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pogman

Fuel smelling oil / fuel and oil in catch can

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So i am having some trouble with my rb25 at the moment. The motor was rebuilt just over 1 yr ago and runs on e85 and at every oil change of course there is always a smell of fuel in the oil which i have been told and have learnt to expect from ethanol.

 

But recently i had stopped up from a coastal run to find oil leaking from the front bumper which was traced back to the pod filter as my catch can is plumbed back pre turbo. So clearly my can was overfilled so much it was being pulled into the intake thanks to the turbo and smoothering the pod filter in oil.

 

Now this was the weekend before racewars and as i had no issues beforehand and had done a fresh oil change decided there wasnt much i could do and to just give it a go at racewars. But after 2 runs of the 800m i had again overfilled my 1.8l catch can enough to see oil out the bumper. Now what has me really concerned is the fact that after 2 runs of 800m my catch can and oil both reak of fuel.

 

I have spoken to the engine builer and he isnt concerned with oil and fuel in the can as it isnt a great design and so since this i have read most of the oil control thread and am planning the new catch can system to drain and vent to sump as it should. But i am concerned that even after this i will still have this same issue as im concerned the rings are shagged is there any chance its not the rings?

 

Thank you

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Running an oil cooler?  Might need to be hotter.

Any chance that it's simply a bit rich somewhere in the operating range and washing down?

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Running an oil cooler?  Might need to be hotter.
Any chance that it's simply a bit rich somewhere in the operating range and washing down?
Nah no oil cooler. It normally sits at a stable and decent temp so i think its getting hot enough. It could possibly be running rich but i have had a few people go over the afrs as i wasnt overly confident with my most recent tune and everyone seemed to be faily happy with them?

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Put it back in and i reckon your overfilling the catch can will go away.

 

I run just a basic catch can setup, pcv remains fitted. Hose from rocker covers goes to can and then from can to intake. Works well and never fills even after whole track days.

 

The only time its filled the can is if ive overfilled the engine oil too much.

 

 

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Or if you are worried do a compression test and if keen a leak down test.

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Not an answer to your problem and not sure if this will be of help/interest to anyone

 

Since my last motor work the catch can is filling up faster after some runs than it did before and I thought I had an oil leak  as there was oil under the front of the motor. The overflow used to go to the back through a tube and leak out if I didn't empty it, not ideal. I guess the tube is not there or has been disconnected somehow. About to have it checked out.

Being on E85 I am not sure if I want the contents of the catch can going back into my sump ?

Now I just make sure to empty the catch can and of course the problem stopped. Top the oil up when needed and all good

Maybe some of you have this problem , my catch can is a pain to empty because the nut is pretty well flush with the catch can and when you undo the bolt it makes it hard to catch all the oil and it can be messy , so I just ordered a valve to make it easy as it sits out away from the catch can and I will be able to get a funnel under it, maybe I will be able to put a hose on it once I have a chance to see it.

 

1292224343_OilValveforcatchcan.jpg.54b78db103ec6176e14ccaf84edc6f83.jpg

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Put it back in and i reckon your overfilling the catch can will go away.
 
I run just a basic catch can setup, pcv remains fitted. Hose from rocker covers goes to can and then from can to intake. Works well and never fills even after whole track days.
 
The only time its filled the can is if ive overfilled the engine oil too much.
 
 
Ok ill try putting it back in im just so confused as i went a yr without any issues and now im overfilling the catch can after 2 pulls

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Or if you are worried do a compression test and if keen a leak down test.
Yeh i think i will do a compression test aswell and possibly a leak down if it turns out bad
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Not an answer to your problem and not sure if this will be of help/interest to anyone
 
Since my last motor work the catch can is filling up faster after some runs than it did before and I thought I had an oil leak  as there was oil under the front of the motor. The overflow used to go to the back through a tube and leak out if I didn't empty it, not ideal. I guess the tube is not there or has been disconnected somehow. About to have it checked out.
Being on E85 I am not sure if I want the contents of the catch can going back into my sump ?
Now I just make sure to empty the catch can and of course the problem stopped. Top the oil up when needed and all good
Maybe some of you have this problem , my catch can is a pain to empty because the nut is pretty well flush with the catch can and when you undo the bolt it makes it hard to catch all the oil and it can be messy , so I just ordered a valve to make it easy as it sits out away from the catch can and I will be able to get a funnel under it, maybe I will be able to put a hose on it once I have a chance to see it.
 
1292224343_OilValveforcatchcan.jpg.54b78db103ec6176e14ccaf84edc6f83.jpg
Hmmm sounds interesting maybe the ring gap is abit looser on this motor and so more blowby? I may have to try something similar as although apparently lots of people do it im not sure i want to return the e85 contaminated oil back to the sump?

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I personally do not see the sense of taking a chance that a contaminant from the catch can going back in my oil to save a couple of $s

Before the build the sludge that came from the catch can was brown ish gunk  , E85 has a water content I think and mixing with the oil could change the colour . This is what first made me think I had an oil leak as the oil on the garage floor looked like oil and when I emptied the catch can this time , it looked like oil but probably had a small amount of water mixed with it as I am sure some water came out first.

Probable be some condensation in the mix as well , but ?

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11 hours ago, pogman said:
16 hours ago, Nismo 3.2ish said:
Not an answer to your problem and not sure if this will be of help/interest to anyone
 
Since my last motor work the catch can is filling up faster after some runs than it did before and I thought I had an oil leak  as there was oil under the front of the motor. The overflow used to go to the back through a tube and leak out if I didn't empty it, not ideal. I guess the tube is not there or has been disconnected somehow. About to have it checked out.
Being on E85 I am not sure if I want the contents of the catch can going back into my sump ?
Now I just make sure to empty the catch can and of course the problem stopped. Top the oil up when needed and all good
Maybe some of you have this problem , my catch can is a pain to empty because the nut is pretty well flush with the catch can and when you undo the bolt it makes it hard to catch all the oil and it can be messy , so I just ordered a valve to make it easy as it sits out away from the catch can and I will be able to get a funnel under it, maybe I will be able to put a hose on it once I have a chance to see it.
 
1292224343_OilValveforcatchcan.jpg.54b78db103ec6176e14ccaf84edc6f83.jpg

Hmmm sounds interesting maybe the ring gap is abit looser on this motor and so more blowby? I may have to try something similar as although apparently lots of people do it im not sure i want to return the e85 contaminated oil back to the sump?

Why not? That's where it came from. How far can you afford to let your oil level drop?

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Don't know about you Bob, I have 10.5 Lt sump , it is a street car and I do not do long races where I would think this is a major problem waiting to empty the catch can and maybe running it back to the sump may be the best option for your car's motor internals , I don't know. Then totally change the oil after the race, but I doubt if you use E85 you would leave the contaminated oil  in the car and race again and again , oil is cheaper than a rebuild, but I do not know?

I do have flex tune but use E85 100% atm

I can only go on my limited experience , I emptied the catch can and drove the car 330klm to Sydney to have some work done on it .

Had the head ported, cams modified and the CR up from 8.1:1 to 9.8:1 , the car was tuned and I am sure there were lots of 7500 ish rpm runs on the Dyno before it was done, drove it home 330klms and loading it up as I went, did another 300klm through the hills , then a mate came up and gave it heaps for 120Klms and it used up about 1.2Lts plus some water in the mix. So I had 9.3 Lts of uncontaminated oil left in the sump and for me, I will take a loss of 1.2Lts of crap that is not going back into my sump , than having it returned.

Maybe I am being too careful Bob , but I have spent a shatload on my motor and think I am doing the right thing , but ???

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I thought e85 draws in condenensation and can easily be contaminated.

If it is in the can it can draw condensation through the airways. Same with your conaminated oil in the sump but will more than likely evaporate quickly in the engine and show as condensation on the inside of the oil cap. Saying this hopefully the can is saving the sump oil by being the only atmospheric inlet mildue can get in.

When on petrol the temps are higher and the fuel and moisture evaporate away from the oil easier and qucker.... e85 more fuel and less evap and more drawn in condensation fr9m e85... messure what you tip out compared to what you need!

More blow by will add more.

Does the engine have a breather?
May help if pvc return dont.
I used to use 1 on the top of the can so not all vacum was applied to the motor.
Also the can will be the moisture catcher still.

?It may be to much vacum in the motor pulling the fuel past the rings if they are gaped more? Very queationable!


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3 hours ago, Slap said:

I thought e85 draws in condenensation and can easily be contaminated.

No, E85 makes condensation.  Because of the much higher hydrogen:carbon ratio of ethanol compared to 7-9 chain length hydrocarbons, it simply make a higher % of water vapour in the exhaust gases and therefore you get more of that condensing in the oil.

Oil/sump temperature will be about the same regardless of 98/E85 fuel in use.  It's the upper end of the engine that runs cooler.  The bearings still make a lot of the heat that turns up in the oil, probably more on E85 if it's got more timing/boost/power.  But the water is continuously being made.

It should be safe to return it all to the sump, because the water should boil off again, but by the same token, if there's enough in there it will sink to the bottom of the sump, get priority pickup by the oil pump and f**k the bearings in short order.  So, a large catch can and a very decent breather system that can pull off water vapour before it condenses and send it to be burnt are probably the wisest idea.

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4 hours ago, Nismo 3.2ish said:

Don't know about you Bob, I have 10.5 Lt sump , it is a street car and I do not do long races where I would think this is a major problem waiting to empty the catch can and maybe running it back to the sump may be the best option for your car's motor internals , I don't know. Then totally change the oil after the race, but I doubt if you use E85 you would leave the contaminated oil  in the car and race again and again , oil is cheaper than a rebuild, but I do not know?

I do have flex tune but use E85 100% atm

I can only go on my limited experience , I emptied the catch can and drove the car 330klm to Sydney to have some work done on it .

Had the head ported, cams modified and the CR up from 8.1:1 to 9.8:1 , the car was tuned and I am sure there were lots of 7500 ish rpm runs on the Dyno before it was done, drove it home 330klms and loading it up as I went, did another 300klm through the hills , then a mate came up and gave it heaps for 120Klms and it used up about 1.2Lts plus some water in the mix. So I had 9.3 Lts of uncontaminated oil left in the sump and for me, I will take a loss of 1.2Lts of crap that is not going back into my sump , than having it returned.

Maybe I am being too careful Bob , but I have spent a shatload on my motor and think I am doing the right thing , but ???

Its really only on the track that you do a lot of running at WOT where you could potentially starve the pump of oil. Most people change the oil after each day at the track and yes oil is cheaper than engine rebuilds!

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