Cold Start Daftness
Discussion
HappyMidget said:
Warby80 said:
Please, read this: https://en.m.wikipedia.org/wiki/Wastegate
The wastegate opens to control the amount of boost once a preset level has been reached.
I know how they work but you said fully open, which would mean no boost or an incorrectly sized wg that then cannot open more to dump pressure on the off throttle event to stop the turbine stalling.The wastegate opens to control the amount of boost once a preset level has been reached.
Just to clarify, nowhere did i say "fully open". From the wiki: The primary function of the wastegate is to regulate the maximum boost pressure in turbocharger systems, to protect the engine and the turbocharger. it does this by opening to divert "some" of the exhaust gases past the turbine once full boost is reached.
Apologies for the off topic diversion.
Edited by Warby80 on Monday 23 January 10:31
Pdelamare said:
Fortunately my neighbours love my E63 with Rado downpipes on cold start. It's particularly rude but doesn't last too long.
Try living with that thing of mine with the Weistec system and see if your neighbours still love it Peter. 
Just glad I don't do earlies any more, or any time in the morning come to think of it...
My Z4M with aftermarket exhausts is noisy on cold start up (1,500 RPM) but dips to 1,000 RPM soon after (10-15 seconds) and the noise is audibly reduced to around that of an OEM system.
I was so surprised the first time I started it up I borrowed my Dad's (Maplins) decibel meter and it registered 118 db. Now, I know this can't be possible but you do feel the exhaust pulses in your chest and it shakes the front door/door knocker.
I use the car very infrequently and never early in the morning so my neighbours are rarely in and those that are around give me the thumbs up so before anybody pities my neighbours, don't.
I was so surprised the first time I started it up I borrowed my Dad's (Maplins) decibel meter and it registered 118 db. Now, I know this can't be possible but you do feel the exhaust pulses in your chest and it shakes the front door/door knocker.
I use the car very infrequently and never early in the morning so my neighbours are rarely in and those that are around give me the thumbs up so before anybody pities my neighbours, don't.
My friends M135i on cold start is so loud and sounds clunky, but he likes the loudness and is far enough away from neighbours to get away with it. My little 4 pot cupra 290 has a very small blip on cold start and has a more bassy rumble to it than usual. It doesn't sound like anything when you're next to it, but when someone else cold starts it, I can hear it in our bedroom. No way I'd manage to get away with anything more exotic or louder without feeling self conscious.
Dannbodge said:
I'm not going to bother arguing.
That may be the case for some but as I have said, the BMW N54 (and possible N55) have them open at cold start.
Lovely. Where do the wastegates exit to? Surely they recirculate back to the normal exhaust tract, downstream of the turbo, but upstream of the cats and silencers, therefore there's not going to be any audible difference from them being open?That may be the case for some but as I have said, the BMW N54 (and possible N55) have them open at cold start.
Dannbodge said:
Warby80 said:
The only time the wastegates will ever be open is at full boost.
I'm not going to bother arguing. That may be the case for some but as I have said, the BMW N54 (and possible N55) have them open at cold start.
Ok so firstly I apologise i was wrong, a bit of research suggest bmw do indeed open one of the wastegates on a cold start.
Not something i have come across on any other brand.
Apologies again, ill get back in my box!
TooMany2cvs said:
Dannbodge said:
I'm not going to bother arguing.
That may be the case for some but as I have said, the BMW N54 (and possible N55) have them open at cold start.
Lovely. Where do the wastegates exit to? Surely they recirculate back to the normal exhaust tract, downstream of the turbo, but upstream of the cats and silencers, therefore there's not going to be any audible difference from them being open?That may be the case for some but as I have said, the BMW N54 (and possible N55) have them open at cold start.
they are integrated into the turbo and exit into the down pipe next to the turbine exit. The wastegate makes quite a rattle until it is closed and warms up from what i have read.
underphil said:
HJMS123 said:
I think the cars which blip the throttle on start up (F Types) etc are obviously theatrical but I think most performance cars with reasonably loud exhausts will sound loud at start up, I believe they have to gets the cats up to temp asap as the emmission tests are based on cats at full operating temps. I may be wrong but I imagine if they didn't have this feature they'd be in a tax band or two above.
To the poster who compared a 740i to an M135i start up ... I imagine the 740i exhaust to be much more toned down than 1 series. I think it all depends on how loud the stock exhaust is to how noticeable the cold start feature becomes.
agree this comes into play, but I believe the M135i (much like most BMWs including mine) have a valve that can stem the flow through the near unsilenced part of the backbox, on mine this is open on startup - it could be closed and the exhaust would flow just as effectively, yet be much quieterTo the poster who compared a 740i to an M135i start up ... I imagine the 740i exhaust to be much more toned down than 1 series. I think it all depends on how loud the stock exhaust is to how noticeable the cold start feature becomes.
SS7
shoestring7 said:
Yeah, but why is there only condensation smoke coming from the left hand exhaust after a cold start?
SS7
My A45 does that but then again it is just a 4 cylinder so the number of exhausts/fake tips (whilst aesthetically pleasing to me) is daft. Once the idle settles in the selected comfort mode smoke comes out of both/all four. In Sport + it never really sorts itself out and just comes out the left hand side.SS7
I don't have the sports exhaust so whilst louder it's not obnoxious on a cold start and doesn't blip the throttle just runs at a higher RPM.
I actually like this ::runs and hides::
The reason being I have a very short commute, one I should probably ride a bike for, in the cold the car really doesn't get warm (water makes it, oil mostly and gearbox rarely). So my cold weather routine is:
1) put bags in car
2) start car
3) go get small person from in the house and spend 5 mins fighting/reasoning/bribing him to get in his seat
4) lock the house up
5) clear whats left of the ice
6) lower the security pole
7) answer small persons questions on why the car was bleeping and go to nursery.
This way I find the cars mechanicals have some temp in them and once driving selecting sports+ for the first few roundabouts/traffic lights sees higher RPM and no stop start meaning by work it has at least stood a chance to get warm.
Rightly or wrongly I have convinced myself this is better than driving the car completely cold for a short distance.
Gassing Station | General Gassing | Top of Page | What's New | My Stuff