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Thread: Getting a cat-back pipe size should I get?

  1. #21
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    < What he said!

  2. #22

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    Quote Originally Posted by kmh001 View Post
    BTW Doc's comment is spot on. When the exhaust gases leave the engine they are travelling at supersonic speed at very high temperature. By the time the gasses reach the tail pipe they have slowed cooled and contracted significantly. The pipe diamater can and should decrease toward the rear of the car, even for turbo cars. But this is considered unconventional because accepted wisdom on exhasut design principles usually comes from guys who are not trained in fluid dynamics.
    So putting a huge cannon on an otherwise stock exhaust on a Lancer isn't actually boosting performance? YOU ARE SHAKING MY WORLD HERE!

  3. #23
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    Quote Originally Posted by Nepharius View Post
    So putting a huge cannon on an otherwise stock exhaust on a Lancer isn't actually boosting performance? YOU ARE SHAKING MY WORLD HERE!
    Technically, if you wish performance gains (concerned with exhaust) there's not much point adding a muffler, when the restriction lies at the exhaust manifold/extractors, and small manufactures designed pipework. Don't forget most new cars are designed to keep noise down and keep emissions low - restrictions. It's along the same lines as Mal's comment with regards to fluid mechanics. To some extent A/C ductwork too.

    For example; if you were to install a large air diffuser, but only have small ductwork, the optimal result (velocity of air) is only going to be what the ductwork is capable to handle not how big the diffuser is. Don't expect 1500L/s out the diffuser when the designed pipework size is 200x200mm

    It's the design of the entire system that will determine the velocity of exhaust gas not the muffler. Adding a muffler on the end is purely for sound in most cases. There may be a small increase (straight through mufflers) but it would be minimal. Hence most people get extractors, full exhaust, down pipes etc. They're all in the effort to achieve more power with a "Full exhaust" modification

    With great power comes great fuel consumption...
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  4. #24
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    Good advice

    Do you think Cat back 2.5 inch all the to tip would give less chance of drone...

    Noob question, the resonators are the twin mufflers right?

  5. #25
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    You can add that if the exhaust is too large the decrease in velocity of the gases causes turbulance in the pipe and therefore adding a restriction to gas flow.

    In a turbo engine, the turbo provides sufficient back pressure for the engine requirements. Mufflers are there purely to reduce the noise. Engines MUST have some back pressure because of the valve overlap. No back pressure at all and incoming fuel would exit straight out exhaust. Turbo engines have less valve overlap because of the turbo forcefeeding, they require much less backpressure than a normally aspirated engine.

    It has been hinted at in these posts that there is a science to making an exhaust that increases power. It certainly isn't just fitting a larger diameter pipe.

    I have a stainless corksport cat back system and have been told it sounds terrific. (haven't actually listened to the car go past as no-one allowed to drive my car). For the price, the Corksport is by far and away the best system available. We compared a CPe exhaust and the Corksport on a recent cruise on two white MPS6's - CPe louder, not as good a fit and no where near the quality of the polished Corksport. Both drone, but only under load or when first started cold.

  6. #26

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    picc
    Last edited by carey; 06-08-2010 at 06:28 PM.

  7. #27

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    hey guys

    as doug said am looking into fixing the misserable tips hidden in the oval shrouds. went to super cheap today
    picked up a 50mm by 75mm tip.was to long but angle grinder fixed that! havn't stuck on but put it on and took a photo.so comment please.iam unsure rreally.
    i would maybe also cut am inch off my current exhaust tip so it wouldn't show through the new bigger one.cos they look turd i think when you can see the smaller one throgh the bigger one
    heres a pic Click image for larger version. 

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  8. #28
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    Corksport on MPS6 - amazingly good fit - does not hit even in outlets - fitting instructions suggest cutting a small section out of the heat sheild in the bumper, but it wasn't necessary.

    Only one small problem was the closeness of the exhaust to the plastic shield over the fuel pump area caused the front edge to melt. Melted plastic on exhaust was not a nice smell. I cut about 25mm of shield before I realised a cable tie holing the shield up would have fixed the problem.

    Click image for larger version. 

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    apologies for the dirty car - yet wash for tomorrow's ACT cruise

    Notice oval tips to match outlets
    Last edited by rd415; 06-08-2010 at 08:51 AM. Reason: added exhaust tips

  9. #29

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    RD415, yes, I like the matching ovalness of that setup ...

  10. #30
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    Well tomorrow the exhaust goes in, a bit on edge about how it's going to turn out.....

    Really do not want a sounding system.... only time will tell I guess

    21/2 inch mild steel cat back, Y split before the rear diff (pipe each side of diff) straight through mufflers, 21/2 inch tips

  11. #31
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    MAAAATE.... dont do it !!!!!

    dont waste your money!!

    forget tryin to make the exhaust sound tuff... spend it instead on A GOOD DUMP PIPE, and enjoy the performance gains with just a subtle change to the sound when you step on it

    Leon


    Quote Originally Posted by MZSPD6 View Post
    Well tomorrow the exhaust goes in, a bit on edge about how it's going to turn out.....

    Really do not want a sounding system.... only time will tell I guess

    21/2 inch mild steel cat back, Y split before the rear diff (pipe each side of diff) straight through mufflers, 21/2 inch tips
    Started out with nothing Still got most of it left

  12. #32
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    No resonators and a straight through mufflers may cause some drone, if that is the case you might have to consider 1x (or 2x) resonators fitted. Can only know when its on the car cause I've not heard a system like that on a MPS6 before. Just to reiterate what Leon said above, I would expect very little performance gain, if any, with the proposed system. As far as sound goes, you will definitely hear it! If you wish to pursue the track of power and performance, a Downpipe of sorts would be the go mate (I think you mentioned above you might consider at a later stage) Let us know how it goes

    With great power comes great fuel consumption...
    M P S
    - 6 - RR | Cobb AP | CAI | TIP | ATP GTX28R | 3.25" TMIC | SS DP | REM | 3" Zorst | SSP Anchors & Countershift | DBA Rotors | K/Springs | Upper & Lower Bracing | Alpine Type S 12" sub MRP-M500 Amp
    | Grille | STi Lip | Shark Fin | 6000K HID | Fog Light Tint | Twin DEFI gauges | Custom Decals & Badges | LED lighting | CF Mirrors & Pillars | Black rims Red callipers

  13. #33
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    Yeah Velocity Red I know where you are coming from.... I have owned the MPS for about 2 years now and have thought about it for ages.

    I was not really looking for a power gain at this stage just wanted a bit of sound to compliment the car, I would think in the not to distant future the dump pipe will be going on too.

    Well tonight I picked up the car from having the work done, I also kept the the old system so the seats were laying down with the system in the boot/back area.

    From first turn of the key I was like geeezzzz thats loud.... driving home it hit me, I thought "well there goes the cars virginity, it will not be the same anymore" I thought if anything it lacked a bit of power at the start but by the time I got home it felt like it had a little more and rev'd out smoother. Maybe it was that the ECU was not used to it and had to change or learn the new set-up?

    It didnt drone really at all, not like 4 bangers with canons I have had before! Driving home I was thinking if it would pass the wife-o meter and it wasn't looking good
    I was keen to get home and remove the old exhaust from the back boot area and put the seats back up and go for another drive....
    Straight away from turning the key there was a sigh of relief, I knew it was there but it was not to the level of being annoying. I boosted the streets and it sounded nice and deep with out drumming in the cabin. The wife-o meter might move the eye brows but I think it will not be going back to stock as quickly as I first thought in the minute or two after I first turned the key leaving the exhaust shop.

    Overall I'm happy with the results, pics and wife-o meter charts up soon
    Last edited by MZSPD6; 11-08-2010 at 08:23 PM.

  14. #34
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    Mate, YOU are the only one who needs to be happy with your car... oh AND the missus too

    Glad to hear you are pleased with it.... ENJOY

    How do you fold down the rear seats on your 6MPS? I had read on US forums that it can be done, couldnt find the catches to do so..... asked local Mazda dealer how to do it and he came back with the answer that it cant be done. Needed to do it last month to fit skis in the boot and had to go with a roof rack. My MPS6 is '05 model. Any clues would be appreciated.

    Regards,

    Leon
    Started out with nothing Still got most of it left

  15. #35
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    Yeah I love being able to put down the seats

    Take out the back divider from the boot so you can see the brace supports.

    You have to get your head right in there but you will see two small brass coloured fingers hanging down on each side of the upper support beam.

    These are not the levers the round buttons a few cm's to the side of these has to be pulled across while pushing the seat forward

    You will have to use a key to push a button on the lash belt latch to be able to get the lash belt out of the way.

    Hope that helps

  16. #36
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    Quote Originally Posted by MZSPD6 View Post
    Yeah I love being able to put down the seats

    Take out the back divider from the boot so you can see the brace supports.

    You have to get your head right in there but you will see two small brass coloured fingers hanging down on each side of the upper support beam.

    These are not the levers the round buttons a few cm's to the side of these has to be pulled across while pushing the seat forward

    You will have to use a key to push a button on the lash belt latch to be able to get the lash belt out of the way.

    Hope that helps

    It sure does, thanks so very much for that

    Regards,

    Leon
    Started out with nothing Still got most of it left

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