dgross217

I'm in the market for a catback on my 08 mazda 3, just wondering what exhausts everyone has on their mazda 3. Right now i'm looking into magnaflow, hks hi power, vibrant and borla... and then mazdaspeed makes an exhaust. Let me know what you have, how it sounds, pros and cons of your system. thanks

Thrizzl3

i would say HKS but i would be biased as i am running one. lol most of the people i know are either running magnaflow, vibrant and borla. if i had to choose another exhaust it would definitely be a vibrant.

dgross217

yeah im really liking the hks hipower, but ive been reading around, i've seen people say a couple times that hks hi power for hatchback is only for 04-05 models. i dont see why it wouldnt fit my 08, but then again, i dont have the exhaust sitting in my garage to know for sure. what hks system are you running?

Thrizzl3

i don't know why it wouldn't work all exhausts from 04-09 are the exact same. im running the hi power

ziggaroo

Whatever happened to the "Catalytic Converter Test Pipe Shunt"? You would add it to your exhaust - just a little welding needed - and wire up a choke cable to it. Then when you needed to race you just temporarily opened your exhaust.

Too little back pressure and you risk burning your valves, although that was the rule for big-valved big blocks (some Chevy big blocks had valve diameters over 2 inches!) I'm not sure it still applies AS MUCH today - but it still applies.

dgross217

@thrizzl3 what year is your mazda?
@ziggaroo can you go into a little more depth as to why the year difference would affect it? even if it is back pressure

ziggaroo

You need some back pressure, at least in the range of what was assumed when the exhaust head was designed, because if it is too small the flame front will not get damped by the back pressure and some flame will escape the chamber when the valve opens. This is what causes burned valves.

This is more of a concern with large-valved cars like old Detroit V-8s as I alluded to in my first post on this subject. The alloys used in those days were also not as "hi-tech" as today. But in general the exhaust valve stems DO NOT want to see flames. It will hurt and weaken them from a phenomena called age hardening, which is exacerbated by heat. If you lose the seal the exhaust valve makes with its seat due to valve burn, you're in a "heap of trouble".

Too many people these days think Bolt-Ons are trouble-free. They rarely are IMHO, and the combustion envelope that hi-revving 4s are designed with make it questionable if they are worth it.

Maybe an ADJUSTABLE back pressure regulator would be the way to go; something like a water valve. Then you could dial in different pressures and see when:

1) your HP peaks
2) your valves self-destruct

dgross217

yeah that makes sense... you got me all worried now lol

Thrizzl3

she's a 2005. although ive only seen 07+ models with either a borla, magnaflow or a vibrant. none of them use an HKS

dgross217

yeah i am starting to really like the magnaflow...

glenn1

Just bought an used 05 SP23 sedan 5spd manual with 32k miles on it. The previous owner put on a catback exhaust system. I haven't had a chance to raise the car and check out what type of system it is. Looks high quality with a nice burble at idle and great looking exhaust tip. But the downside is at a steady cruise on the hiway the exhaust can be heard. Not too loud, but noticeable. If I keep the vehicle I plan on returning the exhaust to stock. Anyone out there wanna trade?

cpdaboss

i bought the complete exhaust system from srmotorsports.com which includes a high-flow cat and the magnaflow exhaust system for like $900 and it sounds really good if you are considering magnaflow check this out because it is a magnaflow cat back exhaust that requires no cutting and piecing together stock parts with after market parts and for just a couple hundred bucks more includes a high flow cat which pretty much makes the car sound beastly not ricy