Exhaust - let's talk about this one!

[Silver Ecstasy]

From a really good engineer friend of mine (avid car enthusiast and proud STI owner):

Regardless of anything, a free flowing intake and exhaust will ALWAYS help. It doesn't matter how big or small the change is. An inlet pipe will help if it isn't corrugated, a cai will help, a 4" exhaust with no muffler will help. The biggest restriction on the entire car IS the turbo. If you can make it so the turbo is the ONLY restriction, then you've maximized efficiency.

[Radioactiveman]

Originally Posted by Silver Ecstasy Link please? I've checked my inlet pipe and it's not moving.

If you logg out, come back to mazdaspeedforums.org, do not log in it is about 1/2 way down the page. not sure were else it is.

I have a homemade by very good local racer, alumninum (cant spell) inlet tube.

scratch that it is like the second thing you see, so only maybe 1/5 the way down

Originally Posted by Silver Ecstasy From a really good engineer friend of mine (avid car enthusiast and proud STI owner):

he is very much correct. although you are not looking to drive the piss out of your car. you said you do not drive hard and are just wanting to start conversation?????

I work on diesels and I will say that the turbo is the biggest (smallest) restriction in the system, you have an oulet of 3.5 in the imediatly swells to 5-6inches on most buses, and then goes though and intercooler, then to the intake. exaust is like 6 inches... it is just freakin huge.

but, it you are restricted by boost, fuel, and other perameters, the opening up anything will only go so far... it you are going in order, should be intake, TB exhaust, meaning do stuff attched to turbo mostly because this car has a cat, that is not monitered, it is just there for better / cleaner emissions, and a huge muffler, that is a deflection muffler. if you need to know, straigth exaust will kick the crap out of deflection any day on a boosted car. less restriction is more pwr period.

[Silver Ecstasy]

Well as I said earlier, you can start with safe mods for the intake and exhaust side of things.

Level 1 - CAI/CBE
Level 2 - Inlet/DP

You're right, I don't drive hard, but for the sake of conversation, the entire point was to say that the CBE should have some relevance in upgrading on the car.

[Radioactiveman]

it does, but you need to get rid of the extra cat before you will notice much more than just noise. I believe some gains are made, as I have witnessed dyno days with Mitsu's, and exhaust usually added 7-12whp, depending on mods and AWD or FWD. also Import Tuner Mag did some test on the SRT (i know different car) but they showed 12 whp on there dyno with just exhaust, and another 10 from a SRI. from what I have heard and read, numbers are close to the same on the MS3.

I have every bolt on but have never messed with Tuning, need to save the money for it. I want to bad, I know that I can get another 15whp no problem. I am at around 285whp and that again is every bolt on, No I will not touch meth, and stock ECU and boost. mine pulls from my buddies stock one like nothing. he was pissed when I got. he he.

anyhoo, I am not fighting you in anyway, just giving opinions on what I would do first if mine was not built when I bought it.

[Silver Ecstasy]

Yeah definitely! It's all good here. Your input has been slightly more valuable than "I have this DP, get it!"

Ultimately, I value my warranty and have seen my share of smoking turbos to go down that route. I also don't have the opportunity to swap back to stock whenever I want, so it's going to be a safe and enjoyable mod for me.

Now the debate is whether or not I should un-do the suspension or just cut it.

[HoustonMS3]

Someone asked if there was any evidence that the stock inlet sucked....

I took my car in on a totally unrelated issue to the dealer and they told me they replaced the inlet. I asked why. They said it was falling apart near the clamps and that I shouldn't worry about it, they had seen it a lot.

[Crossbow]

When modding the stock exhaust, you effect the turbo spool time, allowing power to kick in harder much sooner in the power band.

To put this in perspective, with a full turboback exhaust, you've basically shifted the entire stock powerband 750 rpm sooner. That's huge.

(Though I love CP-E products, I am using these graphs to help explain the effects of exhaust mods regardless of manufacturer)

One of the fundamental problems with dynographs, is that most people don't know how to read them. They look for two numbers. Peak torque, and peak horsepower. These are the numbers you should be paying the LEAST attention to. They tell you very little about what the mod is doing, other then at peak rpm's.

What IS the most important part of a dyno graph? The AREA between the stock and modded graphs. It's this space that is most important, and tells us exactly what is happening to the car.



This is the area you should be looking for on ALL dyno graphs. This is the most important change. The area tells you how much the overall gain effected the car...if it hurt the car at some rpm ranges, if it only works in the upper rpm range, if the mod is fantastic and effects the entire powerband, etc. Tons of info in between the graphs! It's here you can also figure out the "max" gains of a mod (largest gap between curves). The max gain is usually where the butt dyno records it's highest reading .


Lets take a closer look at these graphs shall we?



This is a cut section of the torque graph. I cropped this to allow everyone to concentrate on the angle of the line. Note that the modded line is roughly 75 degrees, while the stock line is roughly 40 degrees. This is a MAJOR change. The aftermarket exhaust is allowing the turbo to spool faster, causing torque to increase much sharper. (Huge butt dyno change, pushed back into the seats gain)

This is a major change in power output, and as such, causes the car to reach stock peak torque BY 2750 rpm!!! (instead of 4200rpm). By 4750 rpm, the turboback car is producing over 40 ft/lbs more torque then the stock car. So not only is the car reaching stock torque levels over 1500 rpm sooner, but it's utterly blowing away the stock car around 5k rpm. Max gains are close to 45 ft/lbs. (To put that in perspective, you can spend about 2k USD on a Mazda6 and still not get that kinda of torque gain).



Now lets look at a cropped version of the HP graph. Look closely...the powerband has shifted to the left. In this example, you're making the same horsepower at roughly 750 rpm's sooner now. You are making the same power at 4k rpm, that you used to make at 5250k rpm! You reach the stock power output at 4750 rpm, as you were (stock) at 5500 rpm. Max gain's are close to 35 whp.

Dyno's really should be presented in another way. They really need to have...

1) Peak Horsepower
2) Peak Torque
3) Min and Max Torque Differences
4) Min and Max HP Differences
5) Shaded or crosshatch between the area of the two graphs
6) Some sort of number (area between two graphs) giving you a rough estimate of the power gain across the entire rpm range.

Without that information, we all have to step back and very carefully look at the graphs to see what's really happening.


I imagine if you were to replace the entire exhaust, manifold to tip...the car wouldn't even feel like a speed3. I think that's my plan now. I'll do catback/SU TP, then when funds become available, medieval and DP.

[serium]

Very powerful information... this really goes to show you how restricted the stock exhaust is... get downpipe and racepipe NOW!

[PaPaSpeed]

Originally Posted by Crossbow I imagine if you were to replace the entire exhaust, manifold to tip...the car wouldn't even feel like a speed3. I think that's my plan now. I'll do catback/SU TP, then when funds become available, medieval and DP.

Crossbow, I just got my CP-E Catback Friday, it's sitting in the garage. Maybe I should wait on the install til SU puts a deal on those test pipes. Or, if I installed the Catback, would it be real difficult to add the test pipe later?
I installed a catch can today, so I'll be stiff and sore for a few days anyway, and won't be anxious to tackle the catback. lol, on the sofa.

[Silver Ecstasy]

From what I understand, installing and uninstalling the test pipe is real easy.

I'd say install the catback first, then install the test pipe later. That's actually what i'm planning doing as well.

[thanox2]

Originally Posted by Silver Ecstasy Got an intake, love it. "Stock inlet sucks"...how so? Just because it looks smashed? No one has done any testing or proof to say that a new inlet would improve anything. Not trying to be a jerk, but seriously, I haven't seen one piece of evidence.

Got the Cobb Inlet, spool time decreased, the car feels better, the turbo sounds louder, love it. Now to remove the stock one I just pulled it... it wasn't even clamped to the turbo. And yes it does look smashed, and it is smashed, its a fucking restriction. No need no evidence, just personal experience.

[PaPaSpeed]

Originally Posted by Silver Ecstasy From what I understand, installing and uninstalling the test pipe is real easy. I'd say install the catback first, then install the test pipe later. That's actually what i'm planning doing as well.

It may be easy for you, but when you're a novice like me, nothing is easy.

[Silver Ecstasy]

Shit, i've never installed exhaust on my own, so we're both in the same boat!

But if you look at the actual product.., it's a single pipe with 2 bolts on each end. I can't imagine it being difficult at all. Maybe breaking the bolts loose off of the stock pipe. I'm sure compressed tools would make a world of a difference. A buddy of mine swapped his test pipe back and forth before on his MS6 and it was a piece of cake. You probably spend more time getting the car lifted and ready to work on than you do actually doing the work.

[PaPaSpeed]

Originally Posted by Silver Ecstasy Shit, i've never installed exhaust on my own, so we're both in the same boat! But if you look at the actual product.., it's a single pipe with 2 bolts on each end. I can't imagine it being difficult at all. Maybe breaking the bolts loose off of the stock pipe. I'm sure compressed tools would make a world of a difference. A buddy of mine swapped his test pipe back and forth before on his MS6 and it was a piece of cake. You probably spend more time getting the car lifted and ready to work on than you do actually doing the work.

Well, maybe next week I'll try the catback. I still have to wait for SU Mark to have a deal on the test pipe. Then we'll see how easy it is.

[Silver Ecstasy]

Well if you find out what's going on with that deal, let me know, I may want to make that purchase as well. Supposedly the test pipe and the mscbe is a great sound combo.

[iracer7]

Originally Posted by Crossbow PaPaSpeed, All Maryland does is plug into your ecu, and checks for cels, and does a readiness test. Takes like 5 minutes through a drivethrough. Nobody opens your hood, or looks under your car. Heck stretch is in MD too, and he has a completely catless sti, using tuning software to hide his cat cel, he's passed emissions twice! lol. MD emissions is a joke! Now VA has inspection, thats a whole different story.

How's the VA inspection? I'm in VA.

[06speed]

go with CP-E

[Crossbow]

I don't live in VA, but I'm pretty sure they give a visual inspection. So you better have a catalytic converter under the car...or at least something that looks like one, with an O2 sensor going in it. (or someting that "looks" like an O2 sensor).

The big thing with exhaust installs (silver and papa), is to get some sort of pb blaster and spray on the bolts/fasteners ahead of time. (If possible the day before, and an hour or so before). This will make things ALOT easier.

If you are at 50k+ miles, and in the snow belt, it's a good chance some of the fasteners might be basically welded in place. (One of the big arguments for doing a DP earlier instead of later, is because you can actually remove the O2 sensors....)

As such, the SU test pipe install looks to be pretty straightforward. Just make sure you put it in the right direction. It fits one way, 180 degrees and it won't fit.

[martyxattack]

Originally Posted by PaPaSpeed It may be easy for you, but when you're a novice like me, nothing is easy.

this test pipe is 4 bolts. 2 on one and and 2 on the other. easy as pie.

[Silver Ecstasy]

Originally Posted by thanox2 Got the Cobb Inlet, spool time decreased, the car feels better, the turbo sounds louder, love it. Now to remove the stock one I just pulled it... it wasn't even clamped to the turbo. And yes it does look smashed, and it is smashed, its a fucking restriction. No need no evidence, just personal experience.

I totally missed your post for some reason, until I noticed you "Groaned" me.

No need for evidence or proof huh. I guess automotive engineers are all just complete fucking idiots and have no real rhyme or reason behind what they design huh. They just design it so it fits and has no real flow or contribution to the car.

Again, just because it looks smashed doesn't mean it's actually "worse" than a straight through design of a TIP. You probably just "hear" the turbo spool up faster due to the materials used in the aftermarket TIP that makes you think it's spooling faster. And it's not like you have any paper proof showing it does and neither do the manufacturers. So on the TIP, to each his own!

[buttdart]

how much better can a test pipe be over a gutted 2nd cat?

[jwdp54]

i saw they tested that theory somewhere but if you think about it a stock test pipe is only 2.5" and an aftermarket is 3". to be honest in my own opinion switching out the test pipe is better than just replacing the cbe. plus it's ALOT cheaper.

i still have stock cbe(i still think ours is pretty good for the car) but have a dp/rp combo. it's a lot cheaper to go that route and you gain more from it. plus normal driving it's quiet but going wot it sounds mean.

[Silver Ecstasy]

Keeping the stock CBE and switching out with an aftermarket test pipe makes NO sense.

DP---TP---CBE
2.5"--3"--2.5"

Explain the logic in that one.

[jwdp54]

our stock cbe's are actually pretty good and i had good results with just a test pipe. when you add in the dp i made awesome results. u my as well just go to a muffler shop and get the resonators cut out and weld in a straight pipe.

why would u want to push air through 2.5" piping with 2 cats then to a 3" exhaust? your still having a restriction i'm guessing.

not being sarcastic i'm just sharing from opinion and what i've done. i never upgraded my cbe just because it didn't seem worth the price. for you though it would probably be worth it since your mostly stock and i was too. just depends on what your wanting in the future. plus if you have dealership issues an aftermarket exhaust is harder return back to stock than just switching out a test pipe.

[Silver Ecstasy]

Yeah I am not tryin to be sarcastic either. Thankfully my dealer is mod friendly and I am pretty visual throughout the dealership. Service, parts, sales they all know me, and i've referred a lot of business there as well.

The restriction on the downpipe would be similar to the restriction in the stock inlet. However, opening up the further intake point (CAI) would also benefit by opening up the furthest area that expels those gases (CBE). That's the logic i'm going off of. After opening up the CBE to 3", then a test pipe would make more sense, and eventually some day, a downpipe, if I plan on having the car that long or modding it to that level.

[Sacrilicious]

Originally Posted by Silver Ecstasy Keeping the stock CBE and switching out with an aftermarket test pipe makes NO sense. DP---TP---CBE 2.5"--3"--2.5" Explain the logic in that one.

it actually does make sense, because the stock TP that you took out had a cat in it, and (i'm assuming) the 3" aftermarket one you put in is catless. the restriction you're removing is the added backpressure caused by the stock cat you just took out.

as far as CBE is concerned, i'm highly doubtful that you will get more than negligible gains from upgrading to a 3" pipe. here's why:

our turbos spit out air heated to roughly 1300-1500F when it's really working hard. by the time the air gets past the cat/cats and gets all the way down to the end of the DP, you've likely dropped 500F+ in temp. this is true because our exhaust temps drop VERY quickly as you leave the turbo housing. this is the reason why aftermarket EGT gauge manufacturers recommend that if you install your EGT on the DP, you do it no farther than a few inches from the turbo outlet. 6" can easily lose you 200F+ in exhaust temp.

now, the reason why this is so important is that hotter air takes up more space than colder air (same reason why everyone wants to cool their intake charge). if your DP is 3", and the air gets significantly colder by the time you get to the CBE section, then the fact that you increase the size of the CBE is pretty irrelevant...it wasn't causing enough restriction to make a difference in the first place. this is why you'll notice that the cobb DP actually tapers from a 3" pipe down to a 2.5" pipe (to mate with the stock CBE): it doesn't really matter that much.

this is why you'll notice people coming on here ranting about how their car drives like a completely different animal when they put on a DP/RP, but not so much for the CBE...=/ in fact, the only thing you usually hear about from the CBE modders is that it "sounds so much more aggressive". the only reason i bought my cobb CBE is because i knew it would do a good job toning down the drone that the stock exhaust has. let me tell you, the sound quality (i reaaaally don't want cops looking at me twice) was literally night and day when i put on the cobb CBE...i LOVE it still!

[Sacrilicious]

btw...as per the post i just made: if you want max benefits as far as backpressure goes, you should start your exhaust modding from the top down: DP and then TP...or simply by removing cats.

EDIT: for the record, i'm not a fan of running catless, because removing too much backpressure messes with the tuning of our cars. remember: our boost is controlled using load targeting during the majority of heavy/WOT throttle operations, so if you go removing too much backpressure, you'll start overboosting past what you intended. AP users with DPs have run into this trouble when trying to use stage 1 maps.

[Frequentflyer]

I would spend $140 on a test pipe and see how you like the sound of the exhaust if you're not looking to go as far as replacing the DP. You will feel a power gain and get a throatier sound for a fraction of the cost. If it's still not enough for you, get the CBE.

[ptperformance]

Originally Posted by Crossbow When modding the stock exhaust, you effect the turbo spool time, allowing power to kick in harder much sooner in the power band. To put this in perspective, with a full turboback exhaust, you've basically shifted the entire stock powerband 750 rpm sooner. That's huge. (Though I love CP-E products, I am using these graphs to help explain the effects of exhaust mods regardless of manufacturer) One of the fundamental problems with dynographs, is that most people don't know how to read them. They look for two numbers. Peak torque, and peak horsepower. These are the numbers you should be paying the LEAST attention to. They tell you very little about what the mod is doing, other then at peak rpm's. What IS the most important part of a dyno graph? The AREA between the stock and modded graphs. It's this space that is most important, and tells us exactly what is happening to the car. This is the area you should be looking for on ALL dyno graphs. This is the most important change. The area tells you how much the overall gain effected the car...if it hurt the car at some rpm ranges, if it only works in the upper rpm range, if the mod is fantastic and effects the entire powerband, etc. Tons of info in between the graphs! It's here you can also figure out the "max" gains of a mod (largest gap between curves). The max gain is usually where the butt dyno records it's highest reading . Lets take a closer look at these graphs shall we? This is a cut section of the torque graph. I cropped this to allow everyone to concentrate on the angle of the line. Note that the modded line is roughly 75 degrees, while the stock line is roughly 40 degrees. This is a MAJOR change. The aftermarket exhaust is allowing the turbo to spool faster, causing torque to increase much sharper. (Huge butt dyno change, pushed back into the seats gain) This is a major change in power output, and as such, causes the car to reach stock peak torque BY 2750 rpm!!! (instead of 4200rpm). By 4750 rpm, the turboback car is producing over 40 ft/lbs more torque then the stock car. So not only is the car reaching stock torque levels over 1500 rpm sooner, but it's utterly blowing away the stock car around 5k rpm. Max gains are close to 45 ft/lbs. (To put that in perspective, you can spend about 2k USD on a Mazda6 and still not get that kinda of torque gain). Now lets look at a cropped version of the HP graph. Look closely...the powerband has shifted to the left. In this example, you're making the same horsepower at roughly 750 rpm's sooner now. You are making the same power at 4k rpm, that you used to make at 5250k rpm! You reach the stock power output at 4750 rpm, as you were (stock) at 5500 rpm. Max gain's are close to 35 whp. Dyno's really should be presented in another way. They really need to have... 1) Peak Horsepower 2) Peak Torque 3) Min and Max Torque Differences 4) Min and Max HP Differences 5) Shaded or crosshatch between the area of the two graphs 6) Some sort of number (area between two graphs) giving you a rough estimate of the power gain across the entire rpm range. Without that information, we all have to step back and very carefully look at the graphs to see what's really happening. I imagine if you were to replace the entire exhaust, manifold to tip...the car wouldn't even feel like a speed3. I think that's my plan now. I'll do catback/SU TP, then when funds become available, medieval and DP.

Or simply put, power across the curve. This will tell you how much you really gained.

[ptperformance]

Originally Posted by Sacrilicious btw...as per the post i just made: if you want max benefits as far as backpressure goes, you should start your exhaust modding from the top down: DP and then TP...or simply by removing cats. EDIT: for the record, i'm not a fan of running catless, because removing too much backpressure messes with the tuning of our cars. remember: our boost is controlled using load targeting during the majority of heavy/WOT throttle operations, so if you go removing too much backpressure, you'll start overboosting past what you intended. AP users with DPs have run into this trouble when trying to use stage 1 maps.

They run into this problem because the WGA duty cycle of the current map is to much. Adjust this parameter and your golden, this is why the ATR software is going to be king for these cars as people start to get used to it.

[Sacrilicious]

Originally Posted by ptperformance They run into this problem because the WGA duty cycle of the current map is to much. Adjust this parameter and your golden, this is why the ATR software is going to be king for these cars as people start to get used to it.

ya, i was trying not to assume he had the AP, so i didn't bother to mention the option of tuning it out.

[jwdp54]

hey if you wanted i would just purchase a used catted cpe dp. i still can't get over the thought of paying 5-700 for a cbe with 5-10whp when u can pay the same price for a dp/rp combo and will give you both more power and a better sound.

also if you are going for basically sound just get straight pipes welded in where the resonators are. probably will gain a couple hp and will give you that exhaust sound. a lot less expensive also

[Frequentflyer]

Originally Posted by jwdp54 also if you are going for basically sound just get straight pipes welded in where the resonators are. probably will gain a couple hp and will give you that exhaust sound. a lot less expensive also

That is another low-cost option. We basically have a stainless-steel mandrel bent exhaust from the factory, which doesn't really need to be 3" unless you upgrade the turbo and are pushing out higher boost. The main thing I don't like about the OE exhaust is the drone and I'm not sure why it drones so damn much with two resonators and a muffler on it, but other than that, it does good for an OE exhaust. I have heard the OE exhaust with the resonators taken out and a test pipe and it doesn't really sound any different than any of the $500+ aftermarket exhausts. Yeah, it may be "ghetto" to clamp two straight pipes in there in place of the resonators, but noone sees it.

[BoostIsBetter]

why not just get an e-cutout?

[MSMS3]

I think many are still missing the point. The stock CBE flows better than the max flow rate of the exhaust side of the K04 turbo. Making the stock CBE bigger or freer flowing is not going to produce meaningful gains. That's also why an electric dump after the second cat is not going to do much either, certainly not better than putting in a good RP. The restriction (and it is a serious one) is upstream of the CBE. It's primarily in the sharply bent and oddly shaped stock DP and its primary cat, and in the secondary cat. The key to power is to open up THOSE restrictions. That's why an aftermarket DP/RP without cats produces such huge power gains, especially midband and up to 5500 rpm, coming on so strong at lower rpm. The same combo with high flow cats will do just about as well.

While my DP/RP is a full 3 inch into the 2 1/2 inch stock CBE, it would perform just about as well if it were 2 1/2 inches because the true restrictions holding the exhaust flow rate below the output rate of the K04 have been eliminated. If I ever go to a bigger turbo, I'll only have to upgrade the CBE. But until then, I'm flowing more exhaust than the K04 can send to the DP.

Hope this makes sense. BTW: once you get the ECU to give you full boost (third gear and up) the impact of a simple CAI and this type of DP/RP mod is dramatic. 60-100 mph times are a full two seconds quicker. That is huge. We're talking 6.4-6.5 seconds, or even quicker in ideal conditions. In that speed range the car will run dead even with a Charger SRT8.

[Silver Ecstasy]

I wanted to bring this thread up because I wanted to ask you guys something.

After having the MSCBE (and having install issues with the clamp -still have a pinhole exhaust leak spitting soot out..), it seems like i've basically lost torque, but gained power up top. The car has basically no oomph at 3,000, where it seems like it explodes at 4,000 rpm now. I can't break the tires loose in 2nd until the rpms shoot way up past 5000.

I'd imagine this is pretty typical since you're freeing up backpressure, that you'd lose torque, but gain hp? Or is this just the consequences of using too large of an exhaust on a car that never needed it to begin with? (like you guys all said - which i'm totally willing to admit now was a foolish purchase).

[Speedsicks]

Magnaflow baby

[Frequentflyer]

Sounds like you need an AP now.

[Silver Ecstasy]

Nah, someone put the fear of God in me, that running "over the shelf" tunes were never EVER a good idea. As everyones car, is different. So you cannot generalize the tune.

[Hectik1]

There used to be dyno graphs too....that helped.

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