Info on exhaust changes and power

[ChazSpeed]

I am pretty green when it comes to how a car performs. Does anyone know of a good place to find articles about how changes to an exhaust system affects the cars power?

It just seems strange to me that just by moving the pieces in the exhaust system to different places along the pipe can make a difference ( I am probably over simplifying this), so I am sure there is a ton of information I am missing out on.

Are there also specific issues you run into when running a trubo?

 

[Hirudin]

I'm also a big newb, but I think the 2 big changes the aftermarket exhausts make are
- increasing the exhaust pipe diameter (bigger tubes flow better, compare a McDonald's straw to a coffee straw)
- eliminating pieces that restrict air flow (like catalytic converters ("cats")/mufflers/resonators(?)) or replacing these parts with less restrictive equivalents - these 'less restrictive parts are more expensive, hence they aren't put on at the factory

 

[ChazSpeed]

That sounds about right from what I have been reading.

Sounds like the cat back exhaust helps as it gives more room for exhaust to flow before hitting the converter so I imagine it causes less pushback into the engine, but that is just a guess

 

[D_Roc7822]

I'm also a big newb, but I think the 2 big changes the aftermarket exhausts make are
- increasing the exhaust pipe diameter (bigger tubes flow better, compare a McDonald's straw to a coffee straw)
- eliminating pieces that restrict air flow (like catalytic converters ("cats")/mufflers/resonators(?)) or replacing these parts with less restrictive equivalents - these 'less restrictive parts are more expensive, hence they aren't put on at the factory

yeah thats a good representation of how exhausts affect cars performance. The less restrictive parts arent really more expensive, cause the 2-3 catalytic coverters that are on cars these days are pretty pricey rather than just have a straight pipe on there for a exhaust. They are restrictive to control emissions and all that good stuff. Like you said the bigger the tubes the better the flow typically.

 

[BONES_GOT_BOOST]

exhausts also have to be tuned with the engine to control backpressure and exhaust pulses. bigger is not always better. if you increase diameter too much you can slow the speed of the exhaust and increase spool time.

 

[BONES_GOT_BOOST]

does anyone know what a company is refering too when they say "drone-free" when they are talking about exhaust

http://www.ghlmotorsports.com

 

[redspeed]

On a turbo engine less back pressure is always better. Thats what you get with a downpipe or a turboback.

Drone free means the exhaust don't have that loud, constant noise that resonates and is annoying as hell.

 

[AllLostThings]

does anyone know what a company is refering too when they say "drone-free" when they are talking about exhaust

http://www.ghlmotorsports.com

"drone" is when you are crusing on the highway at about70-80 and you just hear and feel the exhaust resonate. It gets rather annoying...

One thing I never understood about this car is people saying that a cat-back exhaust is onyl good for sound and doesn't really add power until you do other mods. I woudl think that no matter what, if you go to a 3" cat-back you'll se a bit of a power increase. It always worked on my other cars but this is my first turbo car so maybe it's diffrent.

 

[ChazSpeed]

People are talking about downpipes, racing pipes, and a catback... I assume the catback is the furthest back piece, what is the downpipe/racing pipe for?

Also, do you have trouble meeting emission standards on a catback? I only ask since the cat is now away form the engine and doesn't heat up as quickly it seems like it wouldn't do it's job as efficiently until it gets warmed up.

 

[mooserov]

the spinny thing on the exhaust manifold provides the backpressure. everything after it is just restriction.

 

[Mid_Life_Crisis]

Sounds like the cat back exhaust helps as it gives more room for exhaust to flow before hitting the converter so I imagine it causes less pushback into the engine, but that is just a guess

This looks like a wrong impression. The term cat-back means everything after the cat is replaced, not that the cat is moved back.

For our cars, the single biggest improvement that runs the least likelihood of getting you in trouble with the emissions police is to replace all the cats with high flow versions. The stock layout has two cats in the downpipe (the vertical piping between the turbo and where the exhaust stops going almost straight down and starts following the bottom of the car) and you can probably get away with replacing them with a single cat. Be careful though, as some states allow no changes to cats whatsoever.

The idea that a cat-back exhaust system does nothing for these cars is incorrect. I read a road test where Mazda brought a stock MS3 and one with an MS_CAI (Mazda's cold air intake) and their cat-back exhaust. The rep told the reviewer that the two together are worth 29 wheel hp.

I've seen it theorized that the single biggest relatively easy exhaust upgrade (deliberately leaving out replacement exhaust manifolds) is the downtube. This is right after the turbo, and has those two restrictive cats in it. You'll either need a replacement with a high flow cat or no cat and a CEL light cheater kit. This sounds right to me, as the idea is to let that turbo breathe, so taking out a big bottleneck right at its outlet makes a lot of sense.

We have some guys on this forum with a lot of experience working with turbos, and I'd love to see some of their thoughts on this. It makes sense to me, but hey, I could be wrong.

 

[Mid_Life_Crisis]

the spinny thing on the exhaust manifold provides the backpressure. everything after it is just restriction.

LOL - I have this image of a geeky kid wearing one of those beanie hats with the propeller on it holding a propeller on a stick. Thank you, I needed a laugh.

 

[redspeed]

The idea that a cat-back exhaust system does nothing for these cars is incorrect. I read a road test where Mazda brought a stock MS3 and one with an MS_CAI (Mazda's cold air intake) and their cat-back exhaust. The rep told the reviewer that the two together are worth 29 wheel hp.

Yeah, Thats because the ms cai added like 25hp and the cb 4hp. The cat back is pretty much useless on the ms3. Now, if you get a downpipe with the cb, then you have a TBE(turbo back exhaust) and that is the perfect combination.

 

[Mid_Life_Crisis]

I am not getting sucked into the debate of how many horses a CAI is worth by itself. That issue has been beaten to death in other threads. I will state only that I disagree with you regarding how much a CAI is worth, and I have the Mazda version.

 

[redspeed]

I'm Sorry. (kiss)

 

[ChazSpeed]

You are correct, I had the wrong impression when I originally posted that

I have read up some more, and I would definitely go the route of the TBE as long as I could still pass my emissions tests here in texas

 

[dcomiskey]

No way in hell a CAI is giving anyone 25hp. Sorry.

Anyway, yes, full TB is best of all worlds. You're giving the system more room to breathe, which is what turbo-charged motors like.

Has anyone posted dynos of a full TB system (DP, CB, etc.) on here yet? Very curious to see what the gains are.

 

[Haltech]

No way in hell a CAI is giving anyone 25hp. Sorry.

Anyway, yes, full TB is best of all worlds. You're giving the system more room to breathe, which is what turbo-charged motors like.

Has anyone posted dynos of a full TB system (DP, CB, etc.) on here yet? Very curious to see what the gains are.

I think you need to start looking up Dyno threads... (uhm)

 

[abbadabba]

i heard the ms3 cai is only warrantied for a year , what do you have to do to keep warranty up buy a new intake every year and have the dealer install it?

 

[Rotus8]

i heard the ms3 cai is only warrantied for a year , what do you have to do to keep warranty up buy a new intake every year and have the dealer install it?

What do you think is going to go wrong with a CAI? It's a piece of pipe and a few hose clamps.