oil pressure reading - the head or at the oil filter?

[blacksheep]

This is an age old question and I am unclear on the answer.

This is a general question although it pertains to the Evo as well.

There are 2 options as mentioned above:

1) Tap sender into the head (Evo has a hex bolt when removed allows a sender to bolt-up)
2) Tap sender into oil filter housing (Evo has hex bolt when removed allows a sender to bolt-up)

But, I am sure at the head pressure reads lower than at the filter. So, question remains:

Which is better or lesse of the two evils?

I assume one loses oil pressure at the head first when the pump goes, yet people seem to argue that this is a location for oil feed and the oil filter is better.

Any advice appreciated!

Thanks!

 

You're going to get the most accurate reading from the oil filter housing. It'll give you the closest reading of what pressure the crank is getting.

Tapping from the head will give you a considerably lower number as that fitting is the last area to get oil before it's returned to the pump. Not 110% sure on the Evo 4G63, but that's how it is on the "older" 4G63s.

 

[DarkDevilMMM]

get 2 electronic sender, a switch, and a gauge.

tap into both, so u can see how much pressure lost is taken place inside the engine to determine clog galleries /ubbthreads/images/graemlins/dunno.gif maybe?

 

[atc250r]

+1

The oil pump housing will be closer to what the main bearings are seeing and that is what really matters. I disagree with the head losing pressure first. If I lose pressure due to a failed pump then the pressure at the pump will drop off first. Look at it this way, you are spraying your car with a garden hose from 20 feet away and you let the handle on the hose slam shut. Doesn't water continue to hit the car for a brief moment even though the nozzle has stopped spraying?

John

 

[JB]

Good analogy John. /ubbthreads/images/graemlins/applause.gif

 

[joemoto]

If the hose emptied itself from the shutoff valve then I would agree, since the water that has left the hose prior is not affected by the valve any longer I would disagree with the example. Since water and oil do not compress to store energy I believe that once the oil pump fails or a faucet is turned off there is no longer any pressure to move either the water or oil.
If you have a straw in a glass of water and put your finger over the top and then remove the straw from the glass the water will stay in the straw.
For what it is worth.
Joe

 

[blacksheep]

Ok, I am no electrical genius. But, I can buy 2 senders and 1 switch. I am not sure how to wire it all up and don't know if I need to go to this extent. I would like to monitor oil pressure with 1 gauge at one spot - so which one would I use?

John - you made absolute sense. Thanks!

 

[atc250r]

I vote the filter housing. If you want I can make you a simple schematic to have both senders work with one gauge using one single pole double throw (SPDT) switch from Radio Shack.

John

 

[blacksheep]

There you go confusing my foreign ass again.... /ubbthreads/images/graemlins/rofl.gif Well, I am going to do the oil filter location.

if I get brave to do the dual senders, I'll bug you more. Thanks, John!

 

[PJGross]

...maybe, but it is not a correct analogy, as mentioned above.

A garden hose continues to spray because it expands under pressure. When the faucet is turned off, the expanded hose now contracts to regain equilibrium, which continues the flow of water out the hose. This is why the water continues to flow through the nozzle. If the garden hose were a pipe, like in the car (with much less volume too) the flow of water would be instantaneously stopped. It wouldn't matter where the pressure Gauge was at, both would drop identically from their respective operating pressures...unless there was air in the system that was compressed, but there shouldn't be.

Basically, even if you have a warning light or buzzer wired in the circuit, you will be lucky to catch a catastrophic oil pressure failure before damage is done. I have and use oil gauges, but they're more of a "nice to have" than an engine saver since I don't have a warning system with them, and even with an "idiot light" the response time is too fast.

Oil or water "temperature" gauges are much more forgiving and useful in analog form, as the temperature response is more gradual than pressure. However, with my Impala even with a water temp warning buzzer for my electric h20 pump, a bad connection only gave me enough time to pull over and shut down before the temp gauge went through the roof. I think you'd be lucky to save your bearings with a catastrophic oil pressure failure.

-PJ

 

[blacksheep]

Thanks, PJ.

 

[ken inn]

how the heck can the location of the sender make a difference, you probably gotta be looking right at it when the pump/pressure dies, then you only got a few seconds. so, picture kc winding first, then checking out his neighbor, and as he speedshifts second, the oil pump fubars, right at 7k. "CHECK OUT THE TIGHTNESS OF THE SHORTS!!! probly bounce a quarter off them buns. whoops, what's that noise?" dead motor. it would be better to hook up an audible warning, like the stall horns on an airplane. by the time you see the gauge is 0, it is over.

 

[CO VR4]

If you want more security, install an Accusump with a warning light when it starts to discharge. That way you have ongoing pressure (from the Accusump discharge) AND immediate warning that you are losing pressure. /ubbthreads/images/graemlins/smile.gif

 

[atc250r]

The gauge IMHO is more of a life saver if all of a sudden you develop a leak (oil return pipe cracks?) and you'd probably notice the gauge fluctuating a little when the pump would briefly go dry around a turn. In that case it'd save you a costly repair. I still stand behind my original statement that if the pump fails then the gause will show the loss closest to the pump first even though my analogy is not technically correct it still expresses my point properly. Anyone wanna volunteer to try it? /ubbthreads/images/graemlins/devil.gif

John

 

[jepherz]

Dual senders would be easy, if you really want that extra equipment and room for leakage. For us vr4 dooods, we could use one of the automatic switches in the console

 

[Polish]

Get this and you won't have to worry about staring at your neighbor. /ubbthreads/images/graemlins/wink.gif

Solves all the "You can't shut it down in time" arguments. Even so I would still want a gauge. Mine is tapped into the filter housing fwiw. I have been contemplating one of the sensors I linked above though, for 12 bucks it's more than worth the money. /ubbthreads/images/graemlins/cool.gif

 

[PJGross]

+1 for Accusump. Used frequently in Impala applications for roadracing and autocrossing. Several guys with 383s that can't run stock windage tray have eaten bearings on the roadcourse, but with an Accusump no problems. It is relatively inexpensive and big insurance. I'd still run a gauge b/c I like to watch things, but the Accusump will save your engine in a catastrophic failure b/c it will bleed off like a garden hose, but you'd still only have a few seconds so hook up an alarm, too!

Another benefit of the Accusump is you can switch it on for startup to reduce startup wear on bearings, too.

-PJ

 

installed mine at oil filter location...i wished i've done this earlier caused me a knock enginedue to il pump failure


What?

 

[number3]

I am using a mechanical gauge and mine is tapped in at the oil filter.