Can a benz start experiencing noticable levels of lagging performance after 80,000 km? Although it is regularly maintained and looked after.


Eibach springs
18" AMG Monoblocks staggered.

Fault: Loss of pickup speed after 150 km/h.

I thought after upgrading wheels from 17", I was suppose to have better high end speed?!

 

I would not expect to have any noticeable drop in performance until well over 300,000 km on a well-maintained and non-abused engine.

Did this performance penalty coincide with the fitting of new wheels/tires?

If so, they must be the source. This is possible for a few reasons:
1) large diameter wide wheels weigh more than the standard ones, increasing unsprung weight, which in turn reduces performance and roadholding on anything but mirror-smooth roads;
2) extra-wide tires have a LOT more friction with the road surface than the standard tires. This can enhance roadholding on very smooth pavement, but it also will reduce acceleration and ultimate top speed. In a hot country like yours, that could be an extra-large problem, as the rubber on hot asphalt gets extremely soft, further increasing friction;
3) the wider tires also upset the aerodynamics somewhat, possibly adding 0.01 or 0.02 to the coefficient of drag, which again, penalises performance at high speeds (because the aerodynamic resistance increases exponentially with speed, even a small change in aero efficiency can have a large effect).

 

thanks alot mike, although the loss in high end speed did'nt really coincide with the wheels change, but i'm assuming you're absolutely right. But what can i do to compensate that? It's just that a freind with a similar car turned me inside out once we hit that speed!!

to be honest mike, although once in a blue moon, but my car use to clock at 250 kph easily, now it squeezes 230!

 

By changing the wheel diameter you have effectivly changed the final drive gearing and this would have an adverse effect on acceleration and perhaps top end due to the ratio change and less power to the drive wheels. When you make changes to a standard car you effectivly become a test pilot as there is no engineering data available for all perameters that are effected by the change

 

thanks sosh...

i'll try to fit back my 17's and see how it goes. Should clear my mind.

 

Just to report back after 21 years, it was the MAF!

I know I know I'm such a LOL. Thought it would be funny though. On a more relevant note, sold her in 2004 and bought her back again in 2021.

 

Thanks for the update! Some people were still wondering what happened.

I recall escaping the USA in 2013 and somewhere in the Aztec region of Mexico (Baja Cali) my MAF decided to go wonky. Was getting codes about "fuel trim" problems and car would stall out at random times/places. Luckily unplugging the MAF made the engine control computer default to a fixed air/fuel mapping and I was able to make back into the USA for repairs.

 

Whoda thunk it?

Thanks for the long-awaited update. I had hair 21 years ago.