Filter Minders for Dummies

[davidbrady]

(03-26-2013 09:34)al perna Wrote:  Thanks David , sounds like a mod on the air intake makes good sense .

Hi Al,

Sure, I'd be glad to take some detailed photos of my intake system.

If the intake system's air flow restriction on our LXi's exceeds Detroit Diesels specs for clean and dirty air filters:

clean filter: 12 inches of H2O
dirty filter: 20 inches of H20,

then modifications make good sense. The point the others and I are trying to make in this thread is that we can't rely on the FM for that data - what the FM is telling us may be an anomaly. To determine if restrictions exceed spec we need to measure the pressure drop from the inlet of the intake system to 5 inches before the turbo. We need a differential pressure gauge.

If we're grossly out of spec, believe me, I'm going to be the first in line to make some mods, but for all the reasons listed above, I don't think we are. My hunch is that there's something else going on with the FM.

Before letting someone make changes I'd like to see proof of the actual pressure drop on our stock systems. Remember, there's always trade offs. BB and other manufacturers have a long history of positioning the air inlet up high, above the plume of road debris and moisture kicked up by our drive and tag axles. The stock air filter is well protected from excessive moisture, the air inlet is housed in a box of relatively still air protected by a louvered panel, plus the stock air intake system does a good job of keeping intake noise at bay.

Over the years I've grown to respect the choices made by Blue Bird. Often what seems odd at first glance is actually the correct thing to do once the science is understood.

[pgchin]

As a DATAPOINT. I can tell you my 475 HP s60 has never had an issue with the FM. Always in the green and when I pulled apart the 10 year old air filter from the PO it looked brand new with NO water intrusion. I run a "short pipe" with a 45 degree cut facing the road side. I'd have a tendency to agree with David here and speculate that there isn't an issue here with air flow but a true test setup as David described will provide real data to act / react on. I also drive like grandma. Sixty-two most time at about 1500-1600 RPM's. I can also still pull 30-35 on the turbo under load on a cool 60-75 degree morning when the engine is warmed up. Example, route 40 from Tom Johnson's in Marion county heading west into Asheville, NC. Its a pull in the east mountain directory slated at about a 6% accent. I run a STOCK air inlet system and STOCK exhaust / muffler system, no stainless less restricted stuff. DDEC III stock programming. So NOT everyone has an FM issue albeit I'm a 475 HP guy, most others are 500HP.
FWIW, the factory made changes for NO rhyme or reason, as an example, the air inlets on LXI's. Sometimes it was for an engineering change based on dealer feedback (which also could be the case of the LXI inlet), MOST times it's because that's all the parts they had in the bin so they built out what they had. I've said this over the decades, I've talked to them in person at the factory about this very thing. EACH one of these things is custom, built by the same or different guys and gals. They start with a standard set of prints and if a customer custom order required a change to the routing or a part in the print, they'd do it on the fly, it is NOT in the print. I've even seen anomalies in 95's at rallies where the SAME subsystem is wired / set up differently. DIFFERENT people worked the line and buses on different days. They only time they updated the prints is when they brought out a new subsystem. That's why, for example, my factory 95 set of prints I bought at the factory have print dates from 90-95 on them. Some of my subsystems are common with 90's, so I have their prints, subsystems common to 95, new ones, have new prints. I paid 275 bucks for them back in the day and when I saw the different dates on the prints, I was NOT happy!!!! I MADE Bennie and Earl both go back to the computer and pull the print part numbers TWICE EACH and compare them for my build number to confirm the above story about the line builds (that's when they spilled the beans) and to make sure I had the correct print set for my build number.

[al perna]

pete

our pipe is on a 90 also, but the cut is facing inside , I have also seen them cut lower leading me to beleive BB may have been looking for a beter soulution .

David

would a DD be able to check the H2O readings as you state ?

[pgchin]

(03-26-2013 13:29)al perna Wrote:  pete

our pipe is on a 90 also, but the cut is facing inside , I have also seen them cut lower leading me to beleive BB may have been looking for a beter soulution .

Al, although your theory is plausible, it it not absolute. It could be simply that was the length of pipe that particular installer used on that particular build. The factory was NOT that precise on the builds, as I stated previously, not always the same installer. I know from their OWN ADMISSION to me. I believe you are giving the factory too much credit for EXACTNESS......... If Bluebird engineering, for the sake of argument, were looking for a better solution, as you state, then the exhaust prints would have handwritten annotations on them and dates indicating an EC (engineering change) what the change is, and date for the line build changeovers for that model year. Next model year might indeed have a new print for the inlet and exhaust system. My exhaust prints do not have that, leading me to believe it was a line inaccuracy deal (90-95 at least) since you yourself state you'd seen it on a 90 and my prints are for a 95 up through 95. On some of my prints, for other systems, I have those exact EC handwritten notes as I previously described indicating EC line changes and when approved by BB engineering for build line changes. That's why the prints would be common for a model year and only the builds after the EC date cut-in would have the new change, the previous builds would have the "old" stuff. Now, what WOULD be interesting is know which year LXI had the "cap" on the inlet and look at those engineering prints for that year to see if the change was written there either in the form of a handwritten EC or a new exhaust print. If it was, then that would support your supposition that the factory was told about an air inlet issue and was trying to re-engineer the inlets on 500HP s60's to find a better mousetrap.

[al perna]

Pete . maybe a Johnnie A or a George could answer that question , but it does seem strange to me they would in later years place a cap on the pipe and lower it . When we see Davids Pic we will see if BB made any additional changes on the 03 LXI .

[pgchin]

(03-26-2013 14:39)al perna Wrote:  Pete . maybe a Johnnie A or a George could answer that question , but it does seem strange to me they would in later years place a cap on the pipe and lower it . When we see Davids Pic we will see if BB made any additional changes on the 03 LXI .

See above Al, I was reediting my post about capped inlets and our posts crossed in the mail.
this is the reedit you missed above;
"Now, what WOULD be interesting is know which year LXI had the "cap" on the inlet and look at those engineering prints for that year to see if the change was written there either in the form of a handwritten EC or a new exhaust print. If it was, then that would support your supposition that the factory was told about an air inlet issue and was trying to re-engineer the inlets on 500HP s60's to find a better mousetrap. "

FWIW the capped deal might have also been an attempt to fix a water intrusion issue and NOT an air inlet issue even if we found the above to be true. Reverse engineering a defunct factory and an out of production product is FUN but still only supposition until you get facts, like what they told me about prints when they were open. As for Johnnie, George, or Parliment's prints, I'm NOT that curious enough to write them a check for their time to find out, remember I Don't have an FM issue but feel free to call them and write them a check if it tickles your fancy! :-) David's "test" data idea I feel is the best way to go and scientific fact you'd be able to react to and make an informed decision about whether or not to cut metal, etc. Why try to figure out what they were thinking or what dealers were reporting to them when David's idea is real time data you can act upon? Again, it is fun though and brings back great memories for me hangin in the factory nest!!!!!!! :-) At 18 years old, my ole s60 is hummin along just fine!

[davidbrady]

Since I don't know what the restriction of the air filter is I'm going to replace it with a 7" 90 deg elbow and I'm going to calculate the pressure drop, in inches of H20, for my LXi intake ductwork (all the intake pipe-work, from atmosphere at the inlet bell to the turbo, minus the air cleaner):

I have two 90 deg long radius, 6" diameter elbows:
Equivalent Straight: L = 20(6)/12 = 10 ft,

I have one 90 deg long radius, 7" diameter elbow:
Equivalent Straight: L = 20(7)/12 = 11.67 ft

I have 3 feet of straight 6" pipe joining the turbo to the air filter.

I have 2' of straight 7" pipe joining the inlet bell to the top of the air filter.

A 500 HP Detroit Diesel Series-60, at full tilt, moves Q = 1170 cfm of air at standard conditions.

The density of air at 65 deg F is: S = 39.6/(65+460) = .0754 lb/cu ft

The pressure drop of an equivalent length section is: L*S*Q**2/(187*D**5) in of H2O

Pressure drop of 6" pipe (two elbows plus straight): (10+10+3)*.0754*1170**2/(187*6**5) = 1.63 in H2O

Pressure drop of 7" pipe (one elbow plus straight): (11.67+2)*.0754*1170**2/(187*7**5) = 0.449 in H2O

Total pressure drop of the intake duct = 1.63 + 0.449 = 2.08 in of H2O

[DOSZORROS]

David:

Thanks for your great pipe loss review. I haven't done any pipe loss calculations for longer than I will admit here but your numbers are not far from what I had anticipated. I had previously done a sight over your thumb estimate and thought it might be around 5" or 6" drop.

Good work as always!

[davidbrady]

(03-26-2013 21:02)DOSZORROS Wrote:  David:

Thanks for your great pipe loss review. I haven't done any pipe loss calculations for longer than I will admit here but your numbers are not far from what I had anticipated. I had previously done a sight over your thumb estimate and thought it might be around 5" or 6" drop.

Good work as always!

Thanks George, and I must say, you have a very accurate thumb!

So a 2 inch of H2O drop for the duct work allows for a 10 inch drop across the filter, that is if we wish to stay within DD's spec. Or, we could sweat the 2 inch drop, try to cut it in half to say maybe 1" by throwing a few C-notes at it, and gain maybe 0.01% fuel mileage???

[travelite]

Ms. Bee,

I don't want to speak for Pete, but to me it sounds like Blue Bird gave some leeway to the factory staff on certain build assemblies. The tip of the intake inlet may have been one of those items. If there were several options that fulfilled the requirements for an assembly then the choice may have been left up to the factory staff. Just a SWAG.