e39 540 slow in heat

[Hypr5]

Hey guys,

I currently have two 6cyl 5ers (had 3) and when its hot outside, they all lost some performance. They ran a bit more powerful in the cool night air. However, my 540 feels like is loses at least HALF its power because of the heat. I'd say I lost a good 15% on the 6cyl models, but at least 25 - 30% on the 540.

Is this normal? When it starts to cool down, you can really feel it start to get gradually more powerful.

Why do the 6 cylinders not lose as much power due to heat?

- I don't know if the e34 540 has it too, but I relocated the IAT sensor and it helped a little bit, but it feels like when it's real hot out, my trans isn't using 1st gear unless I decelerate very slowly.

Also - I noticed that if I really get on it and bring it into the high rev range once.... power is decreased from then on out until I shut the car off and let it sit for a while.

To me it sounds like something wierd is goin on with the trans... but what could that be??? Anybody have similar issues / situation?

[joshua43214]

all cars perform better in cooler weather generaly, I notice a small decrease in power when the temp gets over 90 or so, but noting like you are talking about. what is the condition of the air filter? Are you using the factory air box? Most of the after marker "performance" air filter intake systems reduce power, and some of them reduce it alot since they draw in too much engine bay air.

Does turning the AC off make a difference?

I would verify all the pluming is in good shape and there are not hidden cracks any where, then consider either a fuel pressure issue of even possible a bad MAf sensor.