Crankcase Breather? [Archive] - GrandAmGT.com Forum

PDA

View Full Version : Crankcase Breather?


chris_gt_74
11-08-2012, 04:16 PM
What did you guys use for the hose that goes back to the rear valve cover for the pcv system? Can I just remove it and install a breather in it's place. The reason I ask is that I just switched from an lx5 65mm throttle body and was utilizing one of the barb for that hose. Well now I got my hands on a TCE 65mm throttle body and I don't have a place to attach it. I do not want to put it in the intake like the stock location was because it's ugly to me. If I can install a breather that is the way I'd prefer unless someone knows of a clean air location I can attach the hose to.

AleroB888
11-08-2012, 04:51 PM
What did you guys use for the hose that goes back to the rear valve cover for the pcv system? Can I just remove it and install a breather in it's place. The reason I ask is that I just switched from an lx5 65mm throttle body and was utilizing one of the barb for that hose. Well now I got my hands on a TCE 65mm throttle body and I don't have a place to attach it. I do not want to put it in the intake like the stock location was because it's ugly to me. If I can install a breather that is the way I'd prefer unless someone knows of a clean air location I can attach the hose to.

I got a small oval mower filter at Autozone, attached a 1/2 inch hose to it with a plastic barbed fitting. It works fine, I'll make something better eventually, though.

AaronGTR
11-08-2012, 05:36 PM
You should NOT just put a breather on the rear valve cover. It will work, but technically by doing that you are pulling in unmetered air (that hasn't gone through the MAF sensor and been measured) and it will throw off your fuel trims a bit. It's essentially the same as a vacuum leak.

Watch the video I posted here. http://www.grandamgt.com/forum/showthread.php?t=85606&highlight=PCV Explains all about PCV systems. I've posted lots of other info on here about them. I personally had to do a lot of research to come up with something that worked properly with the S/C.

AleroB888
11-08-2012, 06:34 PM
You should NOT just put a breather on the rear valve cover. It will work, but technically by doing that you are pulling in unmetered air (that hasn't gone through the MAF sensor and been measured) and it will throw off your fuel trims a bit. It's essentially the same as a vacuum leak.

I don't think there would be any big difference, the MP62 kit was emissions complaint with it routed from the airbox. If anything, I think it would be more stable routed from the filter. The flow through the PCV system is not constant. There would be fluctuation of metered air when the PCV valve operated, when placed after the MAF. I would like to see exactly how much the trims would be off, but even then, it's likely to be compensated by calibrating the MAF. Even very small vacuum leaks affect the Fuel Trims, but I have yet to see anything measurable from that routing to the rear cover.

chris_gt_74
11-08-2012, 07:35 PM
I just decided to switch back to the old weapon-r intake piece I had laying around. It has the nipple on it for the hose. I'll have to come up with something I like better but this works for now.

Here's a pic: Don't mind the wires, I need to clean them up a bit lol

http://i289.photobucket.com/albums/ll234/grand_am_gt_74/IMG_20121108_192155.jpg

If snyone is wondering, the bigger hose running over the intake is my coolant hose and the 2 hoses running to the pcv valve and intake are running to a catch can.

AaronGTR
11-09-2012, 09:56 AM
I don't think there would be any big difference, the MP62 kit was emissions complaint with it routed from the airbox. If anything, I think it would be more stable routed from the filter. The flow through the PCV system is not constant. There would be fluctuation of metered air when the PCV valve operated, when placed after the MAF. I would like to see exactly how much the trims would be off, but even then, it's likely to be compensated by calibrating the MAF. Even very small vacuum leaks affect the Fuel Trims, but I have yet to see anything measurable from that routing to the rear cover.


Ok, stop and think about what you just said there, and tell me how that makes any sense.


The flow from the PCV does fluctuate but it is running for the majority of the time. It doesn't matter if there is flow or not though, because if it's pulling air from behind the MAF then it is always pulling air that has been metered when it is running. When it's not pulling air, that air stays in the intake and goes through the TB, and it's still metered. If you pull air from in front of the MAF through the PCV system, then when it's running, you are pulling in unmetered air.


Also, I don't know what you were thinking but the Magnacharger kit was NOT emissions compliant. It was not legal for sale in CA/NY when it was made. They only made 20 of them and never submitted it for CARB approval.


Like I said, the car will run with a breather on the back, because the PCV valve also acts as a flow restrictor to control the flow rate and the small amount of air pulled in... the fuel trims have enough adjustment range to compensate for that. But it will still be off. I measured a 1-2% difference in my LTFT's on my car, with no other changes to the tuning or engine, when I fixed my PCV system.

AleroB888
11-09-2012, 11:48 AM
Also, I don't know what you were thinking but the Magnacharger kit was NOT emissions compliant. It was not legal for sale in CA/NY when it was made. They only made 20 of them and never submitted it for CARB approval.




The Magnacharger manual says 49-state, which implies compliance everywhere but CA, that's all I have time for right now.....

Malaclypse
11-17-2012, 10:21 AM
Putting a breather on your PCV system is a bad idea on these cars. It does indeed affect fuel trims. Aaron is 100% correct.

AleroB888
11-17-2012, 06:19 PM
Putting a breather on your PCV system is a bad idea on these cars. It does indeed affect fuel trims. Aaron is 100% correct.

The difference is still negligible. And somebody explain how the MAF "knows" that heated, vaporous product is added to the mix without it's passing through the MAF itself.

AaronGTR
11-17-2012, 07:37 PM
The difference is still negligible. And somebody explain how the MAF "knows" that heated, vaporous product is added to the mix without it's passing through the MAF itself.


The MAF doesn't know what amount of crank case vapors are getting added to the mix. It DOES know though how much air has gone through it, and if the PCV system is drawing from the intake like normal, then the air going into the manifold from the crank case has been measured. Yes, a very small percentage of the crank case gases are actually flammable, but for the most part it is just air and pollutants that are getting burned. It still needs to add fuel to the mix to get a proper AFR for that air that is coming in. If you are pulling in air from a breather, it is not meter and therefore throws off your fuel trims, even if it's only a small amount.


I don't get why this concept is so hard to understand?

plastic_indian
11-17-2012, 07:40 PM
Metered air that is 'recycled' via the PCV is accounted for with STFT adjustments according to hydrocarbon saturation via the feedback loop. Given the R&D involved with developing a production engine, I would suspect the airflow (and probable hydrocarbon content) through the PCV system is anticipated in the OE calibration for any given temp/runtime/load/MAP/fuel trim combination. The actual impact of this variable, however, would make a good topic on the DiyEFI.org list. I'm not an ECM hacker, but I've seen enough production vehicles 'smart' enough to compensate for variables within the realm of stock combinations forced into LT adjustments (or even freak out) when the slightest equipment change is made.

The N car's ECM has been shown to be adept in compensating for an open PCV system. In and of itself, the driver will likely never know the difference. In the instance of an application where additional deviations from stock configuration are present or may be anticipated, preventable complications to the ECM's strategy should be avoided.

Besides, I'm breathing the same air OP is. If you've got the money and the skills to modify, you have an obligation to do it responsibly. Modern emission controls are the reason the current generation has no idea what a sun dog is; let's keep it that way.

bricooper78
11-17-2012, 07:57 PM
I already have a good idea of this, but I think this Mark knows a thing or three lol