Obviously, the Y-pipe is the best bang-for-the-buck mod you can do. You get almost a 20hp gain and better gas mileage. There has to be a catch, or else wouldn't that just be they way the car was built in the first place? I really don't think Nissan engineers are dumb enough to lose 20hp and gas mileage just for one part of the exhaust. So whats the reason the engineers did this, or is there something these y-pipe people aren't mentioning? Sorry if I sound like I'm trolling, this mod just sounds too good to be true, that's all.

 

Emisssions. The stock y-pipe contains the pre-cat which is needed for emissions control until the main cat warms up. Getting rid of the pre-cat reduces back pressure but results in increased emissions during warm up.

 

emissions

 

How dumb are consumers?? Nissan engineers have to think about things that the ave idiot can't even fathom. ie.. noise, durability etc.... all are important factors. My stock Y was in perfect condition well after 100,000 miles. Try that with an aftermarket Y pipe. Hell my Cattman VE unit couldn't go 10,000 without busting the flex section

 

I never understood why precats were made used. Im no engineer (yet) but wouldnt there be a more efficient way of cutting the emissions... like making the engine run cleaner?

Compared to other cars many dont use precats. My moms 98 camry v6 does not. Ive heard the argument that its cause as a 'fleet' the average emissions is what counts and the 4 cyls contribute to this average. If thats so, my 98 corvette does not have precats and the 5.7L v8 is all that they've ever come with....

 

From what I know the distance from the headers to the cat makes a huge difference in emmissions because of how long it takes to get the cat up to operating temp. Nissan could have probably moved the cat closer to the engine, but then we'd have a hump on the passenger floor like the Fbodies.
-hype

 

The fleet is all the cars a manufacturer produces. So to offset the additional pollution the Corvettes make, they have to be extra stringent with other models (usually the ones that make up the largest number of their sales). Same concept applies to the average mpg for the fleet. If you sell x number of cars getting 18 mpg, you have to sell many times that number of higher mpg cars to average out to whatever the fleet average needs to be.

So maybe the average Nissan automobile pollutes to the extent that Nissan can't meet emissions standards without a precat on Maximas.

 

Excellent point!

 

Take an advanced IC engines course when you get to it...then you'll realize why.

 

Cold start programs don't run very clean. Ever heard of a choke on a motocycle, old V8 or dual SU carbs on a 510/240z? Engines need alot more gas to operate when the block and heads are cold.

 

We can thank the tree huggers for our pre-cats.

Now that I have that out of the way.... Even though emissions things **** me off, and sometimes their ideas are so radical I want to kick them in the nuts. But then I see how people in Mexico City have to wear masks while they walk to work so they can breath clean air, then I try not to ***** too much. Even with the pre-cats on our cars off they are still probably fairly clean compared to some of the crap I see driving around WI. At least the pre-cats are easily reversible. Other options such as reducing the ring land also helps reduce emissions, but to reverse that you need new pistons.

 

You should thank the tree huggers. It's them that ushered in the need for electronic controls on engines. THAT ushered in advanced fuel injection. And THAT ushered in a new era of power AND fuel control. Do you think 280hp out of 3.5 liters na with decent fuel economy was possible without it? I think not. Not without horrible cold running and severe low end power loss and bad fuel mileage.

 

Sure there are radical environmental groups out there, but for the most part most are pretty sane. You've got to love the fact that todays CARS are achieving nearly any emissions. Less can be said for todays trucks. It seems we are going backwards with that one. Trucks have less stringent emissions regs, they get horrible MPG, and they're outselling cars.

I've said this for a long time, if you don't own your own business or own acerage, then I think you should have to pay a $500+ gas guzzler tax for any sort of truck/SUV that doesn't get better than 18/24mpg. If you've got $40K to spend on a truck, you can spend another $500 in tax. It doesn't seem fair that you have to pay a gas guzzler and luxury tax when buying a 4500lb 7-series BMW that pollutes less and gets better MPG than a 6800lb diesel Excursion.

Sorry, got of track.


Dave

 

Excuse my spelling and grammar. It's terrible these days.

 

If they are buying more gas than they are paying more taxes already, witch over time adds up to more than $500. And what about people who pull campers,and other trailers like that? should we make them pay more just because you have to have a precat??? The bottom line is almost anyone who is going to spend 40k on a truck is going to use it, and they shouldn't be taxed for it.
Just my $.02

 

was your cattman ypipe aluminum or steel?...I was looking to buy a warpspeed steel

 

It would be cool if the engineers could come up with a pre-cat bypass section once the car is past the warm-up phase. For example, the primary exhaust route could flow internally through a nice set of header pipes but during cold starts, the exhaust could be routed to a nearby set of pre-cats mounted on the headers.

The reason L.A. and Mexico City have horrible pollution is because of their topography. Those cities are built in basin valleys -- completely surrounded by mountains. Also compounding the problem is the relatively warm/hot climates experienced in these cities.

A large amount of the particulates come from diesel exhaust from generally dirty diesel fuel that is used in a lot of the mass transit buses and taxis. A lot of the smog haze comes from the high levels of NOx that diesels generate. In localities like Mexico City, there are far higher numbers of older vehicles on the road which makes the pollution problems even worse. In cities like L.A., 90% of the pollution attributable to automobiles are caused by 10% of the automobiles on the road (those generally being the oldest ones).

A lot of cities in Europe are dominated by diesel fuel. Diesels generate a lot less CO2 than gasoline but a lot more NOx. NOx is a primary precursor to smog. Many European cities will always tend to have a smog problem until this changes. For some baffling reason, a lot of Europeans are frightened a lot more from the .01C degree rise of air temperature vs. the carcinogenic and visible effects of smog. Also, having $2/gallon in taxation doesn't motivate people to use gasoline.