Start Up Exhaust Sound

racer172 said:

Keep in mind that I'm a new owner with only 400 miles in the seat, but I just noticed something yesterday that was interesting to me..
You know when you first start the car up cold there is an explosion, all 4 exhaust valves open, then it closes 2 going into normal mode.
Yesterday I noticed starting up the car (when it was already warmed up) that it was not the same explosive sound, obviously only 2 exhaust valves open.
Anyone know the mechanical reasons behind this?
Just curious.

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I noticed this too. I’m assuming that the resting position for the baffles in the exhaust are normally open (loud mode). When we start up cold the Engine Control will richen the mixture and increase RPM for quicker start and warm up. (Engine has to be in Closed Loop fuel control within 90 sec per law). I think the rich mixture start with baffles open (they close in a couple seconds), causes the pop/explosion which does a great job a rattling my neighbors windows. (Heh, heh...)



BTW- what part of San Diego? My brother is in Ocean Beach...

JimT said:

causes the pop/explosion which does a great job a rattling my neighbors windows.
BTW- what part of San Diego? My brother is in Ocean Beach...

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Yeah I start my car up with the garage door closed for that very reason. I live in a condo and our alley way is like an echo chamber. Haven't gotten any complaints yet..
I'm in the Del Cerro/San Carlos area, that's about 2 miles north of SDSU.

That is not how it works . . . When the car is cold and off, the valves for the inside pipes are 2/3 open, when you push in the clutch the valves will cycle closed , opened, closed and they do this 2 times which takes about 3+ seconds. If you want to start the car cold in "quiet" mode, hold the clutch in and count to 4 or 5 then hit the start button. If you just push in the clutch and hit the start button, you will start in the middle of that cycle and you get the loud start.
When the car is warm, I'm not sure of the temps involved, the valves are shut and will not cycle when you go to start.

I never really paid attention to this. GT Dave is correct. If you hold the clutch down for a few seconds before startup, you can hear the valves cycle and it will start quietly.

I wondered this as well and like Racer172 have been doing morning cold starts with the garage door closed. Will try holding in the clutch next time - good information Dave and Barstowpo, thank you!

GT_Dave said:

If you want to start the car cold in "quiet" mode, hold the clutch in and count to 4 or 5 then hit the start button..

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interesting, I'm glad I started this tread, I learned something new here.
my car is warm now but I'll give this a try tomorrow morning. thanks.

racer172 said:

interesting, I'm glad I started this tread, I learned something new here.
my car is warm now but I'll give this a try tomorrow morning. thanks.

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Sure take ALL the credit...

^ ok, another way of putting is I'm glad I asked the question... is that better?

racer172 said:

^ ok, another way of putting is I'm glad I asked the question... is that better?

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LOL, just messing with ya, in a goofy mood this afternoon

GT_Dave said:

If you want to start the car cold in "quiet" mode, hold the clutch in and count to 4 or 5 then hit the start button.

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Why on earth would anyone want to do that?? HAHAHA! The first start after my resonator delete scared the crap out of my son. He just came walking around the back to get in as I was hitting the starter button! Hilarious...but glorious.

I am really surprised after almost three years now that someone doesn't have a dead/disable switch or something that will leave the valves open all time without throwing a code or a CEL.

This is great, at least I don’t have to pat my head and rub my stomach. Thx Dave

(... though I still enjoy shaking my neighbors windows.)

So I was able to start her up in "normal" mode this morning, Dave was right. thanks!

I don’t even know you people any more.







LOL

galaxy said:

I don’t even know you people any more. LOL

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If it's any consolation, every time there is a Prius or a Smart Car next to me at a stop light I'm in sport mode and I make sure they know I'm there

racer172 said:

If it's any consolation, every time there is a Prius or a Smart Car next to me at a stop light I'm in sport mode and I make sure they know I'm there

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Awesome, now there's the spirit!!