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Start up exhaust noise
Posted: Wed Dec 14, 2016 5:22 am
by jury
Started the Modrod up this weekend.....afew big blips of the throttle sounded like a "crackle" noise.
Anyone with a good ear hear anything strange ?
https://vimeo.com/195577258
Cheers
Chris
Re: Start up exhaust noise
Posted: Wed Dec 14, 2016 8:16 am
by KS
That's just a plug clearing itself. At a guess...
Re: Start up exhaust noise
Posted: Wed Dec 14, 2016 9:14 am
by mycar
My 911 used to do that on cold mornings. I put it down to a discordant exhaust manifold/heat exchangers/silencer internals resonance.
Does it sort itself out as the engine warms up ?
Re: Start up exhaust noise
Posted: Wed Dec 14, 2016 4:24 pm
by 911hillclimber
If that clears and it runs well after I would ignore it.
as an aside, my 2.9 Boxster from a 2 week lay-off and a cold day start makes strange noises from the exhaust and that goes after 30 secs or faster, runs a dream from then on.
My stock 3.2 can send a few odd notes out after a similar lay-off.
Does your do this after a long lay-off?
Re: Start up exhaust noise
Posted: Fri Dec 16, 2016 5:05 am
by jury
Thanks guys much appreciated.
The noise (on the first blip) sounds bit like a 'beetle'...I first wondered if it was running on 5 cylinders.....but the noise isn't there on the others revs.
KS wrote:That's just a plug clearing itself. At a guess...
I have heard the noise sometimes when driving...when setting off from traffic lights etc at low revs.
When the most recent work was done on the car to sort out the running rich issue, the guy said it was still running slightly rich at idle after the adjustmenst...I wonder if the noise comes from the plug fouling at idle and not firing correctly when setting off ?
As I say, it sounds abit like a VW Beetle (proper air-cooled one
)
Any thoughts ?
Cheers
Chris
Re: Start up exhaust noise
Posted: Fri Dec 16, 2016 3:50 pm
by 911hillclimber
After a good run and hot, kill the engine and coast to a halt. Pull the plugs and check the colours.
If one is rich it will show.
Or:
Fresh set of plugs in and see if it takes time to appear.
Or:
Clean up the ignition circuit connections from points to plugs inc coil and observe the condition stays or intermittent etc.
My 3.2 is a grand old lady at about 130K miles. If it stands for a long time (a month say) some oil will get into a bore and on start-up hesitates to run immediately on all 6.
Any re-start after a run and all is well. Does not do it all the time (garage floor dead level)