Oil pressure drop with bypass oil filter

[Johnstra]

Hey all,



I have a mechanical oil pressure gauge on a "T" at the port I'm drawing oil pressure from (oil filter housing).



I get quite a drop at cold idle (from ~65 psi to ~50 psi) with the bypass running wide open. I have an inline needle valve on the input side and I can choke down the flow so the pressure returns to almost normal. With the flow choked down this way the filter still gets good and hot at operating temp so I know I'm getting flow through the filter. I have not attempted to measure the flow rate yet.



Has anyone else noticed a pressure drop with a bypass filter installed?



Thanks,

-john

 

[Cal Brewin]

I do not know specifically for your GC filter, but for my Frantz, a 1/16" restrictor orifice on its inlet was required to slow the flow, and keep oil pressure up.

 

[Arkapigdiesel]

John,



I see you switched trucks again

 

[Johnstra]

Yeah, I couldn't stand driving an auto (not to mention a PSD) any longer. Actually, if the Ferd had been a 6-speed I'd have stayed with it longer. The 7. 3 is a decent engine and I'd gotten to know it pretty well.



So what do you think about my oil pressure drop?



-john

 

[steved]

I see no drop in pressure with my setup... remember, the target for most bypass systems is between 1 quart and 1 gallon/minute at HOT idle. The flow at cold idle should be almost nothing (literally... I get 0. 25 quart/minute COLD idle). You want a slow flow/little volume as to not starve the main system of oil and to allow residence time in the bypass filter.

For our trucks, I'm running a 0. 0520" orifice (a #56 wire drill??) with my Gulf Coast with no loss of pressure and no more than 1 quart/minute flow at HOT idle. A 1/16" orifice provided exactly 1 quart/minute COLD idle with my first bypass system.

I would suggest building a fixed orifice of between 0. 046" (I believe this is the Amsoil orifice size for the EaBPs) and 1/16". I believe there is posted literature about a 2MM orifice recommendation from Cummins.

You can build a fixed orifice for about $15. You need a male 1/4" NPT barb, 1/8" NPT pipe plug, and a female 1/4" NPT barb... and a 1/8" NPT pipe tap and drill bit for the orifice diameter. You tap the inside of the male barb's threaded end for the 1/8" plug and screw the plug into the barb. Drill a hole through the plug for your orifice, then screw the male barb/plug combo into the female barb... you now have an fixed restriction orifice.

steved

 

[Arkapigdiesel]

Yeah, I couldn't stand driving an auto (not to mention a PSD) any longer. Actually, if the Ferd had been a 6-speed I'd have stayed with it longer. The 7. 3 is a decent engine and I'd gotten to know it pretty well.



So what do you think about my oil pressure drop?



-john

Well, you shouldn't be getting a drop in pressure. Does the Gulf Coast have a restrictor orifice on it? With a restrictor orifice there shouldn't be a drop.



You stated you have it running "wide open"? Does that mean the oil is able to push through the element w/o any restriction except the element itself? If so, I wouldn't recommend doing that. You need a restrictor orifice attached to either the inlet or outlet port (I recommend it on the outlet port).

 

[steved]

Well, you shouldn't be getting a drop in pressure. Does the Gulf Coast have a restrictor orifice on it? With a restrictor orifice there shouldn't be a drop.



You stated you have it running "wide open"? Does that mean the oil is able to push through the element w/o any restriction except the element itself? If so, I wouldn't recommend doing that. You need a restrictor orifice attached to either the inlet or outlet port (I recommend it on the outlet port).

The Gulf Coast does have a orifice, but it is 5/64" and, IMO, would be too large for the 5. 9CTD. I made an orifice and placed it on the INLET side of the filter (the same side as the OE Gulf Coast location).



I believe orifice placement depends on the filter setup... a canister like a Frantz or Gulf Coast probably should be on the inlet to limit the pressure on those "large" seals... for a setup like the Amsoil or the Baldwin/Fleetguard that use a spin on element, it probably doesn't matter as much.



steved

 

[Johnstra]

Thanks guys. For now, I'm using my needle valve to restrict the flow to 1 qt/min. I'll look into making an orifice as Steve describes.



Steve - Do you have an aftermarket oil pressure gauge installed? My factory gauge does not show the same drop in pressure that my aftermarket mechanical gauge does. The mechanical gauge is connected to the same "T" I'm drawing oil pressure from. I don't know if having it that close to the "T" might somehow throw the reading off.



-john

 

[steved]

Steve - Do you have an aftermarket oil pressure gauge installed? My factory gauge does not show the same drop in pressure that my aftermarket mechanical gauge does. The mechanical gauge is connected to the same "T" I'm drawing oil pressure from. I don't know if having it that close to the "T" might somehow throw the reading off.



-john

My oil pressure gauge sender (aftermarket) is also in a "T" in the line between the supply and the bypass filter. I'm using 1/4-inch hydraulic line for my bypass, and the "T" is about 16 inches from the supply. Being mine is electrical, and not mechanical, it might see slightly different "reactions" than yours... but:



I am seeing upwards of 80psi cold cruising and 60psi cold idle. When hot, I'm seeing 25-30psi idle and 60-65psi cruise. And this is in the 1/4-inch line between the supply and the bypass, which indicated to me the restriction is sufficient and has the line pressurized.



Clear as mud?? If needed, I can take a picture of the "T".



I wanted to ask, where did you mount your 0-1??



steved

 

[Johnstra]

Way clearer than mud



Your pressure numbers are very close to mine except for cold idle. Your pressure sensor is a little bit further downstream than mine - don't know if that matters. I have a 12" grease gun hose coming off the filter housing and a "T" on the end of it. One side of the "T" goes to the GCF and my gauge pickup is out of the other side.



I mounted the filter under the passenger floorboard. I have about 8' of hose going to and coming from the filter. I tapped the valve cover for my oil return.



-john

 

[steved]

I mounted the filter under the passenger floorboard. I have about 8' of hose going to and coming from the filter. I tapped the valve cover for my oil return.



-john

I mounted mine under the passenger front corner of the bed... in front of the rear wheel... got a leaking Amsoil swivel I got to fix now...



steved

 

[Johnstra]

Well, I got this sorted out.



The problem with my oil pressure dropping was a gauge plumbing problem. I don't know anything about fluid dynamics, but the way I had my oil pressure line plumbed it was giving bad readings. As I mentioned earlier, I had a 12" grease gun hose coming out of the oil filter housing with a "T" on the end of it. One side of that "T" went to the Gulfcoast filter with an inline needle valve and the other side had the pressure gauge tubing. With this configuration, when I opened the needs valve the gauge would show a 10-15 psi pressure drop.



I changed the plumbing so the "T" comes straing out of the filter housing. The gauge tubing is still right off one side of the "T". I moved the needle valve to the end of the grease gun hose. With this configuration, I see no pressure drop at all.



I still put a 1/16" restrictor on the input side of the filter just to make sure the flow is sufficiently throttled.



Thanks for all the help.



-john