10 replies to this topic

[bloke]

Hi there, just a quickie question, as the title says, when I decelerate you can hear the exhaust popping a little bit.

Does this mean that there is unburnt fuel in the exhaust system being ignited by the catalyst, and does this mean that it could be damaging the catalyst? 

 

It doesn't do it any other time, and to be honest I hadn't even noticed it until the window was open.

 

Thanks in advance, Bloke.

[Chris Jones]

Mine does this when warm, if i shift from 3rd to 2nd and don't give it any gas. Running Stage 3 with a straight through single box maniflow exhaust. To a lot of people this is an achievement, look on a Jap forum at people asking how they can make their Scooby exhausts pop etc!

[Alpenflitzer]

First of all this will damage the cat.

Secondly I noticed that popping on my SPI. I changed the old lambda sensor (85.000 km) what a surprise when I saw the old sensor!! Then I replaced the catalytic converter.

 

Now suddenly popping stopped and I got excellent exhaust values which was great for the TUV (MOT) exam.

[brivinci]

i was just thinking the SAME thing today on the way in. My car will pop if I let off high in the revs and let the car decel in gear. I think I have figured out that might foot needs to be ever-so-slightly on the throttle. That said, I have an LCB, no cat and a twin-box maniflow system. Brand new lambda sensor and brand new head. I was wondering if this means something isnt right with my fueling.

 

Now, I have TR6 with some dual exhaust setup that pops like MAD all the time but not just one or two pops, but the kind that follows the revs all the way down. I also once drove a AC Cobra rep and actually got pulled over by the police for having 4 foot flames shooting out the side pipes. I talked my way out of it but it was CRAZY!!! I'm fairly certain there some something not right with that cars fueling system:-)

[Chris Jones]

http://minispares.co...px|Back to shop

 

Problem solved

[brivinci]

Thats what I have on mine.

[bloke]

Thanks everyone for the replies, sorry for the delay, have been ill. I'll dig out the old Gunson CO2 gadget from the loft and see if the results are too extreme. 

[bloke]

Ok, so this was getting really bad, now that we're in the hot weather it was genuinely popping like crazy.

 

I decided to replace the coil pack as things seemed to be pointing to the pack draining a lot of current. ( a whole lot more than the specs say) anyway, I was just going to undo the four security screws (why rover, why) when I noticed a dodgy bit of wire trailing off poked down the tubing.

 

After undoing the insulating tape, I found some of the worst soldering I have ever seen connected to a wire, which connected the ignition coil to of all things a spare tab on the starter motor.

 

I unplugged and started the car, it ran okay. So I disconnected the wire, repaired the soldering and insulated the cables, plugged it all back in, and took it for a drive. Absolutely perfect. 

 

For whatever reason, someone decided this was a clever thing to do, however in reality all it was doing was dropping the voltage to the coil pack by about a volt and a half, causing the intermittent misfire. 

 

I'm now going to have to go through the entire wiring on this little Mini, and see what other madness has been done to it. 

 

I'm keeping my fingers crossed that this has cured the problem, as it ran really nicely, and was genuinely pleasant to drive. Fingers crossed, Bloke... :) :)

[jamesquintin]

I thought my MPI exhaust was popping because it had a small hole in it, now I'm worried!

[sirjakethebrit]

Isn't popping and banging just caused from advances in ignition timing on over-run??
Plus it sounds cool 😎

[bloke]

Ok, so, replaced the Fletcher stainless exhaust for a RC40 stainless one and ran some Cataclean through the system, feels like new again. I must say, I was very sceptical about putting things in the fuel, (ok, so redex years back), however, as the miles gradually went by, I could feel the engine becoming more relaxed, and gear changes are now almost as good as the carburettor mini, (it now blips the revs properly) and a lot better than the SPI Mini that I had. 

 

And true to its word, the emissions measured with the Gunson CO2 meter, have gone down by about a third. So I think I'll probably try and find some more of this stuff for around MOT time. 

 

I'd have to say, I'd recommend this stuff to anyone who has a lumpy Mini, as the speed of the Lambda sensor has gone from about a third of the second to half of that, so it looks like it's given that a clean as well.

 

Pretty chuffed at the moment.