Losing oil pressure during WOT?

[terryk2003]

Ok, I just noticed this last night and I'm a bit concerned. When the car was cold I had 65ish PSI but when i went WOT it would drop to 20 or less then come back up when I let off. At first I thought that maybe it was low on oil and the motor was tilting enough to pull the oil away from the pickup so when I got home I revved it up in the parking lot and to my surprise I has the same problem without the car actually moving. I'm not sure how long its been doing this because I normally look at the road under WOT but I happened to see it out of the corner of my eye last night. I changed the oil about a month ago and I'm running a K&N filter and I'm wondering if this could be causing the drop? Or a faulty pressure sending unit (it's about 4 years old now)...any ideas would be helpful. Thanks!

[AL]

If your actually losing pressure... thats not good at all... I really dont know what could cause it but I would replace the sensor anyways

[RobertISaar]

oil pressure is dependant on a couple of things: oil viscosity, oil temp, restrictions to flow and pumping volume.

 

now since it's an instant drop, i don't see the viscosity or temp changing dramatically enough in that amount of time to cause it, so we're left with restrictions to flow and pumping volume.

 

now, the oil pump SHOULD pump the same amount of oil in every revolution, but obviously at higher RPMs, it's pumping a lot more oil in the same amount of time compared to something like a 1600RPM cruise. unless you have some kind of variable displacement oil pump, in which case this doesn't apply.

 

now, i'm no 3800 expert but MOST motors have a bypass valve in the block that opens up and allows unfiltered oil to run through the motor if the pressure difference between before and after the oil filter is too great(i believe for gen2 60V6, it's ~10PSI?). now, if your OPSU reads pressure between the oil pump and the filter, this will be seen as a drop in oil pressure since the oil is venting around the filter and with less restrictions, there is less pressure. if it reads after the filter, but before the rest of the motor, then it SHOULD stay relatively the same, possibly higher due to more volume in the same area.

 

so, i would grab a spare filter and throw it on, see if it still happens.

[BXX]

sounds like oil pump cavitation due to the oil filter not flowing enough or being restricted.

 

throw a delco on there and report back with results

[Addicted to eaton]

Im with bob on this one. Make sure the delco is not a plastic core. Do you hear any abnormal chater at higher RPM?