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Cold start question with PSE.

Old 01-11-2019, 08:35 AM
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adcampo
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Default Cold start question with PSE.

I've noticed that cold start isn't as loud I would have expected. With Sport+/PSE on or off.

In my M4 there was a pre start sequence you could follow to get the valves open and really make it howl on cold start. Loved it although my neighbors and wife didn't.

Am I missing something to get a louder cold start?



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Old 01-11-2019, 09:02 AM
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.1 or .2?
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Old 01-11-2019, 10:21 AM
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Rennolazine
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I believe valves are open on cold start
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Old 01-11-2019, 10:45 AM
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.1
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Old 01-11-2019, 10:46 AM
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A 991.1 with PSE is not particularly louder with PSE on vs off, at cold start. The way you do it is, turn key on to position 1, turn on PSE, then turn key to fire engine.
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Old 01-11-2019, 10:48 AM
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Originally Posted by Rennolazine View Post
I believe valves are open on cold start
I think you're right, but it seems to be missing the full deeper tone of Sport+.

My M4 was obnoxiously loud on cold start and in M mode. It sounded like a lawn mower after warming up though lol.
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Old 01-11-2019, 11:44 AM
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M4 cold start is loud because the wastegates are held open, along with retarded timing and other things to make the intitial combustion a bit warmer than normal. The open wastegate allows the warmer than normal air to move quicker down the exhaust system and warm the cats.
That's how BMW does it to get the CATs up to temperature...once they reach it (around 30-45s), the wastegates close and the engine parameters go back to normal.

I don't have a PSE, but I did have the stock Porsche exhaust and it was noticeably quieter than an M3/4 cold start. Even quieter than a modded N55. That said, once I replaced my muffler with the Fabspeed X-Pipe, my cold starts became very loud and throaty. Been around quiet a few S55s; definitely sounds louder.

I'm pretty sure Porsche opens up the waste gates during cold starts to warm up the CATs. My guess is the stock PSE muffler is just really good at muffling sound lol.

Get the Soul Performance Race-pipes then do cold starts. Guarantee the sound will be louder than an M4.


***Edit, noticed you're a .1, so N/A. No wastegates....that said, the engine parameters during the cold start are still altered to increase the exhaust temperatures to increase cats. The N/A 991s have a split exhaust system; my guess is that while the PSE might still be activated and allowing for greater flow, the mufflers are still really good at doing their job. Hence the "quieter" sound.
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Old 01-11-2019, 02:23 PM
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Originally Posted by Aatish View Post
M4 cold start is loud because the wastegates are held open, along with retarded timing and other things to make the intitial combustion a bit warmer than normal. The open wastegate allows the warmer than normal air to move quicker down the exhaust system and warm the cats.
That's how BMW does it to get the CATs up to temperature...once they reach it (around 30-45s), the wastegates close and the engine parameters go back to normal.

I don't have a PSE, but I did have the stock Porsche exhaust and it was noticeably quieter than an M3/4 cold start. Even quieter than a modded N55. That said, once I replaced my muffler with the Fabspeed X-Pipe, my cold starts became very loud and throaty. Been around quiet a few S55s; definitely sounds louder.

I'm pretty sure Porsche opens up the waste gates during cold starts to warm up the CATs. My guess is the stock PSE muffler is just really good at muffling sound lol.

Get the Soul Performance Race-pipes then do cold starts. Guarantee the sound will be louder than an M4.


***Edit, noticed you're a .1, so N/A. No wastegates....that said, the engine parameters during the cold start are still altered to increase the exhaust temperatures to increase cats. The N/A 991s have a split exhaust system; my guess is that while the PSE might still be activated and allowing for greater flow, the mufflers are still really good at doing their job. Hence the "quieter" sound.
Since there's no much flow through the engine during a cold start, the wastegate position doesn't matter. However, the retarded timing does produce a hotter exhaust and retarded fuel injection timing might even promote some combustion while the exhaust valve is open to produce even more heat to light off the cats.
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Old 01-11-2019, 02:34 PM
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Originally Posted by Valvefloat991 View Post
Since there's no much flow through the engine during a cold start, the wastegate position doesn't matter. However, the retarded timing does produce a hotter exhaust and retarded fuel injection timing might even promote some combustion while the exhaust valve is open to produce even more heat to light off the cats.
There's less flow through the engine during cold start, correct. Waste gate position does matter however. A closed wastegate would incline the exhaust gases to route through the turbine, and then into the exhaust. Turbo charger is also cold during a cold start, so theoretically the exhaust gases would warm that as well as cool the exhaust gases through the energy transfer. CATs wouldn't be heated up as quick as a result since something else is being warmed first.

Where as a open wastegate would incline the gases to route directly to the exhaust setup (first major component being the CATs), hence heating them up early than the turbo assembly (in theory).

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Old 01-11-2019, 05:19 PM
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Originally Posted by Aatish View Post
There's less flow through the engine during cold start, correct. Waste gate position does matter however. A closed wastegate would incline the exhaust gases to route through the turbine, and then into the exhaust. Turbo charger is also cold during a cold start, so theoretically the exhaust gases would warm that as well as cool the exhaust gases through the energy transfer. CATs wouldn't be heated up as quick as a result since something else is being warmed first.

Where as a open wastegate would incline the gases to route directly to the exhaust setup (first major component being the CATs), hence heating them up early than the turbo assembly (in theory).
Hadn't thought about that, but it makes sense. Even if only some of the exhaust gas passes through the wastegate, there would probably be some improvement in catalyst light-off time. Good point.
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Old 01-11-2019, 05:54 PM
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You guys are beyond my pay grade. I just want extra loud and obnoxious on cold starts. Lol.
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Old 01-11-2019, 05:56 PM
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Originally Posted by adcampo View Post
I just want extra loud and obnoxious on cold starts. Lol.
Squirt some ether in the cold cans. Then fire engine.

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Old 01-11-2019, 06:26 PM
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Originally Posted by LexVan View Post
Squirt some ether in the cold cans. Then fire engine.
That's more a low brow solution I was looking for. Get some fire too!
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Old 01-11-2019, 06:35 PM
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Like someone mentioned earlier, the valves are opened upon startup so need need to manually open or hit sport button. I think the sound insulation is pretty good, from the outside, the PSE sounds really nice, but inside is pretty subdued.
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Old 01-11-2019, 08:57 PM
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Originally Posted by adcampo View Post
You guys are beyond my pay grade. I just want extra loud and obnoxious on cold starts. Lol.
Straight pipe lol
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