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M

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Discussion Starter #1
When my car and exhaust is hot, when trailing the throttle, I get lumpy pops and farts from the exhaust (which is standard). Sounds great, but I think it may be linked to my poor mpg. The exhaust doesn't have any holes in it (apart from the exit), so i'm thinking unburnt fuel is igniting in the hot exhaust when the exhaust gases are not being forced out. Like I said, it actually sounds great and makes the car sound as though it's tuned to FCUK, but i'm worried about long term affects on the Cat. Anyone know if the Cat will be destroyed ???

Marlon

BTW, the car has always done this since I bought it.
 
I

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Discussion Starter #2
I think if un burnt fuel is getting to the cat it will destroy it. It sounds like your plugs may need changing or a bad lead, the secondary plug fires when the exhaust valves are open and in theroy should ignite un burnt fuel reducing emmisions. If this is the case the your primary plugs or leads may need looking at, as the sound will be the secondary plug fireing with the valves open.

Cheers
 
M

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Discussion Starter #3
Thanks Ian
i thought about renewing the plugs etc anyway.
Now I better do it.

Marlon
 

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I wonder if it is something to do with your modified induction kit? Just a thought
 
M

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Discussion Starter #5
Na.....the car has always burbled when you take your foot of the gas.

Marlon
 
F

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Discussion Starter #6
Unburnt fuel, it will kill the cat, need a Bosch tune up.

Id love someone to explain to me how firing this second plug in an uncomressed spent mixture is going to clean the exhaust gas. Fuel up those flying Pigs.

The 2 plugs are there to fire togethere to produce a better burn, less distance from the spark to the fuel you see, one is smaller than the other because two big ones wont fit in the head.
 
F

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Discussion Starter #8
Yeah but you 8 Valves have loads of room in that antique engine. :)
 
M

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Discussion Starter #9
that's true..............but we also don't have the costs of the 16 valvers (belts, fancy plugs etc)
wink wink :D

Marlon
 
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Discussion Starter #10
fkcream, look at the arrangement of the plug leads under the cover, the coilPack sits directly on top of the main spark plug(small) and the lead from this coil pack goes to the opposing cylinder to the secondary spark plug(large). It's not ment to give more power just burn the fuel, thus does not need to be compressed.

I can only talk about 16v's as mine's a 97 not any 8 valves. " Fuel up those flying Pigs
" For those sceptics look on the internet and it'll tell you how the process works if you really would like to know.

wink
 
F

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Discussion Starter #11
So how does it burn uncompressed spent fuel ?

Its impossible :)
 
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Discussion Starter #13
There are a lot of myths about the twinspark thingy, my understanding is that the combustion proces is not very efficient and the second spark just makes sure the job is done better. It fires whilst the fuel is compressed as the sparks are so closely timed.............could be wrong tho wink

wrinx
 
J

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Discussion Starter #14
The TS system works like any conventional ignition system (read ford fiesta!!!), and uses a technique called "wasted spark".

If you closely examine the way that the coil packs are installed, you will see that the coil pack on cyls 1 and 2 fire directly onto the main plug, and on cyls 3 and 4 the coil packs sit directly onto the smaller "side" plug.

Thus the system is wired so that the coil on cyl 1 fires the main plugs on both cyl 1 and 4, the coil on on cyl 2 will fire main plugs 2 and 3, coil pack 3 fires side plug 2 and 3 and coil 4 fires side plug 1 and 4.

The side plug is not located in the centre of the cylinder, but towards one side in the "squish" are of the cylinder, and as far as I can tell, this plug fires at the exact same time as the main plug. This should (theoretically) generate a more even burn in the cylinder.

Obviously, because of the way the system is wired up, if you fire main plug one, you also fire main plug 4 etc etc, thus the rumor of firing on a stroke that is not under compression - this is happening - and is generating the "wasted" aspect of the spark.

So where does this tie up with a lowly ford fiesta...

Well, these use a single coil pack, that is split in half, and is wired so that on half fire cyls 1 and 4 and the other cyls 2 and 3 - not disimilar to the ts system - just one less set of plugs, and it is all done from a single coil!!

Hope this clears up the myth!!

Cheers

James
 
M

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Discussion Starter #15
Replaced my plugs and HT leads last night. NO MORE POPPING AND FARTING !!!!

I now look forward to getting better fuel consumption andthe car passing its MOT (next week).

Marlon
 
F

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Discussion Starter #18
JamesM, i couldnt of explained it better myself !

Twin spark means 2 sparks , hence 2 sparks in one cylinder. The wasted sparks are there on all engines , they dont clean up the exhaust gas.
 
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