Dyno shows big loss 3100-3800 RPM, but air fuel ratio not affected.
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Member
Joined: Apr 2017
Posts: 86
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From: New Zealand
C55 Wagon Midnight Blue, SL55 Brilliant Silver, E55 Designo Mystic White
Dyno shows big loss 3100-3800 RPM, but air fuel ratio not affected.
Puzzled;
Three runs in dyno mode, same loss 3100-3800 then another smaller at 6500 RPM each time mean wheel spin can be ruled out I think. Operator suggested tune was forcing car to back off timing, but my mechanic noted air/fuel ratios would probably blip if car went into limp mode, so suggested torque converter.
Transmission guy today saw fault codes, cleared, told me to drive it hard then bring back to see if they reappear; On to-do list for next week.
This car used to have the jerky problem from start in first, which same mechanic suggested was because too much torque, does not do it anymore. Now, feels like gearing is too tall, lots of slippage, a CVT flaring.
I recently bought SL55 which we all know has same trans (except different final drive), and in that particular car is like night and day compared to my C55 right now; It is tight, shifts fast at exactly the right moments when cruising, quite jerky coming to stop, creating a feeling of tamed beast.
Need to know;
Would air/fuel ratios change at WOT if going into limp?
Does torque converter lockup when in dyno mode?
Can anybody who understands dyno charts make an educated guess whether this is engine or trans?
TIA.
Last edited by idlebumski; Sep 12, 2020 at 04:54 AM. Reason: Spelling
Senior Member
Joined: Jun 2019
Posts: 453
Likes: 91
From: DFW, Texas
2017 AMG C63
See bold below
need to know;
Would air/fuel ratios change at WOT if going into limp?
Yes.
Does torque converter lockup when in dyno mode?
Not sure about Dyno mode on your car, however all car should lock up under wide open throttle.
Can anybody who understands dyno charts make an educated guess whether this is engine or trans?
Definitely trans. Notice how the line on the dyno picks up the exact same curvature it would have had without the dip? Shows the engine was doing fine and Just didn't put power down during that range. If the engine had problems , usually the line would stay lower or slowly climb backup.
TIA.
Would air/fuel ratios change at WOT if going into limp?
Yes.
Does torque converter lockup when in dyno mode?
Not sure about Dyno mode on your car, however all car should lock up under wide open throttle.
Can anybody who understands dyno charts make an educated guess whether this is engine or trans?
Definitely trans. Notice how the line on the dyno picks up the exact same curvature it would have had without the dip? Shows the engine was doing fine and Just didn't put power down during that range. If the engine had problems , usually the line would stay lower or slowly climb backup.
TIA.
