B Feelgood

The last 2003 SL55 that I had made 498 horsepower and 565 ft-lbs of torque at the wheels in third gear. In 4th gear it made 511 horsepower and 585 ft-lbs of torque to the wheels.

This latest 2005 SL55 that I Just finished up just made 447 horsepower and 510 ft-lbs of torque to the wheels. We could not do a dyno pull in 4th gear as the transmission kept downshifting to 3rd every time for some reason while in dyno mode.

Both cars had the exact same maintenance suite completed and same modifications except for two differences. The latest 2005 has 550cc injectors and cast 20" wheels while the 2003 had forged wheels and stock injectors. Also, the 2003 had 37k miles while the 2005 has 30k miles.

*MODIFICATIONS*
- 77mm clutched pulley
- Belt wrap kit with Gates K080525 belt
- 550cc injectors (Bosch EV14 52lb)
- Green air filters
- Additional heat exchanger and Pierburg pump
- Split cooling
- Secondary cats and resonators deleted with x-pipe
- Custom dyno ECU & TCU tune

Now there was about a 20 degree ambient temperature difference between dyno days for the two cars but it was the same facility and on the same exact dyno. The AFR was also a touch leaner on the 2003.

I've tried replacing the belt tensioner with a new OEM piece and checked for boost leaks. Both cars peaked at around 12.8 lbs of boost during a log.

Not sure if the ambient temperature difference and the couple of aforementioned hardware differences constitute a 50whp delta between the 2 cars or not but I was expecting closer numbers?





2003 SL55 4th gear pull



2003 SL55 VS 2005 SL55 3rd gear pull

drothgeb

Man, those curves look almost the exact same, just 50 different. I would chock it up to larger heavier wheels or different settings. Try not to get too hung up on numbers from different car dynos at different times.

The only thing I can think of you didn't mention was timing, if you wanted you could compare some timing logs if you have old ones but other than that you have same boost levels, and similar AFR car to car so I wouldn't sweat it.

Use the dyno to get as much power out of your current car that you safely can, and let the 1/4 mile be the comparo.

LandCruzer94

SL55 is geared a little lower on the final drive, would that make a difference? Edit Nm thought the 05 was an E55

hachiroku

20 degree's ambient air temp is not 20 degree's at the manifold...its probably 35+ degree's difference at the manifold. when you have more heat, you have less ignition timing.

but that being said...dyno's generally compensate for any changes in environment. does the car feel slower? the curve is dead on. have you logged boost?

seanol

The dyno did take into account the difference in conditions, it added 6% to the blue run and 8% to the red run.

IAT's were higher and the ecu pulled timing. When you pull timing the AFR goes richer and you see exactly what is on the graph. Your ambient on the second run was 93 degrees. You loose 3 degrees of timing at 94 degrees and 3 more at 113 degrees.

None of the cooling you have will get you below ambient so I would say you have no issues other than dynoing in higher heat. These cars need cold IAT's to make highest horsepower.

Since the curves are functionally identical just lower I would say heat and the requisite reduction in timing and richer AFR were the contributing factors.

In other words, looks normal to me!