So forgive my ignorance in advance :-)

First, my car has a problem in that I leave black smoke behind me, especially when starting. So, I know I'm running rich (I also know its time to replace cap, rotor, and plugs).
What's the most common cause and solution to running too rich?


Second, looking at possible upgrades:
Seems like one thing that can help keep things from running too rich and incidently get some horsepower and torque by improving effciency is to replace the AFM with MAP.
I've read the recent MAP/MAF thread, but my goal is different then blowing away M3s. :-) My 951 is a daily driver and at ~85miles/day I also have to at least pay some attention to fuel mileage. I think for my application, all the upgrades at vitesseracing are all overkill since I'm not track racing (though it would be fun :-)
I am leaning towards the Stage2 MAP from gururacing. Is that a reasonable choice to run with the stock turbo?

Thanks,
-Brett

 

Your Autothority chips will run rich at full throttle. However, running rich at start-up sounds like a different problem. Causes could be bad fuel pressure regulator, leaking injector(s) or bad temperature sensor for the DME (NTC II sensor, located under the front of the intake manifold near the throttle body.)

Start by pulling your spark plugs. If they are all carboned up equally, then it is probably not an injector. If one or two are carboned up, that (those) injector(s) may be leaking. Pull all your injectors and send them in for cleaning/flow testing at a local fuel injection shop.

If all plugs are carboned up, measure your fuel pressure at the rail. With the engine off, remove the DME relay and bridge from terminals 30 to 87b. The fuel pressure at the rail should be between 2.3 and 2.7 bar (33 to 39 psi.) With the engine at idle, the pressure should be 2 bar (29 psi.) High readings would indicate a faulty pressure regulator.

The NTC II sensor can be tested either between terminal 13 of the DME plug and ground, or at the sensor (remove the round black single wire connector.) The specs are: 0C/32F: 4400 to 6800 ohms; 15-30 C/59-86 F: 1400 to 3600 ohm; 40 C/104 F: 1000 to 1300 ohms; 80 C/176 F: 250 to 390 ohms; 100 C/212 F: 160 to 210 ohm. Note that high readings or a break result in rich conditions. If the sensor is installed, the temperature refer to your water jacket (coolant) temperature.

I would sort out my car before I modified it to correct a rich problem. Do the full tune-up and find out what is causing the smoking condition on start-up. If these steps don't solve it, next things to check would be your AFM and TPS; there have been good topics recently on testing each of these and on retracking your AFM if necessary.

Changing to a MAF or MAP will not solve your problem (unless it happens to be your AFM), and your problem will make it hard to sort out the new modification. For a reliable higher-mileage daily driver, I would either go back to stock chips, or go with the Guru chip only package. If you do decide to go with a MAP, the Stage 1 would be appropriate for you; the only advantage of the Stage 2 would be to allow a bigger turbo in the future, which does not seem to be in your plans.

HTH.

 

That helps a lot, thanks. I will certainly do the tuneup and check the injectors before I do anything else. :-)
I was thinking of the Stage2 over the Stage1, not for the chance at a bigger turbo, but because of the relocation of the filter to pull in cooler air, plus the cleaner intake path. In terms of percentage increase, the cost didn't seem THAT much higher :-)
But all this will be later, after I sort out current problems :-)
Thanks for the reply :-)
-Brett

 

If your AFM is mis-calibrated it would be fooling your computer into thinking more air is flowing than acutal. The result will be too much fuel.

So check the AFM's voltage at idle and some other operating speed to make sure it's not out of spec. You can tap into the AFM signal at DME#7 a green/red-stripe wire:

0.79-0.85v - idle
2.00-2.15v - 3000rpm @ steady-state 45mph in 3rd gear

If these check out, then you might want to verify FPR pressure.

Does the smoking go away once the car's warmed up? If the air-temp sensor is off, it will cause the cold-start enrichment to be too excessive.

So far with the stock turbo, we're seeing the same 255-265rwhp out of the stock turbo with both our Stg.1 and Stg.2 MAP upgrades. People are getting more consistent torque numbers in the 295-300-lb•ft range, so I suspect the HP differences is based upon the amount of boost-drop in the upper-RPMs due to the stock wastegate and turbo combination.