downpipe
 

I have read that "adding a downpipe gives better turbo response and HP gains" and that "a downpipe will also significantly lower underhood temperatures, extending the life of all underhood components" and that "a downpipe alone does not require any fuel enrichment." Are these statements true?

Also, will adding a downpipe

1) increase emissions?
2) increase noise?

Re: downpipe
 

Yes.

1) Yes
2) Yes

Will adding a downpipe make it difficult to pass emissions inspections?

What kind of and how much extra noise will result from adding a downpipe?

Are there any other reasons not to add a downpipe (e.g. decreased turbo life)?

If the emissions person really LOOKS then it may not pass. It will make your aftermarket exhaust sound a little louder not much. Not sure about the stock exhaust. Adding a DP is one of the best mod you can do fro reliablity. It should've came with a DP straight from Mazda but it was an emissions issue.

As long as everything else is in working order, and the car is mostly stock, you can pass emmisions once you have the main cat on. I've seen it done in both VA and MD. A DP should be no problem.

They look for your main cat during inspections.

A DP will add noise, but not as much as a striaght exhaust system, or large cat-back would. Honestly, just go with the mod, there are far more pros, than cons.

The FD has a hard time passing emissons in stock form sometimes. There are many other components to the emissions than just the exhaust. However, *if* everything else is working properly, the downpipe shouldn't cause you to fail an emissions test.

Retaining the stock cat and stock catback, it will only be slightly louder. Just a little extra rumble, nothing obnoxious.

The only reason I can think of would be to keep the car completely stock (for it to eventually be some non-driven collectable car or something).

Re: downpipe
 

Yes to turbo response.
yes to lowering temps
no not really with other mods of course but alone probably not

yes and yes to the last two

Thanks for the help so far. I'll follow your advice and go with the mod.

Now, could someone explain how "adding a downpipe gives better turbo response and HP gains," in layman's terms?

You are replacing a restrictive 2-1/4" catalytic converter with a wide open 3" pipe. This allows exhaust gases to exit the engine more quickly, which increases turbo response (higher velocity=faster spool-up) and horsepower (more air in and out of engine--more power).

If you are otherwise stock, you will notice a slight noise increase and you'll be able to hear your turbos spool easier. There are no real negatives. Get one today!

Last question:

Are you certain that faster spool-up does not decrease turbo life?

not compared to having a several hundred degree oven parked next to them.....spooling up faster does NOT mean the max velocity of the wheels are faster, it just means they accelerate to top speed faster.

I think you need to relax. If you are keeping the car mostly stock and only boosting stock boost levels (10 psi), your turbos should last over 100k. Nothing is guaranteed of course. If you are truly concerned, use synthetic motor oil as it will help your turbos last longer (this is NOT an opportunity to start the dyno juice vs. synthetic debate again....).

Thanks everyone!

I have 159,264K on my original turbo's if that helps.

Re: downpipe
 

I dont know about "significantly" lowering underhood temps. No matter what it still gets pretty damn hot in there. The biggest heat advantage would be when you shut the car off and everything is starting to cool down. The stock pre-cat is a huge chunk on metal that retains alot of heat. A DP will not retain nearly as much thermal energy so it and everything connected to it will cool down faster. Since the pre-cat is hotter than the engine, the block temps can actually go up before they go down. In the long run the dp is definately worth it for heat reasons but dont expect that you can pop the hood and feel a big defference in the temp of the air in the engine bay.

In didn't notice any difference in the noise, other than I could hear the turbo more clearly.