Pops and bangs and runs rich
Pops and bangs and runs rich
Author
Discussion

Barreti

Original Poster:

6,689 posts

266 months

Thursday 23rd July 2009
quotequote all
Reading something about a lack of pops and bangs over on the Chimaera boxedin forum made me wonder about my own car.

It not only pops and bangs like a good un but occasionally spits fire out of the exhaust.
it also runs rich if the smell and a light greasy feeling on the back of the car is anything to go by.

Does it mean it needs fettling, or is this likely the result of the stainless sports manifolds and it being a pre-cat so there's a nice straight run of pipes to the back of the car and there is nothing to 'worry' about?

350Matt

3,896 posts

308 months

Thursday 23rd July 2009
quotequote all
My 4.3 precat also behaves like this but without the rich running smell, the UEGO sensor I've got in shows about 12:1 on fulll load and about 14.2:1 at idle what sort of fuel consumption do you get?

Podie

46,649 posts

304 months

Thursday 23rd July 2009
quotequote all
er... I thought they popped and banged becuase they ran lean, not rich.

Might be worth checking the fuel lines and carbon canister if it smells of fuel.

FlipFlopGriff

7,144 posts

276 months

Thursday 23rd July 2009
quotequote all
Mine takes some serious provoking do make and pop or bang noises. It used to flame occasionally but doesn't seem to now. Maybe its the new ACT cherrybomb?? It runs very rich as evidenced by the near choking when reversing it into the garage and the grimey crap that still appears on the ass end despite having the exhaust made 2" longer than standard which I hoped would cure that.
I'm going to get Jamie to have a look at it as I know it leans out at highter revs. Just want to check evrything is within tolerance.
FFG

RichB

56,275 posts

313 months

Thursday 23rd July 2009
quotequote all
...and I thought they popped and banged due to the overlap on the cam allowing unburnt gasses to pass through the exhaust valve in order to scavenge the combustion chamber. More overlap on your particular cam profile meaning more popping and banging on the over-run scratchchin

FlipFlopGriff

7,144 posts

276 months

Thursday 23rd July 2009
quotequote all
RichB said:
...and I thought they popped and banged due to the overlap on the cam allowing unburnt gasses to pass through the exhaust valve in order to scavenge the combustion chamber. More overlap on your particular cam profile meaning more popping and banging on the over-run scratchchin
Does that mean my cams on the way out?
FFG

Barreti

Original Poster:

6,689 posts

266 months

Thursday 23rd July 2009
quotequote all
350Matt said:
My 4.3 precat also behaves like this but without the rich running smell, the UEGO sensor I've got in shows about 12:1 on fulll load and about 14.2:1 at idle what sort of fuel consumption do you get?
Fuel consumption? You want me to measure my fuel consumption?! Are you trying to make me cry

I have no idea Matt (not really sure I want to TBH)

Hoover.

5,993 posts

271 months

Thursday 23rd July 2009
quotequote all
Mine used to pop n bang n flame...... smell of fuel, and kick lots of black sooty crap out the rear (not oily stuff)..... over time this then affected starting with major over fueling....

this was all tracked down to a dodgy non standard relay for starting, and some fettling with the afm....... how ever the car does not seem as spritley..... the rollers will hopefully not back this up.

Tildo430

67 posts

241 months

Thursday 23rd July 2009
quotequote all
Popping and banging is definately evident in my pre-cat.

Interestingly my Bro's post-cat cherry bombed chimaera can be provoked to pop and bang with a very light throttle almost to order where as mine does produce under the same circumstances but not as easily. I'm not sure what this shows other than TVR's are special as i don't remember the last time i saw any other car on the public highway go off like a machine gun......

I would be interested to know if the popping and banging is a sign off over or under-fuelling and if it needs attention to get better performance.

LordGrover

34,164 posts

241 months

Thursday 23rd July 2009
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I used to get great flames. People following me have said that as the flames shoot out and sometimes join they then swirl in a vortex behind me.
I'm pretty sure I don't get them at the moment but off to Custom Chrome Racing tomorrow to see what can be done.

Barreti

Original Poster:

6,689 posts

266 months

Thursday 23rd July 2009
quotequote all
Seems there is a recurring theme here for us pre-cat boys, and it sounds like its a characteristic of the car!

I'm thinking I should leave alone and let anyone behind me enjoy the show earsI SAID ENJOY THE SHOW
hehe

ETY

152 posts

268 months

Thursday 23rd July 2009
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mine was coughing and spluttering and carbon fouling , although it was a weak spark caused by the distributor cap breaking down

gopher

5,160 posts

288 months

Thursday 23rd July 2009
quotequote all
I thought my pre-cat was running rich and this was proved correct on the rolling road at the Growl last year, someone suggested a new air filter which I did and ran it again the next day. Stopped running rich, gained 5bhp and more bangs and pops (and gurgles, which is pleasant).

blitzracing

6,422 posts

249 months

Thursday 23rd July 2009
quotequote all
Barreti said:
Reading something about a lack of pops and bangs over on the Chimaera boxedin forum made me wonder about my own car.

It not only pops and bangs like a good un but occasionally spits fire out of the exhaust.
it also runs rich if the smell and a light greasy feeling on the back of the car is anything to go by.

Does it mean it needs fettling, or is this likely the result of the stainless sports manifolds and it being a pre-cat so there's a nice straight run of pipes to the back of the car and there is nothing to 'worry' about?
Dont forget the non catalyst cars fueling is set by the CO trim adjustment on the side of AFM, and this will effect the fueling up to about 2500 rpm. You can simply set the DC voltages, or simply wind the adjustment anti clockwise until the idle starts to drop and become rough (to lean), then wind it back in until the idle is stable and smooth, but no further. This is on the Lucas 3am unit, but Ive heard a it said that not all AFM's wind the same way for rich / lean.