Yep. Depends on the turbulence. What may happen is more air flows past the MAF that provides less force on the MAF so airflow going in maybe more than what the ECU senses. The O_2 sensor is what measures your AFR so it sees this and corrects for the change by adding fuel. Thats a possiblity to how you can get a fuel trim creep in the other direction. The creeping Fuel trim should eventually hover at a point where no more adjustments are needed but if its really bad it could be outside of the acceptable range and trip a CEL. If you find the your trim starts creeping for no reason (meaning everything was fine for a while) chances are weather can play a factor or more likely there is a leak in the system some where. Negative trims indicate a boost leak, positive trims indicate a leak in the intake after the MAF or somewhere where its a vacuum leak.

You may think most boost leaks should be very identifiable by less boost than normal and a CEL. BUT ive had a boost leak where a tiny plastic nipple on the lower charge pipe for the vac line snapped off. No CEL. Boost didnt seem that much lower than normal since it changes with weather you might not notice it. The turbo will also be working hard to maintain its target boost so you may not see a boost drop at all. What did happen is I saw my fuel trim creep negative over the next week. Then it hit the magical # of -20.0 or -21.0 and I enjoyed seeing a CEL. lol.

Now... the fuel trim wont keep going negative continuously... because.... your not always in boost all the time, if your cruising then your in vacuum. If your in vacuum, then the trim may go the other way. Right? right. So even small leaks become difficult to Identify.

 

Gotcha...so we are talking about some unstable charge flow rates and tumbling then correct?

I guess none of this really matters as long as it can be tuned out...but the problem is making sure it stays tuned out even at peak heat levels...

So the K&N and ZZP....IAT readings good? I have read in some cases people reporting higher air temps....? I am wondering if these aftermarket intakes are actually adding 10 hp when the engine heats up and its sucking hot air? Anyone done a dyno after the engine is hot?

 

Hey Cuda Joe, I noticed a couple years ago in another thread you mentioned that the OEM intake causes LTFT to drift also. Has that been proven to be the case or was that just speculation at that point?

Anyone?

 

Your referring to some of the arguements, we've had over tuners using LTFTs being +5 or -5 as a selling point to tune the car. Yeah they marketed that like crazy and when you told them the car is fine between those LTFTs since the stock airbox had the same kind of swings, they'd mention the STFTs are crazier and its hard to tell cause they change so much quicker or something... The LTFT is a series of measurements meaned from the STFTs. So they are saying if your STFTs swings -20 and +20 repeatedly, you'll see a 0.0 LTFT. Only when you do fuel cut off does the STFT ever swing. pretty much every time you shift the transmission cause you took your foot off the gas.

I had been switching between the K&N and the airbox to see if the fuel trims swings were really different back then. I found the K&N had slightly more swing in either postive or negative direction but they both showed changes due to temperature and atmospheric pressure. K&N swings could also be associated with turbulence but out of all the intakes tested with out a tune, it was the closest to a decent LTFT. My LTFT was +1 to -3 always with a stock tune and K&N intake. Funny thing is, I bought a new filter and put it on with a HPtune that showed a 0.0 average fuel trim on the old filter. Now with the new filter, im seeing +2 to +4 LTFT, same filter orientation as before... Guess I need a new tune, right tuners?

 

Its not drift, its swing in the case of the stock airbox. Drift means it just keeps going in one direction until you get a CEL.

K&N intake and stock airbox both swing dependent on weather, humidity included. You will only get drift if the intake tube diameter is soooo different from the stock airbox that the built in MAF calculation for air flow is off. Basically it knows that the tubes diameter is say.... 2.75", but now you throw a 3" intake tube on and its 3" where the MAF sits. well now what it thinks is an air volume with a diameter of 2.75" is applying 1.43 lbs per sec, its really 3" diameter of air volume at 1.43lbs per sec which translates as a higher AFR or leaner AFR and then the trims adjust to compensate. Only problem is their compensation will never make up for the calculation always being off so the trims will keep adjusting. This would be an example of a + LTFT drift.


From what ive read and know on here. K&N intake, Stock airbox, airbox mod, and ZZP intake tube with airbox are the setups that should work without requiring a tune. Hahn parts turn to rust, Treadstone doesnt support the platform anymore, ZZP does support cobalts. K&N intake will make loud turbo noises if your looking for that.


And your question about hot air for the K&N intake. Yeah the IAT1 will get really hot over time since it is pulling in air from the engine bay but thats not a big deal cause it only happens when the car is sitting still at a red light or something. As soon as you start moving, those IAT1 temps drop to ambient. The IAT2 reading is probably more important since its after the intercooler, thats the air thats going in your engine. It gets alittle warmer at a dead stop but nothing to be concerned about. IAT1 reading is important to get the correct air flow volume calculation.

 

Okay, I thought from what I read that the stock airbox was causing problems too...and that a tune should be done on it.

THANKS

 

Even if we say no gains associated. The K&N sound is worth every penny of it. Been running it a year/40,000km now. My intake air temperature before and after the K&N install remained the same strangely enough. Always 1* hotter than outside air.

Besides the Forge BPV there is also a Forge VTA. I just installed mine a few days ago and the blow off is out of this world. The VTA will require a tune where as the BPV does not.

 

Edited a statement in my last comment, please read for an elaboration.
Its in bold.

You wont see hotter temps when the car is moving. Only when its sitting still with a SRI (short ram intake).