Car running lean on max boost?

[Eclipse98_RS]

When i open my car up i get about 10-11 PSI of boost(dont have my MBC hooked up or it would be more ) But when i shift into the next gear and look at my Air/Fuel guage its showing all the way lean and i can really smell gas. It eventually goes back to normal, but just wondering why it does that? I just got a bunch of little boost leaks fixed so thats not the problem. Any ideas?

 

[andymoraitis]

Blinky blinky narrowband A/F gauges are unreliable for tuning purposes. Get a wideband if you want to tune the actual A/F ratio. Also, if you're blowing rich, it could be that your correction factors on the AFC aren't matched properly to your injectors. Post a log if you have the ability or at least let us know the correction points.

Andy

 

[Eclipse98_RS]

Just got it tuned at LSE Performance in Minnesota. Dont have a logger or any of that cool stuff yet. (need money for stuff) I know that is really more of a guide and not to tune with it. Just wondering if i should pay any attention to it at all?

 

[andymoraitis]

The only thing that a narrowband A/F will tell you is if the front O2 is cycling properly. I'm assuming that your dyno tune was done with a wideband output so that they could dial it in, but if you're using an AFC only for tuning purposes, I would definitely invest in a logger. Running without one means that your tune can be entirely too lean and you can easily hurt the motor. I'm not saying this is the case, but it's pretty much standard to have one with an AFC or MAFT to see the effect of tuning changes.

Now, you can't read knock on a 2G without a Keydiver chip or DSM Link, but what you can do is log a third gear pull from 2500-7000 RPM and look for any spots where the timing dips. In general the 2G ECU will hold timing at 7 counts of knock and subtract one degree of timing for every three counts above that. In practical terms, one degree of timing retard is 10 counts, 2 is 13, etc. etc.

If your profile is accurate, I'd also invest in larger injectors and a better way to control them if you really want to play with that 50 trim. The bad thing about using an AFC as your only tuning device is that as you correct for larger injectors, you lower the airflow signal that the ECU sees. As a result of lower (false) airflow readings the ECU adds a bunch of timing and this can make tuning on pump gas very difficult since it has low knock suppression capabilities.

I'd look into an EPROM ECU with a Keydiver chip or DSM Link if you really want to have some fun along with a set of 750 or 850 injectors.

Let me know if that makes sense.

 

[Oneavenger]

my car did that as well above 5500rpm, traced it to not rewiring the fuel pump. that took care of it.

 

[andymoraitis]

Fuel pump re-wires are a great thing, but this is a different issue. The original poster is talking about blowing rich while the narrowband reads lean. Since narrowbands are crap and he has no logger, he needs to show us correction values and log a run to see what the story is. The timing and airflow numbers will pretty much tell the whole story.

 

[YiNYaNg]

<= MN guy too.... DSMStyle

If it's in good working condition and reads lean instead of rich when it's suppose to be rich (regardless if it's a narrowband) your in trouble but since you can smell gas I assume it's broken and nothing but a light show or could be your o2 sensor.

Just my guess at it.

 

[andymoraitis]

but since you can smell gas I assume it's broken and nothing but a light show or could be your o2 sensor.

That's entirely possible, but without a wideband it's tough to tell how rich. Your assumption that a failing O2 will run rich while showing lean is correct however and they may not always trip a CEL when they start to go bad. Typically though power loss and a substantial mileage decrease will accompany a bad sensor. If these things are happening and the front O2 has never been replaced, I'd change it. If the motor is behaving normally I'd look to the tune first and that's where using the logger has merit. You can also isolate the front O2 by observing if it cycles properly. If not, the O2 is on it's way out.

Regardless, you make a good point.