NPP Exhaust louder on cold start
06-17-2018, 02:40 PM
#1
Melting Slicks
Thread Starter
NPP Exhaust louder on cold start
Curiosity question. I noticed when starting up the car (I have M2W installed), even with the flaps open, the exhaust is louder on a cold start. Something else opens up at that time, then after a few seconds it quiets down. Just curious what is happening there, and guessing it's something that can't be controlled, would be nice mod (I think) to have it like that all the time.
06-17-2018, 02:46 PM
#2
Race Director
I agree, they do sound better upon startup, wondered about that myself.
06-17-2018, 02:52 PM
#3
Drifting
On cold start the mixture is richer in order to heat the catalytic converters.
06-17-2018, 04:37 PM
#5
In addition to having a richer fuel ratio condition, it also starts at a higher idle to warm up quicker and then idle starts falling off...
Last edited by lakemg; 06-17-2018 at 06:59 PM.
06-17-2018, 05:33 PM
#6
Le Mans Master
^^^ This, which is common with most vehicles. It’s just more noticable due to the louder exhaust.
06-17-2018, 06:43 PM
#7
Le Mans Master
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Good answers. When I want to show the car off I back it into the garage the night before my relatives come in to town and then do a cold start the next morining. Wakes them up and the neighborhood as well. I have that Borla Xpipe to boot. 
06-17-2018, 10:46 PM
#9
Melting Slicks
Thread Starter
Interesting, didn't think a richer mixture would make that much of a difference in the sound, thought something was opening up and maybe that in turn would help heat things up....
06-18-2018, 08:57 AM
#11
It's more rich for start up purposes as it is easier to start an engine on a rich mixture than lean. The reason the exhaust is so loud is due to a reduction in overall ignition timing which serves to create combustion closer to the time at which the exhaust valve opens allowing a hotter mixture to enter the exhaust and heat the cats up faster. It is louder as there is more energy entering the exhaust than at more advanced ignition.
Last edited by subieworx; 06-18-2018 at 08:57 AM.
06-18-2018, 10:27 AM
#12
Burning Brakes
Cold starts in track exhaust mode are one of my favorite things about this car.
06-18-2018, 10:33 AM
#13
Le Mans Master
I'm normally such a good neighbor. I get along with everyone, keep my yard neat, and so on. But I fire the Z off with pride in Sport mode every morning and shake the neighbors anyway...
I mean I'd avoid it if I could, but that's just the way the car is ;-)
I mean I'd avoid it if I could, but that's just the way the car is ;-)
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