VDO oil pressure gauge, tell me your readings (videos added) and good news at post 32. Options

[malcolm2]

I have about 1000 miles on my freshly rebuilt 1911 engine. I added a VDO Oil Pressure gauge and sensor using an 18" or 20" long paint ball gun hose. I mounted the sending unit on a small DIY "L" bracket on top of the fan housing.



I am curious what I should be seeing for oil pressure.

Recently: Engine warm, CHT at 340F, Oil temp reading above 100, I see the oil press gauge dropping very low, maybe below 10 during acceleration prior to shifting at 3000 to 3500rpm. At a level RPM when cruising OP is 20 to 30. At idle, it is higher, maybe 40.

This is the 1st time I remember seeing the OP drop that much during acceleration.

Is is normal to see a pressure drop during acceleration? Didn't I read that that is how these AC vw engines run? Is the pressure fluctuation I am seeing normal?

Thanks,

Clark

[McMark]

What oil are you running and is it at the full mark?
What about the windage tray?

You may be sucking air if the oil is sloshing away from the pickup, or if the windage tray is keeping oil from returning from the heads.

[old dog]

I have about 1000 miles on my freshly rebuilt 1911 engine. I added a VDO Oil Pressure gauge and sensor using an 18" or 20" long paint ball gun hose. I mounted the sending unit on a small DIY "L" bracket on top of the fan housing.



I am curious what I should be seeing for oil pressure.

Recently: Engine warm, CHT at 340F, Oil temp reading above 100, I see the oil press gauge dropping very low, maybe below 10 during acceleration prior to shifting at 3000 to 3500rpm. At a level RPM when cruising OP is 20 to 30. At idle, it is higher, maybe 40.

This is the 1st time I remember seeing the OP drop that much during acceleration.

Is is normal to see a pressure drop during acceleration? Didn't I read that that is how these AC vw engines run? Is the pressure fluctuation I am seeing normal?

Thanks,
Wow ! I hope your gauge is somehow wired backwards. Pressure is normally lower at idle and increases with RPM. Rule of thumb is approximately 10psi per 1000 rpm.
Clark

[malcolm2]

What oil are you running and is it at the full mark?
What about the windage tray?

You may be sucking air if the oil is sloshing away from the pickup, or if the windage tray is keeping oil from returning from the heads.

Brad Penn 20 W 50. Just ran about 500 miles on it, After changing the break in oil. I checked the oil last week and it was actually maybe a 1/4 qt over filled. I remember being careful to put 3.7 qts in and it still came out extra full.

What is the question on the windage tray...? I did re-install it during the rebuild, re-used the orange seals.

Dr. 914 suggested that I put a temp. mechanical gauge on to compare. I'll see if Auto-zone rents one. Tractor supply has some oil filled ones with 1/4" threads for @ $8. So I'll have to find some fittings to match.

[brant]

Did you line bore the case when you built it?

[Black22]

At operating temp I'm running slightly above 20psi at idle and around 55psi on the freeway. My engine has a little over 2,000 miles on it after a full rebuild. Brad Penn 20/50 oil.

[somd914]

Though running a 2056 I'd expect similar values to your 1911. Warmed up idle is around 8-10 PSI, cruising at 3,000-3,300 RPM pressure is around 35-38 PSI, do not see a drop during acceleration nor have I ever experienced such with any car, nor have I seen higher pressure at idle than cruise. Agree that your values sound backwards.

[gunny]

Is the sending unit well grounded, normaly the stainless hose provised a ground but with the rubber hose you need to make sure the sending unit case is grounded.
sounds more like wiring problem, crossed wires at gage mabe. (seems to be reading bakwards)

I have the same type of setup and I read ~10-15 at oil temp 200deg and Idol and ~35-40 at 3000 RPMs.

My motor has about 52,000 miles on it.

[malcolm2]

Thanks all. It is warming up to the 40's over the next day or 2. So I will drive the car again and verify my numbers and the gauge operation. Along with some sort of mechanical gauge closer to the port.

[Dave_Darling]

The pressure numbers should go up with RPM (until it gets high enough that the relief valve opens), and should go down with warmer oil temps.

The behavior you are seeing is NOT normal. Re-confirm with a mechanical gauge; your gauge and sender may not be "talking" the same electrically.

If your oil pressure is really doing this, you need to stop driving and start disassembling things to figure out what is wrong. Driving with very low oil pressure like that will wear out everything that can wear, pretty quickly. It could also lead to more catastrophic issues--and that engine looks far too clean to require extra holes punched through it by a thrown rod...

--DD

[914itis]

Crossed wires . Swap the temp wire with the pressure.

[malcolm2]

The behavior you are seeing is NOT normal. Re-confirm with a mechanical gauge; your gauge and sender may not be "talking" the same electrically.

If your oil pressure is really doing this, you need to stop driving and start disassembling things to figure out what is wrong. Driving with very low oil pressure like that will wear out everything that can wear, pretty quickly.

--DD

My "glass half empty" mentality is making me think the worst. I have seen statements on the forums about the 10 PSI per 1000 RPM, but I also vaguely remember seeing that fluctuations happen while driving, oil sloshing around etc...

I've read several posts about track cars taking turns and having idiot lights flicker kinda things.
Being that I have not had this car on a track or at track speeds or turns is a worry. The half full side is hoping for a gauge issue and will check everything possible.

I'll start the car tonight and video the gauge, might have a mechanical one in place too.

[stugray]

What you are experiencing is exactly why I did this:

(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1367906573.2.jpg)

And my mech gauge and VDO agreed almost perfectly.
I will remove the mech gauge before any serious driving.

[malcolm2]

What you are experiencing is exactly why I did this:

(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1367906573.2.jpg)

And my mech gauge and VDO agreed almost perfectly.
I will remove the mech gauge before any serious driving.

That looks like the Tractor Supply or Northern Tool gauge I found last night.

Is it? I like the set up, you might not have to remove the gauge...very nice.

They were $6 to $15 and I could get today. Another website had them with the proper threads, TSC and NT was a 1/4" npt, i need 1/8" or some fittings.

[stugray]

It is a pressure gauge for an accusump. I think I paid $40 at Summit or pegasus.

[malcolm2]

(IMG:style_emoticons/default/icon_bump.gif)
With some new info for the VERY LOW pressure. Turns out the signal wire on the sender was loose. So I tightened it up and shot this video. I should have commentated, but anyway 1 of 2 shows the gauges with KEY off, then on, then start and some revving, but mostly cold. I had to shoot 2 videos, 2 of 2 is with the CHT at normal 340-ish. Oil temp never moved.

I end up with over 50 psi at idle and it drops to 20 at 3200. so the very low condition was fixed by tightening the wire.

Take a look and please comment.

pre-start and cold running:

https://www.youtube.com/watch?v=5PsTowPa2cw


warm engine:


https://www.youtube.com/watch?v=UjZGrtzlS7Q



I was able to purchase a mechanical gauge (gauge from TSC: 1/4" npt, 1/4 to 1/8 stuff at HD) and fittings to attach to the paint ball hose, so I might work on that tonight. but the comparison will be forthcoming.

Clark

[Dave_Darling]

I still suspect a problem with the gauge. It should have lower pressure at lower RPMs, and higher pressure at higher RPMs. Yours is backwards, which either shows something very funky going on inside the motor (oil pressure control pistons? bearing clearances? other?) or a gauge issue.

--DD

[AE354803]

The way your pressure gauge pegged high, even before the engine was on makes me feel like it's operating exactly backwards of how it should. I can't think of a mechanical way that this would occur.

Check your wiring.

[ThePaintedMan]

I still suspect a problem with the gauge. It should have lower pressure at lower RPMs, and higher pressure at higher RPMs. Yours is backwards, which either shows something very funky going on inside the motor (oil pressure control pistons? bearing clearances? other?) or a gauge issue.

--DD

(IMG:style_emoticons/default/agree.gif) It should build pressure, not lose it. Did you check the ground for the sender yet? Very important to get the right signal.

[rmdinmd]

your "hot" and signal wires might be reversed. try swapping the wires on the + and s terminals and see if it acts normal then.