What determines filter size ?

[Merkava_4]

What are the engineers thinking when they specify a filter size ?

I was surprised to see that a 2000 Lexus ES300 with the 3.0L V6 and a 2000 Lexus LS400 with a 4.0L V8 take the same Wix 51348 filter. Meanwhile, a GM 3.8L V6 and a GM 4.3L V6 specify two different size filters. Maybe Toyota designed the V6 and the V8 at the same time and decided to use one filter.

 

[ZeeOSix]

If an engineer was going to design an oil filter from square one, I think he would consider these factors.

1) Oil viscosity range specified to be used in the engine.
2) Engine's oil pump output at red line.
3) Oil pump's pressure relief valve setting.
4) Debris generation rate of the engine.
5) Recommended oil change interval.

The filter's media flow and filtering characteristics, as well as the total area of the media would be designed around the factors listed above to ensure the delta-p across the filter is tolerable (probably shoot for for around 4~5 PSID at redline with hot oil with a new filter). The filter's bypass valve would be set high enough to ensure minimal bypass events through the use period of the filter, unless the filter was horribly clogged from a sludged up/dirty engine. Of course, there would be some "safety margin" designed into the filter to ensure it could handle the use conditions with ease. Don't want to design it on the edge/limit and risk failures.

To do it right, I think at least that much work would go in to an oil filter's design. Once all those characteristics listed in 1 thru 5 above are known about a particular vehicle, then the filter manufacturer could match up the closest filter they already have designed, and just put the right base and threads on it to fit the particular engine.

 

[Merkava_4]

ZeeOSix,

Why would the GM engineers specify a larger filter for the 4.3L V6 than the 3.8L V6 ?

 

[ZeeOSix]

Originally Posted By: Merkava_4
ZeeOSix,

Why would the GM engineers specify a larger filter for the 4.3L V6 than the 3.8L V6 ?


Could be various reasons. Larger filter for the larger engine makes some sense. Maybe the 4.3L has a high volume oil pump, or maybe it produces more contaminates into the oil.

And don't always be fooled for the size of the can. I've seen cans that are larger than another actually have less media area inside the can.

 

[Merkava_4]

Originally Posted By: ZeeOSix
Could be various reasons. Larger filter for the larger engine makes some sense. Maybe the 4.3L has a high volume oil pump, or maybe it produces more contaminates into the oil.

And don't always be fooled for the size of the can. I've seen cans that are larger than another actually have less media area inside the can.


And what I found interesting is the filter for the 3.8L and the filter for the 4.3L are both rated at the same 7-9 gallons per minute. Logic would dictate that a larger filter flows more oil.

 

[ZeeOSix]

Originally Posted By: Merkava_4
And what I found interesting is the filter for the 3.8L and the filter for the 4.3L are both rated at the same 7-9 gallons per minute. Logic would dictate that a larger filter flows more oil.


Well, maybe one flows 7 GPM and the other flows 9 GPM ... therefore, they both meet the 7-9 GPM spec.

And that flow spec is very nebulous. There are many factors involved when flow of that magnitude is happening.

Read this thread if you haven't ... it gives some insight to how an oil filter flows oil, and what causes the delta-p across a filter. The optimum design goal is to filter at high efficiency and keep the delta-p low at the same time. It isn't really rocket science to achieve that.

http://www.bobistheoilguy.com/forums/ubb...451#Post1619451

 

[salv]

Location of the filter on the motor and the motor's orientation in the engine bay will determine the amount of clearance for the oil filter. This has more to do with selection of filter size for an engine than anything. The trend in the industry is toward smaller filters due to tighter clearances in engine bays. These shorter filters can be used where taller filters are specified without issue. One of the most ubiquitous examples is the downsizing of the FL400, to the FL400s, to the FL910s.

 

[CharBaby]

Different teams of engineers that were working on these two different engines at different times coming up with different specs.

Though, both engines being old school designs from years ago(and working quite well in modern times). The 4.3 is built off of the old Chevy small block V8. I don't remember where the 3.8L derived from though, it goes back to the 60's

 

[dlundblad]

I have often wondered this. The filter for my 4.0 jeep is much larger than the filter for my dads 6.2. 195 hp vs 411 hp is quite a difference. Lol.

 

[Wilhelm_D]

Originally Posted By: Merkava_4
What are the engineers thinking when they specify a filter size ?

I was surprised to see that a 2000 Lexus ES300 with the 3.0L V6 and a 2000 Lexus LS400 with a 4.0L V8 take the same Wix 51348 filter. Meanwhile, a GM 3.8L V6 and a GM 4.3L V6 specify two different size filters. Maybe Toyota designed the V6 and the V8 at the same time and decided to use one filter.

For reasons known only to the engineers they'd often rather spec a new filter than utilize a perfectly good filter that already exists.

A good example of commonsense is the Hyundai/Kia use of one filter across the board for their spin-on applications. Unfortunately they did not follow this practice on their cartridge type filters for the newer V-6 and V-8 engines.

The parameters are flow, expected capacity requirement, available physical space, and cost.

Bypass valve settings involve the design of the lubrication system and the expected application - family sedans tend to be set lower than sports cars.

 

[dnewton3]

IMO, all personal use vehicles could be satisfied with less than a dozen offerings across the entire market. But good luck trying to get OEM brands to agree to it; they can't even be consistent across their own lines.