Crankcase Evacuation System on Stock Engine

[FC-Pilot]

I'm getting ready to add this to my street car. Have a few customers that say they work great. Can only expect 4-5" @ 12.5 volts. More with more. I'm going to run it through the PVC.

We use that same thing on our dyno for street type engines. It saves us fiddling with pcv valves and somebodies poor crankcase ventilation getting the floor all oily (“I did not want a breather in my polished valve covers! I paid good money for them and I don’t want to cut a hole in them!”). We have an oil separator after the pump. Maybe if we put it before the pump we would still be on our first one.

Paul

Hi Paul,

where exactly is the vac pump plumbed to ?

I ran it to a valve cover. If the engine owner does not have a hole in a valve cover to draw from I put one of mine on.

One of these days if I have a good repeatable engine I will see if there is any real hp gain with it. I like using it just to keep things clean and consistent.

Paul

[MadBill]

What’s the best crankcase evac system that has been designed that uses the manifold vacuum to pull a crankcase vacuum at low rpm and exhaust collector vacuum to do the same at high rpm WOT?

I have wondered if peak manifold vacuum could be stored in a big "can" then applied to the crankcase for a drag strip run. This could be in addition to an exhaust or electric system that could provide a few inches all the time. Just a thought. No design, never saw such a thing.

I think Grumpy Jenkins used a combined manifold vac./ exhaust evac. system like that as far back as ~ 1970. I'll scare up his book for details.

I gave some thought to the 'big can' approach a while back, but never got around to testing it. As proof of concept I planned to put a check valve in one rocker cover to allow any blow by to escape, hook up a 20# propane tank to manifold vacuum through a cable-operated ball valve (as used in an Accusump system), then with the valve open, run the engine up in neutral accel/decel, closing the valve* when the trapped vac was maximized. (likely ~28" Hg., depending on altitude) (*Of course, a throttle-triggered solenoid would be used in a race-ready version.)
To test, you would load the engine to WOT then open the valve just as you started running it up through the rev range, checking how much power difference resulted** and videoing how fast the vacuum decayed. The RPM/sec. could be adjusted to make the pull time equivalent to your expected 1/4 mile time. I'll run the numbers a little later, but with a little luck and decent ring sealing, you shouldn't need a 55 gal. drum to make it through the quarter...
**To just approximate the potential power gain, David Vizard hooked up two big shop vacs in series. I'm not sure what vacuum resulted, but I'll check it out the potential max on my ported 6.25 HP Craftsman plus a second smaller Sears unit later today.

[ptuomov]

Aren’t the engine crankcase and valve covers themselves together a big vacuum canister?

[MadBill]

Yes, that's the principle on which "Da Grump's" system operated. Manifold vacuum pulled the crankcase down during staging, then the exhaust evac slowed the decay rate after launch. Of course it wouldn't work with say a trans brake, when there is no appreciable vac...

[RDY4WAR]

How would you plumb both a PCV and pan evac?

[MadBill]

They operate independently; both have check valves allowing air to only exit the crankcase, so if say the exhaust can pull 6" Hg. max but the intake vacuum is presently 20", the crankcase will evacuate down to 20" through the intake check valve, while the exhaust ones remain closed. If the combination of blow by and leakage through seals, etc. bleeds the crankcase down to below 6", the exhaust components will start adding suck.
As mentioned before, including additional one way venting of blow by out of the engine is prudent to prevent gasket blowout if excessive blow by should develop.
BTW, a dash-mounted crankcase vacuum gauge is a good barometer of engine sealing health.

[cardo0]

Something else to consider is the vacuum reading from any pump or evacuation device will be controlled by the size of the clean air source inlet. Most PCV systems use the air cleaner as a filtered clean air source and that air source flow provides a negative pressure/vacuum loss when reading the crankcase vacuum. Make the filtered inlet bigger with a huge valve cover filter (or two) and it will be hard to obtain any crankcase vacuum reading. You could block the clean air inlet off but that is not a good representation either though it will show what your evacuation system is capable of. It's best to read the vacuum on the crankcase vent system as it will be used but I suggest take the measured reading close to the evacuation device as further downstream the vacuum reading will have losses due to the restrictions it encounters.

Hope this can help more than it confuses.

[RDY4WAR]

On a somewhat related question, I wonder how crankcase evacuation would benefit fuel economy? I would think the benefits of ring seal and windage would help with efficiency at steady-state cruise conditions. I'm sure in the OEM's endless quest to meet more stringent fuel economy standards that it's been experimented with.

What if a PCV system could be equipped with a 5 psi (~10 inHg) check valve on the inlet, filtered side going in the engine with the PCV to manifold side left alone. When vacuum exceeds 10", the valve opens and regulates fresh air into the crankcase at that depression.

[ptuomov]

On a somewhat related question, I wonder how crankcase evacuation would benefit fuel economy? I would think the benefits of ring seal and windage would help with efficiency at steady-state cruise conditions. I'm sure in the OEM's endless quest to meet more stringent fuel economy standards that it's been experimented with.

What if a PCV system could be equipped with a 5 psi (~10 inHg) check valve on the inlet, filtered side going in the engine with the PCV to manifold side left alone. When vacuum exceeds 10", the valve opens and regulates fresh air into the crankcase at that depression.

I believe that such system might help both performance and fuel economy in the short term. Say, if turned on selectively.

However, one thing to consider is that avoiding oil degradation into sludge is probably more important in long run use, considering emissions warranty period, long term fuel economy, etc. Intuitively, I think that to get rid of the water vapors one needs a sufficient flow of fresh air they the crankcase. The vacuum limiting valve might not allow enough inflow in normal circumstances for that.

One idea might be an electronic valve that would regulate a high vacuum and low air flow when the engine is cold, facilitating early boiling of water out of the oil. Then, when the engine is hot, regulate the vacuum to produce a sufficient flow for venting. Just an idea.

[rustbucket79]

Part of the success of getting a stock eliminator car down the track as quick as they are is to use the restricted power output as efficiently and as early in the run as possible. Think torque multiplication at the launch, at the expense of having the engine’s tongue hanging out across the finish line. (Very risky with factory powdered metal rods, cast crank and a 2 bolt block) High ratio low gear in the trans, lots of stall speed (not sure how that would work with the stock camshaft)

Sounds like an interesting project, keep us updated please!

[turbo camino]

Why is RPM a problem with PM rods? Is it because they're made from powder? (checks calendar to see if this is Groundhog Day again...)

[RDY4WAR]

Part of the success of getting a stock eliminator car down the track as quick as they are is to use the restricted power output as efficiently and as early in the run as possible. Think torque multiplication at the launch, at the expense of having the engine’s tongue hanging out across the finish line. (Very risky with factory powdered metal rods, cast crank and a 2 bolt block) High ratio low gear in the trans, lots of stall speed (not sure how that would work with the stock camshaft)

Sounds like an interesting project, keep us updated please!

Stock eliminator has always fascinated me. I love making power out of nothing. It just gets so darn expensive though.

I have a bunch of questions in my head about how I can make this thing faster.

Will keeping the front end down on the launch (heavy springs, less front end travel), so long as it keeps traction, be quicker?

Will lowering the car 1-2", while still maintaining positive A/S, make it quicker?

Would it be quicker to delete the alternator as well, so the crank pulley spins nothing, and go to a 16v system?

Would rebuilding the TH350 with lightweight parts and a steeper 2.75 1st gear make a substantial difference?

Would running a 7qt oil pan with just 4-5 quarts of oil in it make a worthwhile difference?

Would cooling the fuel down below ambient temperature make a substantial difference?

Is there ET in a full manual valve body vs letting it shift itself if the shift points are on point either way?

Would drilling the thermostat (or using a restrictor) to bring the staged coolant temp down from 160-170*F to 130-140*F make a substantial difference with OEM parts and clearances?

I'm sure there's still a bunch I'm leaving on the table.

[naukkis79]

What if a PCV system could be equipped with a 5 psi (~10 inHg) check valve on the inlet, filtered side going in the engine with the PCV to manifold side left alone. When vacuum exceeds 10", the valve opens and regulates fresh air into the crankcase at that depression.

Late 90's up BMW has this kind of system - there's something like 4hg vacuum in crankcase. They didn't use more vacuum as sealing becomes problematic, even stock system needs working crankcase sealing, a leak will lead to rough running.

[SpeierRacingHeads]

[rustbucket79]

Everything you listed has potential, and the quick legal stockers have tried everything and have shelves full of parts to prove it.

With fixed rules, it’s all about a bunch of minute gains throughout the car rather than one or two big gains.