Well, installed a new camshaft, and I was pretty sure I would need to run AlphaN, sure enough, not much vacuum at idle, about 5 to 7 inches of vacuum, so I switched my parameters to run AlphaN, but the car won't run real well. Now I know I have to make some changes, but where should I start with the changes. When I could get the car to run, the o2 says it's real lean, but it smells real rich. I checked a plug, it's looks pretty rich. I added pulse width, but that didn't help, actually made it worse. So I guess what I'm asking, what tables do I need to change to make it run. Also, do I have to change MAP sensors, I'm using the factory Map, not mounted in the intake, but mounted outside the intake. Is this correct? Thanks for the help.
Alpha N Help
- Thread starter CSJTA
- Start date
Craig Smith
That was easy!
- Joined
- May 25, 2001
The O2 sensor is reading an artificial lean condition because there's hardly any air moving across it. Exhaust reversion at low engine speeds often causes this problem. You'll need to tune the idle and driving around stuff just by feel and by smell.
I learned this the scary way myself when I started working here. My own headers didn't fit our dyno so I had to our in-house stuff. The exhaust I used was much smaller, and there are mufflers on it. Had my car idling perfectly on the dyno in closed loop. When I put it in the car with the larger oen headers, the car went DEAD fat. I thought for sure I had screwed something all up. I noticed that it was reading 15.94 until I really revved it up. So I set it not to go into closed loop until about 5000 RPM and it took care of the problem. When asking someone about it later it was explained to me how exhaust reversion impacts O2 readings. Basically, it's the "garbage in, garbage out" theory in motion.
Rev your motor up, and even put a bit of a load on it like brake torquing. I think you will see that the O2 sensor will begin reading properly.
I learned this the scary way myself when I started working here. My own headers didn't fit our dyno so I had to our in-house stuff. The exhaust I used was much smaller, and there are mufflers on it. Had my car idling perfectly on the dyno in closed loop. When I put it in the car with the larger oen headers, the car went DEAD fat. I thought for sure I had screwed something all up. I noticed that it was reading 15.94 until I really revved it up. So I set it not to go into closed loop until about 5000 RPM and it took care of the problem. When asking someone about it later it was explained to me how exhaust reversion impacts O2 readings. Basically, it's the "garbage in, garbage out" theory in motion.
Rev your motor up, and even put a bit of a load on it like brake torquing. I think you will see that the O2 sensor will begin reading properly.
And a new term is born?.
I've only heard it being called dilution from the self EGR'ing effects of a cam with more overlap.
Reversion is typically used to explain the intake charge hitting the closing intake valve and then backing up the intake tract.
Just picking nits.
Craig Smith
That was easy!
- Joined
- May 25, 2001
It's not "picking nits" it's nitpicking!!!! LOL 
Sorry, I just couldn't help myself.
It sounds like your description is more accurate. Reversion is the term that I have for some reason become accustomed to using to describe this. I agree that reversion sounds more like what happens in an intake than a collector. True reversion probably wouldn't cause problems with O2 readings.
I leave this post as a smarter man... I think.
Sorry, I just couldn't help myself.
It sounds like your description is more accurate. Reversion is the term that I have for some reason become accustomed to using to describe this. I agree that reversion sounds more like what happens in an intake than a collector. True reversion probably wouldn't cause problems with O2 readings.
I leave this post as a smarter man... I think.
Craig Smith
That was easy!
- Joined
- May 25, 2001
Once it's warm, just work in the base fuel table. If you are running in closed loop at all you can also set a target a/f ratio, but you aren't going to be able to run in closed loop at an idle. Just work with the numbers in the base fuel table for this one.
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