oil pumps

M

MiniStocker

New member
Hi guys, Got a tough one for you. Here's the question. I've heard that all early oil pumps for watercooled VW's featured a 90lb pressure relief spring. Sometime later VW switched to a 60lb spring for lower pressure. Does anyone know when the cutoff was or what engines have this pump? I have too much oil pressure running 20W50 valvoline oil in a 84gti pump. I tried a 85 golf pump that was used and had the same pressure. I bury the 100lb guage when cold. After getting the watertemp up to 190, the oil pressure is at least on the guage, but is still over 100psi. After a hard 20lap feature, the pressure is 90 at idle and if I touch the gas, it sends the pressure over 100. I really would like one of the lower pressure pumps. I think running at 60 at idle and 80 at speed would be great. Right now I'm 90 at idle and probably 150 at speed.

Really looking forwards to your comments,
Scott
 
I don't think these motors were designed for such a thick oil. I run a 5W-40 weight synthetic and oil pressures are still high when cold, but 60psi when hot at high rpm.

[This message has been edited by Joe Craven (edited September 18, 2002).]
 
We run 0-30 oil synthetic,and loose motors with the small hydraulic pump,and see 45 psi
hot at 4000 rpm ,seems to be all we need.
suspect that you are giving up some HP with
your setup.
 
I race a Rabbit in addition to an ITB Capri with a Ford 2000 motor and the original builder who dyno'd the car told me that he saw that the motor needed 1hp for every 10psi oil pressure. I've never confirmed but sounds reasonable to me.
 
You can calculate the horsepower draw of the oil pump if you know how much oil volume it delivers.

Horsepower = ((Gal's per Min * PSI)/% efficiency) / 1714

The maximum horsepower draw will occur at maximum engine speed since the oil pump delivery will be at its highest (which in turn causes the highest pressure since you are trying to push all this volume thru all the passages, bearings, etc).

There are fixed frictional losses in the pump design as well. The actual horspower draw of the pump is actually pretty low.

Picking 20gpm as number out of the air (this is probably too high but good enough for a demo) and 75% efficiency

((20gpm * 60psi)/.75)/1714 = .933 HP

going to 80psi requires 1.24 HP

Looking back, I suspect that 20gpm is much too high since most oil pumps can be turned over with a small fractional horsepower electric drill, a common engine builders trick on some engines (i.e. small block V8's)to prelube the motor before starting it up for the first time.
 
Well, I called BSI racing and they said that my choice of pump is fine. However they said that by bearing clearances should be .003"=.004". They said my oil is fine, but the .002" clearance is too tight and that the oil can't get out of the bearing so the pressure gets driven up.

So I'm going to have a crank machined with more clearance. I plan on .003"-.0035" to start with. It sounds as though I may have been washing the bearings out so that the oil actually wore them faster.

Sound about right to you guys?

Scott
 
eh...what's the manual say for crank bearing clearances?

The bearings in which your cam rides will also have to be checked. All the bearings contribute to the pressure status.

Were you puffing up the oil filter?
 
Scott, are you talking crank bearing or rod bearing clearances?

I just changed out my head, from a hydro to a mechanical, and had new pistons and new rods installed. I'm also seeing very high oil pressure's at cold. Once I did getwater to over 200 and oil temp up to 100c, idle is around 55 psi, and over 100 psi over 4,000 RPM.

I never touched the crank, so I have to assume that the removal of the hydro head had something to do with the higher oil pressure, and the fact that the rod bearings might be a little "tight". I'm running 20w50 Kendal GT right now, but plan going with the Kendal synthetic after my first practice (Oct 5-6) so that should reduce the pressure as well.

Fingers crossed for now.




------------------
Tim Linerud
San Francisco Region SCCA
#95 ITB GTI, GP for 2002
http://linerud.myvnc.com/racing/index.html
 
On the subject of oil pump specs, up through about 1983, there were low-volume (about 25mm gear height) pumps with 90 psi relief springs designed for the solid-lifter heads. In 1984, the Audi 4000 1.8L "JN" engine was the first VW/Audi in the US to get a hydraulic head. These engines still had small gear pumps with unknown relief settings. 1985 may have been a strange year for oil pumps, as VW seemed to decide that the hydraulic heads needed more oil volume, so no guarntees on what any given engine received. From about 1988-on, ALL installed pumps from VW were medium-volume (about 30mm gear height) with the 60psi relief spring. Somewhere around 1992, high-volume pumps (about 34mm gear height) started appearing, still with the 60 psi relief. I have no idea what the current supercession is through VW, but I did have trouble getting the correct pump at the dealer a few years back. The dealer seemed to want to sell me the high-volume 34mm pump 1992-up pump for my 1983 engine rebuild, probably so people with worn out engines would be happier. It took an act of congress just to get the medium-volume pump through them. The low-volume pumps were on national back-order indefinitely. Absolutely no idea on any aftermarket pumps. Note that the relief spring is really part of the pick-up assembly or bottom portion of the pump, so either relief spring housing can end up under any given pump! That's just the gas oil pumps. I have no info on the diesel pumps.
 
Scott, are you 100% sure your guage is right?
Machining the crank is the last approach. Run a light 0w synthetic if you think the guage is correct and see what you get for pressures. Keep us posted...

PS - Where are you reading the pressure at?

------------------
Bill Sulouff - Bildon Motorsport
Volkswagen Racing Equipment

[This message has been edited by Bildon (edited September 27, 2002).]
 
Bildon, I appreciate your help, and everyone elses on this board. I have tried two mechanical guages. One used, then I tried a new one. I've tried two solid lifter pumps, and one '85 GTI pump. I've used 20W50 Valvoline oil, and I've used 10W30 synthetic Mobil one oil. I always get the same pressure. I am very concerned about using light oil as my races last up to 20 min. with cautions. Since it's and oval track, the RPM range on track is 5500-7600 and then back to 5500. I never reach below 5000. I'm concerned about oil breaking down and overheating.

For the gentleman who asked what factory specs were, .001-.0035. .005 is the service limit.

If I can figure out how to keep the bearings in good shape, this thing could be a top five car, despite having the smallest engine in the class. (Mostly mustangs with Esslinger 2.3's)

Thanks guys,
Scott
 
I think the oil pressure relief is sticking too. It happened to me and blew the filter off. It does not take much junk to cause it to stick.
Run light weight synthetic oil. It will not break down. A valvoline oil engineer told that that for every 10 degrees over 200F, you half the life of convensional oil. I would get oil temp on a stock VW gauge in 84 GTI showroom stock car of 150C+. This meant the oil was good for only one track session- 25 miles. The Engineer told me to run synthetic. Redline has been very good. We have run 8 races this year with no problems.
 
I agree w/ Bill, your relief valve is stuck. If you're seeing the same hot pressures w/ 10W/30 as you are w/ 20W/50, that's pretty much a dead giveaway that the relief valve is sticking. And don't worry about the oil breaking down in a 20 min. race through those rpm ranges. I ran B-G 0W/30 in my ITA AW11 MR2, and that thing made no power at all below 5500 rpm. It stayed between 5500 and 7300 all the time, and I ran it in some 1 hour and 2 hour enduros. Never had a problem w/ oil breakdown. But, use a good synthetic.

I've been running Redline 15W/50 in my ITB car, but will probably be swtiching to 10W/30.

Edit: Also, think about it. B-G, Redline, etc. make racing oil. Can't imagaine they'd sell much of it if it was breaking down after a 20 min. session. And they do sell lower viscosity grade oils.

------------------
MARRS #25 ITB Rabbit GTI
SCCA 279608


[This message has been edited by Bill Miller (edited September 29, 2002).]
 
I thought about the pressure relief valve, but I thought the chances of having three stuck valves was pretty odd. Especially when two of them were new. I guess maybe the bigger oil clearance and possibly going to a lighter oil should help. I hope...

Thanks alot, as always,
Scott
 
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