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Thread: Custom QUIET Performance Exhaust

  1. #51
    Still Plays With Cars Loren's Avatar
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    Oh, before I lose this bit of info... WEIGHT:

    Stock Manifold and First Cat w/ Heat Sheild and all = 9.9 lbs
    Stock Cat Back (including 2nd cat) = 18.5 lbs

    SuperCircuit Header = 5.5 lbs
    1.75" Header Back (including cat, muffler and resonator) = 20.5 lbs

    The header is 4.4 pounds lighter, but the exhaust is 2 pounds heavier. Complete system is 2.4 pounds lighter with weight shifted slightly to the rear.


    Simplify and add lightness.

  2. #52
    Moderator Eggman's Avatar
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    Quote Originally Posted by Loren View Post
    I guess there's one benefit to doing so many rainy autocrosses this year. I have three in-car autocross videos, all in similar weather with the windows up or nearly up, so less wind noise. You can definitely hear the difference.
    Of your three videos, I can't really tell a difference in exhaust noise.

    The racing looks like fun. I have a question - why don't you hook your thumbs on your steering wheel spokes? I was taught that in my driving school as a method of maintaining control of your vehicle. Is that not taught anymore?
    Last edited by Eggman; 07-05-2018 at 08:49 AM.

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  3. #53
    Still Plays With Cars Loren's Avatar
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    Quote Originally Posted by Eggman View Post
    Of your three videos, I can't really tell a difference in exhaust noise.
    Well, that's good! If you listen to just the start and the acceleration through first on each one back-to-back, I think you can probably tell the difference. The header is subtle, but the full exhaust is definitely a deeper tone.

    The racing looks like fun. I have a question - why don't you hook your thumbs on your steering wheel spokes? I was taught that in my driving school as a method of maintaining control of your vehicle. Is that not taught anymore?
    For autocross, I do a lot of "shuffle steer". My hands are all over the place all the time. And unless I'm making big transitions (exaggerated slaloms), you'll almost never see my hands go "over center". If I have time to do it, I instinctively pre-position my hands for any significant turn such that my hands are in the optimum position to make precise corrections in the middle of the turn.

    For street driving, my pet peeves are one-handing the wheel and grabbing the inside of the wheel while turning. My wife does that, makes me crazy. I'm usually pretty casual and will let my students figure out what works for them as far as handling the steering wheel (if they're new and fumbling, I'll give them as many tips as they need). But, those two things I will always correct. Hands inside the wheel is sort of similar to "hooking thumbs on spokes". I would teach against that for the same reasons. 1) Spokes are in different places on different cars. If your hands are never on the inside of the wheel, the spokes are never in your way. 2) The big one on a modern car is that if you've flipped your wrist over and grabbed the inside of the top of the wheel to make a turn (cringe!), now what happens if you get t-boned or hit a curb or whatever, and your airbag goes off? There goes your wrist! Sort of the same thing to a lesser degree if you're hooking your thumbs. Airbags were a game changer. I always recommend keeping your hands to the outside of the wheel while you're turning it. While you're holding "standard position", find the comfortable position that works for you in that car with that wheel, anywhere between 9 & 2 or 10 & 3... and maybe even a touch lower than 10 & 3... as long as both hands are on the wheel.

    If you saw me street driving this car, you'd see my hand position alternate between the 10 & 2 that I start with in these videos, and "hooking" my thumbs (but, more resting than hooking) at a natural 9 & 3 that fits this wheel. You'll notice that our steering wheel is ergonomically designed to work with both. It's got nice thumb pockets for 9 & 3, and finger-nubs on the back for 10 & 2. I really do like the wheel in this car!

    So, yeah. If you're explicitly teaching a new driver at that level... "thumbs up" is probably a better way to teach in the modern world. Light touch, no "death grip". Relaxed and confident. But, I rarely get that much into it unless they're grabbing the inside of the wheel or not using both hands. I worry more about where they're looking, what they're seeing, and that they're learning to keep their space.
    Simplify and add lightness.

  4. #54
    Still Plays With Cars Loren's Avatar
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    Here's the official "final sound readings":

    I didn't do any "throttle blipping" in the baseline testing. The stock exhaust is nearly silent no matter what you do. But, the full exhaust DOES get louder with a quick rev, so I included that as "worst case". Bottom line is that while the 1.75" exhaust is a little louder than stock, it's still very quiet. I've taken sound readings with the same meter at autocrosses, 50 feet back accelerating away from a stop, and 83-85 db is pretty typical for most stock cars. I'm still quieter than, say, a stock Subaru BRZ.

    The very interesting thing is that the sound level at 6000 rpm is actually quieter (vs the header w/ stock exhaust) in car and up close with the 1.75" exhaust. Slightly louder at a distance. Acoustics is a funny thing.

    In-car dBA
    stock > header > full 1.75" Exhaust (throttle blip)
    48>48>48 - Idle w/ no fan
    50>50>51 - Idle w/ fan on 1
    57>57>58 - Idle w/ fan on 3
    63>65>68 (73) - Rev to 3500 rpm
    75>79>77 (78) - Rev to 6000 rpm
    71>72>77 - Cruise at 2500 in 5th
    72>74>76 - Cruise at 4000 in 3rd
    74>76>79 - Cruise at 5000 in 1st
    83>85 - Accel to redline in 1st and 2nd

    Outside Car dBA
    stock > header > full 1.75" Exhaust (throttle blip)
    64>64>63 - Idle at 10 feet
    73>77>76 (84) - 3500 rpm at 10 feet
    85>93>85 (88) - 6000 rpm at 10 feet
    50>50>50 - idle at 50 feet (ambient, couldn't hear it)
    58>58>65 (72) - 3500 rpm at 50 feet
    69>69>72 (77) - 6000 rpm at 50 feet
    Simplify and add lightness.

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  6. #55
    Still Plays With Cars Loren's Avatar
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    And I redid the final acceleration test runs. Here's the data. Continue to bear in mind that my testing method is NOT very accurate, though it is fairly repeatable. The I'm measuring video frames at 30fps, so each frame is .033 seconds. That means that each data segment could be nearly that far off. And the total run time could probably be about double that far off (starting and ending error).

    I'm kinda disappointed at the results of the full exhaust, but I know there's more to be gained. I think the fall-off on the top end can be aided by cutting out the 1.5" neck-down at the end of the header. (it's there for the stock exhaust donut gasket, and I'm not using that) And, I haven't touched the intake, or done any tuning at all.

    I do like how the exhaust gave a nice boost in torque in the area that I most need it for autocross. But, I'd also like to restore/improve the very top end.

    Neat graphing gear ratio calculator here if you want to dig up your gear ratios and tire diameter. Our 1-2 shift really sucks! No wonder it feels so bad when you grab 2nd too early and you actually need to accelerate!

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    Simplify and add lightness.

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  8. #56
    Still Plays With Cars Loren's Avatar
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    Somebody got some external video of my Mirage in action last weekend. Doesn't sound bad at all.

    Simplify and add lightness.

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    2of9 (12-14-2018),bloodehunter (08-01-2018),Top_Fuel (07-18-2018)

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    Moderator inuvik's Avatar
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    Looking and sounding good!

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.5 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.6 mpg (Imp)


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    Administrator Daox's Avatar
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    Agreed, not obnoxious at all.
    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

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        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)


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  14. #59
    Still Plays With Cars Loren's Avatar
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    Quote Originally Posted by Loren View Post
    Oh, and the CEL hasn't come back on yet.
    6/19 - 7/28 with no CEL. Lots of city driving, various speeds and conditions. Autocrosses on 6/30, 7/14 and 7/28.

    Finally got another CEL today at the autocross. Same one, low O2 voltage.

    Not worried about it in the least. If it comes on every now and then under extreme circumstances, but doesn't bother me during daily driving, I'm fine with it.
    Simplify and add lightness.

  15. #60
    Still Plays With Cars Loren's Avatar
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    Update:

    The CEL came on a while back again. I didn't bother resetting it. (didn't have the OBD reader handy, and was lazy) It actually turned itself off after about a week... but, then it came back on again. I'm just going to leave it and check the code from time to time rather than keep resetting it.

    The muffler (the big round can main muffler) developed a rattle and horriffic buzz. Something inside it broke loose. So, I ordered a replacement and installed it today.

    The first muffler was a Walker Tru-fit, which was about the cheapest muffler available in that size. This time, I did some more research and opted for a slightly more expensive muffler, the Walker Sound FX, which is reported to be very quiet. I'm just hoping it stays together and doesn't fall apart in a matter of months like the cheaper one did!

    So, the new muffler is a few inches longer. I didn't weigh it, but it might be a 1/4 or 1/2 pound heavier. And now that it's on the car, aside from not having a rattle and buzz... it IS quieter. I'm not going to bother redoing my sound measurements, but, inside the car, it is notably quieter. It wasn't loud before, but had a nice little subtle growl to it. That is gone. It sounds pretty much stock now. There's a little bit of raspiness at high revs that you can hear when the windows are down... similar to what it was before, but probably quieter.

    If you're ever looking for a truly quiet muffler: Walker Sound FX. Impressively quiet.


    Simplify and add lightness.

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