Oil pressure jumping around at higher RPM's - add a windage tray?

[CrazyAndy]

One interesting thing I found with my 1.6 vs the 1.9 aaz engines I have is that the IM shafts drive pulley is considerably smaller on the aaz vs the 1.6.

making the im shaft speed greater, possibly to speed up oil pump.

Yes, but would the pulleys interchange?  The IM shafts are different IIRC.

Also to chime in on the oil pump flow/pressure thing, the main reason higher volume oil pumps are installed is to be able to maintain a higher oil pressure at higher oil temperatures, and do it for longer in the engine's service life.  Couple that with modifications (A turbo and piston cooling jets to feed, an oil cooler creating more volume in your pressurized oil circuit) and a higher-volume oil pump becomes not only a good idea but sometimes a necessity on higher power applications/  Don't forget that some components like the turbo use oil as a cooling medium, so the more oil flowing through them the better.  This could all be simulated by increasing pump speed by swapping on an AAZ IC pulley, if it can be swapped, but the only question i'd have for an already used engine is would it increase both oil and vacuum pump wear (the IC drives the vac pump too, don't forget).

[Jetmugg]

[/quote]

IIRC the dipstick should be fine if the dipstick tube and dipstick are correct for each other. The early 1.6 gassers and I think the early 1.5 diesels had a 3 qt pan. That is why I asked you earlier if you needed a 4 qt. pan. The later vw 8v engines all had the 4qt pan...making it a 5 qt oil change with the filter. The early pan you could only do around 4 qt oil change with the filter and that smaller pan.

One interesting thing I found with my 1.6 vs the 1.9 aaz engines I have is that the IM shafts drive pulley is considerably smaller on the aaz vs the 1.6.
[/quote]

OK - it's time for me to learn about the differences in the various oil pans, and how to ID them.  I have at least 2 pans that I could use.  I'll do some measuring and inspecting to try to figure out if they are different from one another.  Are the oil pump pickup tubes the same for the 3qt and the 4 qt pans in terms of "depth"?  I'm hoping that the larger pan isn't any deeper, but maybe has some other dimensions modified to give the extra volume. 

Regarding the AAZ pulley, the IM shaft would definitely be sped up.  I don't think I need that.  IIRC, the timing belts are the same on a 1.6 and a 1.9.  The smaller pulley has to play a part in allowing the same belt to be used for either application.  Since the 1.9 has the taller block, it would need the smaller pulley.

Steve.

[libbydiesel]

If the issue is aeration and your turbo return is already coming from above the oil level, then you either need increase the oil level so the bubbles are higher, draw from lower in the pan if that is possible or created some added baffling so that the bubbles separate from the oil you are pulling into the oil pump.  You really don't want any aerated oil entering the oil pump.  You want the bubbles to rise out of the oil before it is drawn into the pickup tube.  Increasing the capacity by changing the pan and yet keeping the oil level and the level of the pickup tube the same may reduce the issue some but will not eliminate it.  I'd shoot for eliminating it.   

[Jetmugg]

All options are on the table.  I have another pan I could modify, and I am willing to buy a different pan if necessary, although I'd prefer not to spend $500 on a pan.

Steve.

[southernman]

Steve, you can simply click on my avatar to get to my profile/postings, and thanks for responding.

I doubt the bulkhead fitting is affecting your oil pressures - unless the lines and fitting are under sized and inhibiting return to the pan. Such condition would result in the same "pooling" in the upper end I described above, and the turbo seals would probably be leaking some...

Also, my post wasn't about whether or not our engines 'can' work above 6K. I'm sure some do, but doing so with cast pistons, and stock rods, under boost, in excess of 500 lbs cylinder pressure, guarantees we won't do it for long... My discussion was focused on 'optimal' pressures. Unless you're running alt fuels (like Nitro methane where cylinder pressures can destroy parts even at idle), anything beyond 10 psi/1K rpm is excessive.

The 'turbo' pumps, used in conjunction with the hydraulic lifter are indeed based on volume - not pressure. The additive volume based on turbo's consumption, 16 'hollow' lifters, and squirters to keep pistons alive, require additional 'volume - not pressure'. The turbos I've ran over the years always used restrictors to limit both... However, matching a turbo/hydraulic pump should not result in additional pressure.

Excessive oil pressure in any engine is counterproductive, not to mention a drain on horsepower, and economy, as rpm's, and viscosity, increase...

Regarding the mechanical gauge; temporarily install it where the existing sender is threaded and fish the poly tubing to a gauge long enough to check it. The ONLY way your pressure will drop, is due to the oil level in the pan dropping below the pick up - assuming the engine you're running meets, minimal, factory blueprint/specs... If that's not the case, then loss of 'restriction' due to excessive clearances will cause a drop in pressure, but it's usually constant, not intermittent.

I hope this helps...

Just for reference guys, here's my latest project: a 528 cu. in Mopar Wedge sporting a Precision ceramic 106mm turbo. Estimated 1200-1500 Hp and setting it up to run Yellowbullet's door slammer division. Should be good or 8 second quarter mile times...

[libbydiesel]

The ONLY way your pressure will drop, is due to the oil level in the pan dropping below the pick up - assuming the engine you're running meets, minimal, factory blueprint/specs...

Aeration of the oil can occur without the oil level dropping below the pickup and drawing in aerated oil will cause the oil pressure to drop in direct proportion to the amount of air bubbles in the oil.  I have observed several VW TD engines (both higher mileage and completely rebuilt with every oil clearance well within spec) that would drop oil pressure in direct relation to boost.  I have observed the oil pressure drop 30+ psi without the rpms changing.  The only explanation I have for that behavior is aeration of the oil.  It can be seen in the design of the baffles in the 1.6TD vanagon pan that the VW engineers were aware of this issue.

The typical solution is to have the return oil from the turbo enter above the oil level.  This typically works well enough, but I can see where an engine running high rpms and high boost would be circulating the oil in the sump faster than the bubbles could rise out of it.

To address aeration, I would add a semicircle to the perimeter of the pan that had a gap at the bottom (say 1/4"), with the top of the enclosure extending a little way above the oil level.  The semicircle would contain the oil return fitting and would catch all of the aerated oil from the turbo.  The bubbles would float and stay inside the enclosure and the non-aerated oil would return to the main portion of the pan through the gap at the bottom of the 'fence'.  I would add a second similar baffle around the oil pickup.  I would use the large capacity oil pan.  I would also measure to see if the oil pickup could be lowered closer to the bottom of the pan.  I would also add the windage tray and experiment with raising the oil level.

[southernman]

Libby, thanks for responding.

Doesn't change the solution since uncovering the pump inlet is behind the loss in pressure in either scenario...

In essence, your take here is frothing of the oil creates a condition where there is inadequate time for air saturated oil to return to the pan in a fully liquid state. Air has displaced liquid; the pump starves; and the OP gauge responds accordingly. You may be right, and the most simple test here is to cut the engine and stop the vehicle,  after a max rpm blast, and pull the dipstick...

Option 1, you're either pursuing a dry-sump solution, which is designed to control such conditions - or Option 2, you're dropping the oil sump and pickup and increasing the volume to buy time for the oil to eject entrained air.

Option 1 is the bucks up solution, and probably requires homebuilt engineering for the 1.6, but could be done.

Again, thanks for the reply,

Southernman

[Jetmugg]

There is at least 1 dry sump solution commercially available.  I have talked to them, and it's definitely a "bucks up" solution that I don't think I'd be able to pull together before Bonneville (although it would be very nice).

Optimizing the "stock" setup is more realistic.  I'm headed out to the garage right now, attempting to figure out some oil levels, volumes, and position of my current oil return line from the turbo.  I think it's above the static oil level, but will check to be sure.

Pan baffling is certainly do-able.

The key is that it has to work for more than a 1/4 mile blast.  It essentially has to work "steady state", as even the short course at Bonneville is 3 miles WFO.

Steve.

[Jetmugg]

OK - another update.   

I do have one of the deeper pans "in stock" in my garage.  I believe it's actually from a code 9A 2.0 gas engine that I bought last year.  It is somewhere around 5/8" deeper than the other 2 pans I have, including the one that was on the engine.

I will be using the 9A pan.  It needs to have a weld bung installed for the oil return from the turbo.  What are the thoughts on the bung location?  As high as possible on the pan, or down towards the bottom?

Also, this is the oil pump and pickup tube that's currently on the engine: 

http://www.partsplaceinc.com/products/product-detail.aspx?keyword=VW+Diesel+Oil+Pump68-115-105&sku=1300

Measuring from the bottom skirt of the block to the bottom of the pickup tube, it's showing about 3-1/2".  For comparison, I measured another 1.6D engine I have laying around (with no oil pan).  The OEM pickup appears to be about 4" down from the skirt.  So right away, I'm giving away 1/2" of oil that can't get picked up.

When I go to the deeper pan, that dimension (from the bottom of the pickup tube to the bottom of the inside of the pan) will be over 1"!!!

I need to either come up with a different pickup tube, or weld some tubing into the one I already have.

Back to the garage for now.

Steve.

[libbydiesel]

Keep tho oil return bung as high as you can.  Drop the pickup as low as you can.  Keep the 36mm pump.  If you are thinking of swapping oil pickup tubes, be sure to swap just the tube and not the bottom plate of the pump as that houses the pressure relief valve which is matched to the pump.  I'd still add baffles to  prevent aerated oil from getting to the pickup. 

[Jetmugg]

Sounds like a plan!

[theman53]

I am hoping that is the issue, you were just running low on oil to pump. I second what Libbydiesel says to keep the oil bung as high as possible. While welding mine in I found that you need to keep it cool. I warped the pan where the gasket seals and there was always a little leak there. Tig would be your friend on that one. I kept mine about 1" from the top of the pan as I needed to be able to get a wrench on my fitting on the drain line.

[southernman]

Steve, there are a few other thing that you may want to consider:

In my decades as an engine builder (mostly V-8's, naturally aspirated; supercharged; and turbo-charged) centrifugal force plays a huge role in 'where' oil resides inside your engine.

For example, any V-8 engine that is revved to 6K and beyond can hold at least 4 quarts of oil on the crankshaft alone. That's also how most race builders came up with deep pans of 8 quart capacity (with 4 qts clinging to the crank, and 5 available for everything else once you include filter capacity). Where crank scrapers are employed, the pan volume can be reduced by 1-2 quarts, hence the 'compromise' pans at 7 quarts, which also help keep the sump out of the path of speed bumps for those inclined to drive such on the street.

My recommendation, based on the information above, would be to calculate, based on 4 cylinders, using half the oil retention of V-8's @ 2 quarts with 2 additional quarts for the remaining mechanicals. A minimum of 4 quarts for the pan (for a high-revving) engine, is where you should start. 4 in the pan, 1 for the filter, total of 5 quarts.

If you look at the pan from the side, you can see it's profiled like a skid plate and IIRC, the pickup, as I recall, is near the center. This means, if you run stock pans, you also need to check the location of the pickup to ensure the pickup is located toward the rear of the sump as possible - not in the middle or forward of the sump.

If I was contemplating your high speed trials; I'd take an old pan and slice it down the middle (front to rear of car; north/south) where the pickup tube intersects, and do a visual to see where everything 'lives'. Or, if you're anticipating turbo return 'ports' for the pan, simply cut the hole oversize enough to see the pickup/pan relationship. Then I'd take my soon-to-be custom pan, remove (cut) the sump out of it, weld a 2" strip/panel into it, and then cut and re-angle the pickup tube rearward for max immersion under acceleration. Also, cut and extend the pickup tube to locate it 1/2" above the pan floor. If you have the pieces already cut and fit, the same shop that TIG's your bung can weld your pan, pickup tube, and baffling for cheap - IF YOU'VE DONE THE CUTTING AND FITTING BEFOREHAND...

One other thing to consider is decelerating; whether or not you kick the car into neutral (coast then brake) at the end of a run, or use compression braking (leave it in gear) and use the engine/brakes to decelerate and stop the car. For the latter, include a provision for baffling to keep the pickup tube immersed when oil can abruptly move to the front of the pan under hard braking...

While the pumps out; put another 2-3 thousands clearance in the bypass piston's bore (factory clearance it TOO tight causing them to stick) and put a threaded allen screw behind the spring for retention, which would allow you to change springs later and 'tune' oil pressures.

I hope this gives you some ideas, and good luck with those high-speed trials.

Southernman

[Jetmugg]

There are some really good ideas in your post, Southernman!  Thank you very much.  I do have a spare "shallow" pan that I am willing to cut apart to get a visual impression of where the pickup is in relation to the bottom of the pan.

What I've done to check clearance so far is use a big ball of Silly Putty, stuck to the bottom of the pickup, then push the pan into place, checking the distance from the pickup to the bottom of the pan.  I have also used a straightedge spanning the bottom rails of the block, and measured to the pickup, then used the reverse technique to check the depth of the pan.

I have a couple of weld-in -10 A/N bung fittings.  I will weld one to the new pan, after checking clearance between the weld bung location and the windage tray, just having a look to make sure the oil looks like it's returning to a good place.  I'll also do the modifications to the pickup tube myself.

At Bonneville, there is plenty of room to coast after the 3 mile mark.  The conventional wisdom is that the vehicle's brakes are only for loading and unloading the trailer at Bonneville.  If you are going so fast that you need to slow down - use a parachute.  Otherwise, just coast down and turn gradually towards the return road.

The information about modifying the oil pump for adjustable pressure, and opening the bypass piston bore is valuable.  I haven't had one of the oil pumps apart yet, but I do have several of them.  What would you use to open the bore?  A reamer?  Very small hone?   I'll have to get one taken apart for an internal inspection.

Steve.

[southernman]

Steve, I'd ream the bypass piston bore and polish the piston before putting it back together. Purchase a shallow, threaded, allen screw (oversize set screw), drill an tap the hole for the allen screw, replace the spring and piston, and you've got a fully 'tunable' oil pump. Changing the springs wire diameter in either direction will help you optimize pressures for the intended use.

You'll find a driven plug behind the bypass spring, and it takes a little effort, but will pry out of the hole. Every one I've pulled apart, I had to force the piston out of it, due to debris getting between the piston and bore. You'll see scoring and scratches on both once they're apart.

Remember, oil being bypassed is non-filtered oil (actually, oil passing through the pump gears is unfiltered as well, but the pumps are not deep rotor pumps, so it's not a problem for them), but 2-3 thousands of debris between that bypass piston and bore could drive low, or high, oil pressures depending on when the debris gets trapped and seizes the piston...

One other thing regarding your pickup: if you do increase pan depth and pickup to match, be sure to weld some "extensions" from the pickup mouth, that extend down and nearly touching the bottom of the pan (or you can bend short 90's where they do contact the bottom of the pan and have them touching). Logic ? Should you accidentally smack the bottom of the pan, the force will move BOTH the pan and pickup - but not close up the suction window(s) on your pickup. I hope that make sense. If not ping me back and I can send a pick or sketch.

Southernman