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Capping PCV valve/manifold nipple for track use only
I did a track day at Gingerman last weekend and experienced the infamous James Bond, turn 10 smokescreen. I've had it in milder forms at Mid Ohio (Carousel) but it was so bad at Gingerman that I was losing power until it cleared up. This convinced me that I needed to do something to fix it. I'm interested in the least invasive options as I plan to only do this for track time, which is not the bulk of usage of this car (5-6 weekend DEs per year, typically). The car is an otherwise bone-stock 2001 AP1 and I don't need the oil smoke mitigation for the street.
I'm specifically interested in two lesser-discussed solutions to this. First is the idea of simply capping the PCV valve and the corresponding intake manifold nipple at the track only. Second is putting a small-engine style fuel filter in-line with the PCV valve and intake manifold. Emissions are not a concern as this will be a track only modification.
I first read about capping the PCV valve and manifold over on Rob Robinette's website. He mentions simply clamping the line. I'd rather not do that and risk damaging the line, hence the caps instead. I've read mixed reports on this type of setup. Some report blowing engine seals such as the valve cover and rear main, although I suspect there are preexisting problems in these extreme cases. Others report that it works like a charm. They are also hard to generalize to my use case as those reports seem to pertain to built NA motors, FI motors or situations where there are other modifications involved. Again, my setup is bone-stock. This means that the inlet hose, which goes to the intake, before the throttle, could still act as the breather on track. It seems to me that this already handles the bulk of flow at WOT since the difference between the intake and manifold pressure is negligible in this state and it's the less restrictive route for the gases to take. My concerns with this solution are mainly popping up the dipstick and causing a mess under the hood. I'm aware this setup may spray more oil vapor over the throttle body assembly. I am okay with that trade off as this would be for track usage only. I'm not concerned about oil longevity since I change it according to the severe service interval during track season anyways.
The next option in terms of invasivness is putting a small-engine style fuel filter in-line between the PCV valve and the intake manifold. I've seen in this in another thread (Something with, "Oil Mist," in the title) and the OP claimed it eliminated the problem of large smoke clouds. I'm not sure how this would be accomplished as the filter (To my mind) would still be permeable to oil. Perhaps it aids in turning the oil into a finer mist which can be more completely burned? If someone else can verify this works (Particularly with an otherwise stock setup), that would be very helpful. This solution has the benefit of maintaining the stock positive ventilation setup. I believe this would not eliminate oil consumption but I don't mind that part, just the actual smoke screen.
I'd like to restrict the discussion to my solutions above prefer not to have a catch can dangling around in the engine bay for a variety of reasons.
Last edited by IndyS200090; 07-20-2020 at 07:36 AM.
I thought I'd update this for posterity and in case anyone comes across this via the search function: I successfully ran with my PCV valve and intake manifold nipple capped with a couple of silicone caps at a track day yesterday. This worked perfectly. I blew zero smoke and actually consumed no oil. This was at a track where I would typically consume about 1/4 to 1/2 quart. I simply reinstalled the factory hose for the drive home. Total time for the, "Mod," was about 10 minutes. This includes both time at the track, disconnecting the stock hose and fitting the blanking caps and doing the reverse, and time spent prior to the track day prepping by wrestling off the stock hose (106k miles, it was stuck on there pretty good) and reinstalling it with some silicone paste lubricating the manifold nipple and pcv valve for easy on/off at the track.
Total cost was about 5 dollars for an entire bag of 5/16ths vacuum blanking caps.
This is one of those subjects that attracts varied opinions.
I will keep it simple by stating that it is best not to have excessive crankcase vapours/pressure building up under the pistons for long periods of time. Every vehicle needs to have a method of relieving crankcase pressure. In the old days it was vented to atmosphere, modern cars still need that relief but they vent it back to the combustion chamber under vacuum to control pollution.
If you cap the pcv valve, it is best to have some form of relief for crankcase pressure to vent. Venting to atmosphere is one way, how it gets done is for someone to figure out, I am not sure the single hose running to the intake arm is enough to help with that.
I would have suggested the ap2 valvecover which I always ran on my ap1, but I see that is not an option you want to consider.
OP, where do you keep your oil level? If you run it on the high mark, you will smoke a lot on track. Running the oil level in the middle will reduce the problem significantly, in some cases completely.
I'll admit that I made the mistake of running it topped off at Gingerman. In fact, the pit out worker mentioned that I shouldn't top it off upon seeing the plumes of smoke. It did indeed become less and less as the day wore on and I dumped more oil through the PCV. However, I was still smoking a fair amount even with the oil about halfway on the dipstick later in the day, hence my search for a alternative solution.
07-20-2020, 06:33 AM
Capping PCV valve/manifold nipple for track use only
