I am new to the Tuner world

I have recently picked up a 2.0L LSJ 06 Cobalt from a dealer.
After getting my new car the Air/Fuel sensor went so i was directed to a local shop because the sensor was not stock and they could not fix it, when i get to the shop the owner recognized my car and informed me of many mods that were done.

The questions i have are

1. Is my boost direcly related to my RPM and is my boost i am getting normal?
I get 80 kPa at 3000 - 4000 RPM 100 kPa at 4000 - 5200 and 120 kPa at 5200+

2. I have an new air fuel sensor and it constantly jumping from 4.5 to 5.5 to 13.5 when just idaling. Also when i hit the 120 kPa boost it drops to from average 15 to 10 - 9 and when i gear down it jumps up to 25 or 30. I have no clue what any of the means and if it is warning me because i am hurting something.

Thanks,

 

To answer question one, yes the boost will raise on a supercharged setup. They are belt driven and the boost will raise as the rpm's raise. As far as your idle I am assuming you ment 14.5 to 15.5 to 13.5. This is because your fuel trims / ve table / maf table *depending on how your tune is setup* is not dialed in 100%. This causes the air to fuel ratio to jump around during idle.

When you slam the gas down, aka wide open throttle the gauge should read a lot lower. 10 and 9 afr is a little low, you would like to be around mid to high 11s for a dialed in tune. This is something that you should have changed when you can, like soon. If you have a tune running that rich you risk washing out your cyl walls with fuel. Not only that but you don't know how much timing you are running and that is always dangerous. I wouldn't beat on the car until you have been retuned.

What wideband are you running? As far as it jumping down to 25 or 30 when you let your foot off the gas, or shift, etc this is good and normal. This is called DFCO, aka deceleration fuel cut off, basically means exactly what it says, it's cutting the fuel to the motor so the wideband will read lean because you have more air then fuel.

So to give you a short explanation of what your gauge is telling you, it's how much air and how much fuel is going into your motor. When your not wide open throttle, aka your foots not in it a lot, not in boost etc, you are always running at 14.7. The gauge might not read 14.7 but you are at 14.7, if the gauge is not reading 14.7, it's normal, don't worry. A lot of widebands jump around between higher 13s and lower 15s, but the more and more you get your car dialed in via tuning, the closer you will be to your stoich 14.7 number. When you are wide open throttle though, your car should be a lot lower then 14.7. You said you are at 9 to 10. 9s are extremely rich as I said, but you could live and deal with 10s, as Gm leaves their vehicles around that afr.

If you have any other questions please feel free to ask

 

the wideband seems to be jumping from stoich to lambda. i had this problem when i broke the calibration switch on the back of my uego. what type of gauge is it? i usually hit about 11.5 wide open throttle, idling it'll hang around 14.5-15. when you let off the gas is the only time the engine should run lean (15.5ish and higher)

 

Stanced - I don't believe that is his issue, I think he was trying to say that it's jumping from 14.5-15.5 to 13.5 at idle and then drops to 9 and 10 at wot. This is normal for a wideband reading stoich with a maf and or ve table that is not dialed in. He is also just running to rich.

 

Yes Zach06CobaltSC you are completly understanding me. Thank you for all the info.

For a bit more info i have only seen the 9 once i usualy get 11s or 10s when i open it up.
today is was an overly cold morning when i hit the 9 so i dont know if that would make a diffrence.

One last question when i reverse and i am a bit light on the pedal i hear a loud metal on metal Rattling/Clanking from under my car almost from my mufler. Any ideas? It hapened all the time when i first got it and rarly now that i got the clutch down.

 

ooooh that makes sense now. idk why i didnt catch that. well thank you for clearing that up.

 

zach you said any questions so I will ask one. I have never tuned my idle never really had to because its been perty good. How do you go about tuning your idle? cause the maf changes when the heat in your car changes. so like if you tune your idle at 130 degrees and your car sits for another ten min and is at 150 degrees thats will throw your tune off wont it. Also dfco is there anyway to tune your dfco cause mine goes from 20.1 and then so high my lc1 just says o2.