The engine in the Z8 has a number of air temperature sensors and the engine's CPU uses their input to make decisions concerning ignition timing and air/fuel mixture. As the ambient temperature level rises, ignition timing is retarded and air/fuel mixture is enriched to keep the engine cool and to prevent detonation. This results in a loss of power. At the same time, warm air is less dense than cool air, so for a given volume sucked into each cylinder, there is less oxygen available for the combustion process, thus less power is generated. The same thing happens as you go up in altitude where the air is thinner, i.e., your engine makes less power. Combine these three situations and you are going to notice a significant drop in power.

Not all CPU's react in the same way given the same temperature conditions. Depending on the location of the sensors, some are much quicker to react than others. Dinan found that the air temperature sensors on the M5 were giving misleading readings to the CPU due to their location and wound up relocating them to prevent premature power reductions. Those same sensors are known to be somewhat variable in their performance which might account for differences from one car to another when dealing with temperature changes.

Please note that even though the temperature gauge on the dash stays in the normal range, that does not mean that the CPU isn't lowering power output: it is reacting to ambient temperature readings, intake air temperature readings, cylinder head temperature readings, as well as engine coolant temperature.

Thus would we want to change these CPU's, or their position, or is this something best left alone? Also does the Dinan kit S2 kit for the Z8 alter them, and their effect?

The CPU (Central Processing Unit) is the car's computer brain. The temperature sensors are little sending units scattered about the engine compartment, the air intake, and located within the engine itself. I do not know whether the temperature sensor, which was relocated by Dinan on the M5, is in the same position on the Z8. I will try to find out and report back. If the one in the Z8 is providing false temperature information to the CPU, then relocating it would help prevent premature power loss in warm weather, but would also require reprogramming of the CPU to compensate for the change. This is something Dinan could do (as they did on the M5) and again I will investigate the possibilities. Keep in mind that the air intake system on the stock M5 is different from that used on the Z8, which is why Dinan installs an entirely new air intake system on their S2 modified M5s (but not on the Z8s), therefor the Z8 may not have the same problem with the temperature sensor because it may already be in a better location.

Grease Monkey