Running rich

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08-09-2004, 08:28 AM
brock

Running rich

I have been suspecting for some time that my car has been running rich, and the dyno day this weekend proved it.

During my pulls on the dyno my air-fuel ratio never dropped below about 13.7. It started out at around 14.5 to 15. The torque curve also started falling away progressively sooner after the first pull.

Is there a way, short of getting an aftermarket ECU, to possibly fix this?

I am getting ready to replace the front O2 sensor when I throw in a new header and :cat: . The car is a 97 and has 96k on it, and it had the cat and both O2 sensors replaced at around 45k with Mazda parts due to a problem with plug wires and misfiring. (Melted the :cat: and killed both O2 sensors. :banghead: )
08-09-2004, 10:53 AM
rx7gslse

rich? 13.7 isn't rich....

My car runs below 10 anything above 4500rpm... now THAT is rich...
08-09-2004, 02:55 PM
Treibenschnell

No...

Now that's rich! http://www.buckscountyplayhouse.com/...ages/lynde.gif
08-09-2004, 03:12 PM
Mark52

Quote:

Originally Posted by Treibenschnell

No...

Now that's rich! http://www.buckscountyplayhouse.com/...ages/lynde.gif

ThreeBean, where do you find this stuff!
08-09-2004, 05:10 PM
rx7gslse

so much for a productive thread...

:roll:
08-09-2004, 06:47 PM
altiain

We have productive threads around here? Someone is going to have to put a stop to that... :evil:
08-09-2004, 07:02 PM
Treibenschnell

Quote:

Originally Posted by rx7gslse

so much for a productive thread...

:roll:

:oops:
08-09-2004, 07:48 PM
EvilSpeeder

Re: Running rich

Quote:

Originally Posted by brock

I have been suspecting for some time that my car has been running rich, and the dyno day this weekend proved it.

During my pulls on the dyno my air-fuel ratio never dropped below about 13.7. It started out at around 14.5 to 15. The torque curve also started falling away progressively sooner after the first pull.

Is there a way, short of getting an aftermarket ECU, to possibly fix this?

I am getting ready to replace the front O2 sensor when I throw in a new header and :cat: . The car is a 97 and has 96k on it, and it had the cat and both O2 sensors replaced at around 45k with Mazda parts due to a problem with plug wires and misfiring. (Melted the :cat: and killed both O2 sensors. :banghead: )

Thats not rich, thats around stoich. 14.7:1 is stoich. Na engines usually run the best right around there. Its possible to run a little leaner and make more power. Forced induction should be much more rich.
08-10-2004, 09:04 PM
TooManyIDs

While 14.7 is ideal for part throttle tuning, you want a bit richer for wide open throttle mode. 13 is a typical target for Vette tuning (no boost), don't see why a Miata would be any different.

At 13.7, you are a little leaner than you should be. Does the car knock at all? Running too lean can burn a hole through your piston, but don't think you would be running that hot at 13.7 .

YMMV. If it is knocking, could be due to other causes, also.
08-11-2004, 07:03 AM
brock

I was just wondering if something was wrong, since the only "tuning" I have done was with my brother's Talon TSI. Anything over 13:1 was a waste. I also have black stuff on my bumper right above the tail pipe that keeps coming back every couple of days.
08-11-2004, 07:48 AM
TooManyIDs

Quote:

Originally Posted by brock

I was just wondering if something was wrong, since the only "tuning" I have done was with my brother's Talon TSI. Anything over 13:1 was a waste. I also have black stuff on my bumper right above the tail pipe that keeps coming back every couple of days.

I've noticed a few posts from the MSM crowd that mentioned bumper crud, but they are running around 10:1 since Mazda was too conservative in tuning, guessing they want to minimize warranty work.

Could you be burning oil? Does the Miata pull oil from the PCV into the intake manifold?