A friend of mine used to be big into BMWs, and he was saying that the S52 engines (in the later E36 3-series) were designed to consume exactly one quart of oil every 3,000 miles through the PCV. He said that that oil was actually counted on for additional top end lubrication and to help fight combustion chamber temps so that a hotter spark could be used.

Of course, that's why they required really high-quality oil. Nissan doesn't seem to insist on that for our engines, so that's why I doubt that the same thing applies. But I figured I'd ask anyway, to see if anyone had any thoughts.

 

What could possibly be lubricated though the intake tract? Oil lowers the octane rating.

 

, this is the reason why alot of 3.5 guys are installing catch cans on their Maxs. The 3.5s seem to have alot of blow-by so it gets sucked back into the intake with oil and lowers the octaine rating of the mixture, thus making them prone to nasty pinging on the top end (where ignition timing is at its highest, so the last thing you need there is lower octaine gas). This pinging for SOME REASON seems to go away with the oil catch can. So that should speak for itself. At least that is the case with the VQs.

I have one on my 3.0 and for every 3k miles i have about 4-5 tablespoons worth of oil gathered in there. Better in the can than in my intake manifold and back of my valves.

 

fuel help lubricate the top end of the stroke that oil doesnt reach, maybe oil from the top just helps

 

Exactly.



10bits

 

If anything fuel would wash away any oil left on the cylinders. I also contend that oil though the intake tract is not nearly atomized well enough to do anything but settle on the manifold and collect on the back side of the intake valves. Ever see oil caked all up on valve stems with worn out stem seals?

Plus "top end" to ME, means the upper valve train.

The only thing fuel did other than power the engine was to help prevent valve seat wear. But that was when fuel had lead and before aluminum heads featured stainless steel seats.

But I could be wrong.

 

You have got to be kidding.

After the combustible components have burned away, all that is left of any oil that gets into the combustion chamber is carbon and a tar-like residue.

This is the same stuff that causes:
1) hot spots (possibly resulting in pre-ignition)
2) deposits on the valve seats (possibly causing burnt valves as they fail to close fully)
3) loss of compression and scored cylinder walls from rings that have seized in their grooves from burnt oil residue

Here are some pics of a VQ35 with 30K on it that I tore down to rebuild. The reason for the teardown is that it failed a leakdown test miserably (>40%) on all 6 cylinders.





Tell us again why you want to have oil in your combustion chamber.

 

Because it's the cool thing to have .

 

i know what burnt oil does. really. i was just commenting on what he said. i dont think it would be a good idea either, but someone said that some bimmers were designed to burn oil, so i was just saying its to help the lubrication by fuel. we all should know that fuel helps lubricate the top compression ring, maybe they think oil would just lubricate better. i dont agree that it would, it messes EVERYTHING up, not even just inside the engine but the cats, exhaust valves get coated, blah blah... Burning oil also lowers your octane raising the risk of detonation. i dont want oil in my engine (i have a blowby catch can), just saying maybe someone thought it would help lubrication

 

Sorry, you're right. I meant the top of the cylinders.

What my friend was saying was that BMW required high-quality synthetic oil so that it wouldn't burn off as quickly and leave such deposits. Maybe he left out some important design details about the engine...

Either way, as I said, I pretty much figured Nissan isn't doing the same thing because they don't insist on a particular oil in the same way. I take it that agree with the consensus, then? I just figured I'd ask, because I am using high-quality synthetic oil...

 

Catch cans are only needed in cases where the PCV discharges a significant amount of oil. Typically boosted motors. In the case of the VQ the discharge is very limited. Still I would recomend removing it from the intake tract for the reasons described already. I have mine routed with lines down to discharge below the car. Even when running hard the line never has a constant flow coming out of it.

 

On my SR20 there is a stock oil separater/catch that if you switch a couple of lines up it very effeciently allows any blow by to drain into it, and because of internal baffels wont allow the oil to re-enter the IM. Most of you understand this process, because thats the whole point of a catch, but where its alittle different is that instead of oil collecting and having to empty it over time, there is a drain at the bottom that connects directly to the block and puts the oil back where it should be.

I know there have been alot of questions about installs on catch cans and the installation, but has anyone found a way to drain this back to the vq?

 

Actually what you would want is a 100% burn. A partial burn like you are implying will only lead to more gumminess. ie.. partially burnt oil all over the chambers, exhaust manifold, cat etc...

I also can't believe BMW would ever advocate a substance that actually lowers the octane of the gas in their high compression ratio engines.

 

It'd be fairly easy to create a drainback for the catch into the upper oil pan by drilling and tapping a correctly sized hole; basically identical to a turbo drainback. Seriously though, I can't see a need for these on VQ's. The oil that comes out of the PCV is very minimal and thus will not rapidly lower the oil level in the pan. On a motor that was designed with a catch I would expect it to put out a significant amount of oil and require a drainback.

 

I just run a small breather on each side of the valve covers, no pcv no lines.

 

I found my engine idled a little rough when I ran with a breather just on the LH valve cover.

Must be nice to have a "body double" for e-testing.

Did you put the Z IM back on or is that an old pic?

 

I haven't noticed any difference in idling Dave with a breather on both covers. Ya having another car for e-testing saves a lot of work but I understand now that if you have an engine swap you don't have to get it e-tested (considered a hotrod) but I haven't confirmed that for sure.

I have the Z IM back on, just took that pic today, had it on for the race on the weekend and leaving it there until I have proven its not as good as the stock or modified one. I did a bunch of runs on the road with all 3 and compared the times from 3 runs and the Z IM was the best all around except for the initial start in 1st gear in which the stock unmodified IM was best.

Going to an 1/8th mile event this weekend in Shannonville which I think has a $1k purse for street so will be a good chance to see what it will really do

 

According to this you still have to get tested but it is to 1980 standards.

http://www.driveclean.com/help/faq18.html

 

thanks for trying this and sharing.

i have a idea tell me what you think ive already started to work on it but here it is the elbow that unbolts on the back of the 3.5 TB . i want to remove that and in the back bolt a TB right there . so the the butterfly from the TB will literally open into the IM.

I have got the IM ready for its part already, now iam just making the plate that the TB bolts to.

and yes i have fitted it all in my bay and the setup the way iam doing it clears firewall

 

Hmm never though of trying that Kris and not sure what it would do. Be interesting to hear how it goes. Keep us posted and I would like to see a pic of the plate you made.

 

well put

 

Update in case anyone cares:

I spoke tonight with an aquaintance who has a brother with a 1997 E36 M3, which has the same engine as in the original post. That car apparently does not consume a drop of oil despite being driven pretty hard, and it's running sweetly. So unless this is somehow a freak car, I guess that does it for my friend's theory.

 

definitely kills the theory, not only does it not burn oil, but he knows it wasnt designed to burn oil...