Fuso air filters

kerry

Expedition Leader
#1
Someone mentioned on here that OE Fuso filters flow better than aftermarket. Since I have a vacuum gauge/filter minder on my air intake and had a new aftermarket filter installed I decided to experiment. Got a new OE Fuso filter and took pictures of the gauge with the aftermarket and Fuso filters. You can see there is less vacuum in the intake with the Fuso filter than with the aftermarket filter. Both pulled down to that level immediately upon installation. Even with the new filter it seems like too much vacuum to me compared to the vacuum I have seen in my 6.5 Chevy diesel and the CAT 3208 I owned. Neither showed much movement at all on the yellow indicator until the filter got really dirty. So our engines are not flowing air all that well. No idea why? Is the snorkel in a bad location? Is there a vacuum behind the cab? Anyone changed the location of the snorkel and found improvement?

Filter on the right is the OE Fuso. It seems to have more well defined spaces between the filter material for air to flow.
 

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SkiFreak

Expedition Leader
#2
Got a question for your Kerry....
How did you determine which model of indicator should be used?

I must admit, I have not looked in the manual yet, but I expect that it will not specify the air intake vacuum (in inches or millimetres of water) in the specifications.
I am loathed to contact my Fuso dealer to try and get this type of information, as past experiences have led me to believe that they are next to useless when it comes to this kind of stuff.

I have been considering adding an air filter indicator on my truck for a while now, but need to know that I am getting the right one for the job.
 

kerry

Expedition Leader
#3
It's just a regular run of the mill generic indicator. It's the same one I put on my CAT and GM diesels. I suppose a person could put a standard vacuum gauge on there. I have no idea what the 'right' vacuum is but I do know that on my CAT the dirtier the filter got the higher the EGT's since I had probe on it.
 

kerry

Expedition Leader
#5
Mine is not threaded. It just snaps in to a grommet. Perhaps the unthreaded style comes in different versions also but I never saw or never acted upon that option if I saw it .

Am I wrong in thinking that little or no vacuum is ideal. Any vacuum is an indication of restricted air flow? What puzzles me is that my 6.5 GM diesel has a much smaller air filter on it yet lower vacuum than the Fuso. I have assumed that a larger filter would reduce vacuum but that's not the case in this comparison.
 

kerry

Expedition Leader
#7
One factor to consider is that I live at a mile high where vacuum gauges read lower at their maximum. But all my comparisons have been made at the same altitude.
 

SkiFreak

Expedition Leader
#9
Mine is not threaded. It just snaps in to a grommet. Perhaps the unthreaded style comes in different versions also but I never saw or never acted upon that option if I saw it.
Yep, those come in two different models too.

Am I wrong in thinking that little or no vacuum is ideal. Any vacuum is an indication of restricted air flow?
There will always be a vacuum in the intake manifold when the engine is running because it is inherently a low pressure area. The intake vacuum will vary quite a bit, depending on engine speed.
But when it comes to determining if a filter is dirty or not, a higher vacuum will indicate less flow through the filter.

What puzzles me is that my 6.5 GM diesel has a much smaller air filter on it yet lower vacuum than the Fuso. I have assumed that a larger filter would reduce vacuum but that's not the case in this comparison.
The physical size of a filter does not necessarily dictate the amount of airflow it will allow to pass. It normally has to do with the porosity of the filter material.
The surface area of the filter element is another factor. The more ribs, and the depth and spacing of those ribs will affect the surface area of the filter element. A larger surface area does not necessarily increase flow, but it should increase filter life, as it will take longer to block when there are more pores.
 
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kerry

Expedition Leader
#10
Yes, I see that about intake manifold and vacuum but I'm not clear on pre-turbo vacuum ranges in general. My CAT 3208 with an aftermarket turbo showed no measurable vacuum on the indicator with a new filter. (according to the filter minder) My 6.5 GM diesel does have measurable vacuum pre-turbo on the gauge. That difference may be because the PCV system is plumbed into the intake pre-turbo and needs vacuum to suck the gases from the crankcase. My Fuso crankcase is just vented to atmosphere so there's not that need for pre-turbo vacuum so the lower the vacuum the better as I see it.
 
#11
Some other things to consider:

One filter might flow more because it filters less or it might flow more because it has more surface area to flow through. Kind of what Skifreak touched on.


Unless something is lost with the more restrictive filter, I would be inclined to think it's just a better filter. Without a dyno test with O2 and egt readings, you're really only relying on feel unless there is an obvious issue with the more restrictive filter
 

kerry

Expedition Leader
#12
Yes. How would one get O2 readings? I did the experiment because someone on here somewhere at sometime mentioned they felt the difference between an OE filter and an aftermarket one. I haven't felt the difference. I do know that one time when an exhaust leak dirtied my filter with soot on my CAT 3208, the EGT's skyrocketed to a dangerous level. But I never conducted any tests correlating various levels of restriction with EGT's so I don't know how if it's a linear increase or not.
 
#13
It's my understanding that more air correlates to lower EGT's assuming the same fuel. You could weld a bung and probe into your exhaust to test it.
 
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kerry

Expedition Leader
#14
In an ideal world I'd have an EGT gauge, boost pressure gauge, fuel pressure gauge, vacuum gauge on the vacuum pump, and a pre-turbo vacuum gauge. Most of the causes of my real dystopian world lie in my own will.
 
#15
Yes. How would one get O2 readings? I did the experiment because someone on here somewhere at sometime mentioned they felt the difference between an OE filter and an aftermarket one. I haven't felt the difference. I do know that one time when an exhaust leak dirtied my filter with soot on my CAT 3208, the EGT's skyrocketed to a dangerous level. But I never conducted any tests correlating various levels of restriction with EGT's so I don't know how if it's a linear increase or not.
You can install a wideband O2 gauge and sensor and or an EGT gauge and sensor. Or if you were to find a shop with a chassis dyno, they could measure the O2 and possibly the EGT but your exhaust would need an EGT bung.