Adding a little burble to the exhaust under decel using fuel, afr target and timing?? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 08-06-2013, 01:37 PM   #1
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Default Adding a little burble to the exhaust under decel using fuel, afr target and timing??

OK, on my old map/tune/firmware, I had a nice little burble when I'd decelerate in gear (decel fuel cut turned off), but with Jeremy's new map, it doesn't do it anymore.

I know it has to do with running toward lean and changing the timing. The timing is what I don't know which way to go and the consequences of changing it too much. I did go in the AFR target table and changed the value on the higher mmHg values (IIRC it was 552 to 708 or there abouts from 1500 rpm to 4500 rpm) from 14.7 to 18. I also used the same block of manifold pressure (since it is never there except while under engine braking/between gears when WOT). I also went into the fuel target table and reduced fuel values by 20%. The ignition table has been left alone.

Now this brought back a little, pleasant burble ~2k rpms. If I make any changes to the timing, can I add a bit more aggressiveness to the burble? I don't want the ricer Neon SRT sound, just a little more as I decel...and between gears at lower rpms.
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Old 08-06-2013, 01:42 PM   #2
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overrun.
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Old 08-06-2013, 02:50 PM   #3
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Why?
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Old 08-06-2013, 02:59 PM   #4
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Because it sounds cool and blows flames.
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Old 08-06-2013, 03:42 PM   #5
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I know it sounds dumb to some, but I like a light burble/popping on decel...and when it happens lightly between shifts. Just like those who like to hear their exhaust...
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Old 08-06-2013, 04:15 PM   #6
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I was actually thinking about doing something like this as well.

My plan was -
1) retard timing a lot in high-vacuum area of the map (e.g. bottom row-> -1* timing)
2) dump some fuel in same rows and turn off auto tune
3) delay fuel overrun cutoff by 2-3 seconds. so I could get 2-3 seconds of gargle and then quietness.

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Old 08-06-2013, 04:24 PM   #7
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you need longer than 2sec; mine's delayed two seconds.
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Old 08-06-2013, 04:25 PM   #8
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Do you mean the burble/popping on decel that is generally caused by deleting the EGR kit and/or running rich? My car has that annoying burbling/popping sound. I'll trade you my sound for your silence and increased fuel economy.
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Old 08-06-2013, 04:31 PM   #9
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Quote:
Originally Posted by Braineack View Post
you need longer than 2sec; mine's delayed two seconds.
Baby, 2 seconds is plenty for me.
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Old 08-06-2013, 04:56 PM   #10
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I never got any popping. Overrun turned off, added fuel in high rpm, high vac rows and still nothing. How do I become racecar?
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Old 08-06-2013, 05:19 PM   #11
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I had it without trying. decel fuel cut engaged, timing to 0-10 BTDC.

best yet, just drill a hole in your downpipe to atmo.
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Old 08-06-2013, 06:05 PM   #12
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invert your fuel map
it will burble everywhere

lol
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Old 08-06-2013, 06:46 PM   #13
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If you want burbling on decel you want to lean that area out. Rich won't do jack, youll keep adding fuel and then when you finally add enough you'll get large bangs and blow your cats guts out.
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Old 08-06-2013, 11:41 PM   #14
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Not caring to reference my tune, and tell you my settings. I can choose when to do this by lightly, and i mean very lightly putting my foot on the gas pedal on decel.
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Old 08-06-2013, 11:42 PM   #15
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Cat? What's that?
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Old 08-07-2013, 12:40 AM   #16
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Those gray things in my avatar.
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Old 08-07-2013, 05:43 AM   #17
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Quote:
Originally Posted by concealer404 View Post
Cat? What's that?
Something I personally need to keep in working order to keep my car legal and roadworthy.
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Old 08-07-2013, 04:11 PM   #18
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Quote:
Originally Posted by richyvrlimited View Post
If you want burbling on decel you want to lean that area out. Rich won't do jack, youll keep adding fuel and then when you finally add enough you'll get large bangs and blow your cats guts out.
This. The extra fuel can also kill your WBO2 quickly.
As far as timing goes, and correct me if I am wrong, but retarding the timing actually decreases vac., so increasing timing would increase vac. pulled. I know I was playing around with my timing map and added 5* to the bottom area (idle and low rpm/ low load) and saw my vac. increase..and the idle seemed to gotten a little smoother as well. I may start taking the area of the map that only sees use when in decel and play with adding timing or pulling fuel, will try each individually before mixing the settings. I'm also hoping to get a little burble between gears....because it sounds fast lol.

My only other wonder is, by running lean or running unusually high spark advance under decel, will there be any problems with EGTs? Will it affect the turbo? i.e. slow it down or spool it up to where when I open the throttle to accelerate I will have any problems? I understand going lean makes EGTs hot, and that can kill all kinds of things, but does it matter under vac./decel? I know there are the decel fuel cut settings, and that doesn't have any negative impact, but I'm really wondering more about the timing....
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Old 08-07-2013, 04:23 PM   #19
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you can turn off fuel cut and add a row at 10kPa for fuel and spark...
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Old 08-07-2013, 05:39 PM   #20
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?

One of the first things I did when I got everything up and going with the 2.7 was to uncheck the decel fuel cut lol. But the adding a row at 10kPa is where you lost me....
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