Usually it is unburnt fuel pre-igniting within the exhaust itself due to the high heat.
Rotary engines are famous for this
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| Exhaust crackle https://ausmini.com/forums/viewtopic.php?f=2&t=21197 |
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| Author: | Dixon Bainbridge [ Mon Aug 07, 2006 2:14 pm ] |
| Post subject: | Exhaust crackle |
Does anybody know what causes exhaust crackle when you let your foot off the accelerator pedal? I don't have any myself, but I reckon it sounds awesome, rally cars tend to crackle heaps. Has anybody managed to get a nice healthy crackle from their mini? |
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| Author: | Gilly [ Mon Aug 07, 2006 2:38 pm ] |
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Usually it is unburnt fuel pre-igniting within the exhaust itself due to the high heat. Rotary engines are famous for this
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| Author: | WasabiPimpNinja [ Mon Aug 07, 2006 2:39 pm ] |
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Rally cars generally get the "cackle" from an Anti-Lag system which as I understand it, dumps fuel into the exhaust/turbo which explodes to keep the turbo spooling while off the throttle. This way when they get back on the throttle they have instant boost. My mini used to do it and I thought it was awesome till I realised it was due to a 6" crack in my exractors. As for how to achieve it "properly", I wouldn't have a clue sorry. I presume something to do with the cam timing? Wasabi |
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| Author: | speedy [ Mon Aug 07, 2006 3:52 pm ] |
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I used to have it, when it was running way too rich. It's gone now that my mixture is sorted, and my fuel economy has gone from 10L/100kms to 7L/100kms as well  .
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| Author: | gibovski [ Mon Aug 07, 2006 3:54 pm ] |
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It is worth 3 litres per 100kms for a decent crackle...
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| Author: | sports850 [ Mon Aug 07, 2006 3:55 pm ] |
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An earlier mini of mine (aka the smurf) used to do it , it wass a worked 1310 with 3 into 1 extractors to a 1 3/4" pipe with only a hotdog on the end , not sure about mixture being rich or not but it had a very throaty sound with almost a trumpet blast/note at 3000 rpm and crackled and barked when lifting off the pedal . |
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| Author: | jbeenz [ Mon Aug 07, 2006 4:16 pm ] |
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i have a 1700cc alfa 33 Qv which is a boxer 4 with 2 webber idf carbies, you want crackle, drive an alfa  just unburnt fuel, a fairly non-restrictive exhaust and a little valve overlap (read the camshaft tech on hotbricks site).
failing that, a good exhaust leak near the front will do it. |
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| Author: | TheFly [ Mon Aug 07, 2006 4:44 pm ] |
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I know that the B & S Utes get the crackle using a Hot Dog exhaust. That would sound great on a mini. |
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| Author: | buztoy [ Mon Aug 07, 2006 5:29 pm ] |
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yeah rotors are famous for this as said before, i was told how it happend with a rotor but not a piston engine, it also has something to do with the texture of the wall in the extractor, exhaust ports in a rotary are about (depending on 4 port or 6 port) 30mm by 50 - 70mm, and as it goes through the end plate it exspands and gets to the exstractor and then sounds like it exsplodes in the exsrtactor but its really just a prolonged exsplosion that lasts till it gets to the exstractor, rather than fireing in the rotor housing and then following through to the exstractor, i also have noticed but you dont here it all that often with efi, could this also be a carby thing or just better exhuast technology, |
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| Author: | Molina [ Mon Aug 07, 2006 6:10 pm ] |
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sports850 wrote: An earlier mini of mine (aka the smurf) used to do it , it wass a worked 1310 with 3 into 1 extractors to a 1 3/4" pipe with only a hotdog on the end , not sure about mixture being rich or not but it had a very throaty sound with almost a trumpet blast/note at 3000 rpm and crackled and barked when lifting off the pedal .
My mini makes that lovely crackle noise... i have pretty much what you describe... a 1 3/4" pipe with just a single straight through muffler, 1330cc, LCB extractors, cam and now a Weber (although it also did it with the 1 3/4" SU). I love it... although i wear earplugs when i drive the thing for longer than 20min because it's too loud. When i get time it's going for a muffler operation to make it quieter. |
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| Author: | willy [ Mon Aug 07, 2006 6:49 pm ] |
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My rover does it. I have a couple of small leaks in the system... Which is why I am fitting extractors, to resolve the problem (standard systems suck  )
While i'm at it, I will be fitting a 40DCOE (if i can get my hands on one) |
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| Author: | speedy [ Mon Aug 07, 2006 6:51 pm ] |
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willy wrote: My rover does it.
I have a couple of small leaks in the system... Which is why I am fitting extractors, to resolve the problem (standard systems suck )While i'm at it, I will be fitting a 40DCOE (if i can get my hands on one) Make sure you fit a nice quiet exhaust to yours like you did to mine you hard of hearing bastard!  
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| Author: | jbeenz [ Mon Aug 07, 2006 6:52 pm ] |
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willy wrote: My rover does it.
I have a couple of small leaks in the system... Which is why I am fitting extractors, to resolve the problem (standard systems suck )While i'm at it, I will be fitting a 40DCOE (if i can get my hands on one) I thought it was forsale? |
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| Author: | awdmoke [ Mon Aug 07, 2006 7:17 pm ] |
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That was last week! (it's willy, remember) |
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| Author: | willy [ Mon Aug 07, 2006 7:35 pm ] |
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jbeenz wrote: willy wrote: My rover does it. I have a couple of small leaks in the system... Which is why I am fitting extractors, to resolve the problem (standard systems suck )While i'm at it, I will be fitting a 40DCOE (if i can get my hands on one) I thought it was forsale? It is. I am getting it fixed for the sale
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