92RSB4C

Here's the deal, the Houston/Galveston area is lowering freeway speed limits to 55MPH. Their reason being that the Feds test the air pollution and if the air fails, then the Feds cut funding. Their solution is to drop speed limits, and make it illegal to mow grass in the morning. My thoughts are: Since most cars are in OverDrive at 55MPH and 70MPH, will this equation, time spent on freeway vs. engine RPM at 55MPH vs. harmful emissions output, have less emissions output than this equation, time spent on freeway vs. engine RPM at 70MPH vs. harmful emissions output? Also, when summer comes, people will be forced to mow in the afternoon. People will die of heat stroke! The death rate is bad enough as it is!

------------------
Chevy World Home Page Tripod Home Page Speak up for our hot rodding rights!!!

Enkil

There's a little bit more to take into effect than just speed, since the same RPM can mean vastly different speeds depending on the gearing. And that said, it's going to take more throttle to have an engine running at 2000rpm doing 70 down the highway than it would take to have an engine running at 2000 rpm in neutral. That's an extreme example, but it's the same idea as the difference in throttle needed between 55 and 70. Granted, in a single car, the difference in emissions isn't THAT much, but if multiplied by a lot of cars, it might make a difference.

But that seems like a strange way to cut emissions in an area.

------------------
89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

92RSB4C

Let's just pretend we have an example car, a 1999 Chevy Tahoe with a TBI Vortech 350. Let's say the Tahoe can do 55MPH at 1,600 RPM in OverDrive, and 70MPH at 2,0000 RPM in OverDrive. Let's say we want to travel 200 miles. The first 100 miles we will be doing 55MPH, and the second 100 miles we will be doing 70MPH. So, here's my equation for the first 100 miles, 108 minutes vs. 1,600RPM vs. harmful emissions output(x). Here's the equation for the second 100 miles, 84 minutes vs. 2,000 RPM vs. harmful emissions output(y). Will x be greater than y, or will y be greater than x, or will they be the same?

------------------
Chevy World Home Page Tripod Home Page Speak up for our hot rodding rights!!!

Jason M 91Z

Personally, I'd say stay out of HS algebra...

Emissions output has alot more to do with than just engine RPM and speed. You'd also have to take into account an engines volumetric efficiency at those given RPM's and load variables. I bet an engine would produce less NOx at 55 than 75, but at 75 may get better fuel economy and produce less CO. They're probably trying to clean up the NOx pollution from cars. BS way to do it though...

------------------
-Jason M. 1991 Camaro Z28

ATOMonkey

Emissions are measured in grams/mile. The car will make less grams/mile at 55 than at 70 because everyone tunes for 55. Having said that less g/m means less pollution in one area. That is why they lower the limit. They could also be doing it because of speed reasons and emissions reasons too.