question regarding air temp and Prowler performance

[halicat]

How many of you guys notice the Kats performance change between the cool days and the hot days ?


I drive my car between April and November and often notice the increased horsepower I am making on the colder days.... on the days that I'm going to work at 6:30am and the temperature is just a bit above zero... my Kat is really working well..... also on the hot days it seems sluggish....

does anyone have any data on horsepower values at different temperatures., not just for the Prowler but 6cyl engines of the same HP in general ?

[BLEW BUYOU]

Jimbo, physics and experience at the drag strip tell the story. Optimum HP is developed at 60 degrees, 35 % humidity, at sea level. This is without introducing man made atmospheres, turbo's, super charger's. Generally speaking the colder the fuel air mixture the more HP, in the above conditions. On a 440/375 Mopar, by filling the "charcoal filter canister" with copper tubing gas line coiled up and dropping in some dry ice the HP rating went up a full 15 HP on the dyno. The gas line going into the carb was below zero. Needless to say it became routine to set this up each weekend for more power.:devil

[halicat]

wow.... great info....

60 degrees or cooler here in Nova Scotia is lot of drive time....

15 Hp running in the morning when its just a bit above freezing sounds about right...

Thanks..:tu:

[TooHipCat]

On a hot day, or at high altitude, or on a moist day, the air is less dense. A reduction in air density reduces the engine horsepower. Density altitude is defined as the pressure altitude corrected for the effects of temperature and humidity. Density altitude affects engine horsepower of a normally aspirated engine. A reduction in air density reduces the amount of oxygen available for combustion and therefore reduces the engine horsepower and torque.

This makes perfect sense! This is the reason why we ALL use an increased amount of gasoline in the colder weather. Yes...you get an increased amount of horsepower but your gas mileage will suffer.


Brian;-)

[BLEW BUYOU]

Brian, With computer controled ignition timing and sequential port fuel injection, we are not, in the true sense, running normally aspirated engines in the 3.5 V6. The colder the incoming air is the better the fuel burns (more complete or efficiently), creating increased HP on the same amount of fuel usage and better mileage(mpg). The older polispherical head V8's with a carbureter only burned fuel at about 70% efficiency, on a good day, the same cu. in. engine with carb. and hemispherical heads would register almost 90% efficiency of burn and produce more HP simply by getting a better burn ration for the same amount of fuel used. Moist, high altitude air robs power even with all the computer controls, but we don't have to put up with the spark knock anymore.

[TooHipCat]

Brian, With computer controled ignition timing and sequential port fuel injection, we are not, in the true sense, running normally aspirated engines in the 3.5 V6. The colder the incoming air is the better the fuel burns (more complete or efficiently), creating increased HP on the same amount of fuel usage and better mileage(mpg). The older polispherical head V8's with a carbureter only burned fuel at about 70% efficiency, on a good day, the same cu. in. engine with carb. and hemispherical heads would register almost 90% efficiency of burn and produce more HP simply by getting a better burn ration for the same amount of fuel used. Moist, high altitude air robs power even with all the computer controls, but we don't have to put up with the spark knock anymore.

The fuel burns more effeciently and completely...I agree...but when it's really cold up north...you definitely burn more of it during the Winter.
I know that's not the case down in Florida.;-)

Heck...my Corolla commuter car always uses much more fuel in the Winter in addition to the engines operating temperature being so much lower. I'm sure I'm one of the few that would rather have a little less HP with a decrease in fuel usage.

[halicat]

I will take better fuel mileage less HP in my Corolla.....

and more HP and less MPG in the Prowler.....

hows that for sitting on the fence....8-)

[BLEW BUYOU]

I spent 17 years in Toledo, Ohio, over a 3 week period it seemed, and fuel usage goes up for 2 reasons. First the auto choke kicks in, throwing in twice as much fuel to air as normal, second most every one lets the engine warm up some on colder mornings, sometimes 2 to 3 times a day, that is not done on warmer days. Even the computer controlled engines change the fuel to air ratio when it is colder.
We had 21 degrees the other night and I actually saw the raw fuel coming out the exhaust of the PT turbo, all computer controlled. Now I know 21 is spring weather for you N. Easterners, but to us, that was Alaska Tundra weather.:devil