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I always attributed the jet air to the following valve (circled)
Currently, I have vacuum lines plumbed here as well. I have added a one way check valve to this line a few months ago.
So, the jet air line in the stock configuration recieves fresh air from the intake. In my system it recieves oily air from the crank case.
Yesterday, I noticed that the installer had two T pieces to split the air. I had attached a catch can to one of the lines and the other line was running directly to the jet air. This means that it was injecting oil into the LIM.
I got rid of the bypass and I noticed an improvement on how the car ran as the joint was leaking oil and loosing vacuum....every bit helps.
I thought we had that jet air discussion several months ago? As I recall we were not in agreement about it being supplied pre-turbo (atmospheric) with a check valve vs post-turbo (boost) without. Now you're saying it was connected to a catch can plumbed into the oil sump gases and also sending oil to the intake? Wow, just wow ...
I have attached a one way check valve to the vacuum pipe that goes to teh valve on photo 2.
I only traced the new lines to the pipe to photo 1. Originally, the oil filler cap had vented cap which allowed it to draw fresh air however, I was getting blow by issues so I replaced it with a cap.
I could the jet air to the intake as per the stock as a trial. However, applying vacuum via the filler tube has benefits as well.
Not really. The benefit is only for engines with crankshafts, rotary engine is zero benefit. Running oil sump gasses to the intake is good for emissions, but not performance.
For FI my recommendation is disconnect the sump entirely from the intake system and instead vent it to a catch can and then atmosphere through a small filter such as a K&N. The jet air and oil metering nozzle air lines should receive filtered intake air after the MAF. It sounds like you need to go through them all and get it squared away properly.
Not really. The benefit is only for engines with crankshafts, rotary engine is zero benefit. Running oil sump gasses to the intake is good for emissions, but not performance.
For FI my recommendation is disconnect the sump entirely from the intake system and instead vent it to a catch can and then atmosphere through a small filter such as a K&N. The jet air and oil metering nozzle air lines should receive filtered intake air after the MAF. It sounds like you need to go through them all and get it squared away properly.
Edited for accuracy
So you reckon venting to atmosphere will not cause a problem with the tune as we have unmetered air.
I had a couple of instances when the vacuum pipe attached to the oil filler nozzle popped off and the car ran horribly with the revs at idle climbing to 2000rpm and car going into limp mode.
On the other hand it is a learnt behavior and if the ecu is reset and operated with a vented crank case then it should be ok??
Of course it did, because you have it connected to the intake system and created a huge intake leak after the MAF.
Per my recommendation, you vent the sump entirely to the catch can *and* plug the connection points where it was previously connected to the intake. When you do this the sump gasses go to atmosphere the same as exhaust gasses. The sump and the intake are then completely separate from each other.
Otherwise all the air is metered when it came in from the intake. When the sump is connected to the intake you're recirculating contaminated air back into the engine like an EGR emissions system. My recommendation keeps fresh air coming to the intake.
IMO you're thinking isn't straight. It needs to be setup properly first, then tuned properly second. Doing it any other way is a guarantee for poor performance.
with your sump gasses going into the lim. It is also being unmetered. It might have some fuel in it, but it might not also. That could risk your engine leaning out.
Thanks guys, I will get it changed around. Its amazing how forgiving the engine and ecu is to cope with such things and still perform at the track and daily driving without breaking down. i have done 50 000km on the engine with an inefficient setup.
Can someone please advise on the function of the marked pipe. It looks like it is the same pipe as the jet air. If it is the same line then I have already added the one way valve to it at the other side.
I will now plumb it to intake post MAF to get fresh air
Here is what I'm running quite happily.
Jet air=>Supplied by boost source directly. (Mimics stock function)
OMP=>Supllied by boost source directly. (Mimics stock function)
Oil Fill Vent => Catch Can => Check valved vac source. (Prevents pressurizing the sump)
Rear oil vent => capped. (Works just as well from a pre-turbo metered air source as well).
There is no need to remove the stock function from the oil sump. It keeps the oil dry which we need, and all you need to retain it is a catch can and a check valve. I would not go to a breather alone for the sump on a street car, but to each their own.
With a check valve and cap your sump is getting pressurized during boost because there is no way to relieve the blowby gasses until the engine has a vacuum condition. Granted a street car likely isn't under boost for long, but understand that the original OE system did not put a vacuum on the sump and I never had any issue since buying mine in April/2005. We don't have severe winter conditions here though.
IMO the only way to do it correctly that way is to have it connected to the intake post-MAF/pre-turbo to simulate the original OE system, but with the catch can in-between to collect oil. I personally don't like the idea of having it connected to a vacuum source or the idea of running it back through the turbo. So my choice is to separate and vent it to atmosphere, but to each his own ...
Any 06+ has a slight vacuum on the sump to pull dry air from the intake into the sump and remove moisture. I'm not concerned about a hypothetical situation where my car is under sustained boost long enough for blowby to pressurize the sump and become a problem. When it's not in boost all the water from the combustion gasses in that blowby is being pulled out of the oil as opposed to lazily letting the oil vapor vent to the intake.
Simulating the original OE system seems silly when they went to the trouble of a TSB to replace it.
How about go the the next step and put a tee with 2 check valves. one 1/4" or so goes out of the intake to the catch can. So blowby can make it's way out. Then the other on the lim ports that will pull a vac on the sump when off throttle.
Ok I have rerouted the jet air line to the intake post MAF.
The vacuum has now been disconnected from the oil filler neck and the catch can is vented to the atmosphere.
Car is running well and vacuum has improved slightly. I may see less soot on the tail pipe as the intake was getting extra oil injected into LIM from the blow by oil.
Everything is operating well however, a new issue has developed.
I did a hard reset of the ECU and the car is propably repopulating LTFT. This issue I have at the moment is that some times the car idles higher than normal. I then do the 20 stomp and it sometimes resolves and othe times it takes a few goes before it finds the right profile.
When it settles into the correct profile the car performs at its best in terms of power, great vacuum at idle and response. When I restart the car then sometimes it will behave differantly again so I hunt for the correct setting again.
Catch can is bone dry after making the latest changes. The vacuum was propably pulling some of the oil in the old setup.
I still have the intermittent high idle issue which seems to come and go. Now that the vacuum lines have been simplified there is not many areas to check up on.
I am suspecting a possible O2 sensor issue from the car running rich. Any thoughts anyone?
07-04-2015, 01:41 AM
