restrictor in oil line to alternator

[bevans6]

this is an addendum to a post I made about low oil pressure in my 8v71.  Searching the archives led me to a thread where a restrictor in the oil line fitting at the alternator was mentioned.  Based on suggestions there, I disconnected the alternator oil line from the manifold with the pressure sensor  and plugged it.  High idle OP is now 65 psi up from 25 psi.  So the question is, if I put in a restrictor - the other post mentioned that the restrictor in the alternator fitting is supposed to be .050", what is the chance I will ruin my alternator due to lack of cooling oil flow?

I'd really rather have proper oil pressure if I can.

Brian

[Bob & Tracey]

Brian,

I started the other thread you are refering to and I have not found an answer yet. I have an extra alternator and I can see the restriction in the oil inlet, it appears the hole, threads and the smaller restriction hole are machined into the alternator case. It is not like you could remove the restriction. Using a drill bit I compared the size of the restriction hole in the unmounted alternator and while I do not remember the size it was the same as the one on the bus. I have not found a another place to measure the oil pressure from either, I see only two sources to measure the oil pressure and one is oiling the air compressor and the other the alternator, I am hesitant to change this arrangement.

Bob

[bevans6]

Hi Bob, thank you for replying.  If I understand correctly, the restriction is in alternator casting at the bottom of the fitting that the oil line attaches to, which makes a ton of sense.  if you have your spare alternator where you can get to it, can you measure the hole?  Or are you pretty confident of the .050" ( which is slightly under 1/16") that you quoted in your previous posting?

thanks again

Brian

[gmbusguy1]

Gentlemen, I have recently had the exact same issue with my 8v71turbo aftercooled 4106 and tried some of the same things you have here is what I discovered.

1. the generator oil restrictor is as Bob said is cast into the housing just below the threads where the oil line attaches

2. my oil pressure as read at the dash from the electric sender was erratic mostly at idle

3. we tried 3 or 4 mechanical oil pressure gauges and a couple of electric gauges too
all with the same stupid and dumbfounding results

4. after much pondering and worry over how much or little pressure we truly had I was replacing the air compressor and walla the light bulb went on

5. I removed the oil feed line that lubes the compressor and installed a brass tee in the compressor so we are feeding lube oil from a different source entirely than the electric sender manifold on the bulkhead then installed a mechanical oil pressure gauge (one of the many I had just lying around LOL)
into the new tee at the compressor

Poof plenty of pressure

the manifold turned out to be the culprit in this case

however the piece of mind seeing lots of oil pressure was priceless

Chris

[bevans6]

well here is what I did.  I researched the Delco Remy web site, it has documentation that calls for up to 2 gal/min of oil, and another place that actually calls for 1 gal/min at 35 psi.  When I blocked off the alternator oil line at the oil pressure sensor manifold, the oil pressure was 65 psi at high idle.  So I calculated the orifice size for between 1 and 2 gal/min oil flow at 65 psi, I came up with a 5/64" drilling and 1.35 gal/min.  Thank you for Google, even I can do pretty complex calculations!

So I blocked the fitting for the oil line to the alternator and drilled a .078" hole in it and put it all back together.  As expected the oil pressure dropped with the alternator re-connected, to 45 - 50 psi.  The drilling orifice I put in will flow 1.12 gal/min at 45 psi.  So oil flow will be within spec.

Why is this even an issue?.  The oil line to the manifold is quite small, only .22" at the fittings.  So it can't flow much oil.  The alternator obviously doesn't create much backpressure to the flow, it just accepts all it can take.  Perhaps the orifice that is supposed to be in the casting isn't there, one poster said that some alternators don't have the restriction.  So, with no restriction, no pressure, and the gauge doesn't work.  A better solution would be to find another source of oil for the  alternator, or find another source of oil for the gauge.  Neither was handy for me in my installation, and I don't feel like starting to take bits off the engine to find a handy source of oil.  

If anyone can shoot holes in my theory here, please do!  Also, i believe the second line to the top of the body of the alternator may be a vent, not a second oil line.  The Delco Remy site says that belt drive 50DN's need to be vented.

Thanks, Brian

[gmbusguy1]

Brian, the Delco Generator is oil cooled and lubed so be careful if you restrict the oil flow to it. also just behind each exhaust manifold is a oil gallery you can use for anything you like

Chris

[Tony LEE]

"Also, i believe the second line to the top of the body of the alternator may be a vent, not a second oil line.  The Delco Remy site says that belt drive 50DN's need to be vented."

It is an oil supply line too. One feeds into the diode chamber and one into the top of the stator windings.

Separate venting isn't required because the large drain at the bottom gravity feeds into the sump

[Bob & Tracey]

Chris,

Are the oil galleries you mention on both ends of the heads?

Bob

[gmbusguy1]

Bob, I know on my 4106 the oil gallery has a 3/4 or maybe 1" plug or reducer for an oil line fitting. they are in the block itself just behind the exhaust manifolds on the rear by the bumper on the right side of the coach

Chris

[Bob & Tracey]

Thanks Chris, that is where my air compressor is getting its lube oil from. I think I will put a tee in at the compressor and see if I get a better oil prerssure reading from there.

Bob