I am lost about the whole chip needed for a breather cap, why? If the reason is because unmeasured air is getting in causing the truck to run either to rich or to lean than my question has to be, how can you measure unmeasured air? How can you prepare for UNMEASURED air? And why can't the stock computer compensate for this but it can compensate for a 2lb pulley? Am I just completely wrong in the way I think or does my case hold water (reference to "My Cousin Vinnie" )? I have a breather cap and installed it without a chip after talking with another L owner and listening to this argument. Maybe someone can clue me in as to why a chip with a breather cap program is needed.

 

im wondering the same thing, i think it's a waste to buy a chip/reprogram a chip just for a little $20 part.......

you can put a breather cap in a mustang or camaro and not have to get a chip, so why not the lightning???

good ? insomniac

 

When you put a breather cap on, you open up the crankcase to outside air. Normally the system is closed off. The crankcase system has a constant blow-suck happening in it at all times. When you put a breather cap on, on the suck portion, outside air is ingested into the crankcase/valve covers. This area is directly connected to the intake boot via the plastic hoses. So now you have added oxygen, that has NOT been measured by the MAF. But the O2s read it, because the motor is using it, so it affects the fuel trims. When we make an adjustment for it in the chip, we compensate for it. How much you compensate, just comes from experiance.

Hope this helps.

 

This what I came up with, on the dyno, for the air/fuel ratios with the only change being the oil breather cap.

_RPM___________Breather______________Oil cap_
3300....................15.09..................... ....12.96
3400....................14.49..................... ....12.80
3500....................13.46..................... ....12.28
3600....................12.47..................... ....11.79
3700....................11.81..................... ....11.46
3800....................11.48..................... ....11.28
3900....................11.20..................... ....11.16
4000....................11.10..................... ....11.13
4100....................11.04..................... ....11.12
4200....................11.11..................... ....11.17
4300....................11.22..................... ....11.28
4400....................11.33..................... ....11.39
4500....................11.41..................... ....11.44
4600....................11.50..................... ....11.57
4700....................11.58..................... ....11.63
4800....................11.65..................... ....11.65
4900....................11.69..................... ....11.65
5000....................11.67..................... ....11.61
5100....................11.66..................... ....11.66
5200....................11.68..................... ....11.71
5300....................11.72..................... ....11.79
5400....................11.78..................... ....11.89
5500....................11.89..................... ....11.98
5600....................12.05..................... ....12.07
5700....................12.10..................... ....12.10
____________________________________

 

So there is not a set # that you compensate for, its just sort of how you much you feel it needs to be safe. And does the computer not compensate because it doesn't get read by the MAF? How unsafe is it running this without the chip? I am only being stingy on the chip idea due to the fact that I am not to keen on the idea of voiding my warranty being that I am only 17 and use my L as a daily driver for the daily grind (school, work, fun ), soon enough I will have my chip and all the goodies that follow but as for now I am going with the very minor mods.

 

can you explain that chart to me odins wrath, I see that around 3700 rpms the numbers seem to start to get sort of similar, what does this mean and what do the numbers stand for?

 

The numbers represent the air/fuel ratios at a particular rpm. If you'll notice, with the breather cap, the mixture stays lean longer at tip-in but is compensated for by the time it reaches about 3600-3700 rpms. This is under WOT only. What it looks like at part throttle is anybody's guess. I'd say there is less difference under part throttle, or at least that it is compensated for sooner in the rpm range. I'm sure someone will correct me if that is a bad guess.

 

So by the middle of acceleration it is compensated for...right?

 

Everyone at JDM told me to take the breather cap out that they had originally sold to me and replace it with the original oil cap because the SES kept coming on. When I asked them if I needed to send my chip back for reprogramming they said it wasen't necessary!

I don't understand that because when I got their chip and all they said that it had to be burnt for the breather cap, but now that the cap is off and the stock one is in, why doesen't it have to be reburn't? Even in their website they claim that the chip has to be programmed especially with the use of the breather cap.

 

Unless you are running too lean already, I wouldn't worry about a reburn for a breather cap. If you are already walking the lean=mean line of insanity with your program........ Send that puppy in quick.

 

Under WOT conditions (dyno run) you probably won't be sucking any unmetered air in through the breather.

Snap the throttle closed and it's a whole different situation.

This could throw off you fuel trims and actually make you run too rich at WOT.

Tuners... ???

 

it seems like my truck has run pretty rich from day 1. only a few days after cleaning my ex tips, they turn black again. befor i learned of the breather cap=reburn thing, i put a cap on and my tips still turned black after only a few days. when i heard that i needed a reburn, i took it off. im not real sure why i shared this, just seemed somewhat relivent...chris

 

To avoid confusion I stayed stock with this one...

PEaCE.............

 

Right, the breather cap barely affects WOT. What it DOES do, is alter part throttle closed loop fuel trims. In closed loop, the computer is monitoring the O2s, and it will see the extra oxygen. It then tries to compensate for it. Two problems can arise from this. 1- sometimes the compensation is so great, that fuel trims get slammed all the way in one direction, and that's what sets the check engine light. 2- when the truck is at WOT, the programmed fuel tables work ON TOP of the adaptive fuel trims. So if your fuel trims are skewed from the breather cap, when you go WOT, even if your chip is set a certain way, it will also be off.

 

Well the open breather cap causes a "LEAN BANK ONE, LEAN BANK TWO" code and the CHECK ENGINE LIGHT to come on. I have chips from JIM and Sal and they have both been told numerous times that I had an open breather cap but non of their reburns, and I have had a bunch, kept the CHECK ENGINE LIGHT from coming on. I finally got tired of disconnecting the battery to reset the light every day so I went back to the closed cap. I was greeted by two plesant surprises. The light didn't come on any more and my truck quick using 1 qt of oil every three thousand miles. The hell with the "open breather cap."
noelvm