talk about thicker oil, turning up tension on rear bypass, 26mm+ pumps, etc

[Jim Ratto]

what really happens with 26mm+ oil pumps, thicker oil (15W40-20W50, etc), and if you elect to stiffen rear (pulley end) bypass?

Bruce where are you?

[John Rayburn]

How adult.

[Jim Ratto]

 

[Sarge]

 

Ignore him.... maybe he'll go away

[John Rayburn]

 

Ignore him.... maybe he'll go away

                                                                    Did somebody call me?

[Bruce]

what really happens with 26mm+ oil pumps, thicker oil (15W40-20W50, etc), and if you elect to stiffen rear (pulley end) bypass?

Bruce where are you?

26 or 30mm pumps, both can give normal oil pressures.  VW used both size gears in 1600 dual port engines, so neither is wrong.  I elected to use a 30mm pump to compensate for the added restrictions I placed in my engine's oil system.  I don't have to rely on using molasses to have decent oil pressure numbers, the larger pump provides more flow with lighter oil at normal pressures.

I have thought of stiffening the rear spring to force more oil through the cooler.  One time I tried to stretch it.  You could shim it with washers.  I may try that one day.

Then there's the longer plunger with the groove in it.  This should divert more oil through the cooler with the existing spring.  That's because the pressure at the top of the plunger will be only slightly higher than the pressure in the groove.  This means that the effective area of the plunger that the oil pushes on is drastically reduced.  Less area = less force pushing the spring down at a given pressure.  This is also on my list of tests to run on a road trip in hot regions.

[Jim Ratto]

what really happens with 26mm+ oil pumps, thicker oil (15W40-20W50, etc), and if you elect to stiffen rear (pulley end) bypass?

Bruce where are you?

26 or 30mm pumps, both can give normal oil pressures.  VW used both size gears in 1600 dual port engines, so neither is wrong.  I elected to use a 30mm pump to compensate for the added restrictions I placed in my engine's oil system.  I don't have to rely on using molasses to have decent oil pressure numbers, the larger pump provides more flow with lighter oil at normal pressures.

I have thought of stiffening the rear spring to force more oil through the cooler.  One time I tried to stretch it.  You could shim it with washers.  I may try that one day.

Then there's the longer plunger with the groove in it.  This should divert more oil through the cooler with the existing spring.  That's because the pressure at the top of the plunger will be only slightly higher than the pressure in the groove.  This means that the effective area of the plunger that the oil pushes on is drastically reduced.  Less area = less force pushing the spring down at a given pressure.  This is also on my list of tests to run on a road trip in hot regions.

I talked a little about what I did to the motor in my car, in a thread JHU posted a while back. I used the Bugpack press-a-just adjustable bypass cap (normal cap with threaded screw and plunger that pushes up on factorly bypass spring [I use type 3 grooved]). I cranked the adjuster up so the spring's bottom seat was about .080" higher than stock cap allows. No idea on what this did to spring pressure, BUT this engine, with higher CR, runs cooler by a measurable amount (~15F oil) under same conditions (85F+ ambient, 3700-4200 rpm steady cruise, mixed with 2500-6000rpm blasts up and down 2nd-3rd gear through canyons in Ventura County). My question, is once oil is "hot" (160F+), does it really matter... by then isn't the bypass spring overcoming oil pressure in the rear bypass anyway, and all the oil gets thru the VW cooler? Or as revs rise and fall, and pressure does the same, is that rear bypass constantly re-routing oil to and away from VW cooler?

[Bruce]

  ....Or as revs rise and fall, and pressure does the same, is that rear bypass constantly re-routing oil to and away from VW cooler?

I think this is what's happening.  A few times I've watched the temp while driving down long grades like heading north on the 5 from Magic Mtn.  If you drive down in gear (4000 rpm), the oil temp does not drop very fast.  If you pop it into neutral, and coast while the engine idles, the oil temp drops much faster.  Turn the engine off, it cools even more. (btw, my record top speed coasting is there, 86mph!)

Calculating the pressure where the oil gets diverted isn't difficult.  One only has to measure the position of the plunger in the various locations, then measure the spring length at those positions.

[Jim Ratto]

  ....Or as revs rise and fall, and pressure does the same, is that rear bypass constantly re-routing oil to and away from VW cooler?

I think this is what's happening.  A few times I've watched the temp while driving down long grades like heading north on the 5 from Magic Mtn.  If you drive down in gear (4000 rpm), the oil temp does not drop very fast.  If you pop it into neutral, and coast while the engine idles, the oil temp drops much faster.  Turn the engine off, it cools even more. (btw, my record top speed coasting is there, 86mph!)

I've experienced the same thing. If I push it, on the highway (4200+, yes I know, I shouldn't be driving so fast, but sometimes I wake up late for Classic), the oil temp will hover in the 180-190F area, depending on ambient. This is at steady cruise, not full load, stock lower pulley size, etc. Once off the freeway, running city streets, mostly under 3500, or even 3000, the oil temp will plummet. I don't know if this is attributed to the higher psi (VDO gauge says 60-ish @ 4200+) is enough to start steering LESS oil to doghouse, and then once at lower rpm, say 2700-3500 (~40psi) it has backed enough off to make the spring force it all through doghouse. The canyon road I drive home everyday, Box Canyon, is a steep windng two laner that stretches maybe 8-10 miles between SF Valley and Simi Valley, very slow 2nd uphill stuff heading home (NW), and in recent days it's been 100-104F @ 5pm, by about mile marker 4, my oil temp is closing in on 160, by mile 6 it's nudged 180, but once in town, light to light, it will, in a matter of another 2 miles or so, drop back to 160 or so. Since the oil temp has yet to see 200F, I'm not worried about oil temp, I'm just trying to better understand what happens if you mess with the rear spring, pump gear length, etc.
I'm sure the fans on the Strab and vehicle speed throw some variables into the mix too.
JHU any thoughts?

[Brandon Sinclair]

I wanted to touch on this topic some more.  The single port or type III oil pressure plunger with groove in it is a bit longer then the no groove plunger if memory serves me right.  If you use this grooved plunger with the normal spring it will just up the spring pressure and amount of pressure needed to push that plunger down to bybass the cooler.  I also heard of people using a shim or dime to increase the pressure of the spring in that bore or to make up for material that was removed from the seating area when the pressure bores were resurfaced.  Some have even just removed the crush washer to make up for the removed material.

In both cases, is the result of this that more oil is forced to go directly through the stock cooler first before going to the bearings?  If this is the case then I guess there is a limit to what you can allow before possibly blowing a cooler.  Am I thinking of this correctly?

[Jim Ratto]

I wanted to touch on this topic some more.  The single port or type III oil pressure plunger with groove in it is a bit longer then the no groove plunger if memory serves me right.  If you use this grooved plunger with the normal spring it will just up the spring pressure and amount of pressure needed to push that plunger down to bybass the cooler.  I also heard of people using a shim or dime to increase the pressure of the spring in that bore or to make up for material that was removed from the seating area when the pressure bores were resurfaced.  Some have even just removed the crush washer to make up for the removed material.

In both cases, is the result of this that more oil is forced to go directly through the stock cooler first before going to the bearings?  If this is the case then I guess there is a limit to what you can allow before possibly blowing a cooler.  Am I thinking of this correctly?

I use the T-3 plunger with the Bugpack press-a-just

life is good

drove car 158 miles Sunday, mostly in 95F heat, on freeway @ 3900rpm+,  aside from drive hom in evening. Oil temp never went over 180F

oil is Valvoline 20W50 four stroke cycle.

[Brandon Sinclair]

Thats pretty good Jim.  Do you have an external cooler too or just running the stock doghouse?

[Jim Ratto]

Thats pretty good Jim.  Do you have an external cooler too or just running the stock doghouse?

VW doghouse, VW stock shroud and Setrab cooler up by trans (two fans switched on by Rabbit fan switch @ about 82C), fed by ducting down by torsion tube. 9.7:1.


I built it to drive fast

[Brandon Sinclair]

What is the reason for the groove in that one plunger and how does that effect oil flow throughout the system?

[Jon]

One thing to remember is that the oil cooler loop is always used... (even when the oil is cold)  The plunger just stops the oil from going directly to the bearings. So spring rates plays a role in TIMING as opposed to how much... I think.