Smelly PCV?
 

A bit of background on my SCCA rallycross car:

-1990 rusty beater.
-Escort GT swap with an M45 Stupidcharger on it. 1.5 bar boost.
-Escort valve cover (PCV fresh air at back of engine by coilpack, PCV vacuum at front on intake side.) -Actually just changed this to a protege one, but its the same as the escort one.
-Metal PCV valve
-PCV fresh air line running to inlet air tube.
-The inlet air system is routed through a hole I drilled in the firewall, so that the filter is at the cowl, right in front of the driver.
-I am also now running E85 (which is very smelly).


Some pics
https://www.miataturbo.net/attachmen...ine=1399374094

https://www.miataturbo.net/attachmen...ine=1399374094

Sweet E-85 content sensor
https://www.miataturbo.net/attachmen...ine=1399374094

The issue:

Whenever I do a WOT pull, immediately after getting out of the throttle, I get a giant waft of fuel smell. After ~5-10s or so, it goes away. I can be going like 50mph, and still get the smell in the cabin. So, I'm looking for some insight here.

Some ideas:
-The metal PCV valve I am using is a little loose/sloppy in the grommet in the valve cover. Maybe blowby is coming out there under boost?
-Is the fact that my filter is in the cowl just mean that the smell is much closer to my face, and this is going to happen no matter what?
-Maybe the PCV system needs a complete redesign?
-

you're saying teh pcv is at the back of the head at the firewall going to the intake?

then what's the tube going to the IM?


if you're smelling fuel, you have a fuel leak. plain and simple.

Maybe some nomenclature issues in the description above.

The PCV valve is in the valve cover at the front of the valve cover. It is hooked up to the intake manifold in the normal miata location.

The fresh air inlet portion of the PCV system is attached to the valve cover at the back of the engine. The other end is attached to the supercharger inlet air system.

Yes, you can see both of the PCV lines in the photo above.

I would think that if a fuel leak was present, it would be present all the time, and not only following a WOT pull. But, maybe since the FPR is referenced to manifold vacuum, that the leak only happens when the fuel rail is at the higher pressure under boost? Seems unlikely, but I'll try and see if there are any signs of a leak.

Also might be an exhaust leak?

Check EGR pipe connections?

An exhaust leak can produce a gas smell because of unburned fuel if your running rich.

What engine management are you using? Do you have overrun turned on? Maybe the settings need adjustment with E85 when you come off throttle. (I'm not even sure if that's an issue with E85, but someone will probably chime in.)

Wait... did i really just read that you're pushing an M45 to 1.5bar?

Custom engine management - this is what I do for a living (control systems engineer in Detroit should be a pretty good tipoff).

Decel fuel shutoff is enabled, so injectors are off when closed throttle. But, the smell also happens when in part throttle. Stopped at a stoplight, if I do full throttle in first and second, then cruise at 50mph = massive smell for ~5-10s. Then no smell.

I'm thinking its an exhaust leak. I'll pressure test it to see.

The strange thing is that there is absolutely no smell when parked and idling. Also no smell when the windows are up. This has probably been going on for months, but it only recently got warm enough here to open the window when driving.

1.5 bar absolute (Map sensor reading). 0.5 bar gauge. Sorry for the confusion.

Ah ok. I wasn't sure if i should :bowrofl: or just :rofl:

Well, I did a pressure test on my exhaust, and found a few leaks. Looks like there is a crack in my muffler, a pinhole in a weld right before the cat, and then the OEM header is leaking at the collector, right where all the pipes are welded together. Looks like a weld on one of the pipes might have cracked, but was hard to pinpoint with it still on the car, and the supercharger in the way.

Seems like a good excuse to slap on an aftermarket header. Anyone got one cheap?

I had the same problem. I put my charcol canister back in and the problem went away.

shit happens... lol


M45 on mini right before total meltdown. lmao
https://www.miataturbo.net/picture.p...pictureid=3193

So, after finding a crack in the OEM exhaust manifold, I replaced it with a known good one (another OEM NA8). Also bought a brand new OEM PCV grommet and GTX PCV valve.

IT IS STILL SMELLY! WTF?

I'll check the new manifold for leaks again. Any other ideas?

OK, this is really pissing me off - So, I'm in full-retard troubleshooting mode.

I plumbed the Fresh air pcv line from the valve cover to - my face! Yup, I routed a line directly to my hand in the cabin, so I could see if the smell was coming from the PCV. Kinda looked like I was taking a hit from a bong while driving around.

https://www.miataturbo.net/attachmen...ine=1400626108

So, the PCV definitely smells bad. But it is a little more oily smelling than the smell I am normally getting in the car. I can actually see the blowby smoke coming out though - that is maybe a bit disturbing!

So, then I plumbed it out past my trunk to make sure it was well behind the driver while driving.

https://www.miataturbo.net/attachmen...ine=1400626108

https://www.miataturbo.net/attachmen...ine=1400626108

The verdict - the smell was still there even after plumbing the pcv to behind the trunk. So, back to the exhaust system...

I'm telling you man, I bet it has something to do with the fact your charcol canister is removed and your purge valve no longer functions. If you have that shit still, install it and go for a drive just for shits and giggles. I had the same problem, both after a WOT pull through a few gears and even sometimes sitting in traffic. I put my stuff back in and I have not smelled fuel since.

Well, when I removed the charcoal canister, I just left the lines open. So today, I did the recommended "line loop" and connected the two lines that were formerly attached to the canister. It appears that one line comes from the tank, and the other is a vent that is attached to the lower subframe -(not sure why it is attached to the subframe, but whatever).

In any case, no change in smell.

For what it is worth, since I don't have the capability of regulating the purge solenoid with my controller, adding the charcoal canister back in the system will accomplish absolutely nothing. The canister normally gets filled when the fuel in the tank is warmed up (creates vapor), and is then emptied when the engine is running and pulls a vacuum on the canister through the purge valve. If you don't ever turn the purge valve on (for instance, if you are using a Megasquirt), then the charcoal canister fills itself to capacity, then just vents to atmosphere. So, after like 1 day, having the canister back in location will be functionally identical to looping the lines.

Besides, there should not be any additional fuel vapor caused when doing a WOT run. In fact, there should be less vapor, since the engine is consuming more fuel, therefore returning less hot fuel back to the tank.

So, in conclusion, I'm hoping that isn't my problem, as I don't have an easy fix for it.

Tried some more stuff.

Hooked up the vent line from the tank to the intake manifold to make sure it wasn't the lack of charcoal canister that was causing the problem. Since I don't have a purge valve anymore, the flow was completely uncontrolled - running all of it! Needless to say, the engine was pulling 20% fuel from closed loop operation, and was still running at 0.75 Lambda - so was running 45% richer than normal due to purge vapor at idle. Holy crap, lots of vapor!

In any case, this didn't help at all. Still lots of smell. So, rule that out as the problem.

Then managed to get some time to check the exhaust system for leaks again. And, it was leaking pretty badly right at the header to downpipe flange connection. So, I ordered a another brand new Felpro multi-layer steel gasket and installed it. Still leaked the exact same amount in the exact same location. Crap - looks like one of the flanges is warped! So, I had a friend make me a new gasket using a sheet of the thick Mr. Gasket generic exhaust gasket material. Much more compliant than the thin MLS gasket, so should hopefully account for any warping. Installed that, and the leak went away. YAY!

But, the smell is still there!

Also at some point during this, I decided to upgrade my PCV system. Based on earlier testing, it seems like the PCV system was not the problem whatsoever, so obviously I had to mess with it to make it better! See the logic there?

After browsing alot of PCV/Catch Can related threads on this site, I noticed that the goal seems to be to increase the flow capacity of the system on the clean air side in order to account for the additional blow-by that occurs under boost. Of course it seems that it isn't really required for the low boost level I am using on this car, but what the hell, why not.

So, I was at the local autozone again, and I noticed a fancy looking Edlebrock breather meant for old school V8's. It intrigued me due to the low price, and the fact that it also acts as a baffle for oil vapor, and has huge flow capacity (1/2" line).

https://www.miataturbo.net/attachmen...ine=1401105144

So, I figured I could hack up the Escort GT valve cover I have lying around and make it work. I pulled the baffle covers off of the underside of the valve cover, and drilled out the transfer hole from the center baffle to the rear baffle. Also removed the steel insert limiting flow between the two chambers on the rear baffle. Removal required heating with a Mapp gas torch and a pair of vicegrips (see it pulled out in the photo).

https://www.miataturbo.net/attachmen...ine=1401105144

Then I found a good location inside the rear baffle to drill a hole for the new breather. So, now there would be the old baffling, plus a bunch more inside the breather. More baffle = more better, right? Also means I won't have to run a catch can on this side of the PCV, and theoretically any oil caught in the breather should drain back into the valve cover. Dug out the carbide cutter and went to town on the ribbing inside the baffle.

https://www.miataturbo.net/attachmen...ine=1401105144

https://www.miataturbo.net/attachmen...ine=1401105144

Also pulled out the stock rear exit fresh air hose nipple, drilled and tapped for 1/4" NPT plug. And, finally drilled a giant hole in the top of the valve cover. 1.25" hole using a step drill bit. Also note, I ground off the blue oval on the escort valve cover to make the area flatter for the new breather.

https://www.miataturbo.net/attachmen...ine=1401105144

https://www.miataturbo.net/attachmen...ine=1401105144

And, here is the finished product:

https://www.miataturbo.net/attachmen...ine=1401105144

https://www.miataturbo.net/attachmen...ine=1401105144

https://www.miataturbo.net/attachmen...ine=1401105144

And, after all that work, the smell is still there!

Also added a catch can to the vacuum side of the PCV. Leak checked it to 20psi using my air compressor, and the 323 GTX purge valve seals pretty well. It's not a 100% seal, but the leak amount is tiny.

https://www.miataturbo.net/attachmen...ine=1401106492

Still smells.

Engine bay is super dirty from the rallycross yesterday. Came in first place out of 10 drivers in Modified RWD though!

I love this, its good to know someone else out there troubleshoots things like I do :bang:

This may be a silly question, but have you checked things like your shift boot, or the multitude of grommets on the firewall that are supposed to seal that stuff out?