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#1931770 - 06/23/10 02:14 PM Bypass PSI for Onan 122-0800 oil filter
Stewman Offline


Registered: 06/23/10
Posts: 3
Loc: Southern California
I would like to get the bypass psi for the Onan 122-0800 oil filter.

I am new at this, and don't know much about oil filters. I have an Onan rv generator that uses an Onan 122-0800 oil filter.
I found the Wix 51762 (NAPA 1762) replacement filter which is 8-11 psi. I would like to get the bypass psi for the Onan 122-0800 to double check this. Can anyone tell me what it is, or can you tell me where I can look it up?

I have seen a couple of places on the net were people said the Onan filter is 8-11 psi, but I am not completely confident with those. Of couse, the cross-reference would indicate that Wix thinks it is 8-11 psi. But I can't find anything official.

I called Onan, and they read something to me that said the bypass pressure is "maximum relief valve leakage at 5 psi - 0.1 gpm, and minimum relief valve leakage at 16 psi - 3 gpm." I guess I don't understand bypass valves, because this seems backwards to me. Anyway, does this mean it is 5-16 psi? If so, would the Wix 8-11 psi filter be good enough? Otherwise, where can I look this up?

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#1931892 - 06/23/10 03:59 PM Re: Bypass PSI for Onan 122-0800 oil filter [Re: Stewman]
Gary Allan Offline


Registered: 09/28/02
Posts: 39806
Loc: Pottstown, PA
I don't know who makes the OEM, but the xref in Wix/NG is the 8-11.

In a Donaldson P550400 it's a 7-10 bypass but they refer to it as the FL400 equivalent (same size)

It's a flat 14 in the Purolator L35098

Very minor distinctions between the 51762 and the 51516.


Part Number: 51762
UPC Number: 765809517622
Principal Application: Kohler and Onan Engines
All Applications
Style: Spin-On Lube Filter
Service: Lube
Type: Full Flow
Media: Paper
Height: 4.529
Outer Diameter Top: 2.966
Outer Diameter Bottom: Closed
Thread Size: 3/4-16
By-Pass Valve Setting-PSI: 8-11
Anti-Drain Back Valve: Yes
Burst Pressure-PSI: 200
Max Flow Rate: 7-9 GPM
Nominal Micron Rating: 21

Gasket Diameters
Number O.D. I.D. Thk.
Attached 2.865 2.421 0.217

Part Number: 51516
UPC Number: 765809515161
Principal Application: Ford/Lincoln/Mercury (81-09), Chrysler/Jeep/Mitsubishi (02-09), Mazda Trucks (94-10), Various Industrial Equipment
All Applications
Style: Spin-On Lube Filter
Service: Lube
Type: Full Flow
Media: Paper
Height: 4.828
Outer Diameter Top: 2.921
Outer Diameter Bottom: Closed
Thread Size: 3/4-16
By-Pass Valve Setting-PSI: 8-11
Anti-Drain Back Valve: Yes
Beta Ratio: 2/20=14/31
Burst Pressure-PSI: 275
Max Flow Rate: 7-9 GPM
Nominal Micron Rating: 21

Gasket Diameters
Number O.D. I.D. Thk.
Attached 2.734 2.430 0.226
_________________________
http://lube-direct.com/gallan/

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#1931901 - 06/23/10 04:12 PM Re: Bypass PSI for Onan 122-0800 oil filter [Re: Stewman]
willix Offline


Registered: 12/16/09
Posts: 1889
Loc: minneapolis mn
_________________________
96 Eldo, M1 5W30 EP
2010 Fusion SEL 2.5L M1 5w20 EP

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#1932015 - 06/23/10 07:25 PM Re: Bypass PSI for Onan 122-0800 oil filter [Re: willix]
Gary Allan Offline


Registered: 09/28/02
Posts: 39806
Loc: Pottstown, PA
I'd say that most of them are made by Wix with the last one being a Purolator LOL
_________________________
http://lube-direct.com/gallan/

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#1932149 - 06/23/10 09:37 PM Re: Bypass PSI for Onan 122-0800 oil filter [Re: Gary Allan]
Stewman Offline


Registered: 06/23/10
Posts: 3
Loc: Southern California
It seems that most of the replacements are 8-11 psi, except Fram which is 12 psi. Either Onans are too complex to have a straight psi, or they are mucking it up so that we can't compare them to the other brands.

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#1932345 - 06/24/10 01:13 AM Re: Bypass PSI for Onan 122-0800 oil filter [Re: Stewman]
Gary Allan Offline


Registered: 09/28/02
Posts: 39806
Loc: Pottstown, PA
There are very few engines that have a short spec bypass valve rating. Most have a range from onset to full open.

First I thought it was a manufacturing tolerance, but later found out it was a performance spec. Onset to full open.

There are two Honda filters (20Mx1.5 thread) that are identical except one has a range and one does not. It's for the Acura.
_________________________
http://lube-direct.com/gallan/

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#1932398 - 06/24/10 05:17 AM Re: Bypass PSI for Onan 122-0800 oil filter [Re: Gary Allan]
dnewton3 Offline



Registered: 05/14/07
Posts: 5540
Loc: Indianapolis, IN
Originally Posted By: Gary Allan
There are very few engines that have a short spec bypass valve rating. Most have a range from onset to full open.

First I thought it was a manufacturing tolerance, but later found out it was a performance spec. Onset to full open.


EXACTLY! People want to think of this as a static singular set point, but it's not for a few simple reasons.

1) the bypass is typically made with either a wound metal spring, or even a flat spring. All these types of springs are most often of simple, linear rate design. (IOW - not a "progressive rate" spring"). Therefore, the more it opens, the greater pressure it takes to displace each linear increment of opening.

2) to have a true singular opening pressure rating, there would need to be an elaborate control mechanism in place that went from a "closed" position, to a "full open" position capable of maximum flow; a sort of "pop full open" device. That would be a very elaborate and complex thing. It certainly could be designed, but who needs such an expensive addition when not required?

3) the bypass pressure is not really all that critical, as long as the range is near factory specs. A few psi up or down does not make a discernable difference to the safe operation of the equipment.

4) there are two important criteria for the filter bypass feature to meet. One - As long as the full flow of the bypass feature can pass enough volume to safely protect both the filter and the engine pump from damage, then all will be well. Two - the bypass will need to open at a reasonable pressure as to assure something does not over-pressure the desired protected components.


So, all the major aftermarket manufacturers have looked at the application, reviewed their product line-up for many criteria including size, flow, efficiency, lifecycle, pressure ratings (both burst and bypass), adbv, etc, and made a recommendation (or sometimes two).

I'll give you a good example of how much "wiggle room" there can be at times:
My Kubota L3430GST used to be only spec'd by Wix for the 51311 filter. Upon the next generation of tractor, they have upgraded the filter choices to either that 51311, or the 51307 filter (coincidently which is the ONLY one recommended for my neighbors L3240GST Kub). Now, the engines in our two tractors are the same except for the HP rating, dictated by the fuel injection system. But for some reason, Wix recommends either filter for mine, but only one for his. The 51311 is rated at 16 psi; the 51307 is rated at 8-11 psi. So my tractor can endure either, but his is only rated for the lower one? I find that dubious. And not for one second do I think that the 51311 has a single-point opening pressure. Go figure ... shrug

My point is that the filter makers know what they are doing and if Wix and Purolator have available products for your Onan, you'll be fine chosing either. I'd trust either brand to make a solid recommendation for any application. Don't sweat the small stuff; someone has already done that for you.


Edited by dnewton3 (06/24/10 11:40 AM)
_________________________
Conventionals vs. Synthetics isn't about which is "better"; it's about which lasts longer, while assuring safe operation, in relation to cost. Any product can be over or under utilized. The same applies to filters.
Make an informed decision; first consider your operating conditions, next determine your maintenance plan, and then pick your lube and filter. Don't do it the other way around ...

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#1933167 - 06/24/10 10:27 PM Re: Bypass PSI for Onan 122-0800 oil filter [Re: dnewton3]
Stewman Offline


Registered: 06/23/10
Posts: 3
Loc: Southern California
Everyone, thanks for your imput. So it looks like the margin of error must be pretty big, and I should just trust Wix and the other companies to do it right.

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