Quote:
Originally Posted by BrineSI
Just a question: does this 10 degree drop in temperature mean from the intake to TB or TB to engine. My worry and thought is that it would take a drastic drop in air intake temperature to even see a 2-3 hp gain as the heat of the TB etc. is so hot that it's sort of working like a hair dryer: cool air enters from the back but because the internal components are so hot, it blows out hot air on the front end instantly - air can be heated up so quickly that cooling down intake temperature even 10 degrees seems like it wouldn't help much, intercoolers on turbos work well because they drastically cool down the air... correct?
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That is a great question. My understanding is that we are talking about the intake charge in the air cleaner/airbox area. This is generally where temperature differentials are measured.
I think that the colder, denser air with more velocity will override the TB. Whether it be a TB or a carburetor, the incoming intake charge is what increases performance. This same idea applies to nitrous as well, which is introduced in the intake stream before the TB. My G35 has the nozzle in the z-tube which is before the TB.
One more thing: we all have noticed how much better our cars or any car for that matter, performs on a cool, fall day where the air is denser as compared to a hot, summer day where the motor feels kind of flat. It has to do with the air that is being ingested into the motor. Anything that can cool down that intake charge whether it be an intercooler, nitrous or ram air will have a corresponding effect on the performance of the motor.
Here are a couple of things I found out about the effects of air temperature:
Air Density: Cold Air and Ram Air Power gains
Most people who doubt ram air merely call them cold air intakes delivering a cooler denser air charge to the motor and that is where they achieve there power, not from any CFM flow or Psi increases. Well, it is a combination of CFM and air density caused by lower air temps or altitudes. Once again this is system and application dependant but generally they say (text books) that a 10 degree drop in air temperature is worth about 2 Hp. We like to think of this as a raw number because this application is a street driven LS1 or LS6. We are talking about a Mass Airflow Meter controlled vehicle that will tune or adjust to the weather conditions for you. When in cooler weather the computer will not back the timing out of the motor as quickly and it will richen the car up for you to some degree to take advantage of the added air, basically tuning the car for you. This is worth more than the 2 Hp you are seeing at peak power. It translates into a lot more power under the curve. Air flow rate, air pressure and air density is our priority. If you had to prioritize them in order you would be making a mistake. They all work together. Air Flow Rate
Vararam Industries - About
The special ducted fiberglass hood that was designed for use with the Camaro is probably one of the best examples of style and function combined. The hood was intended primarily for the Trans-Am competing Z/28s. It was designed to take advantage of the high pressure area at the base of the windshield in order to draft fresh cold air to the induction system. This method was chosen over forward facing scoops which create greater pressures and increased ram effect but have problems associated with air turbulence at the carburetor air horn. As for effect, an approximate 1% horsepower increase is gained for every 11 degree drop in temperature providing the fuel mixture is adjusted accordingly.Air Density
Z/28 Cross Ram
This from Miata.net in Australia: Using the rule of thumb that a 4 degrees C temperature drop is worth an extra 1% power, this would imply that I could expect up to 7% extra power over the standard system.
Air Pressure
When we deal with a ram air system whether it be from the cowl or the lower bumper area, we need to consider air pressure, air velocity and air temperature. All three have a considerable bearing on greater power. This is why I initially proposed cowl induction because a typical intake system only increases power by using a cone filter, not by utilizing higher air pressure and velocity and lower air temperatures.
Hope this helps. I also suppose that use a TB bypass would enhance performance too during the summer months as would a composite intake manifold like Skunk2 is working on. Anything to reduce the temperature of the intake charge should have a positive effect on performance.