Exhaust Modifications

Kedis82ZE8 said:
I don't really notice any droning... it is louder than stock in most occasions other than just cruising RPMs where sound is almost like stock.
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resonators do exactly what they say - resonate your exhaust flow. it creates this turbulent flow similar to backpressure which improves exhaust sound and increases torque. always good to have your resonator in place.

I dont know why mazda didnt do this, but ideally you want your resonator to be underneath the rear seats. I think they place it more forward then that. but anyways resonators are your friend in the exhaust world
 
GJ-Molestor said:
The muffler on this car is great Stuff, I don’t want to remove it. It creates back-pressure which helps low rpm driving without being restrictive at all. I wouldn’t remove the mid muffler (resonator) because that little bottle thing fine-tunes and exhaust sound while filtering out unwanted droning/frequencies. Sounds better with it in place. I would recommend putting back the resonator and see how that changes the exhaust note, it won’t become any quieter but the sound will simply improve.

Why don’t you do a cat delete and just put them back on in two years when it’s time for your smog test?

Here in Toronto, our emissions testing is very lenient, but most places will not pass you if you’re fully catless unless you personally know the shop owner. They scan your car to ensure the cat is in a ready state, but they also stand behind your car while it’s idling to smell the exhaust which is an easy way to tell if the cars catted or not.

I am thinking of deleting the small second cat (which is before the larger main cat, right after the exhaust manifold) this is still illegal, but your car will pass emissions as long as that big main car is in place.

For my BMW, I removed the secondary cats and replaced the restrictive stock muffler with a magnaflow. It’s a pretty decent way to get some sound and open up a few HP while still easily passing emissions. I got an emissions test with my secondaries removed because they don’t look underneath the car here.

Oh, and another option for you would be to have a muffler shop weld two resonators where your muffler used to be with exhaust tips welded on the end. Worth every penny, you will love the sound!
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California, where tibimakai is, is the worst state to delete a CAT on because they actually enforce regulations/laws there. It is not just the EPA they have to deal with there, but also CARB, which is even more strict than the EPA. Even just intakes need to have a CARB EO#, otherwise you will fail inspections.
 
finch204 said:
California, where tibimakai is, is the worst state to delete a CAT on because they actually enforce regulations/laws there. It is not just the EPA they have to deal with there, but also CARB, which is even more strict than the EPA. Even just intakes need to have a CARB EO#, otherwise you will fail inspections.
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Commiefornia...am I right? ;)
 
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So i stumbled across this imagine again today and decided to have another look, and realized that the WU-TWC is inside the exhaust manifold, meaning you cannot remove the monitored cat unless you get aftermarket headers. this means that removing the second cat will not cause any codes and your ECU can adjust to the mod on it's own within 500KM without the need for any sort of tune. this should open up a couple HP (or more, not sure how large this cat is) and will improve the sound without making it annoying. while you're underneath there, I would also recommend taking the factory mid-muffler/resonator and relocating it to underneath the rear passenger seats.

so, is anyone willing to try this out and report if they feel any difference in power? I will look over some older Mazda forums to see if I can find info on this, because older Mazda exhausts are similar.
 
CBE on my 370z was worth around 15 to 20 whp. I don't think there is much on the table with a low rpm 4 banger like in the cx5 though.
 
GJ-Molestor said:
sy2kd4.jpg


So i stumbled across this imagine again today and decided to have another look, and realized that the WU-TWC is inside the exhaust manifold, meaning you cannot remove the monitored cat unless you get aftermarket headers. this means that removing the second cat will not cause any codes and your ECU can adjust to the mod on it's own within 500KM without the need for any sort of tune. this should open up a couple HP (or more, not sure how large this cat is) and will improve the sound without making it annoying. while you're underneath there, I would also recommend taking the factory mid-muffler/resonator and relocating it to underneath the rear passenger seats.

so, is anyone willing to try this out and report if they feel any difference in power? I will look over some older Mazda forums to see if I can find info on this, because older Mazda exhausts are similar.
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Removing the 2nd cat will not cause any codes because it is behind the last of the 02 sensors, as can be seen in the diagram. I believe Corksport sells a catback exhaust for the Mazda6 that takes off one of the catalytic converters. It still is pointless without a tune. All you're getting is a louder car without more zoom zoom.
 
finch204 said:
Removing the 2nd cat will not cause any codes because it is behind the last of the 02 sensors, as can be seen in the diagram. I believe Corksport sells a catback exhaust for the Mazda6 that takes off one of the catalytic converters. It still is pointless without a tune. All you're getting is a louder car without more zoom zoom.
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Why? I've never seen a vehicle that needed a tune for a simple exhaust mod not involve long the upstream cat. The 370z I had was proven to pick up 15 to 20 whp from a cbe. When the muffler bypass flew open on my z06, it was shown to be worth about 10 to 15whp, and nothing changed for engine parameters, the muffler bypass simply flew open at a certain engine load and rpm. No tune change. You could even pull the fuse and drove around in full bypass mode all day.
 
finch204 said:
Removing the 2nd cat will not cause any codes because it is behind the last of the 02 sensors, as can be seen in the diagram. I believe Corksport sells a catback exhaust for the Mazda6 that takes off one of the catalytic converters. It still is pointless without a tune. All you're getting is a louder car without more zoom zoom.
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You do not need a tune when you mod anything from the first, monitored cat-back. The ECU will be confused at first, but within 350Miles it willl adjust. I recommend refraining from full throttle pulls for the first 100 Miles and vary your RPMs (from idle - redline and everything in between) as much as you can throughout this 350mile course with a full throttle pull every 50 Miles or so. The ECU will learn quicker and better if you do this. Try to do half city half highway driving. Youll notice a better sound and more linear throttle response once this period is done. you Will not need a tune to make the most out of the mod.
 
GJ-Molestor said:
You do not need a tune when you mod anything from the first, monitored cat-back. The ECU will be confused at first, but within 350Miles it willl adjust. I recommend refraining from full throttle pulls for the first 100 Miles and vary your RPM’s (from idle - redline and everything in between) as much as you can throughout this 350mile course with a full throttle pull every 50 Miles or so. The ECU will learn quicker and better if you do this. Try to do half city half highway driving. You’ll notice a better sound and more linear throttle response once this period is done. you Will not need a tune to make the most out of the mod.
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Does the ECU in this vehicle learn? I was under the impression most modern vehicle ECU's are restricted to a bit of compensation via MAF, and that's it. WOT pulls are typically on the canned tune, and MAF is not in the loop for them. You WILL alter A/F ratios as such, but most vehicles run rich, and leaning them out gains you a bit of horsepower, and just 1 mod won't lean them too badly.
 
Unobtanium said:
Does the ECU in this vehicle learn? I was under the impression most modern vehicle ECU's are restricted to a bit of compensation via MAF, and that's it. WOT pulls are typically on the canned tune, and MAF is not in the loop for them. You WILL alter A/F ratios as such, but most vehicles run rich, and leaning them out gains you a bit of horsepower, and just 1 mod won't lean them too badly.
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I believe so yes. Any modern ECU will be able to properly adjust. The BMW ECUs adjust fully after literally one full throttle pull. These older style ECUs need some more time.
 
Unobtanium said:
Why? I've never seen a vehicle that needed a tune for a simple exhaust mod not involve long the upstream cat. The 370z I had was proven to pick up 15 to 20 whp from a cbe. When the muffler bypass flew open on my z06, it was shown to be worth about 10 to 15whp, and nothing changed for engine parameters, the muffler bypass simply flew open at a certain engine load and rpm. No tune change. You could even pull the fuse and drove around in full bypass mode all day.
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There is only so much air you can stuff into a 2.5L engine. Modern catalytic converters are not as restrictive as they used to be and certainly not restrictive when the engine is only rated for 185 hp. Both the 370z and Z06 on the other hand have way bigger engines. Even just an air intake mod gets them decent gains compared to cars with mainstream economy engines. Without a tune, you will not get the engine to suck in more air, hence the minimal gains.

GJ-Molestor said:
You do not need a tune when you mod anything from the first, monitored cat-back. The ECU will be confused at first, but within 350Miles it willl adjust. I recommend refraining from full throttle pulls for the first 100 Miles and vary your RPM’s (from idle - redline and everything in between) as much as you can throughout this 350mile course with a full throttle pull every 50 Miles or so. The ECU will learn quicker and better if you do this. Try to do half city half highway driving. You’ll notice a better sound and more linear throttle response once this period is done. you Will not need a tune to make the most out of the mod.
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You do not need a tune yes, but you will also not get significant gains. I will not presume to know how the Mazda SkyActiv ECU works, but my guess is that they are load capped. Unless you can increase the load cap, you will not get significant gains. All you're getting with a cat delete and without a tune is a less stressed engine. So you've increased the airflow by removing some restriction (if it even is a big restriction on a 185 hp engine) in the exhaust. So now the engine can move exhaust gasses easier, maybe it can also suck in air a little easier. Without a tune though, you cannot take advantage of this extra airflow.
 
Agreed, there will be some sort of gain but minimal. You will notice a better sound and better breathing at high RPM but thats about it.

The exhaust system on these cars are super well designed. The shape of the muffler allows air flow from underneath the vehicle which helps aerodynamics. The muffler is very well paired with the resonator to provide a smooth, growly sound that flows well without the raspy Honda sound. From the outside of the car the exhaust sounds great too! Anyways for this reason its always to keep your resonator no matter what you do. Delete your second cat and upgrade the axle-back If you want a better sound at most.

The exhaust manifold on this car is an excellent design. Im sure we all know the lengthy 4-2-1 setup. As a result of this, they had to put the main warm up car away from manifold piping which increases start up emissions but allows for better flow. Out of the box, you can tune this engine to rev to nearly 7000RPM. all of you are complaining that its a small engine - 2.5L is a large displacement motor which allows for more power and torque to be made VS. The identical upgrades on a 2L version. Orange Virus claims 20-30HP without any sort of mods and honestly, I totally believe that a solid 20hp can be made with an aggressive tune raising the limiter. The cars low-mid range torque will be substantially improved over stock as well which makes the vehicles gear ratios feel better suited to the engine improving response. Its a shame that Mazda tunes the engine rather conservatively here in North America. The European 2.5 version gets 192hp.
 
Compression for the European models is 14:1. We get 13:1 over here in the USA.

GJ- get the tune, and go get a dyno done. Post the results here. A lot of folks were interested in the OVT, but without 3rd party proof weren't going to spend their money....
 
GJ-Molestor said:
Agreed, there will be some sort of gain but minimal. You will notice a better sound and better breathing at high RPM but that’s about it.

The exhaust system on these cars are super well designed. The shape of the muffler allows air flow from underneath the vehicle which helps aerodynamics. The muffler is very well paired with the resonator to provide a smooth, growly sound that flows well without the raspy Honda sound. From the outside of the car the exhaust sounds great too! Anyways for this reason it’s always to keep your resonator no matter what you do. Delete your second cat and upgrade the axle-back If you want a better sound at most.

The exhaust manifold on this car is an excellent design. I’m sure we all know the lengthy 4-2-1 setup. As a result of this, they had to put the main warm up car away from manifold piping which increases start up emissions but allows for better flow. Out of the box, you can tune this engine to rev to nearly 7000RPM. all of you are complaining that it’s a small engine - 2.5L is a large displacement motor which allows for more power and torque to be made VS. The identical upgrades on a 2L version. Orange Virus claims 20-30HP without any sort of mods and honestly, I totally believe that a solid 20hp can be made with an aggressive tune raising the limiter. The cars low-mid range torque will be substantially improved over stock as well which makes the vehicles gear ratios feel better suited to the engine improving response. It’s a shame that Mazda tunes the engine rather conservatively here in North America. The European 2.5 version gets 192hp.
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I think it's just me. I consider anything less than 3.0L a "small" engine.

Yeah get a dyno done before the tune and after the tune. Make sure the dyno runs are done at the same shop. That should easily shed light on what kind of gains can be had with a simple tune on the 2.5L engine.

Edit: If you don't want to do a dyno run, you can measure 60-100 mph times before and after the tune.
 
finch204 said:
I think it's just me. I consider anything less than 3.0L a "small" engine.

Yeah get a dyno done before the tune and after the tune. Make sure the dyno runs are done at the same shop. That should easily shed light on what kind of gains can be had with a simple tune on the 2.5L engine.

Edit: If you don't want to do a dyno run, you can measure 60-100 mph times before and after the tune.
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1/4 mile trap speeds would be even more worth noting. If he has a local track and can go on days with similar DA, the automatic transmission and awd should make for boring consistent runs, and the trap speed will tell the story.
 
GJ-Molestor said:
http://forum.mazda6club.com/2-5l-i-4/382490-ovtune-mazda-6-2-5l-ss-4-2-1-header-gb-3.html

corksport is projecting over 40ft/lb of torque with these catless headers. $700 for these headers and that includes the tune. what a deal! i am so tempted...
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I closed your other thread. Next time you open a duplicate thread like that,especially when you already have your own (not even old) thread on the same topic, you are getting another infraction (post whoring).. reference your recently closed thread for more information https://www.mazdas247.com/forum/showthread.php?123862251-Want-40ft-lb-Of-Torque-for-700 Also that's not even corksport it's orange virus tuning and the GB is dead just like the thread.
 
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