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Thread: Custom QUIET Performance Exhaust

  1. #21
    Still Plays With Cars Loren's Avatar
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    Okay, I got the header installed today!

    First, things nobody tells you:
    1. The stock manifold gasket is a double-layer stainless steel gasket. You can reuse it.
    2. The stock manifold bolts and nuts can be reused at least once. The lower bolts should be fine to reuse as long as they aren't damaged. The upper nuts are copper and probably intended to replaced with each use... but, but you can get away with reusing them at least once.
    3. The header doesn't come with any hardware. You'll need some to attach it to the cat-back. I just used the OE spring-bolts, but the stock manifold uses captive nuts. So, you'll need at least some nuts to fit that. Or if you want, you can replace the bolts, too.
    4. You WILL need an O2 sensor socket!

    Removing the stock manifold took 3x as long as installing the new header. It took me something like 2.5 hours total. Why so long? Two reasons. First, I've never in my life actually "needed" an O2 sensor socket. I've always managed to get by with a 22mm combination wrench. The way the upper O2 sensor shroud is designed, you need a socket... but, I was too stubborn to go buy one. The problem is that you have to remove the manifold heat shield to access the upper manifold nuts. And to remove that shield, you must remove the upper O2 sensor. My solution was to unbolt the shield, that gave me enough room to get a wrench on the right-side upper nut. But, to get to the one on the left, I had to bend the heat shield. And, of course, that nut was one of two that were Really****ingTight. I had to use a cheater pipe on 3 of the 4 manifold bolts to get them loose... two of them were just stupid tight.

    I didn't take the time to read the manual, but it appears that no thread locker or antisieze is used on the manifold bolts. And upon reassembly, I just tightened them "good and tight" with a standard box end wrench. I'll recheck them in a week or two.

    Weight of the complete manifold/cat assembly with heat shield and everything that wasn't reused with the new header = 9lbs 14.2oz. So, about 9.9 pounds. Compare to the 5.5 pounds of the replacement, that's 4.4 pounds of weight savings. (woohoo!)

    As I was installing, I realized that the necking down of the collector pipe to 1.5" OD that I thought was done for anti-reversion was actually done to allow the OE exhaust donut gasket to be reused.

    Fitment was good enough, but not perfect. The upper O2 sensor bung is off to the right by a couple degrees, which puts the end of the O2 sensor a half-inch or more to that side. This makes the wiring to that sensor aaaaaalmost too short. There's enough cable there to make it work if you pull the cable out of its bracket. I opted to just bend the bracket a little bit.

    The fitment of the collector flange to the cat-back was also off just a little bit. No so much that it wouldn't go together, but not a perfect fit. I'm sure this is why they use the flex pipe.

    Overall, for the price, I'm not at all unhappy with it. Once I got the old manifold off, install took maybe 20 minutes. And I was getting tired and slow by then!


    Simplify and add lightness.

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  3. #22
    Still Plays With Cars Loren's Avatar
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    Initial performance evaluation:

    I've not done any testing yet. Just seat-of-the-pants, hard acceleration doesn't feel all that much different, maybe a tiny bit faster. Still slow, of course. 4-5% isn't all that much. It should show in the numbers, but it's not a lot. But, there's definitely more low-end torque. The general driving experience is that the car feels "easier" to drive. I can drop it into 4th or 5th at just about any speed I care to without feeling like the engine is struggling like it used to. I mean, I can drop to 4th and idle down to 1200 rpm or lower... no bucking. I can even gently accelerate out of that without the engine giving me that "I really don't want to do this" vibe. It's just much smoother on the bottom end, and in normal driving. I now wish I'd done some sort of "basement level" lugging tests for comparison. There's definitely more torque down there in the basement!

    My first drive, I reset the MPG and semi-hypermiled for a couple miles back home. Achieved 48 mpg, which is pretty typical. That included one full-throttle 0-40 sprint to get out into traffic, and sitting at one traffic light for maybe 20 seconds. Top speed 45. So, I don't think it hurt MPG. BUT... you get more power for the same throttle inputs. Which means that if you don't adjust your driving (use less throttle to get the same power and economy that you used before), you WILL see less MPG.

    Lastly, I've already seen my first Check Engine Light. It didn't come on immediately. In fact, it didn't come on until my second drive when I was cruising with VERY light throttle at 40-45 mph in 5th. I cleared it already, we'll see if it comes back. I think it was a P0420 code. Something about cat not warming up quickly enough or something. Basically, it's seeing the 2nd O2 sensor and with the cat missing, it thinks it's not warming up quickly enough due to the readings. If it keeps throwing that code, I'll try the spark plug anti-fouler trick.

    Overall, initial impression is that the header makes the car more pleasant to drive. Just a little happier puttering around without feeling like its struggling as much.

    I'll take some measurements sometime soon to compare.

    Oh, and it doesn't seem to have made the car appreciably louder. Wife didn't notice. There's a common sound with this engine, I think it's the fuel injectors firing. You can sort of hear it resonate through the exhaust when accelerating through the low RPM range. You probably know what I'm talking about. That noise seems to be slightly more prevalant. Maybe. Otherwise, I can't detect a difference. I'll measure it and see if the dB numbers have changed at all.
    Simplify and add lightness.

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  5. #23
    Moderator Eggman's Avatar
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    Loren I appreciate you taking the time to do this and post it here for all to benefit from. I especially appreciate that you are trying to measure and quantify the before & after as much as you are able.

    Thanks!

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 50.0 mpg (US) ... 21.2 km/L ... 4.7 L/100 km ... 60.0 mpg (Imp)


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    Senior Member Top_Fuel's Avatar
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    Quote Originally Posted by Loren View Post
    I had to use a cheater pipe on 3 of the 4 manifold bolts to get them loose... two of them were just stupid tight.
    Whew...at least they didn't break off. That's what I would have been worried about.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 51.3 mpg (US) ... 21.8 km/L ... 4.6 L/100 km ... 61.6 mpg (Imp)


  7. #25
    Still Plays With Cars Loren's Avatar
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    Yeah, I like to quantify things like that. I get a lot of great info from internet forums, I like to think I'm just giving some back.

    So, I drove the Mirage to an autocross about an hour away today. The car felt great at the event. I can't say for sure that it felt a lot more "powerful", but it felt fine. There was rain. Variable conditions, so I never quite got it right. But, the Mirage did not disappoint.

    What was more interesting was that I found that the header DEFINITELY makes it easier to hypermile! It's got more low end, doesn't feel like it's lugging, so I feel better driving it down there. Short shifts, deep pulse & glides, that kind of thing. And as a result, what is typically 47-48 mpg was a pretty easy 49.4 on the way there, and 49.7 on the way back. With correction for tire size, that's over 50 in both cases. And that was not with "obsessive" hypermiling, or doing anything more than neutral-coast pulse & glide, and DFCO coast-downs for stops. Likely would be an easy 55 or so if I got into EOC. Pretty cool.

    Still no acceleration or sound numbers for you. Soon.
    Simplify and add lightness.

  8. #26
    Member Qrush's Avatar
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    Quote Originally Posted by Eggman View Post
    Loren I appreciate you taking the time to do this and post it here for all to benefit from. I especially appreciate that you are trying to measure and quantify the before & after as much as you are able.

    Thanks!
    I totally agree. Loren seems to be a master at doing the numbers and getting qualitative data. A welcome addition for those not as adept as such. Keep up the terrific work. Your a reall asset to our forum, cheers!

  9. #27
    Still Plays With Cars Loren's Avatar
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    Thanks, guys. Glad to contribute. And I do this as much for my own info as I do for anyone else!

    So, I got out and took some more sound measurements today. Here's the before and after. This is JUST the header. I'll do some more testing after I do the full exhaust, whenever that is. (likely won't be this month, too much going on... but, I'll probably get the parts ordered)

    About my measurement method. I have a cheap sound meter. It seems pretty accurate and consistent. It does have a peak hold feature, but I'm not really using it here. I do use it for things like the acceleration numbers, but I'm not reporting the max number that I acheived. I'm going for some approximation of an "average" or "typical" sound measurement. The meter also gives me tenths. You'll note that I'm rounding to whole numbers. I don't want to give the illusion of accuracy here! This is just ballpark testing. Something quantitative rather than just "it's a little bit louder when you get on it".

    Outside measurements were taken behind the car at ground level. The 10 feet ones were done with the meter a couple feet in front of my closed garage door, so there could be some reflected sound adding to the levels there.

    In-car dBA
    stock>header
    48>48 - Idle w/ no fan
    50>50 - Idle w/ fan on 1
    57>57 - Idle w/ fan on 3
    63>65 - Rev to 3500 rpm
    75>79 - Rev to 6000 rpm
    71>72 - Cruise at 2500 in 5th
    72>74 - Cruise at 4000 in 3rd
    74>76 - Cruise at 5000 in 1st
    83>85 - Accel to redline in 1st and 2nd

    Outside Car dBA
    64>64 - Idle at 10 feet
    73>77 - 3500 rpm at 10 feet
    85>93 - 6000 rpm at 10 feet
    50>50 - idle at 50 feet (ambient, couldn't hear it)
    58>58 - 3500 rpm at 50 feet
    69>69 - 6000 rpm at 50 feet

    Synopsis:
    No perceptible difference in sound at idle. A tiny bit louder at a normal cruise, I didn't even notice this, nor did my wife. Louder still as the revs get over 5000, but still a minor difference. What really surprised me was that outside the car at 10 feet, it is significantly and repeatably a lot louder at 6000 rpm. I didn't expect to see anything over 90. But, it's not that loud inside the car, and it dissipates quickly over distance. At 50 feet, the measurements were the same.

    I'm looking forward to doing the rest of the exhaust. What I'm going for or expecting here is maybe 1-2 more dB from where it's at now, and just a barely perceptible "growl". I don't want it to be loud by any means. But, I do like the sounds that the engine makes, and would like to accentuate that in a very subtle way. (but, mainly, I'm just trying to get a little more power)
    Simplify and add lightness.

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  11. #28
    Still Plays With Cars Loren's Avatar
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    Back to driving perception:

    In driving the car around town today, I found that I could really feel the difference in torque a lot more than I did initially. I'm wondering if the ECU adapted timing and fuel trims to better match it? Definitely more feel than within the first hour or so of running with the header.

    I'll try to get some acceleration runs done and crunch those numbers tonight. Should be interesting.
    Simplify and add lightness.

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  13. #29
    Still Plays With Cars Loren's Avatar
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    Well, I did my second round of acceleration testing today. In analyzing it, I realized that I really should have done the video in slow motion (60 fps rather than 30 fps). Doing it in standard 30 fps, the granularity of my data is .033 seconds. With each 500 rpm segment being about a second, that means I can only see change in 3.3% increments. Fortunately, the improvement is generally more than 3.5%, so it does readily show on the graph. But, I wouldn't call it accurate.

    I'll go ahead and redo the data at 60 fps before I do the rest of the exhaust. At least that final comparison can be more accurate.

    All that being said, here it is. Clear 3.5-4.5% improvement in acceleration across the board up to 5500 rpm. I can't explain why there's actually a DECREASE at 6000 rpm, but it was very definitely and repeatably there. I had 3 runs before and 4 runs after, and all of the data, while not exactly the same, was very close and always showed the same trends. It definitely drops off at the last data point.

    But, just look at that torque curve! It's brilliant! I think opening up the rest of the exhaust will raise the torque curve a little bit more, and very likely bring the high end up significantly.

    I'm thinking seriously about cutting out the 1.5" pinch point at the end of the header. I think that's limiting the total CFM that the header can flow, and thus limiting peak HP to near stock levels.

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    Simplify and add lightness.

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  15. #30
    Administrator Daox's Avatar
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    Great testing! Thanks for sharing.


    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing
    Current project: Developing a rear sway bar alternative

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 41.7 mpg (US) ... 17.7 km/L ... 5.6 L/100 km ... 50.0 mpg (Imp)


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