Start up "whirring"

[Gooseacre]

On startup my s54 has a whirring sound - lasts for about 2-3 minutes depending on outside temp. Assuming it is the "auto choke" - not smart enough to know the real lingo. Should I be worried that it seems to be getting noisier on this sound?

Btw it drives good with no feet on pedals just after starting - 25mph with no slowing? Should I worry about this too?

Got to keep my mint with the values going stupid.

Just passed 100k mind.

[bertiejaffa]

secondary air filter... do a search, you can delete it. Gookah did a very smart job deleting his. It is used for the USA market only

[pingu]

I think this is the thread...

http://www.zroadster.net/forum/viewtopi ... =5&t=35131

[bertiejaffa]

I think this is the thread...

http://www.zroadster.net/forum/viewtopi ... =5&t=35131

thats the one thanks Gary - hopefully this is your issue

[Robert T]

secondary air filter...

Pump, not filter.

Cheers R.

[Koolflyer]

Hi Goose

Question is, does your car have a secondary air pump? Black circular unit front left of engine as you look at it, attached to a much smaller circular metal unit. Some do and some don't (added for the American market but not required this side of the pond). If it doesn't I'd suggest the viscous clutch. If an inferior clutch has been added or perhaps the old one is on the way out, this too can sound like a hair dressers salon! When nice a warm the viscous clutch's fan should be virtually wind milling and a rolled up newspaper should stop it and not KILL it! (H&S bull....with caution!). My after market cheap VC was the culpit in this case.
Best take a look at this thread, especially towards the end. Hope this helps

http://www.zroadster.net/forum/viewtopi ... =5&t=39850

Pete

[bertiejaffa]

secondary air filter...

Pump, not filter.

Cheers R.

[Southernboy]

Here's a question about the secondary pump..... I was led to believe from a BMW mechanic the purpose of the unit is to re-circulate unburnt fuel back into the combustion process, thereby making for greater fuel economy... He said that any fuel in the combustion area / injectors etc which evaporated was collected by that pump and on start up, it pumped it back into the "intake side" to be re-used. This was a fuel economy consideration as well as an emissions issue.
Is there any definitive knowledge on the full function it was intended to achieve ?

[pingu]

Here's a question about the secondary pump..... I was led to believe from a BMW mechanic the purpose of the unit is to re-circulate unburnt fuel back into the combustion process, thereby making for greater fuel economy... He said that any fuel in the combustion area / injectors etc which evaporated was collected by that pump and on start up, it pumped it back into the "intake side" to be re-used. This was a fuel economy consideration as well as an emissions issue.
Is there any definitive knowledge on the full function it was intended to achieve ?

I've never looked, but the flap in the exhaust would give the answer. If it is for emissions, the flap would allow gasses INTO the exhaust. If it is for economy, the flap would allow gases to EXIT the exhaust. Without investigating, I would guess that it is emissions as the gas from the exhaust would be hot, but the system doesn't look like it has seen any excessive heat.

I'm assuming that air is pumped into the exhaust to con the exhaust analyser that there is less noxious gas in the exhaust (as a proportion of exhaust gas). If this is the case, it is a complete confidence trick as the volume of noxious gas emitted is unchanged, even though the proportion has reduced.

[Robert T]

From everything I have see/read on the subject, the secondary air pump is used to dilute the exhaust gases whilst the engine is cold to comply with strict California emissions regulations. The hose connecting the pump to the exhaust is not made of high temperature material, and if the pump fails, hot exhaust gasses enter the hose and it melts - there are pictures of such an aftermath on here somewhere. From that I think you can conclude which way the air is being pumped.

Cheers R.

[Gazza]

Btw it drives good with no feet on pedals just after starting - 25mph with no slowing? Should I worry about this too?

.

I would change the TPS (Throttle Position Switch) and check the throttle body linkage.

My Indy suggests changing the TPS at every inspection.

[Southernboy]

Here's an explanation provided by Wiki...

[Mike Fishwick]

The 'feet off' at 25 mph in top gear is simply due tothe higher idle speed wheh the engine is cold - 1000 rpm, which on the usual gearing gives . . . 25 mph.

The flap in the exhaust tailpipe has nothing to do with emissions, and in any case is not fitted to the M engine. It is there to make more noise from about 2500 rpm.

The noise on startup is most likely the idle control valve doing its thing - I do not think the S50 engine is fitted with a secondary air pump, as it was too dirty for sale in the USA.

[Tilly]

The 'feet off' at 25 mph in top gear is simply due tothe higher idle speed wheh the engine is cold - 1000 rpm, which on the usual gearing gives . . . 25 mph.

The flap in the exhaust tailpipe has nothing to do with emissions, and in any case is not fitted to the M engine. It is there to make more noise from about 2500 rpm.

The noise on startup is most likely the idle control valve doing its thing - I do not think the S50 engine is fitted with a secondary air pump, as it was too dirty for sale in the USA.

Mine is a German prelaunch S50 and it does have a secondary air pump. It starts about 15-30 seconds after cold startup and runs for about 3-4 minutes then cuts off. It make quite a noise.

[Southernboy]

Never heard mine whirring.... I do know I replaced some hoses on it right after I bought the car because one was perished. (3.0 - M54)