Cobra4B

Not in this case... it's clearly the oil filter. In my system the pressure drop from the filter clearly matters for oil pressure readings.

And to say that a random 10 psi drop in oil pressure at idle "doesn't make a difference" is foolish. All things consistent if your idle oil pressure suddenly drops 10 psi something is up. In this case the K&N I had in before must have been damaged when I hit the chunk of concrete. Swapping in the M1 filter just kept the pressure at idle down. Going back to a new K&N explained the change.

When your oil pressure gauge is after the filter adding restrictions results in a lower reading. This may not be the case if your pressure sensor is right after the pump, but that's not the case in a LSX.

Fabrik8

Going from 50 to 40 is a 20% difference, which is pretty large. I'd hope that 1 degree and gauge inaccuracy doesn't add up to 20% error..

I understand what you're saying, and I agree that the pressure is still perfectly adequate at idle...

JETSWU87

just so you know i looked at my gauge today when driving.

At idle with 220 oil temp...it was 25psi. 5w30 and ac delco filter(if i remmeber correctly)

I use to read a little higher before my old sender went bad. Also lookin at your tach, your car idles higher then mine. Still on the cam tune?

HerNameIsSway

I am using an oil pressure gauge, its factory on my car, I thought it was oil temp, I was wrong... oops!

LOL I'm gonna do a engine rebuild.

Anyways back on topic, sorry for thread-jack.

Iceman05

Damn, read this thread too late, my first thought once you said you changed the oil was that it was the new oil filter affecting the pressure. Anyway, glad you got it figured out.

Cobra4B

Car still has the cam in it... idles a little higher than stock. I think it's 850 and then 900 w/ the AC on. Stock idle is 700 or 750.

Also... to be clear, the pressure figure never bothered me, just the delta. In fact, if I put a new cam in the car this winter I'm going back to a stock oil pump as the high volume on isn't needed anymore.

Rich

My oil pressure is 95lbs shortly after starting..................that's why it's faster.

Digger70chall

yeah, my original line of thought was that the 1 degree (maybe more with inaccuracies) would change the viscosity affecting pressure...but thinking about it more and looking at some charts it doesn't seem like it would account for the change, the new filter is most likely it.

Where does the pressure gauge sense pressure? It's not directly off the discharge of the pump is it, seems like there are better places to measure at...

Cobra4B

Pressure sending unit is at the back top of the block behind the intake manifold. The concept I'm trying to understand/visualize is supposedly when the oil pump is not in relief the oil pressure will be constant becuase the pump is flowing a fixed volume and all of it must go through the engine circuit... this is what the guys on BITOG.com are saying. They're saying that for restrictions to have an effect on oil pressure the pump must be in relief mode.

It very well could be that my HV oil pump makes over 52psi at the pump at idle (has a 52psi relief spring), and the pressure I'm seeing at the sensor is the drop resulting from traveling down the oil galley, through the filter, and up to the sensor.

Cobra4B

I just re-read this... 1 degree hotter w/ the K&N filter should make the pressure even lower. It'd be different if I was taking a picture w/ the oil at 170 and saying, "see the pressure is higher" but I had it up to 215 and it still wouldn't drop below 49 psi.