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Re: Loss in Performance of 9000T Posted by Ari [Email] ![]() ![]() In Reply to: Loss in Performance of 9000T, 879KT, Wed, 18 Apr 2001 16:52:01 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The warmer the air, the less dense. That's both because warm air has fewer air molecules per cubic inch, and because warm air can hold more water than cold air (higher dew point). Water doesn't burn well.
The engine control measures the MASS of the air coming in, and supplies the correct amount of fuel. The less dense the air, the less mass, so you get less fuel.
A turbocharger helps, because its job is to pressurize the air. But pressurizing air adds heat, and that heat is added on to the outside (ambient) temperature.
So a turbocharged engine has more power, and feels more responsive, at cooler temperatures. A car will feel (and be) a lot faster on a 35 degree dry day than a 85 degree humid day.
The intercooler helps to cool the incoming charge, but it uses outside air to cool - if it's a warm day, you're using warm air to cool off the incoming charge.
So in a word, yes, the car will feel slower when it gets warmer. In general, you'll notice a dropoff around 50-60 degrees, but it shouldn't be really noticeable until you get up into the 80+ range, or very high humidity. That's because the turbo has the capability to pack a lot of air in.
However, if you're noticing a major performance drop-off with reasonable temperatures, this could be due to problems in the system. For example, any air leak will degrade turbo performance, so the temperature differences will be more noticable. Also, as temperatures increase, the engine is more prone to knock. On the fuel your using the engine may not knock at cool temps, but will trip over into knock when it's warmer, and if the APC kicks in, you'll notice a big performance drop. See if the boost gauge is running lower. Try a tank or two of higher grade (higher octane) fuel and see if that helps.
Routing your A/C around will not help. There are a few laws of thermodynamics that tell you it won't work. Two really big reasons: First, the A/C can't provide enough air flow to make much of a difference, and second, the drag of an A/C compressor is MUCH higher than any extra power gained.
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