardy

Thanks for the response and sharing your similar experience. All of the tests that I have done did indeed include the 85mm throttle body. The car runs perfect with all of the mods in the first post (including 85mm TB) but without the 72mm supercharger pulley. Once I add the 72mm pulley, the timing curve gets lumpy and power is not smooth as it's dropping/adding up to 10 degrees (especially in the mid-range section of 2500-4300 RPM). This happens with both the stock ECU tune and custom ECU tune. Fueling, boost pressure, IAT, ECT, TPS all remain great but for whatever reason timing takes a dump. Looking at my logs, the throttle position sensor stays at 100% throughout the entire WOT run with no shutting or decrease in percentage when these little timing blips happen.

Going on feeling, it sure feels like a torque limiter being hit as peak torque occurs in that RPM range. From what I've read, the ECU pulls timing for less serious problems/events and for something serious, it would close the throttle blade, open the bypass valve, pull timing, and and/or change fueling in combination. Both the TCU and ECU tuners have assured me that there aren't any torque limiters in place that I should be running into however (limits raised above stock). I found an old post here on the forum from a member (Finny) who said that torque limiting parameters exist in both the TCU and ECU. On his friends E55, it was measured at 900nm (663 lb-ft). My car made 636lb-ft of torque to the wheels on the dyno which would kind of coincide with that number but again supposedly limiters are raised. I've tried other tuned TCU's with no change/fix but trying another tune from someone else is a bit more difficult.

It could be some weird scenario with to much air flow when combining the 85mm + 72mm pulley but would think that you would hear of the issue happening more often. I see guys running 90mm+ TBs and 18 psi of boost without complaints. However, maybe some owners like us are just more "in-tune" with our cars and notice something happening like this whilst the others don't?

ktwosteve2

It could be some weird scenario with to much air flow when combining the 85mm + 72mm pulley but would think that you would hear of the issue happening more often. I see guys running 90mm+ TBs and 18 psi of boost without complaints. However, maybe some owners like us are just more "in-tune" with our cars and notice something happening like this whilst the others don’t.



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Ahhh, the vagrancies of the m113k motor, one of the most interesting motors ever made by MB. I have had a couple of E55’s of the Kompressor design over the last 15 years. I recently acquired a 06 CLS55 as they seem to be getting scarcer and I have always a thought the sedan/coupe look to be eclectic. I was excited to start modifications on the car as I was building off the things learned on the E55 hoping to reach the next level without opening the motor. All the normal suspects were upgraded especially the cooling capacities, that is essential to the long term health of the motor. The LTH along with the upgraded injectors, Pulleys, looped fuel rail and larger fuel pump were installed along with a moderate VIR ECU & TCU tune. Along the way a couple of baseline Dyno runs were done to keep us going in the right direction. It was at that point I started getting a similar lag in the motor when it hit a certain rpm, it seemed as if it plateaued for a brief few moments and then picked up again but by that point all the gains were compromised.

We started experimenting with increasingly larger TB’s and found that it smoothed out as the size increased, around 90 mm it was better but still had a flat spot that caused a fatal dip in the linear progression. After much debate and a return to earlier days studying fluid mechanics and the like I stumbled on a very likely culprit. All the factory intakes and most after market intakes apparently weren’t designed as well as the engine was. After calculating what the m113k motor would require in cu. ft. of air flow and then factoring in the additional demand the performance options placed on the intake setups it was painfully evident that much like a 880 yd sprinter around 2/3’s of the way through a racing cycle the fresh air demands are so significant that both a runner and a car literally have to wait for their oxygen debt to be diminished before pushing ahead.

We sourced a 105 TB from HC stock and meticulously crafted a all aluminum 3 1/2” tubular intake, the more challenging aspect of the installation was getting it through the radiator/front grill reinforcements preserving the critical cubic area for air flow. It had a remarkable effect smoothing out the air flow and in turn stabilizing the graph showing a absolutely beautiful nearly straight line starting around 2500 rpm all the way to 6,800 rpm. In effect all the performance modifications are going to be compromised unless the basic tenent of the internal combustion engine especially when charged concerning the AFR! I will look for a copy of the last dyno run and get it up.

JoeJErnst

This right here may be your problem. The metal on the back of the coil packs is not for heat dissipation, it's how the secondary windings get grounded to the engine. Scrape off the powdercoat under each coil, and make sure the little feet at each valve cover bolt are also clear of powdercoat so the covers have metal-to-metal contact with the heads.

SICAMG

Not all the time but I have the exact problem. Power will all of a sudden kick in another 75hp and tone of engine changes when it happens.
I will have a timing drop from 17 to 9 degrees, than 7/10ths of a second later jumps to 19 degrees and holds steady. Happens at around 4,500rpm and cleans up at 5,000. A lot of power is lost with so little timing when it happens.

Keep us posted on your progress !

Dr.JassimQ8

I'm having the same issue exactly. Have you been able to solve it?

Thank you.

Robert AMG

iTrader: (1)

this is a known issue with 550cc injectors, revert to stock injectors with a good tune and it should be fine (if problem is only below 3000-3500rpm full throttle)