What's The Problem?!
Discussion
Hi Everyone.
Around two months ago I had a new exhaust fitted to the Mini; its a custom-made stainless steel Powerflow jobbie, with twin rear 3.5" pipes, and is a Cat-Back system. I had it fitted simply for cosmetic and sound enhancement, and it's certainly done the job. Seems to have given me a little bit of top-end too (or is this my imagination?).
I've done around 3,000 miles now with the new system, but have noticed that the inside of the rear pipes is very black and dirty. I've had such exhausts fitted to other cars before, and they've never got so black so quickly. Its actually making the back of the car look quite minging!
I've also noticed a distinct reduction in MPG since over the last two months - probably about 4 or 5 mpg. Although not a huge problem in itself, it certainly took me a little by suprise as again, its never happened with any other car I've had.
Someone has suggested that the air/fuel mix might need adjusting, as this may be the cause of both the black exit-pipes and higher fuel consumption. Does this sound like the case? If so, is it an expensive or difficult job?
I'm the least mechanically-minded person on earth, so it shall be going to a garage to get sorted - assuming its 'sortable' - but I thought I'd ask your collective wisdom for advice first.
Cheers in advance.
Adam
Around two months ago I had a new exhaust fitted to the Mini; its a custom-made stainless steel Powerflow jobbie, with twin rear 3.5" pipes, and is a Cat-Back system. I had it fitted simply for cosmetic and sound enhancement, and it's certainly done the job. Seems to have given me a little bit of top-end too (or is this my imagination?).
I've done around 3,000 miles now with the new system, but have noticed that the inside of the rear pipes is very black and dirty. I've had such exhausts fitted to other cars before, and they've never got so black so quickly. Its actually making the back of the car look quite minging!
I've also noticed a distinct reduction in MPG since over the last two months - probably about 4 or 5 mpg. Although not a huge problem in itself, it certainly took me a little by suprise as again, its never happened with any other car I've had.
Someone has suggested that the air/fuel mix might need adjusting, as this may be the cause of both the black exit-pipes and higher fuel consumption. Does this sound like the case? If so, is it an expensive or difficult job?
I'm the least mechanically-minded person on earth, so it shall be going to a garage to get sorted - assuming its 'sortable' - but I thought I'd ask your collective wisdom for advice first.
Cheers in advance.
Adam
It sounds like the mixture is far too rich. Try taking off the airbox and adjusting the mixture nut at the bottom of the carb - i'm assuming its a carb model?
A guide can be found here - www.niksula.cs.hut.fi/~mdobruck/siililand/mini/diy/3/tuneguide.html
Good Luck!
A guide can be found here - www.niksula.cs.hut.fi/~mdobruck/siililand/mini/diy/3/tuneguide.html
Good Luck!
As I said before I know nothing about engines in cars, absolutely zero. I just know that the mpg seems to have dropped a fair bit, and the spangly new £400 exhaust I put on a few k's ago is already soot-black! The engine isn't burning any more oil than usual I don't think (it hardly uses any anyway) so I'm assuming the black muck is a result of fuel.
If I take this car to a local garage (Not BMW with their £70 an hour charges) are they gonna be able to try and sort this problem out?
I'm not so bothered by the fact that mpg has gone down, as I sort of expected it to anyway. I'm more bothered by the black exhaust.
If I take this car to a local garage (Not BMW with their £70 an hour charges) are they gonna be able to try and sort this problem out?
I'm not so bothered by the fact that mpg has gone down, as I sort of expected it to anyway. I'm more bothered by the black exhaust.
Hi Adam - I had exactly the same problem when I fitted a shiny new fat exhaust to a Stage 1 V8 Land Rover, and as the guys above have said, it was down to improved engine breathing and thus increased fuel use (14 to 12 mpg 
!!). In a carburetted engine, it's simple to weaken the mixture a bit, but I doubt it'll be easy (or even possible) in an injected car as the fuel mixture will be set electronically by the engine management system. So even if it were possible, the next time the car starts the electronics will default to the factory settings again. I've no idea whether a remapping of the ECU is possible/desirable/financially crippling but I fear the odds may be stacked against you here 
. The only consolation I can offer you is that the improved economy you'll get by going back to the original exhaust will pay for the shiny one in about 2 years... 
!!). In a carburetted engine, it's simple to weaken the mixture a bit, but I doubt it'll be easy (or even possible) in an injected car as the fuel mixture will be set electronically by the engine management system. So even if it were possible, the next time the car starts the electronics will default to the factory settings again. I've no idea whether a remapping of the ECU is possible/desirable/financially crippling but I fear the odds may be stacked against you here . The only consolation I can offer you is that the improved economy you'll get by going back to the original exhaust will pay for the shiny one in about 2 years... RickApple said:
It sounds like the mixture is far too rich. Try taking off the airbox and adjusting the mixture nut at the bottom of the carb - i'm assuming its a carb model?
A guide can be found here - www.niksula.cs.hut.fi/~mdobruck/siililand/mini/diy/3/tuneguide.html
Good Luck!
all bmw minis are injection!!
i would guess that the lambda sensor is playing up and tricking the ecu into overfueling the car. i would get bmw (or someone with a code reader) to fault code check it, if it comes up ok the exhaust must be causing the problems. im not sure how you will get round this - id quiz the people who made the exhaust
Just to add, the MINI has already had an ECU remap (an AMD OneClick), although this is something I can actually turn on and off as I choose. Might be worth turning it off and seeing if it alters the fuel consumption?!
Its just gutting to think that the expensive cosmetic exhaust I had built onto the car now looks a bit cheap and nasty!
Its just gutting to think that the expensive cosmetic exhaust I had built onto the car now looks a bit cheap and nasty!
The AMD remap was done over a year ago, and didn't have any real effect over fuel consumption. Its only since the new exhaust was fitted a few thousand miles ago, that mpg has dropped significantly.
Not sure if the old exhaust was any cleaner than the new one as (a) it was much older and so would be blackish anyway, and (b) the new exhaust pipes are so large, open and obviously new that any muck would show straight away.
The car goes in for service in around 6 weeks time - might just leave it till then, and then get BMW to have a quick look for me.
Not sure if the old exhaust was any cleaner than the new one as (a) it was much older and so would be blackish anyway, and (b) the new exhaust pipes are so large, open and obviously new that any muck would show straight away.
The car goes in for service in around 6 weeks time - might just leave it till then, and then get BMW to have a quick look for me.
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