Lilbullet

Hey all,

Long time lurker and previous owner of various Mercs, including a 190E 2.5 16v and 2 R172 SLK’s.

I have had my 55 for a while now and planned on tuning the car on a dyno. The car wouldn’t play ball, maxing out at 4k revs and seeming to be running too lean at WOT.

The tuner guessed that the K&N air filter had damaged the MAF and recommended replacing it, which I’ve done with new. The plugs were replaced last year and the car is not showing any codes.

The car drives well and is still fast and some even opine that it’s OK given the mileage of 120k, but the plot is odd. These cars reach max power at 5750 so it’s way off and I’m guessing leaving power on the table.

I haven’t been back to the dyno since replacing the MAF and the K&N air filter (with stock)

Any opinions as to what I should be looking for before trying again?

Thanks
Dyno plot MY05 SLK 55

Lilbullet

Ok, so it seems like I’ve posted this in the wrong place. I’ll try elsewhere unless anyone can chip in with a view.

HPDECLK55

This is a R172 55?

Crossover at 5250 is normal but the decline in power suggests some kind of restriction, either inflow or out. Honestly it appears as if the torque and HP plots got switched but it's all wrong that way too. Yikes.


Edit: I see now this is an 05, R171. Low power but within range here.

Lilbullet

Thanks. So the plot seems normal but the numbers are down. The car has a replacement cat back exhaust and resonator delete, but peak power should be nearer 5750 on these cars so I’m trying to figure out where I should look next. Could the exhaust, a Becker, cause this restriction?

HPDECLK55

I had made a long winded post about power and driveline loss, then remembered a friend of mine did this on his project SLK a couple years ago. I feel like his estimate on base power is definitely a little low.

Appears your car is pretty healthy but I never did get to see his graphs to see where his TQ/HP curves sit compared to yours. It certainly looks like you're exhaust limited. You can see in his video how the car with stock exhaust struggles to build RPMs on the dyno.


I can say for sure that with a tune and a better exhaust (headers and cat delete) these cars REALLY wake up in the mid-upper RPM band.

Hope this helps.

eurochargedw210

Was it in dyno mode?

Lilbullet

Yes, it was in dyno mode - I made sure by doing it myself.

So I took it another dyno having changed the MAF and the stock air filter.

The first run was similar numbers to the last and then a puff a black smoke, smell of eggs and it seemed to improve, culminating in the final run with the plot. So I put some Cat a clean in the fuel tank and took it for an Italian tune up. Yes, it is fast, perhaps fast enough as is.

Note, the figures are crank figures, which is down about 10%, but I did some more work clearing the cats so I expect it’s probably running closer to stock bhp, with only a Cat back, resonator delete and X pipe.

The plan is to invest in headers (long tube) and a tune, but the car is very fast as is so I might not bother.

Second dyno session

HPDECLK55

32x crank HP isn't bad for a 17-year-old M113.

These cars are super fun and quick. Problem is, after a while, everyone wants more haha.

smsunder

Thanks for your post where I'd like to present my recent dyno results performed June 28, 2023. Here are my results that may help explain what you've encounerted with the dyno and where the power band is of the M113 NA engine.

I bought my 2006 SLK55 AMG last October and my tuner,

=AZUa21IEKKiKCx5FqKERjLHWlVIZU0stj9eeazGi0lHVUDjxwyxUh1IxzGF-3J6rY7syON6DMxm1MdFLF48dFIkOVRB4Fxuco0M3cluJDtY6ahTDQ8QL8v-E4A6Q4L6lZ-m-xQ2plHXfdbYqSc6xj1J5&__tn__=-]K-R]Josh Chase

Facebook Post

from The Mercedes Swap Shop has done the ECU tune(s) where the 2nd update, he added timing and took some fuel out at the power band of this M113 engine (4,500rpm-5,500rpm) and the 3rd tune he removed the rev limiter in P and N!

I had the car dyno'd this morning at Dyno-Comp in Scottsdale who use an inertia type dyno by Dyno Dynamics (typical 15% lower reading than a Dyno-Jet) where their 21 years of dyno and tuning experience cite that an automatic 2wd car loses 27% due to drive train loss and another 7% loss from elevation and ambient temperature (85F) which is shown in the actual dyno graph below so don't criticize the power as I've just explained why. The car is running great with 411crank HP and 421 torque. Stock is 355hp at the crank and 376 torque. Josh's tune added 56 crank HP!

The Dyno Dynamics dyno is known as "Dyno dynamic =heartbreaker" however, it is an inertia dyno. The dyno hp and torque are wheel horsepower and not crank. For true crank horsepower requires the engine out and run on an engine dyno with all accessories (A/C, power steering, alternator, and sometimes even the water pump) are turned off for hp at the crank.
Dyno's are used for tuning taht you mention you're going to do where what you're wanting to see is the "delta" from the initial baseline dyno compared to post-tune dyno.
The RPM range looks normal where the report format RPM range should have been changed on the graph to a starting higher RPM rather than 800 on the low end scale.

Here is a picture of my dyno that will be used as my baseline as I'll be adding custom made long tube headers and replace OEM cats with free flow cats. After these bolt ons then it will be tuned again to take into account the better exhaust flow, TCU tune for sharper/faster shift points at higher rpm, optimzed heat and pressures for improved shifting. My tuner estimates I'll gain another 45-50whp after this work.

In reference to your second dyno on a Dyno Jet where you gained HP mine would be 352 wheel horsepower in its current state.

Lilbullet

Here it is with a Kleemann header and a dyno tune:

eurochargedw210

Lilbullet

@Eurocharged, I’m guessing this is one of your maps. That being the case, do you think my Becker cat back exhaust with X-pipe is impacting the numbers in any way, or is 375 bhp too much of a good thing for an 18 year old car with 115k miles. I’m super pleased with the results.

eurochargedw210

these are numbers to the rear wheels, and if I had the stock 18s on 275, would probably make more power. Not sure what’s up with britts and saying BHP numbers. Which is reality they aren’t real.

375 isn’t enough. I am guessing it’s kleeman shorty headers? MSL is a great company, just can’t believe they let you install those. X pipes are great and needed to make good power. I’ve seen more stock slk55 a make 310 to 315whp. As they are rated more than the older engine, also you have .5 high compression. This car could easily make 350whp with a legit header system, and exhaust.

Lilbullet

Kleemann shorty headers with a downpipe, yes. To be fair, 375 is plenty for this car - 323 was already plenty with the Quaife and semi-slick tyres, so I’m expecting this car to fly.

My view is that for whatever reason, the car made 323 the last time it was on a dyno, so the tune and headers has made an extra 50.

Also for comparison, these headers purchased, fitted and dyno tuned cost less than a set of MBH headers without fitting or tuning. I’m happy with that.

I pick it up tomorrow so I’ll update the thread with my driving thoughts over the 100 mile trip back.

Lilbullet

All, so I picked up the car last weekend and all hasn’t gone well so far. Less than 10 miles into the 100 mile journey back home, the ESP, ABS & Speedtronic fault code lit up and I lost the speedometer reading. This was an intermittent fault and appeared to be engine bay temps related. Another fault that it developed 40 or so miles into the journey was a CEL, later read as P0422 & P0432 (inefficiencies in the rear CATs) which should have been dialled out in the tune.

Getting the car back home and I noticed also that one part of the air intake was broken. The shop doesn’t believe that this would have impacted the tune so I’ll get it sorted and they’ve agreed to sort out the tune to clear the CEL when I get it back there.

As for the ESP, ABS fault, reading through the forum some have had issues with the added heat of the headers and have fabricated heat shields to protect it. Whilst Claus at Kleemann is adamant that the hoarders only reduce temps rather than increase them, the fault does appear as things start to heat up in the engine bay and not from cold. Claus is also of the opinion that the fault, like the CEL, are linked to the tune.

I’ll be taking the car back to MSL on the 27th and hope it’ll get sorted out. The good news is that it achieved 320 rwhp on the dyno and the noise of the thing at WOT is incredible. Butt dyno says the performance is not night and day different - it’s faster for sure, but the noise is addictive.