Question I just installed an open breather on the valve cover of my 93 notch. This has resulted in a slightly lower idle and a slightly rougher idle (has a f303 cam). The car seems to run a little stronger since I installed this. I am running sve heads long tubes cobra intake 24 lb injectors pro m 75 76mm bullet. I think I was slightly rich before adding the open breather but after installing it exhaust seems a little cleaner and the car has an easier time returning to idle speed (doesn't hang the idle as long before dropping to idle speed). The exhaust NOTE definitely sounds choppier at idle with the open breather. Can i continue to run the car this way? I did have to bump my idle speed up a little with the open breather. When I switch over to a stock oil cap from the open breather the idle raises a little and the engine seems a little smoother at idle. Looking for inputs. Thanks
96pushrod is 100% correct.Its odd that your car seems to burn cleaner though with the breathered cap because when you install it and create the leak,that causes the o2 sensors to pickup more oxygen which = a lean condition and once this condition is registered by the ecu,it attempts to compensate for what it deems as a lean condition by falsely richening the fuel mixture.This normally triggers the exhaust to smell like raw fuel/higher emissions.Remember, the o2 sensors dont know where the extra oxygen came from in the exhaust.They just measure the oxygen amount and the voltage value they output is what the ecu goes by,along with other sensors data of course,to adjust the fuel mixture.The vacuum leak usually causes a lower/rougher idle,so the fact that replacing the cap with the oem cap and the idle smoothing out and increasing slightly,is a tell tale sign & a verification that a leak and a lean condition is indeed being created once you install the breathered cap.For whatever reason,some cars tend to be affected more than others when using a breathered cap (i.e.- some claim it doesn't cause a lean issue in their setup & some have the issue,but claim their driveability issues aren't caused by the cap) Yours is clearly being affected.If you wanna run a breathered cap and not create these issues,youll have to get rid of the closed pcv system to make it work without creating a vacuum leak.
So Indy if my engine seems to run stronger with the open breather is that proving that my combo was on the rich side and this was a way to lean it out for better performance? Any harm running it this way?
The car I just bought has been running a open breather on passenger side and pcv system for years. Yesterday I just replaced the breather with a oem style cap.
Wait a second, I thought breathers on VC's were good to vent crank case pressure, I just had AN fittings tig welded onto my valve covers and ran into a catch can. PCV is stock valve, connected to a hose with a breather filter on it, car is setup MAP (NO MAF)
I believe the pcv valve is a controlled vacuum leak already provided for by the ecu,on a SD setup.On top of that,having a breather mounted to the end of the pcv hose instead of having the hose ran straight to an intake vacuum port,is not gonna cause a vacuum leak anyway.If you had a maf sensor in place,intake vacuum at the pcv valve would have to be pulling air into the engine through a breathered cap before an unmetered air condition could occur.
A bit of a hijack, but still in the realm of the same theory....
Lets say you had a one way check valve from the back of the lower intake to the upper as a pcv. Then had a line from one valve cover to the inlet tube after the maf. Then had a check valve breather on the other valve cover. Would you then have a functioning pcv (forgot to mention an inline oil seperator) to vent the crappy oil/fuel saturated air from the crank case, a metered fresh air pathway, and a way to let excessive crankcase pressure out from say a supercharged or turbocharged settup without the whole unmetered air conundrum????
So like adding another pcv valve but just venting it into the engine bay? Would that just be a “cv?” lol
I’d you have issues with nasty stuff getting into your intake, you can indeed run a catch can off an existing pcv valve, then still route the combustion gasses, minus the oil mist back into the upper. IMO this is best once you start making some good power.
Yes, I do understand that the pcv is a check valve. And there are some OE ones like the turbo coupe that are designed to handle some boost, but I'm looking to increase the flow volume.
I will be more specific in my description.
Go from the pcv port on the lower intake, through an oil separator, and into the upper intake. *similar to stock, but filters out the worst of the contaminates.
Go from one valve cover to the pipe right after the MAF. * Not the OE location, but considered acceptable and recommend for supercharged applications.
The third part is the variation on what I've seen done for decades. I know I said check valve breather, as that was where my idea started, but it will be a breather catch cad with a check valve. Same result munus tbe oily film.
I don't know for certain if this will work like I'm planning, but I'm hoping it will result in a higer volume version of what the factory had with the ability to vent excessive crank case pressure while ubder boost. The "PCV" check valve will shut under boost, and the breather catch can will vent when that valve cover is under boost.
I must have autocorrected that in my head. I had to go back and read it again to see the PVC.
Unless theres a thread on proper care and maintenance of fetish clothing....
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