Sounds like it just needs to be tuned then...

Best way to find a leak is to crawl under there with the engine running and feel for air coming out of every joint, especially around where the crossover connects to the manifolds and around the wastegate. Even a very small leak will throw off trims and affect turbo behavior.

 

do you mind taking a screenshot of a good, tuned bias table to give me a starting point? with a stock bias table, when the engine would get about 200*, the afr's would lean out, and i never could tune it right so they wouldnt lean out when the engine got warm

 

Pretty sure mine is stock, and pretty sure that table has very little effect on anything.

Post up your hpt file and ill take a look.

 

alright..

 

It looks fine to me really...I would put the O2s back in and try closed loop. Closed loop means the STFTs correct fueling.

 

well thats what ill do, i appreciate it

 

It's difficult to adjust the tune to account for every possible scenario of operating condition (IAT, ETC, MAP, TPS, etc...). So you do the best you can getting it 90% of the way there, then enable closed loop so the NBO2's can get the last 10%. At least that's my interpretation. If you go for 100% without the NBO2's you'll be chasing your tail for a long time.

 

I had this problem also. The problem is the IAT placement. The IAT is getting heat soaked from the engine compartment, and the radiator. There are 2 temps to be concerned with, first is the engine temp, and the other is the IAT temp. There is a blend ratio that is dependant on air speed. Basically what happens is ambient air enters the intake system, and gradually gets heated up while on its way to the engine. The slower engine speeds mean that the air has a longer chance to get heated up, therefore faster air has a lesser chance of getting heated up. At lower air flow the table is favored towards engine coolant temperature, and at higher speed it is favored towards IAT. The IAT needs to be at outside air temp or as cool as it can be in the intake system. In a naturally aspirated car it should be to the side of the radiator, and as close to the filter as possible. In a turbo engine like mine it should be right after the intercooler. What happens if you don't do this is the IAT reads hotter than it actually is, and believes that the air entering the cylinder is also hotter. When air heats up it expands therefore letting less air entering the cylinder(or at least the PCM believes this) and therefore cuts fuel to make up for a hotter air charge. The problem is more noticable at lower RPM's than higher RPM's as the blend is more favored to the coolant temp.

Does that make sense?

 

yes, i understand the physics behind it quite well. i spent about a month trying to tune the bias table to no avail though, my iat is right before the tb. i know its getting heat soaked in stop and go traffic, i thought about relocating it to behind the passenger headlight, but i spray meth, so i don't want to lose any valuable information about the actual temperature. i can get the afr's within 8-9% of what they should be in open loop at low air flows. but atmospheric conditions change from hour to hour, so i can never nail it down, thats why im just gonna go closed loop and let the computer do it