running rich???

[Redpoint Rallying]

Now have 1000 miles on my 2003 'S' running mainly on B roads and now doing over 4000 revs etc. Have a larger bore 'cat back' Magnex stainless system (fantastic by the way!) fitted. I have noticed black 'sooty' deposits on the tail pipes normally associated with a car running rich.

Any comments anyone?

Cheers

[moorlockx]

For some unknown reason the S is set really rich from the factory. As to why?, I've yet to see an answer for that one on the boards.

[Roger Corby]

I've been mulling this same question. On other threads, I have read that the S is set to run rich because when the blower starts having an effect at 2800 rpm, the mixture leans out. If true, that means the S should NOT be driven for very long under 2800 rpm. My personal experience is that if I spend a lot of time in the city, driving conservatively, the S starts to run raggedly, and it takes a day at high revs to get it back in shape (I'm just getting ready to turn 5000 miles).

I also saw a warning that if you put a smaller pulley on the blower, you run a risk of leaning out the mixture and burning up pistons. I don't think this is a problem, though, at least not with the guys I know who race. They would have burned holes is at least a couple of pistons by now.

Any info from a tech-type guy would be appreciated.

It could be emmissions. Would running rich help this?

-Andrew

[Dark Silver S]

There are more emissions when running rich. That's what Redpoint is finding on his exhaust - particulate emissions.

I've noticed the black, too. I would think that a computer with the power of the one we have would be able to select the correct mix at all revs. That's what it's for.

[Andy@Ross-Tech.com]

I've done quite a bit of logging with a wideband Air/Fuel meter and have observed the MCS' behavior in a variety of conditions. The MCS runs extremely rich from the factory, and changing the pulley has very little effect on this mixture. The reason is, that the fuel pressure is controlled by a fuel pressure regulator that is tied into the manifold pressure. So, the more boost you have, the more fuel pressure you have.

My personal theory is that Siemens (who developed the engine management for MINI) chose to use excess fuel to reduce combustion chamber temperatures to keep away detonation. Why they took this route, I have no idea. Bosch was confronted with a similar design problem in the VW 1.8T and they are able to maintain mixtures MUCH closer to ideal (maximum power is generated between A/F of 12.5:1 and 14.0:1) while producing MORE boost in an engine with a HIGHER compression ratio.

[Redleg13]

ok, so you wipe the exhaust tips once a week and change the plugs more often... no biggie, is there more to this??

[MrWhoa]

Power robbed by running too rich is the problem.

[disdis]

so if we go for a intake mod, then a full, less restrictive full exhaust system.
then the engine will run leaner in effect rite??

and if the factory engine runs "really rich", the car will be better off with the above (w/o ecu mod) rite??

[Andy@Ross-Tech.com]

A/F is definitely controlled by the ECU through throttle opening and injector pulse widths. Here's what the stock ECU accomplishes:

[Andy@Ross-Tech.com]

The difference you are seeing is miniscule (under half a point of a/f ratio). I would read the above graph as identical a/f for pulley and stock. I believe Sleepless posted a/f with the evo chip over on mco.

[Andy@Ross-Tech.com]

I'm not sure which graph you are looking at. At 3900 rpm, the A/F with the pulley was about 12.0:1, compared to about 12.3:1 stock. At 5500, the pulley plot is about 10.0:1 while the stock plot is maybe 10.2:1. I don't see any areas where the two plots deviate by even 0.5:1.

Here's the graph again, for demonstration purposes:

[podger]

Quote:

Originally posted by Redpoint Rallying
Now have 1000 miles on my 2003 'S' running mainly on B roads and now doing over 4000 revs etc. Have a larger bore 'cat back' Magnex stainless system (fantastic by the way!) fitted. I have noticed black 'sooty' deposits on the tail pipes normally associated with a car running rich.
Any comments anyone?

I have EXACTLY the same exhaust, and noticed the soot,I'm not concerned as I'd rather it run rich than lean and I've just clocked up over 17k.

[minimc]

Every time I clean my exhaust tips I can't help thinking of how I am wiping away unspent fuel that should have provided additional milage, horsepower etc. I also recognize that I'm polluting more than need be. I really want to fix this niggle - for any or all of the reasons above.

FYI
I have the ECU mod - the EVOtech, the pulley mod, CAI with cowl mod, Magnaflow exhaust + better wires & plugs. ...And still the black soot builds up in a day or two.

I'd like some opinions on what might be the cause, and what might help to eliminate this annoyance.

I know that there are possible remedies in the form of newer software programs - e.g. Randy's latest product from Powerchips, and a soon to be released update for my EVOtech. This is all great, but I'm not holding my breath for these to fix the problem. I am specifically focusing elsewhere.

At the moment I'm thinking colder plugs with wider gap, MSD ignition & coil + aftermarket header+performance cat. My hope is that I might burn the fuel more completely with the hot ignition and that the header might scavenge better - getting exhaust gasses to the cat with greater velocity, and thus retained heat (enough to burn off).

Thoughts? Suggestions? Differences of opinion? Please share. I don't think I'm alone in this quest.

Cheers!

[davidac]

Doesn't this unburned fuel making it through damage the catalytic converter? I can't recall where I read that.