Temprature and performance

[kd4pba]

So the CX-7 is the first Turbocharged car I have had.

My Previous Normally aspirated V8 suffered in hot weather, IE above 95 degrees. ON very cold days, like 30 degrees and below the throttle response was really good , and acceleration was better. My Theory was that colder air had more density would allow the engine to run richer.

With my CX-7 the opposite seems true. When its warm outside the the lag is less pronounced, acceleration is better and the throttle response is good. Under 30 degrees the car seems to suffer a bit. There is a lot more turbo lag, and acceleration is not near as good.

I run 93 octane consistently.

So is something a miss here or is this normal. Anyone else notice this?


Thanks in advance for the feedback.

Chris

 

[Killer]

You are on the right track with the colder, more dense air analysis. But its not that it runs richer, the air is just more dense. So on the compression stroke you actually are compressing more molecules therefore increasing h.p.

 

[Igve2shtz]

My Theory was that colder air had more density would allow the engine to run richer.

Basically, you are on the right track ... Colder air is denser, which means it has more air molecules (mixture of nitrogen, oxygen, CO2, CO, and others i forget) for a given volume. Modern computers are programmed to run a consistant a/f ratio, thus, if you are putting in more air molecules, you need to inject more fuel molecules to compensate. So, you run the same a/f ratio (not richer). And just like a turbo/nitrous/supercharger, the more air in the cylinder, the more fuel, the bigger the bang.

But back to the question at hand: Ive noticed the same thing. Back with my other naturally aspirated cars, they would run 50% better at night than in the heat of the summer day. Now, my MS6 is alot less responsive. For that, just blame the tuning of the car.