Hey guys, whats the scoop with getting gas in the oil catch can, anyone else see this behavior or can explain why there is gas in there? condensation of gas fumes or what?

 

Hmm, an opportunity to tell Damian to do a search... somehow that just wouldn't feel right.



I think blowby is what's causing this, it's got to do with the combustion chambers not being perfectly sealed. From what I've read on this forum and on Steve Cirian's website, this is somewhat common.


Even in stock cars, you can smell gasoline in the oil if your oil change interval is too long.
https://www.rx7club.com/showthread.p...hreadid=226214


-s-

 

Yeah. I get a strong gas smell after only 500 or so miles. That I would say is excessive, so needless to say there, it's time for a rebuild (for me anyway).

 

When I got a CEL from a bad Intake Air Thermosensor it seemed to cause the car to run very rich, and I got the associated fuel smell/dilution in oil. I still run the stock ECU and don't know much about PFCs, but understand that with them, you don't have CELs. Could something relatively simple like that be causing it and not showing up as a CEL due to a PFC?

 

Yes, gas fumes can condense in the catch can - apparently the oil itself is well-baffled, so you don't get any oil in the can, but the oil is running hot enough to vaporize any gas, and it condenses out when it cools going through the catch can. This would be particularly true for some race fuels, which have much lower vapor pressures than street gas, and, therefore, wouldn't stay vaporized as they pass through the catch can.

 

It's possible, but in my case no. I went through a little hell with that damn sensor and I'm 100% sure it's working fine.

If you're tuned a little rich purposely though I suppose you'd have the same effect.

I realize now that my answer isn't in line with the original question, but I have noticed that I've been getting some gas in the catch can. That said, I'll go along with what Dave said.

 

I have a faint smell of gas fumes in the oil filler neck, but my car current is tuned rich......is this normal?

 

Yes.

 

heheh , ohh crappy my bad, i admit i never searched on this one. ;-)

BUT, I did already know about that link you posted, I have read that back and forth like 10 times back when I was solving my catch can 'overfilling' problem, now I have that solved by using crispy's concept of 2 venting sources, adding the vent by the oil return line that is not used when you go single.


thanks for all the great info guys!!!

 

hey how are ya!! I need your email address again so I can let you know when we are having more MAM events.

ok back to the issue, I dont think there is anything like that goin on here, the car runs perfect and strong, af ratios are good so its not dumping extra fuel in or anything. I am guessing its just a normal behavior that has been exaggerated by the stage 3 porting.

 

ok, so basiacally, since the car is running great, I am not going to worry about it until I need to worry about it :-)

 

Doing great thanks. I'll PM ya.

 

how big is your catch can?? Overfilling...sounds intense?!?!? I have drops in mine after 1K of so.

stage three porting should have no effect on blow-by...blow by is past sideseals -> corner seal clearancing.

 

i have the small jaz catch can, and yeah its intence, its frikkin 20 minute session of ***** out mayhem all day, ...track events baby!!!


the overflowing is due to poor venting ability when using one vent source, its resolved by adding a second vent source on the other side of the pan.

in other words, im not overfilling the can anymore, its not an issue. i was just making sure some gas in the catch can was normal....and it seems it is.

 

Yup. The last motor that I paid to have built for me (back in like 2001 maybe) had a horrible problem with fuel dilution in the oil. Upon teardown we found--- *surprise* ----very loose side seals......