Effects of A/C on Performance?
 

With A/C off, I get pretty good power from the 3.8; not fast, but satisfying response to the pedal. But with the A/C switched on, it gets a little sluggish and doesn't downshift as well. I figure there is some bit of power penalty from driving the compressor, but how much is normal for a Benz?

Try it on a OM617 or a OM616 its even more noticible....A/C is a big power drain and you are going to notice it...more than a little.

That engine should have enough oomph that you would never know the compressor is kicked in. I think that the difference is probably that when you DON'T have the a/c on it is cooler weather. Cool air is more dense, thus giving more power.

Good luck,

A/C certainly has an affect on the 2.3. Like raymr said, it seems to not want to downshift when it should. For me, moderate hills with a/c means full throttle with no acceleration :(
Is this what I can expect with my engine?

Yes, with a small four cylinder this would be normal, but not with a powerful V8.

Have a great day,

That of course begs the question whether the 3.8 can be considered a "powerful V8." It has 155HP, I do believe.

Sorry Larry, couldn't resist. :)