im thinking about trying this crankcase evacuation set up from summit http://store.summitracing.com/partde...5&autoview=sku
i wanna run the evac tube to the top of a vented catch can, replacing the vent with the tube, and runnin lines from the filler tube and intermediet housing to the catch can, and mabe run the fuel vent line to it also. has anyone tried this on a rotary before?

 

Well, if you have valve covers, it might work, lol. All you really need to do is run a vac source to the crankcase/sump.

 

Not that I know of. I guess you could make it work. I dont think Id vent the fuel tank to the ultra hot header though.

 

There are times when simplicity works better than ...

 

well i dont really have much for a vac source since im runnin the rb dellorto intake, it only has one vac nipple for the brake booster, and i have no emissions. i dont plan on using the valve cover breathers, just attach the evac tube the top of the catch can. and i was jus plannin on welding the nipple to my rb header

 

You can tap the intake for another vac source. Without some sort of vacuum, the crankcase/sump won't get the vapors pulled out of it, unless you have a lot of blowby past the oil control rings.

Most of the aftermarket intakes I've seen have 2 vac sources, one for the booster, then another that takes a 1/8" NPT nipple. I have one intake that has a plug in the smaller one, I'll be damned if I can get that allen plug out.

If nothing else, tee into the brake booster line, though I don't recommend it if it's going to be pulling a lot of fuel and oil vapors. I don't know what the long term effects on the booster might be.

 

yea i planned on drilling and tapping antoher line fore the vac advance on the dizzy. i just dont really want to run a pvc system, the evac system creates a vacume, im pretty sure thats how it woks

 

I don't think that Mr Gasket system pulls any vacuum at all. It is the same type of system piston engines had before emmisions, only the vent tube went down to the bottom of the engine bay and was open to the atmosphere. If you're tapping for the dizzy, make 2 taps while you're at it.

 

those vent tubes are meant to be welded in the exhaust manafold. and yes it does create a vacuum. it wouldnt have a one way check valve otherwise. it should make more vacuum than the intake would. ive seen them used before, just not in a rotary application. these accually create a negative crank case pressure, on piston engines this makes the rings last longer, and theres less intake charge contamination. i dont know if its the same for a rotary. thats why i was seeing if anyone uses it

 

Interesting, I didn't look very closely as to how it does work. From your explaination, I don't see any reason why it shouldn't, as long as there is a one way check valve for our more than common backfires in the exhaust system. Fwiw, it works on the Bernouli principle to create a low pressure area around the tube inserted into the exhaust.

 

yea i guess i jus hafta see for myself how well it works. im not sure if a negative crankcase pressure has any ill effects on a wankel. and if there is indeed less intake charge contamination i should pick up some low end. ill post pics when the project is done, hopefully before x mas

 

I just ran a vac line from the nipple on the filler tube to the base of the carb. No more lung mustard, and no apparent issues with this...

 

The best way to eliminate capuccino is to get a cheap (Fram etc) PCV valve from the auto parts store, hook it inline between the oil filler tube and the intake manifold. Preferebly on the primary side (save the secondary side for your brake booster).

Plumb it inline and be sure to install in the correct direction. One with two nipples or one that I found which is number 333 (can't recall the letters) that has a nipple on one side and a 1/8" NPT threaded end on the other. I believe the nipple is 5/16" and the other end can accept a 3/8" hose if you use a hose clamp or something to secure it.

I can't recommend installing the PCV valve's threaded end into a convenient NPT hole in your manifold because I honestly don't remember which way the internal valve flows. From what I remember of doing mybro's RX-4 SC project, its valve was backwards. Knowing that that possiblity existed, I chose number 333 because both ends were virtually the same size and I knew it would be compatible with the breather hoses in whichever direction it worked correctly.

I think I remember now. I blew some compressed air through it and found that it flowed opposite a Mazda PCV valve from the '70s. Therefore the nipple end faced the carb and the threaded end faced the oil tube. I hooke dit up that way and it did not affect idle or direveability at all. The capuccino never returned.

Here is a pic.


By the way, the other small nipple type fitting on the intermediate plate below the oil filler tube must receive a supply of fresh filtered air for this PCV system to function correctly. I plumbed it into the air cleaner assembly.

It's funny. The first 15 minute drive with the SC resulted in lots of water up under the cap. Not long at all, and it built up quite a bit. Imagine how many short trips you do, and how much it builds up without you even knowing. I'm glad I did this, and so will you.

 

There are pictures in this thread:
https://www.rx7club.com/showthread.p...1&page=2&pp=15

of my solution to the lung mustard problem...similar to Jeff20B's.

Rich

 

yea ive seen that set up a few times. i was just thinking of an alternative. goin for a cleaner look. im going to try it on my fc and my friends fb. should be fine. is it ok to hook up both the filler neck vent and the intermiediat housing vent to a vacuume source?

 

No because no air will move. Fresh air must enter the engine through the intermediate plate and exit through the filler tube. The air enters, turns downward and pulls oil vapors down to the pan. The air then changes direction upward toward the dipstick and oil filler tube area. Since steam rises, it makes sense to vent it this way as the filler tube nipple is higher than the intermediate nipple. It's also a lot cooler which allows condensation to form if you don't have something sucking on it.

 

Jeff20B,I was wondering,with it hooked up like this,Under low vacuum conditions like WOT the crankcase wont really get THAT much evacuation,so isn't almost better to have the filler neck evacuated from the suction of the intake above the carb so it does NOT affect idle mixtures to compensate for evacuating the crankcase with a vacuum source? I have removed rat's nest's before on other FB,series2 but this time my purge deal doesn't seem to be working right,so I'm trying to go the PCV route and am a little confused,I searched a ****-LOAD.

 

Or does the PCV hold the vacuum so that you DONT have to compensate for it,the thread leads me to believe that but doesn't specify if it holds it...I really feel like a retard for asking this, but hey,I'd rather ask stupid questions than have stupid problems.

 

The PCV valve does sort of hold a vacuum. It had a one way valve. I don't know exactly how it works but I do know rotaries have a lot of reversion in the form of reverse pulsations or spikes if you will, which get blocked by the one way valve.

The correct way to hook up a PCV valve to a rotary is to plumb it into both primary runners through small holes, Y them together and connect to a PCV valve. The other end is connected to the oil filler tube, as mentioned earlier. Be sure to hook the nipple from the intermediate plate up to the air flilter or some other source of fresh air.

If you were to look into the PCV hole of a '79 or older manifold, you'd see two small holes; each leading to a primary runner. You can use this to get clues for how to hook up a PCV system on an FB manifold.

 

I guess I am just trying to avoid putting my crankcase under vacuum...but if it were under vacuum and had the fresh air inlet it wouldn't be enough to be "harmful" and I am not really sure if that is possible in the first place,someone was quite certain that it was a bad idea to have the crankcase under vacuum,he was in an argument with silver rocket(member).

 

I don't know on a rotary but on a piston engine the crankcase NEEDS to be in VACUUM or negative pressure or what ever term you want to use. I would think the benefit would be the same for the rotary.Easier for the internal engine parts to spin since there is NO friction from the air and oil vapor congragating in the crank case. I don't know about on a rotary though. I've not gotten this far in my research. This is the second time it came up in two days so probably time to figure it out.

For the guy asking about turbo applications I can tell you how to do it right on a piston engine but on this beast I'm not sure yet. If this helps here's the explanation for a piston engine. It is very commonly done wrong. A Mitcubishi 4G63 is a good example of how to do it wrong as most guys have the stock pcv hose intercepted by a catch can. Bad bad idea. On the valve cover you have to access points to the crankcase. One is where the PCV screws into the valve cover so that one is pretty much spoken for. You leave that stock with the stock hose for vacuum from the intake manifold. This works under all vacuum situations like stock. The oil seperator in the valve cover is plenty to seperate the oil under vacuum. Now remembering we have a second port on the side of the valve cover we need to hook the catch can up to this. One side from the valve cover to the can. Lots of people stop here and let the crank case vent to atmosphere. Bad idea you have NO suction on the crankcase just the slightly less pressurized regular atmosphere which will let the pressure seep out. So far this is just like putting a tiny filter on the valve cover or a hose to the back frame rail or nothing on the fitting at all. the only difference is at least your catching the oil in a can. So now we need for this think to work under boost since once the motor boosts up you will have positive pressure in the crank case. But without the case being in a state of negative pressure you get all kinds of issues. Oil pan gasket failures, crank rods and pistons fightingoil vapor and fuel vapor in a positively charged crank case. To fix this you take the other hose from the catch can and hook it up to the intake that is the intake to the compressor of the turbocharger. So when the turbo is making boost it is obviously a vacuum on the inlet right? of course. So what you end up with is vacuum on the can from the turbo that is sucking the pressure out of the crank case that it put in there in the first place. Basically you are using the turbo to clean up it's own mess. Also important to note this can only be accomplished by using a sealed catch can type for this type of situation. The oil vapor can't get into the turbo to de-octane the fuel if you set this up appropriately. The can should have baffels for higher boost applications and it's size should change with boost pressure too. As once there is so much pressure in the case it gets harder and harder to remove.

Now apply this to a rotary and you have it. I will try to look into the rotary's pcv today and see if I can give you a real answer for the turbo guys. I'll need to eventually figure out how I'm going to do my NA motor as well for a slightly cleaner clean up of the case emissions. Stock stuff works perfectly fine but is not the best way to clean it up and keep oil vapor out of the intake charge which like I said deoctanes the fuel and causes you to miss out on HP sometimes. HP is a good thing so I like to have as much for free or as little as possible. (Money wise)

 

it really doesn't put the crankcase under vacuum, it's not a closed system. the pvc reduces the amount of vacuum from the source to a very small amount, barely enough to feel with ur finger. i don't remember the valve i used but it's from one of those threads on the subject. i'm running the RB holley intake so i just T'd it off the supply to the booster, no drilling another hole. ran it to the nipple on the center housing, then ran a hose from the nipple on the fill tube to the clean air side of the air cleaner. totally eliminated the problem.

 

you guys make life too complicated.

 

Quote:"it really doesn't put the crankcase under vacuum, it's not a closed system. the pvc reduces the amount of vacuum from the source to a very small amount, barely enough to feel with ur finger". posted by rxtasy3.

That's what I wanted to hear,Thank You very much!

 

PCV Valve from a 90 Dodge Caravan here.