Topic: Crank Case Venting Options?

[Don R]

 I'd be reluctant to feed crankcase fumes into an air box on a race bike, oil vapor or mist sucked into the intake may cause detonation. The exhaust fitting seems like a good solution, weight and simplicity wise. I'd be curious to see how much crankcase vac could be produced, obviously there won't be as much at idle.
  Anything that would improve the scavenge pump would be a plus, such as blueprinting and new seals. I think hondaman covered that in his book.
  It's really difficult to imagine what's going on inside the crankcase at rpm but any reduction of crankcase pressure allows the oil to fall out of the windage easier and be returned by the pump. We've seen huge differences in oil control between two different moroso pan designs. We had one with mesh screens and always saw an oil light after a 1/4 mile run, the new one has the same scraper and pan shape but different baffles with louvers and we never get an oil pressure light in the shutdown now. We also use a moroso billet aluminum wet sump pump.

[slikwilli420]

We have run the exhaust style vacuum fittings on our race car. They do work, Star racing pioneered the use of vacuum pumps on their drag bikes and the Star vacuum pumps are popular with car racers also. We run a belt drive Moroso 4 vane improved vac pump on our drag car. It's worth 30 hp on a 1,000 hp engine. We use a relief valve and limit vacuum to 7 inches at idle. Ring stability is a plus with a vacuum pump on a big engine but on such a small bore I don't know if ring flutter is as much of an issue.
 Our vacuum relief valve is currently on a valve cover but I think it is better to put it just ahead of the pump so you aren't pulling outside air through the engine. With an exhaust vacuum powered setup or possibly the electric smog pump a relief isn't needed.

Don, I am thinking the exhaust vac plus a one way valve to keep from filling the crank case with exhaust is a worthwhile thing to try. With this setup, would the rest of the engine be sealed up? That would mean sealing the starter plug hole and cam breather in my case.

[Don R]

 Yes, but I would pull from the cam breather, it's well baffled and less chance of sucking the oil out of it which can be a real concern. Also the engine needs good seals and gaskets, any leak will defeat the suction. A V8 with vac pump and a leaky gasket will suck oil like crazy. I'd assume the oil tank will still need a catch tank. I've seen some nice ones on ebay for under $20.

[slikwilli420]

My plan now is to have an overflow tank for the oil tank above the tank near the back of the bike with vent to atmosphere and a return to the oil tank.

The crank case vents (cam cover, case and clutch) will meet in the starter box where a fourth vent from the starter hole will hold the box in place. With all lines going on the top and a baffle between them and the outlet wick leads to the valve and exhaust fitting. Now gases will have to meet the box and get some form of oil separation before leaving the box toward the exhaust. Now I have satisfied the catch can requirements of AHRMA for the crank case and oil tank as well as getting at a minimum, decreased crank case pressure.

[gschuld]

Something like like this...?

George

[slikwilli420]

Something like like this...?

George

Very much the same. I cannot get enough of that Rickman. Got a chance to see the bike and meet Jeff at mid Ohio years ago.

[POPS 911]

On the electric pump we use it's own 18v battery = same battery you use in a 18v battery hand drill per [ Pizza John National NHRA Champ ] who had many years in PS Drag bikes. Star builds a great vacuum pump $$$$$$$$$ but it works.

[scottly]

Here's an interesting read on the subject; note that the test engine used gas-ported pistons and low drag rings, which would make a evacuation system more beneficial than with standard rings and pistons. The Moroso pump was only worth about a 1% gain, and the exhaust siphon was less than 1%.
http://www.hotrod.com/articles/ccrp-9903-moroso-vacuum-pump-test/

[754]

 You mean Pizza John Mafaro....if my memory still works ?
Slik, you will have a nicer oil bucket than the Rik..
That lower fairing mount by the sprocket, dirt simple, yet SO Elegant....Well Done..

[simon#42]

Here's an interesting read on the subject; note that the test engine used gas-ported pistons and low drag rings, which would make a evacuation system more beneficial than with standard rings and pistons. The Moroso pump was only worth about a 1% gain, and the exhaust siphon was less than 1%.
http://www.hotrod.com/articles/ccrp-9903-moroso-vacuum-pump-test/

you can get a 1% variation in power running the same engine twice on the same dyno

[Don R]

 I think anyone running alcohol would see the biggest benefit since they tend to have a lot of moisture to deal with. These things suck the milk right out of the oil.
 I'd agree on a small bore engine the weight of the equipment might outweigh any benefit. That said, we top out our 567" under 8K rpm maybe in the higher rev ranges there is more to gain. one of the things I like is I can see the engine condition at a glance. It the vac. is under 7 at idle I know we have a leaky gasket or a ring problem.

  So I'm not going to write mine off on the basis of one dyno test. Day in day out there are benefits beyond the 20-30 hp we might make using it. The oil is cleaner with less moisture in humid weather, it returns to the pan easier and quicker, the outside of the motor and nearby chassis stays cleaner with less grit stuck to it. If the rings are more stable the cylinder seal may last longer, If there is less windage in the rotating assembly a loose chip or needle bearing in the motor might have a better chance to make it to the magnet in the pan also, and yes that has been an issue at least twice in 10 seasons racing this big old lump.
 

[NitroHunter]

Many years ago one of my pals decided to build an exhaust syphon crankcase scavenging system into his nitro funnycar motor. He ditched the zoomies and built a set of 4-1 headers that ran under the length of the car, tapped into the collector, and took suction at the valve cover breathers.  Boy, did it work; he sucked every drop of oil right out of the motor and blew it out the pipes, onto the track behind him in a blaze of flaming 60wt. One run and done. When the oil pressure hit zero it threw the rods out, but the good news is there wasn't 12 quarts of burning oil under the body causing a fire there... 
FYI all modern nitro funnycars run a dry sump oil system with a windage tray, the dragsters are wet sump deep pans also with a windage tray. I was involved with one car running a 4-stage oil scavenge pump that appeared to show promise - on occasion.
We know there is always positive pressure in the oil pan, it is monitored, and there is an ignition kill switch that shuts the motor off in the event 15psi is registered, ie, a burnt piston, but that is primarily to keep oil off the race track.
In these motors it is fairly typical for the top compression rings to be a Dykes 'L' shaped where the astronomical pressure of combustion gas can get behind and force them against the cylinder walls.
While a 1% performance gain may seem small, I know of at least one professional Top Fuel team that places such a high value on their piston rings sealing that between-run maintenance includes replacing all 8 sleeves. BRAND NEW SLEEVES EVERY SINGLE RUN. PERIOD. They are also pitching the rings every run as well, so every fresh rack of slugs has only new rings in those new sleeves. 

[Don R]

 That's amazing Nitrohunter. I wonder how the headers would have worked without the vent?

  One of the alcohol funnycars we front halved leaked oil from the lower frame tubes on the right side. When we dissected it there was an 1/8" welders vent hole drilled from the top tube into an upright and another from the upright into the lower frame tube. The upper frame tube connects the engine vent to the puke tank in the rear, so on every pass it pumped oil into the upright and then it seeped out almost forever. Lol.
 The owner was most pleased to have that fixed. No more constant drip catching pan,  brakeclean flushing or corks and silicone in the lower frame. Oil control is a big part of crankcase venting.
  What's amazing is you can blow into the crankcase and find a gasket leak. I told a guy at the track to try it and he was sure I'd record it and put it on facebook. I had to walk away before he tried it and when he did, he found the distributor gasket leaking, that allowed air into the motor and let it suck oil into the vacuum pump filling two puke tanks.

[crazypj]

Are you talking about magic windows in the upper case between cylinder pairs? Already planning on that based on comments from Captain in Bill's thread.

 What it is and looks like........

 Captain

Don't tey get covered up by the spigots when block is fitted? I've looked at a lot of motors where cutting holes would only give a weight reduction and do nothing for internal air flow (and the weight loss is only an ounce or two total)

[slikwilli420]

Are you talking about magic windows in the upper case between cylinder pairs? Already planning on that based on comments from Captain in Bill's thread.

 What it is and looks like........

 Captain

Don't tey get covered up by the spigots when block is fitted? I've looked at a lot of motors where cutting holes would only give a weight reduction and do nothing for internal air flow (and the weight loss is only an ounce or two total)

You have to notch the sleeves as well. It's a known performance advantage by allowing the air to move more freely under cylinder pairs.

[crazypj]

I researched it around 2004~6.
With a big bore and stock liners there is a good chance a resonant frequency will cause spigots to 'fall off' where they exit block. It can happen even with full circle if liner gets thin enough. Your also removing support from main bearings by cutting windows

[bear]

I haven't had either of those issues with any of my SOHC motors.
But the top of the curve for my units is 9'500 RPM.

Having said that, I have a mate that runs an 836 up to 14K with "pressure balancing" and I can't remember him complaining of any issues re: sleeves.

Doesn't mean it can't happen though I suppose.
 

Cheers,
Brian

[slikwilli420]

I'm with bear. Racers far more in the know than I swear by the modification. Regarding weakening the main bearings, I am nowhere near close enough to have any effect on that part of the system.

[crazypj]

Interesting, glad to know a few people have had good luck with it. Any idea what crank balance factor is on 14k motor? (I'm assuming rotating mass was dynamically balanced to use with different rods and pistons?) My 550 with 750 pistons often 'saw' 13,500rpm but it was 'mostly stock' 

[bear]

There is no "balance factor" as such with these motors.
It's two up, two down re; rotating mass.

[crazypj]

Yep, but if you fit substantially lighter or heavier pistons you change where vibration occurs plus the 'rocking couple' (due to crank length) changes. You get resonant vibration somewhere factory engineers never expected it. Some bikes are prone to annoying but non destructive resonance (Suzuki instrument clusters vibrating go 'WHOOO, CBR windshields go ZIZZZ, etc) Main issue inside several Honda motors seems to be cam chain saws its way through cylinder without breaking tensioners or rocker arms 'chatter'
I'm not an engineer but I do have 45+ yrs experience of 'autopsy's' on broken motors (luckily, mainly other people's  )

[bear]

While we are establishing our credentials,  Im just a broken down racer that's had to patch #$%* up that I've managed to brake over 35 years of utter stupidity. 
Not that I'd change that for the world.
And I certainly don't want to get into a pissing competition. ( we're both bike blokes after all)

So I'll try to pass on what I was taught by an old bloke (now past) that would craft a replacment crank for me when I'd turn up cap in hand at his suburban home in Melbourne,  long after he'd told the rest of the world that he was "retired".

What you have just described is essentially Static Balancing. A "balance factor" is just a calculation used to come up with a starting point for the weights on a non symmetrical crank such as a parallel twin or a 90deg V8.

A quote from Bill,
"A good crank is not a product of engineering,  it's a work of art."

Cheers,
Brian

[crazypj]

Hi Bryan / bear,
yep, racers always want to win, it kinda sucks sometimes when trying to get a point across. 
Theoretical static balance factors often don't work well in practice and a good crank is always a 'work of art' even when it looks like #$%*e 
I started out on single cylinder motors as it's MUCH cheaper to screw up one of everything rather than 2 ,3 or 4
On a single, static balance can have major effect on running vibration at various rpm, the same applies to a lesser extent on 4 cyl motors but 'rocking couple' is often magnified due to extra crank length with component variations giving some weird vibration characteristics.
 Twin cylinder motors can have worst of both worlds, particularly Japanese motors with 4 main bearings making a twin as wide as a 3 cyl (and heavy as a plain bearing 4 with the built up crank) XS650 crank is about 35 lbs with rods, bearings, etc. a CB350 twin crank almost the same weight

[larry hayes]

its a dry sump engine no need to use pcv or pump !!! vacs it self have burned holes in pistons only have a few drops of oil in puke can