Catch can recirculated to intake on LoveFab turbo kit

I've decided to abandon the idea of circulating the engine fumes back to the intake.
Following my latest track outing at 35°C ( http://www.nsxprime.com/forum/showt...ute-Saintonge-in-France?p=1907510#post1907510 ), the engine had some difficulties to hold it's idle due I suppose to oil fouling the plugs?
I will now try to use the exhaust as a vacuum source.
To do so I purchased an EVAC Scavenger kit from Vibrant Performance.
I wonder where to weld the bung for best efficiency?
It must be where the exhaust gasses are at the highest velocity I suppose?

I found a great article on crankcase ventilation that's definitely worth reading.
http://forum.diyefi.org/viewtopic.php?f=24&t=357
It's the first time I see a good explanation on the PCV valve operation.
According to this article, I should leave the PCV valve connected to the front valve cover intact and pull the vapors through an AOS connected to the rear valve cover?
Why not?
In another article, they simply air the output of the AOS to atmosphere through a tube routed underneath the car...
Sorry it's in French but the drawings are self explanatory.
http://www.oreca-store.com/tutoriels/comment-monter-un-decanteur-dhuile
I wonder how the Nissan GTR's ventilate their crankcases?

The GTRs circulate it back into the motor in most kits, but the kit that has data backing it up, and seems to work very well is the Buschur Racing's kit. Simple in design, but has shown to be very effective.

jones83 said:

The GTRs circulate it back into the motor in most kits, but the kit that has data backing it up, and seems to work very well is the Buschur Racing's kit. Simple in design, but has shown to be very effective.

Click to expand...

So in fact the GTR's recirculate the engine vapors back to the inlet just like the OEM NSX.
With this kit the operation is no more in closed loop due to the small air filter on top of the AOS...
The smell in the engine bay must be pretty bad after a track day!
I now believe that for track days it's a bad idea to try to recirculate the vapors to the inlet at least with a wet sump type engine.
No wonder the Porsche Cayman's and GT3's run with a dry sump!
Why hasn't anyone proposed a kit for the NSX?
I did find this old thread: http://www.nsxprime.com/forum/showthread.php/157869-Dry-Sump-for-NSX-(C30A)/page2

The dry sump is always the way to go. I would run one right now if there was a way to keep A/C with it on the NSX.

You have to be careful with the GTRs because there are some that run dry sumps also. The non extreme ones run a vented AOS for the most part.

jones83 said:

The dry sump is always the way to go. I would run one right now if there was a way to keep A/C with it on the NSX.

You have to be careful with the GTRs because there are some that run dry sumps also. The non extreme ones run a vented AOS for the most part.

Click to expand...

I believe [MENTION=4745]Mark911[/MENTION] had developped a dry sump prototype that kept the AC pump in place?
http://www.mscperformance.com/OilPan1.html

Dry sump always sounds cool, but it is not always the best way to go. This is from someone who has spent the engineering time and $ to make/install it on an NSX. Mine removes the A/C compressor.

As my engine seems to have proven itself reliable so far, I am going to remove the dry sump and go back to a modified OEM. Why? I don't feel comfortable with the scavenger pump drive belt reliability on a street-driven car. Debris concerns me, and this is one of the lowest parts on the car. Race cars have been known to occasionally throw those belts.

Also, IIRC, Marks car (linked above) burned down due to an oil fire. You add a lot of fittings, hoses, etc with a dry sump setup. I have aluminum spray shields located in strategic sources to protect potential oil spray from hot exhaust components, but I still haven't installed my aqueous foam fire system yet. That's still on the to-do list....

Finally, you also need provisions for an oil cooler(s). Obviously, the dry sump setup completely eliminates the OEM heater/cooler. On startup, the oil temps lag the coolant temps. I like to get my oil temps to 180F+ ASAP when driving to help reduce water condensing in the oil. As I transition back to the street and taking shorter trips, this is a concern for me to help extend engine oil life (and reduce engine startup wear).

Just a few reasons (other than cost obviously) to not do dry sump.

CB72: I'm still amazed you have that much blowby. Like you mentioned, add the exhaust-driven suction tube in the smallest diameter exhaust pipe, as long as it is downstream of the catalytic convertors.

Sorry to bump the thread - has anyone figured out a conclusive way of reducing catch can fume smell on the turbo setups?

Thanks,
Ravi

I believe I got the problem solved by letting the fumes escape through an open hose that runs from the AOS to the bottom of the engine.
After parking the car there isn't a drop of oil coming out of the hose.

CB72 said:

I believe I got the problem solved by letting the fumes escape through an open hose that runs from the AOS to the bottom of the engine.
After parking the car there isn't a drop of oil coming out of the hose.

Click to expand...

That is what I am currently doing. I have the Lovefab catch can. Both valve covers flow to the can then i have a long hose with a filer that runs down to the bottom of the engine. When i get off the car a lot of fumes come out of that filter so it gives the impression that the car smokes. Im debating on running that said hose to the in take or the exhaust. After reading this thread im not sure what to do.

runnin9z said:

That is what I am currently doing. I have the Lovefab catch can. Both valve covers flow to the can then i have a long hose with a filer that runs down to the bottom of the engine. When i get off the car a lot of fumes come out of that filter so it gives the impression that the car smokes. Im debating on running that said hose to the in take or the exhaust. After reading this thread im not sure what to do.

Click to expand...

In fact, I discovered what the real issue is all about since I posted here.
The setup is the following
- A Moroso AOS for the front cylinder bank with an output to atmosphere low down the car
- A simple catch can for the rear cylinder bank with a small air filter sitting on top of it.

During normal public road driving, there is no issue whatsover.
No smoke, almost no smell and no drops under the engine when the car is parked.

On the track, no issue with the front cylinder AOS that will fill very slowly with a combination of water, gas and oil and still no oil under the car.
For the rear cylinder bank the catch can is filled with oil after maybe 20 minutes.
This issue was documented many years ago by Dal motorsport Racing.
It is due to the vast amount of oil required by the VTEC operation that fills the cam cover before flowing into the breather tube during hard right corners.
Apparently Honda was aware of the issue and modified the cam covers in their later models?
A simple solution would be to modify the pick up point for the breather tube by fitting it for instance in the middle of the cam cover instead than on it's side.
I haven't tried this yet as I'm waiting for [MENTION=25737]Kaz-kzukNA1[/MENTION]'s advice on the subject.

CB72 said:

It is due to the vast amount of oil required by the VTEC operation that fills the cam cover before flowing into the breather tube during hard right corners.
Apparently Honda was aware of the issue and modified the cam covers in their later models?
A simple solution would be to modify the pick up point for the breather tube by fitting it for instance in the middle of the cam cover instead than on it's side.
I haven't tried this yet as I'm waiting for [MENTION=25737]Kaz-kzukNA1[/MENTION]'s advice on the subject.

Click to expand...

That will fix it. I have a '92 C30 and that's what I did on my rear valve cover when I had it apart for an engine rebuild. I cut and plugged the OEM nipple on the side, and then made a hole as pictured below. Under the rear valve cover, I also modified the air/oil separator holes by welding a plate to block the lower holes (except a few small ones to allow drainage), and then making new holes up higher.

I wish I had taken more pictures of all the things I've changed. I only took the picture below to remember the difference in chemically passivating the magnesium valve covers (the yellow-tinted rear bank valve cover was the passivated one).

View attachment 145303

Mac Attack said:

That will fix it. I have a '92 C30 and that's what I did on my rear valve cover when I had it apart for an engine rebuild. I cut and plugged the OEM nipple on the side, and then made a hole as pictured below. Under the rear valve cover, I also modified the air/oil separator holes by welding a plate to block the lower holes (except a few small ones to allow drainage), and then making new holes up higher.

I wish I had taken more pictures of all the things I've changed. I only took the picture below to remember the difference in chemically passivating the magnesium valve covers (the yellow-tinted rear bank valve cover was the passivated one).

View attachment 145303

Click to expand...

I would be scared to weld anything on the magnesium cam cover for sure!
Can't one just screw an AN type fitting in the right place?
Or what about just extending the current breather tube inside the cam cover so that the pick up point sits right in it's middle?

The fitting wasn't welded. The air/oil separator plate under the valve cover was welded. That's steel.

If you look underneath the valve cover and remove the air/oil separator, you will see why you don't want to simply extend the tube over. It's better to move the breather up higher. I guess you could extend the tube, but also put a 90 degree bend at the end of it such that it takes suction/supply from higher in the cover.

When I built my engine, I had heard about a lot of issues with people not having adequate venting capability from the valve covers. While the covers were off for my rebuild, I wanted to go ahead and modify them once and for all. In hindsight, I didn't need the 10AN AN fittings on each cover as my engine appears to have very little blowby.

CB72 said:

In fact, I discovered what the real issue is all about since I posted here.
The setup is the following
- A Moroso AOS for the front cylinder bank with an output to atmosphere low down the car
- A simple catch can for the rear cylinder bank with a small air filter sitting on top of it.

During normal public road driving, there is no issue whatsover.
No smoke, almost no smell and no drops under the engine when the car is parked.

On the track, no issue with the front cylinder AOS that will fill very slowly with a combination of water, gas and oil and still no oil under the car.
For the rear cylinder bank the catch can is filled with oil after maybe 20 minutes.
This issue was documented many years ago by Dal motorsport Racing.
It is due to the vast amount of oil required by the VTEC operation that fills the cam cover before flowing into the breather tube during hard right corners.
Apparently Honda was aware of the issue and modified the cam covers in their later models?
A simple solution would be to modify the pick up point for the breather tube by fitting it for instance in the middle of the cam cover instead than on it's side.
I haven't tried this yet as I'm waiting for [MENTION=25737]Kaz-kzukNA1[/MENTION]'s advice on the subject.

Click to expand...

Hum interesting. I have both my front and back run to the lovefab catch can and I just recently removed the PCV valve off of the rear. I did some hard driving this weekend so I am curious as to what is in the can.

I modified the catch can circuit for the rear cylinder bank.
Instead of having the catch can on the left hand side of the car, I moved it to the right side next to the alternator.
The idea beeing that the long hose going from the rear valve cover will no longer fill up with oil in hard right hand corners.
I can't show a picture as it seems that photobucket has changed it's policy towards 3rd party hosting...

You can upload pictures directly to NSXPrime as attachments if you want. On the 'Advanced Reply,' scroll down to 'Attachments' and click on 'Manage Attachments.'

I found a picture of the underside of my rear valve cover. You can see the new hole for the vent next to the old OEM tube that I plugged later.

View attachment 145899

I don't believe that the rear head fills up with oil during sustained VTEC. The volume required to do so would deplete the oil pan reservoir and destroy the engine. Under normal driving with engine vacuum, the rear bank is the suction supply for the PCV system. At WOT, there is little-to-no vacuum, and the system switches to pure venting from the front and rear valve covers to the intake (OEM). You now have a few more oily vapors accumulating above the OEM rear valve cover air/oil separator that condense on the relatively cooler valve cover and puddle up along the bottom of the air/oil separator plate (not pictured above). For right-hand sweepers, this either blows and/or centrifugally pushes the condensed oily mixture to your OEM intake or to a catch can.

You can fix it by relocating the vent like I did, and also by placing a more efficient air/oil separator between this rear valve cover line and the OEM intake if you want to keep your engine oil clean and protect the environment.

On a race car I would vent directly to the atmosphere from a top-mounted vent.

I placed my rear vent symmetrically to the front vent, mainly for aesthetics. It shouldn't matter whether you place it near the drivers side or passenger side.

Here's another picture, but it's hard to see the two AN10 vents:

View attachment 145900

It's a dream to see an engine like yours!
If I understand it correctly, there is a metal plate that bolts under the cam cover that comes almost flush with the OEM breather tube.
The oil accumulated on this plate will go straight into the breather tube during hard right corners.
I suppose that one could use the same type of rubber fitting for the rear cam cover as the one used on the front valve cover?
Not as nice as AN 10 for sure but probably good enough.
Strange that no one has been concerned with this issue before us?
I suppose very few people look inside their throttle body otherwise they would be worried by the amount of oil it contains...
Many thanks to you!

I almost cried when I saw how clean that engine and transmission were [MENTION=12356]Mac Attack[/MENTION]. I just cleaned my transmission since it's out for clutch replacement and it's still miles from what you pictured.

CB72 said:

It's a dream to see an engine like yours!
If I understand it correctly, there is a metal plate that bolts under the cam cover that comes almost flush with the OEM breather tube.
The oil accumulated on this plate will go straight into the breather tube during hard right corners.
I suppose that one could use the same type of rubber fitting for the rear cam cover as the one used on the front valve cover?
Not as nice as AN 10 for sure but probably good enough.
Strange that no one has been concerned with this issue before us?
I suppose very few people look inside their throttle body otherwise they would be worried by the amount of oil it contains...
Many thanks to you!

Click to expand...

Correct. There are (13) bolts as shown in my first picture where the simple air/oil separator plate bolts onto. Any oil/water vapor condensation can puddle up there where the vent tube sits and can get sucked into the intake or your aftermarket catch can during sweeping right-hand turns.

Sure, a rubber fitting like the OEM front valve cover would work fine. I also liked your idea about just modifying the tube inside the cover to extend it at a 90 degree angle to a higher spot. Then you don't need to make a new hole in the valve cover. Very simple and clever! :smile:

DAL Motorsports had this issue many many years ago and documented it on their website. The website has been gone for a long time, I think someone mirrored it but that's gone too. I think DAL either made a new vent on their valvecover, or changed valvecovers to the 97+ year.

jwmelvin said:

I almost cried when I saw how clean that engine and transmission were [MENTION=12356]Mac Attack[/MENTION]. I just cleaned my transmission since it's out for clutch replacement and it's still miles from what you pictured.

Click to expand...

Thanks for the compliments gentlemen! What I'm most proud of though is on the inside with how it was built.

Rewelded and reshaped combustion chambers, dimpled ceramic-coated pistons, DLC-coated piston wrist pins, modified OEM titanium rods, custom rod bearings, every edge radiused to reduce stress risers(crankshaft, etc), polished internals, etc.

If this engine dies I will just convert the car to electric to putter around town in.

Mac Attack said:

DAL Motorsports had this issue many many years ago and documented it on their website. The website has been gone for a long time, I think someone mirrored it but that's gone too. I think DAL either made a new vent on their valvecover, or changed valvecovers to the 97+ year.

Click to expand...

Luckily, I printed a copy of DAL's documentation.
Their solution was to route the rear cylinder breather tube to the front cylinder valve cover.
That fixed the issue according to them.
I personally prefer your solution (or mine) to keep oil out of the breather tube at all times to avoid pressurizing the engine gaskets.
Talking about electric motors, I was taken for a ride in the new NSX at the F1 circuit at Spa in Belgium.
A very nice car for sure but no faster than my 7.5 psi LoveFab...
I wonder who will be able to maintain these cars in 20 years time?
Not to mention that there will be no one left to build an engine like yours anymore.

Mac Attack said:

DAL Motorsports had this issue many many years ago and documented it on their website. The website has been gone for a long time, I think someone mirrored it but that's gone too. I think DAL either made a new vent on their valvecover, or changed valvecovers to the 97+ year.

Click to expand...

The wonderful Wayback Machine has an archive of the NSX Info page from DAL Motorports.

Early design





Later spec





I'll just put these here for CB72.
The description is when at idle rpm (vacuum pulling blowby) and not at high rpm (positive pressure at both heads).

Please note not only the changes in routing but also the position of the fitting at the rear bank.
Although the feature is different, from the blowby at high rpm point of view, the early model (black cover) had its port at the side and the later one placed it at the top.

If using early model cover and if your NSX is for track day only, I would even remove the PCV valve and block out the suction pipe at the intake manifold.
Connect the hoses from both the front and the rear bank to the catch can and if your local regulation doesn't allow you venting the remaining gas in the air, connect the 3rd hose to the rubber accordion port before the TH body.
There will be no more PCV so you will be forced to change eng oil at much earlier stage but for track day car, should not be a problem.

For mainly street driving car, the benefit of PCV system exceeds the prevention of blowby getting back into the engine so this modification is not required.


Kaz

Great idea on the pictures Kaz, thanks.

It's interesting the engineers didn't place the insulation on the blowby line for the later spec. I guess there is sufficient slope to prevent condensation from accumulating like the early design.

Kaz-kzukNA1 said:

If using early model cover and if your NSX is for track day only, I would even remove the PCV valve and block out the suction pipe at the intake manifold.
Connect the hoses from both the front and the rear bank to the catch can and if your local regulation doesn't allow you venting the remaining gas in the air, connect the 3rd hose to the rubber accordion port before the TH body.
There will be no more PCV so you will be forced to change eng oil at much earlier stage but for track day car, should not be a problem.

Click to expand...

For those with FI, make sure you place this 3rd hose before the turbo or supercharger!