snapping and popping

[wargriff]

when i release the accelerator pedal i get a lot of popping from the exhaust. What causes it?

Im not complaining but wondered if it is a bad thing.

Marc

[sumoone]

unburned fuel.....

someone more mechanical i am sure will explain.......


does it cause damage?.........perhaps someone more qualified to answer will

Mark

[THREEFISHORANGE]

You could also have air getting into the system where it shouldn't be. The timing or fuel mixture could be out?

[lewton]

Just had the same problem with my Griff.Found that the plug leads were slightly loose in the distributor cap and engine vibration was causing poor contact,so released them one at a time opened the ends up a little to get a tight fit, and bob's your nephew!

[wargriff]

So is it a bad thing ? and will it cause damage or is it only likely to use more fuel ?

[blitzracing]

I dont think a car fitted with catalysts should ever have enough unburnt fuel to cause ignition after the catalysts if they are working, and if the ignition takes place before the catalysts it means air getting in somewhere, in which case the catalysts won't work correctly for an MOT anyway. It wont damage the engine or significantly put the MPG down, and it may only occur at certain throttle openings that you may not hit during MOT testing. As already mentioned a mis fire can also put unburnt fuel into the catalysts that can damage them over time but it might be worth a quick emmissions check to see if troubles brewing.

Edited by blitzracing on Monday 8th June 11:04

Edited by blitzracing on Monday 8th June 11:07

[wargriff]

blitzracing said:

I dont think a car fitted with catalysts should ever have enough unburnt fuel to cause ignition after the catalysts if they are working, and if the ignition takes place before the catalysts it means air getting in somewhere, in which case the catalysts won't work correctly for an MOT anyway. It wont damage the engine or significantly put the MPG down, and it may only occur at certain throttle openings that you may not hit during MOT testing. As already mentioned a mis fire can also put unburnt fuel into the catalysts that can damage them over time but it might be worth a quick emmissions check to see if troubles brewing.

Edited by blitzracing on Monday 8th June 11:04

Edited by blitzracing on Monday 8th June 11:07

My car is a pre cat, does that make a difference ?

[V8 GRF]

wargriff said:

blitzracing said:

I dont think a car fitted with catalysts should ever have enough unburnt fuel to cause ignition after the catalysts if they are working, and if the ignition takes place before the catalysts it means air getting in somewhere, in which case the catalysts won't work correctly for an MOT anyway. It wont damage the engine or significantly put the MPG down, and it may only occur at certain throttle openings that you may not hit during MOT testing. As already mentioned a mis fire can also put unburnt fuel into the catalysts that can damage them over time but it might be worth a quick emmissions check to see if troubles brewing.

My car is a pre cat, does that make a difference ?

Yes it makes a difference as you have no catalysts to intercept the unburnt fuel that causes the popping.
What Blitzracing is saying above is that the catalysts (if working properly) filter the exhaust fumes well enough to ensure no unburnt fuel makes its way to the rear silencers where the petrol is ignited. As your car has no such 'filters' the unburnt fuel can make it's way to the silencers and so cause the 'popping and banging'
Some cars are deliberately set to 'overfuel' a little to create these noises, but again as said above if your car has just started doing this it may be an indication of the car dropping out of tune.

[wargriff]

The mixture was changed to get it through MOT, so im assuming this is the cause. As it does no harm I think I will live with the great noises.

[bigdods]

For best results get >3K RPM in 3rd gear then feather the throttle (Just tickle it a bit). Your rear gunner will wake up and fire a few salvos at the car behind

Also, if you have no cats is possible that those following if its dark will see flames....

[gopher]

I thought the whole point of a pre-cat Tiv was bangs, growls, pops, whistles, grunts and farts (and that's just from the passengers)!

If I can get mine in the 4-5k area for about 20-30 secs she cracks and bangs for ages, gorgeous sound! (and that's the car not the the screaming death proximity sounder in the other seat )

[wargriff]

[Mr MoJo]

Mine has popped and banged like a good 'un ever since the straight through 'sleeved' exhaust mod was done. I beleive it still has the cats in place. You've got me thinking now too