Oil Control In Rb's For Circuit Drag Or Drift

[robots]

For a simple setup, how would you guy recommend to do the best crank case ventilation system on RB ? Just vent it to atmosphere or a something like DG has?

[Adriano]

-15psi is the same as removing the atmospheric pressure to zero.

Crankcase evacuation is usually only used on N/A when you have a set capacity etc to give you the horsepower edge, using a vac pump, -10psi relative to atmo is about the break point where it costs more horsepower to create the vacuum than you gain, however the gains are certainly not insignificant. In forced induction setups its cheaper to add 2psi to get the same gain.

Edited July 2, 2009 by Adriano

[ylwgtr2]

anyone know racepace's veiws on this?Just thinking it would be good to hear another experienced rb26 builders opinion as that guy seems to build some reliable engines...also good point briso

Edited July 2, 2009 by ylwgtr2

[GT-RZ]

-15psi is the same as removing the atmospheric pressure to zero.

Crankcase evacuation is usually only used on N/A when you have a set capacity etc to give you the horsepower edge, using a vac pump, -10psi relative to atmo is about the break point where it costs more horsepower to create the vacuum than you gain, however the gains are certainly not insignificant. In forced induction setups its cheaper to add 2psi to get the same gain.

I'm sorry to drag this off topic but saying -15psi is the same as zero atmoshpheric pressure is completely wrong.

ok i'll start with the basics.

Negative pressure (vacuum) and positive pressure (boost or blow-by in this example) produce the same FORCE. The only difference is that that operate in different directions.

In saying that zero pressure is the same as -15psi is like saying 15psi is the same as zero pressure. it is not.

My previous posts were my best effort to keep things in to a simple perspective and allow things to be understood easier for lots of reasons.

first of all were you under the impression that zero pressure or absolute pressure as it should be reffered to means there is Zero mass within the crankcase? i tend to think so from your comment and you have been mislead.

vacuum is measured in air molecules per cc and the higher the vacuum the lower the count there is no absolute vacuum on this planet that contains absolute zero mass. psi is simply used for a blind rounded figure for comparsion when dealing with vacuums.

Back to the pistons that go up and down. you have already explained that you understand when a piston comes down from combustion it must fight the resistance of positive pressure (a force that is pushing against the underside of the piston).

So with that understanding it must be clear that given a vacuum in the crankcase when a piston rises it must fight the resistance of vacuum (a force that is pulling on the underside of the piston)

So given that you do not like high pressures within a crankcase you should also not want high vacuumes either. Think about this for a second...

Zero pressure or as close to possible would be the ideal then wouldn't it... because then we have a 'neutral' zone where we have neither push nor pull on the pistons from extra mass and a minimal amount of mass for the rotating assembly to dance in.

Also to think that a high vacuum pressures would not have there own problems is nieve. vacuum on earth unlike space, on this planet has a source of 'suction' in our example it can be thought of as a pipe out the block. Considering high vacuum pressure is pulling towards this one point then surely you can clearly see the implications with oil pressure/seals.

In response to your earlier post regarding ring seals. as you will know rings are fitted with a tolerance, that is too allow for heat and expansion etc etc the specifications are provided as the result of extensive testing. a ring is simply a seal designed to compress mass and create pressure.

having a negative pressure on one side and a positive pressure on the other side will not force the rings to seal better!

In an exaggerated example lets say a ring had a failing pressure of 200psi and our combustion produced around 160psi and we increased the vacuum in the crakcase (which for this example will be measured with psi) to say 40psi. the ring now has 160psi pushing down and a further 40psi of vacuum pulling it, we now have a failed ring.

To think that negative vacuum pressure from the crankcase would do something special that the positive pressure from combustion did not (like seal a ring better), seems illogical as BOTH FORCES act in the SAME DIRECTION.

however if you have some information regarding your statement i'm interested to read it.

i'm not sure what you are trying to say about n/a and combustion. it has nothing to do with this topic. nor is it true. a slight vacuum is used inside the crankcase to remove resistance which aids in making HP due to lots of reasons including reliability.

a vacuum is created inside the cylinder when a piston moves down the cylinder, the greater the vacuum the larger the volume of air needed to fill the pressure gap and the bigger the bang. Forced induction just relies mainly on the opposite and shoves more mass in there to increase the pressure and the bigger the bang.

plus vacuum pumps or vents to atmo are mainly needed in turbo or supercharged applications only because generally there is a larger tolerance in the rings and pressure being forced in the cylinder rather than only 'sucked' which results in more excess gas (blow-by).

Never known of a vac pump used in the crankcase to 'pull' in more air through the rings... is this what your suggesting?

Edited July 2, 2009 by GT-RZ

[Keeper]

BB see those large galleries in the rear of the head near the head bolt holes...do you think oil would prefer to drain through these to the sump...or through a tiny little hole through a fitting mounted higher up in the head. ?

Thanks for digging up the pic. A picture tells a 1000 words.

What if the intention is to allow excess oil build up to drain faster, rather than simply drain all oil to the sump? That way you ensure you have lubrication when not under heavy loads, yet when going flat out the head can return enough oil to the sump?

[r33_racer]

I pinched this from a dry sump pump company's website.

FACTS ABOUT CRANKCASE VACUUM

The Cheapest Power You Can Buy

What is the advantage to using a large amount of crankcase vacuum in a race engine?

HORSEPOWER; WHAT ELSE?

And it is the cheapest HP you can buy. If you can achieve a crankcase vacuum level of at least 8 inches HG, you will very likely realize an immediate power gain of at least 15 HP.

If you run a dry sump system with a three stage pump (one pressure stage, two scavenge stages), in most cases you cannot achieve a sufficient level (8 "HG) of crankcase vacuum to achieve that power gain. The extra cost of a four stage pump will net you around 15 HP in most cases. At NRC, it costs less than $100 for that extra stage. How can you beat that price for an extra 15 HP?

HOW IT WORKS

The reduced pressure ("vacuum") in the crankcase is generated by having a substantial excess of scavenging capacity with respect to the engine's oil flow rate. The "vacuum" increases the pressure differential across the ring package, producing an improved ring seal. The improved ring seal allows the use of a low-tension (reduced friction) ring package, yielding a power increase as well. Further, the reduced crankcase pressure dramatically reduces windage losses at high RPM.

Here are a few observations we have made over the years of developing winning race engines. First of all, in most engines, the expected power gains will occur with 8 to 10 inches HG crankcase vacuum. Beyond that point, more vacuum does not generally produce any measurable power gain until (a) you get more than 20 inches HG of vacuum AND (b) you are operating in excess of approximately 8300 RPM.

However, we generally size the systems on our engines to produce around 14 "HG when the engine is fresh. That provides sufficient capacity so that as the engine wears and blowby increases, there will still be sufficient scavenging capacity to achieve the 8"HG minimum, and power does not drop off noticeably.

If you want to run a high level of crankcase vacuum (18 inches HG or more), there must be provisions in the engine to supplement the lubrication that used to occur when oil was being thrashed about by the moving parts ("windage"). There will likely be problems with at least wristpin and cam follower lubrication. The best solution will be the addition of piston oilers and, if your engine has a flat tappet cam, provisions for extra lubrication of the cam lobe-to-lifter interface will certainly be required. If you are trying to achieve over 18 "HG, you will need to install special crankshaft seals (front and rear) which have the sealing lips reversed to hold that higher level.

In order to achieve 8 "HG or more, the engine must be well sealed. In order to check for leaks, you should pressurize the assembled engine. You will need an adjustable pressure regulator with a low range (like 0 - 10 psi) air pressure gauge. With the engine completely assembled, cap off the fitting that feeds the oil into the main oil gallery, and cap off the scavenge exit fittings from the pan. Install a pressurizing fitting into one of those caps.

We use 6 to 8 PSI (which is equal to 12 - 16 inches HG) of air pressure to test our 8 - 14" engines. Start with the regulator set to ZERO and slowly add pressure, up to the max test pressure you decide to use, and listen for air leaks. If you hear any and can't pinpoint the source, spray some windshield foamy cleaner in the area with a hand spray-bottle. NOTE: You will get better sealing with the cork rocker cover gasket than with the rubber steel lined rocker gaskets.

You should be aware of a few potential glitches. Some silicone sealers cure differently than others, and most take weeks to cure if it is 1/8” or thicker. An uncured bead of silicone sealant will tend to be pushed out when pressure is applied or sucked in if not cured long enough. At NRC we think the best silicone sealer is the OEM stuff, and the Permatex Ultra-Gray is also a good product. The OEM and Permatex Ultra-Gray tend to cure harder on the exposed areas which makes it a little harder to be pushed out or sucked in. However, both these products take a considerable amount of time to fully cure when the bead is thick.

We have found that the softer curing stuff tends to develop leaks after the engine has been placed in service, because it moves around during the race. Recently, we have been experimenting with a two-part silicone, which is similar to two-part epoxy, but looks and feels like silicone and cures for limited use in about 30 minutes, and completely cures in 24 hours. So far, the results are encouraging.

DRY SUMP OIL PANS

The pickups in most of the aftermarket pans are horrible. The pickup fittings which are usually found are rectangular boxes with sharp, square corners. Those square corners play havoc with the orderly pickup of scavenge oil and add to the turbulence and aeration which occurs at that end of the system. A good hint about how the pickups should be formed can be seen by examining the interior shape of the pickup attachments on your wife's vacuum cleaner.

Next, almost all the aftermarket pans use dash-12 scavenge fittings. Common sense says there is more volume inside a given length of a dash-12 hose than in the same length of a dash-10 hose. Using the smaller dash-10 hose causes no meaningful increase in flow losses, but it causes a larger percentage of the hose volume to be filled with oil instead of air. Reducing down to dash-10 scavenge lines will help achieve a higher level of vacuum. You can buy the reducers from the common suppliers such as Moroso.

As far as pan design is concerned, the wider and deeper the pan is, the easier it is to control the thrashing of oil, and the easier it is to scavenge the pan well. We also found that the better the pan design (wider, deeper, with scrapers, louvers, one-way-mesh, etc) the expected gains from a high vacuum will be less. The high-vacuum system will produce the best power increases on engines with shallow pans, which are often required as a result of engine placement restrictions or from chassis construction.

Hopefully this will help clear up some stuff with the whole debate Might educate some people on dry sump systems too!

Edited July 2, 2009 by r33_racer

[GT-RZ]

8-10inHG is about 5psi

They only recommend more vacuum pressure in high RPM situations where obviously more blow-by is being created.

Which leads me to believe they are talking about the actual 'suction' of there vacuum system not the atmospheric vacuum pressure in the crankcase. Because if you could maintain the same atmospheric vacuum regardless of RPM then there would be no need to increase the atmospheric vacuum. However given that they only have one point of 'suction' the faster the rate positive pressures climb within the crankcase then the faster they will have to 'suck' it out. So 5psi of vacuum that the machine is pulling with would mean allot less than 5psi atmospheric vacuum within the block at that time depending on the blow-by load.

The patent i read and posted earlier recommoneded around -0.15psi of atmospheric pressure within the crankcase, i assume you would measure this with a seperate gauge attached to the block somewhere, which this system lists in there patent. How much vacuum the 'device' must create to achieve this is not our problem.

The only advantage a LOW vacuum could have for rings that i can see is rather a reduction of pressure on the lower rings due to little or no atmospheric mass interfering with the piston rings (pushing against them) on the downward stroke, which we've talked about earlier just not directed to rings. But like my example above (my last post) if you start to create high negative pressures then you replace the positve force on the rings with a negative force and have the same problem as before.

I would not say that vacuum is good for the rings but rather low resistance is good for rings which would be sufficient at zero pressure / very low vacuum

I'm glad to see the article documents issues with oil feeds under stronger vacuum, that was a given.

It is also a given that if you want for some desirable reason 'high' vacuum' in your crankcase you will have to upgrade ALL of your seals to something stronger because vacuum is the opposite to boost!! Previously your problem may have been oil trying to bust it's way out of seals, now the problem is air trying to bust your seals from the other side.

I think this is all very straight forward. there is no special power behind a vacuum.

If you have positive pressure of 20psi in the crankcase @ 5000rpm before and you introduce a vacuum that keeps the pressure at a steady rate of 0psi @ 5000rpm then you have a 20psi drop in pressure which everything will benefit from.

If you increae the negative pressure to -20psi then you just went and welcomed some old problems back in plus some new ones.

Because vacuum and boost are equal and opposite. they put the same FORCE on an object.

Id like to mention that the ONLY benefit a really high vacuum could have would be un-noticeable change in atmospheric mass in the crankcase which could help an un-noticeable amount with the rotation of the crank (which is why the shape of a crank can be important, the more aerodynamic it is the less you worry about this)

But anything at zero atmospheric pressure or slightly lower is more than enough and any gains are to be made by removing the Positive pressure. As soon as you introduce higher vacuum pressures you add the problems with negative forces acting badly on the pistons/rings and oil/seals etc etc.

Plus yea id love a dry sump as they already use a vacuum and have plenty of advantages in the first place but too much $$$ that i'm willing to spend.

Edited July 3, 2009 by GT-RZ

[NickR33]

anyone know racepace's veiws on this?Just thinking it would be good to hear another experienced rb26 builders opinion as that guy seems to build some reliable engines...also good point briso

I have never seen Benno put a drain like that on any of his motors... I got mine back from him last night and the oil pressure is off the scale, almost bends the needle back on the stock gauge lol... even with the super high pressure he's not seemingly worried about oil pooling in the head, said to just take it easy with the limiter bashing as its got an N1 pump (its weaknesses are well published)... won't reveal what he does to the motors but its all internal modifications as far as I can tell... there are the usual restrictors in the block but that's all I know

[Roy]

Anybody understand why std RB20s dont breathe? Legend01 made 280rwkws at 1.5ish bar with a 3040 on a std motor...all good. AD4M made 300rwkws with a TD06-20G-16cm on std RB20 untl it melted a piston...no breathing. Ran a 12.00 in a manual 4dr. There mut be something inherently different in their designs ?

[Swiper the Fox]

I have never seen Benno put a drain like that on any of his motors... I got mine back from him last night and the oil pressure is off the scale, almost bends the needle back on the stock gauge lol... even with the super high pressure he's not seemingly worried about oil pooling in the head, said to just take it easy with the limiter bashing as its got an N1 pump (its weaknesses are well published)... won't reveal what he does to the motors but its all internal modifications as far as I can tell... there are the usual restrictors in the block but that's all I know

Correct...Ben doesnt use those rear of the head fittings...either do CRD, Godzilla, Red R Racing etc.

Do we all have it wrong?

Building an engine with correct tolerances that doesn't breathe with enlarged returns is the go. Don't worry about high oil pressure...id rather it be high than low as it will keep a good film of circulating oil on the bearings. No chance of picking one up with the crankshaft (spinning a bearing).

Oil pressure is your friend.

[Duncan]

Anybody understand why std RB20s dont breathe? Legend01 made 280rwkws at 1.5ish bar with a 3040 on a std motor...all good. AD4M made 300rwkws with a TD06-20G-16cm on std RB20 untl it melted a piston...no breathing. Ran a 12.00 in a manual 4dr. There mut be something inherently different in their designs ?

Yep....they simply don't have enough bang to cause blow by

Overall this discussion (while interesting) has covered a lot about something (excessive blow by) which isn't a big problem for most people...

and no doubt of course that dry sump is the best option but that is not always available due to price or rules...

[SimonR32]

Anybody understand why std RB20s dont breathe? Legend01 made 280rwkws at 1.5ish bar with a 3040 on a std motor...all good. AD4M made 300rwkws with a TD06-20G-16cm on std RB20 untl it melted a piston...no breathing. Ran a 12.00 in a manual 4dr. There mut be something inherently different in their designs ?

i spoke to adam not long ago and he had finally pulled down the engine and it turned out it didnt melt a piston but merely lifted the head

the only time i have seen a rb20 breathe is when they have a problem internally... otherwise i think roy may be onto something here

[GT-RZ]

Yep....they simply don't have enough bang to cause blow by

Overall this discussion (while interesting) has covered a lot about something (excessive blow by) which isn't a big problem for most people...

and no doubt of course that dry sump is the best option but that is not always available due to price or rules...

Well you may not be too far from the truth in one respect... I have not checked but how big are the standard oil drains in the 20 compared to the 26?

Generally enlarging the returns in 26's would probably prove enough relief, the extra line from the rear of the head just provides an additional channel.

If the RB20 has the same size returns as the 26 then it is clearly better setup to allow movement of oil/gas around the engine since the RB20 has smaller cylinders which in a volume sense given the combustion volume would produce less blow-by if both engines were fed the same boost and had equal wear...

Most of the later discussion was to do with blow-by which really only affects higher performance engines (or not if badly worn out) as they deal with more boost but it would not hurt to be set up for the worst? low pressure or low vacuum in the crankcase is clearly beneficial to everyone. If it's needed or not given the particular setup is a different case.

Edited July 3, 2009 by GT-RZ

[Sydneykid]

20 cents worth of short comments;

RB20 standard oil pumps flow a lot less than RB26 oil pumps.

Oil pressure is measured in the block at the main oil gallery, which is below the flow restrictors. Hence oil pressure has no relevance as to how much oil is in the head.

The big advantage of dry sumps that we see for horsepower is the removal of oil flying around in the crankcase, the crank spins much freer as a result. So when considering the advantage of partial vacuum in the sump, the further lack of flying oil is more important than the partial vacuum (ie; less air) on its own.

Piston rings (eg; top and 2nd ring) seal better with pressure on their upper surface, having a partial vacuum in the sump (ie; below the rings) effectively increases the pressure above them. The need for pressure to push the ring against the bore is why we don't use a gapless ring in the top, only in the 2nd ring. Oil control rings don't need external pressure, they have sufficient internal spring tension.

Cheers

Gary

[PSI Parts]

Very interesting read.

Just wanted to point out that the M Speed engines run the Auto Staff Oil Return.

[GT-RZ]

The only advantage a LOW vacuum could have for rings that i can see is rather a reduction of pressure on the lower rings due to little or no atmospheric mass interfering with the piston rings (pushing against them) on the downward stroke, which we've talked about earlier just not directed to rings. But like my example above (my last post) if you start to create high negative pressures then you replace the positve force on the rings with a negative force and have the same problem as before.

I would not say that vacuum is good for the rings but rather low resistance is good for rings which would be sufficient at zero pressure / very low vacuum

Piston rings (eg; top and 2nd ring) seal better with pressure on their upper surface, having a partial vacuum in the sump (ie; below the rings) efectively increases the pressure above them. That's why we don't use a gapless ring in the top, only in the 2nd ring.

Cheers

Gary

Having pressure in the crankcase means the pistons/rings have to fight against it, that's what i was saying before. Having too much vacuum will still cause a problem rather than a benefit, though.

If anyone has images of the M speed r34 intake side of the engine id love to see them!!! i can't find any, only of every other angle hah.

Simply because if the venturi affect was to have any huge advantage on the intake side then it must be placed offset to the centre of the crank in the positive rotation direction of the engine!

If it is not higher than the centre of the crank on the intake then it merly would be working as a windage escape just like the channel at the rear of the head on the intake side!

Hence why the exhaust side turbo oil drains are lower than the centre of the crank (all RB excluding front drain on rb26? clearance maybe) , ensures no horizontal windage could be pushed up the return. This allows the drain to use the vortex of the crank windage to 'suck' oil down that turbo return (venturi effect).

the position of the connection to the block could be deceiving but is very important!!

Edited July 3, 2009 by GT-RZ

[Adriano]

GT-RZ, i suggest you read up on how piston rings seal, i think it will alter your thinking on the subject.

[AD4M]

my 20 didnt go kaboom so to speak. BUT it did blow the dipstick out (ended up cable tieing it in) and fill my catchcan up with a couple ltr's of oil on a couple of ocasions where it was being driven hard befor it was running and sounding worse for wear.

that was 2bar of boost on a std motor so std 20 oil pump no restrictors or any changes to oil control.

I would only assume if a 26 would have crank case pressure issues there would be the same issue through the entire RB series?

[GT-RZ]

GT-RZ, i suggest you read up on how piston rings seal, i think it will alter your thinking on the subject.

I understand how rings seal. I also understand there primary function is to compress mass and to take combustion pressure. Rings have an order for a reason and only the top one is made to take the brunt of force.

All lower pressure in the crankcase does is remove any additional resistance pushing against the rings in the wrong direction, therfore the more crankcase pressure the greater the Force being applied to primarily the weaker rings at the bottom.

having zero pressure would be optimal or a vacuum that would create marginal force. this would allow the rings to deal with primarily forces from the top, operating in the order they are designed.

To think that the higher the vacuum pressure the better a ring will seal does not make sense to me. A ring is just a seal, the pressure it can properly function in is not unlimited and ringland failure is not uncommon. Like any material if you place too much force on it they will fail.

Just like i said before, when you add a vacuum under the rings you are simply increasing the downward forces acting on the rings. if you were to increase combustion pressures to a point where the rings failed you would get the same effect increasing the vacuum.

200psi of combustion pressure plus 30psi of vacuum effectively has 230psi of downwards pressure. 30psi of that is acting primarily on the lower rings which is an extra stress they were not designed to deal with.

Unless you were talking about something else?

Edited July 3, 2009 by GT-RZ

[Adriano]

I honestly dont think you understand it, especially when you start talking about 30psi of vacuum, as relative to atmosphere 30 psi vacuum is impossible. BTW 200 psi on top of the ring is nowhere near the mark, think 10,000psi

Edited July 3, 2009 by Adriano