MC5 air intake

[lostagain]

I feel that my 6V92TA is still not getting enough air, even after improving it with an Eco filter. I am thinking about cutting a hole on the side of the bus, in front of the rad grill, just above where the air intake comes up. Don't you think the engine is trying to suck air against a vacuum in front of the rad, because of the strong flow from the squirrel cage fan? I got the idea from Fred Hobe on his site: Coach Conversion Central. I tried to copy and paste the picture, but it doesn't work for me. Has anyone tried it? Thoughts, comments...

JC

[artvonne]

  Make a homemade manometer and check pressure readings in different locations, they are very, very simpleto make. If its pushing water up the tube, you have positive pressure. If its sucking it down, well, thats not a good place for the engine to suck air. Guessing at it is like throwing darts blindfolded.

[bevans6]

If you put in a NACA duct there, where Fred has his grill, you would probably get positive pressure into the air filter.  You'd have to construct ducting to the dirty side of the air filter, obviously.  I also  think the factory air intake is a little chintzy, and in an odd place.   The test with the manometer are a good idea.  Air flow along the side of a bus is hard to predict, but you can show just by opening a rear window that there is somewhat high pressure near the rear of the sides of the bus.

What is leading you to think there is an air-flow issue with your current installation?

Brian

[christopher]

i have the orig 3 filter sys and a 692 and have no problems.
must be something else.
Chris
1978 mci 5c

[lostagain]

What is leading me to think there is an air flow issue? Nothing in particular other than a gut feeling. When I first put on the Eco filter (1300 cfm), the FilterMinder restriction gauge showed 7" water column, which is the bottom of the gauge, could've been even less. But it only took a couple of times on a dusty road for the reading to now show 15", and I am blowing black smoke again with less power. I have enlarged the intake hole into the rad opening. I have made a pre filter with several layers of furnace filter material sprayed with oil that I cover the air intake with when in dusty conditions. (Our access road and the dirt bike races we go to are either muddy or dusty.) I have a new filter ordered. I am just thinking that if there is a way to improve the air intake flow, I would want to do it.

JC

[bevans6]

It sounds like you have a non-stock filter set up, which I think I recall from previous posts.  You probably know that the stock setup has four filters in parallel, huge filter area.  maybe you can add another filter in parallel somehow, double your area?  Or just buy a lot of filters.  If your pressure drop is so low with the brand new filter I would not suspect that the intake is a problem, since it gets measure along with the filter drop - it's a total system up to that point measurement.  so you may be thinking of fixing something that isn't broken.

From my racing experience, the pre-filters that you have added can totally kill airflow.  Not that they might not be needed with a really dusty environment, just that a lot of things like that can really kill airflow, which is often not intuitive at all.  My thinking is that if you have proven that the air intake isn't the restriction since you had good/great airflow with the new filter, then improving the air intake won't make much of a difference because it isn't the restriction.

Brian

[lostagain]

Thanks Brian, makes sense. Works great with a clean filter. The problem is the intake is low and sucks in the dust easily. Yes my home made pre filter increases the restriction significantly, but it catches dust, and I only put it on for short durations when going up dirt roads when it is dry and dusty. It makes my expensive filter lasts longer. Oh and I don't really have space for another filter.

I have thought about building an intake duct up to the corner of the roof, but a 7 or 8" pipe up through the bed room doesn't really turn me on now.

My old Courier 96 has the air intake on the roof, and taking in dust was never an issue.

Thanks for all responses, this is one of these problems where other's ideas are valuable.

JC

[bevans6]

Someone had a picture of dual stacks up the back of the bus, one was exhaust, one was intake.  Looked cool - dual pipes chromed and stack up to the roof!  i have a single exhaust stack on my bus, to get the smoke up high in camp ground and keep it off the towed car.

Brian

[lostagain]

Do you have a picture? Or a link to one already on this board.

JC

[bevans6]

It may have been on Ruthi's new bus, I don't really remember. sorry... - and I can't make the search function work for beans, either.

Brian

[bevans6]

found a pic:

http://www.busconversions.com/bbs/index.php?action=dlattach;topic=15607.0;attach=15921

I believe, remembering the original thread on the setup, that the left one is exhaust and the right one is intake.

Here is the thread from when I built my exhaust stack, and another picture of the Ruthi Dina on the second page.

http://www.busconversions.com/bbs/index.php?topic=15495.0

Brian

[Rick 74 MC-8]

JC

  Haven't done it yet but I have the same concerns I plan to open a hole about the same size as the original on the curb side then box off a duct across the top of the engine (bulkhead ?) only need 3 sides on my MC-8 I can cut it into the stock plenum before the filter I figure it will in the same place as the original so I won't have to worry about rain and by the time it makes across the new duct any water will have fallen out anyway. Take a look at yours it looks you might be able to do the same thing



                                                                                            Rick 74 MC-8

[lostagain]

Rick, I went looking at my bus for your idea. There is no way, I don't have any room left in the engine bay for a duct from side to side. It would have to be 7 or 8" diameter or the square equivalent to be effective and their is just not that much room.

JC

[Ncbob]

JC, I've got a 5A with 4 stock dry air filters. You, I assume, have a Saudi model which was operated in more severe conditions than mine. Do you have the 6-71 or an 8-71?  Most of the 5C's I've run acrossed have the 6-71.

Check with Jack Conrad or Jim Robinson to see what the standard air filter arrangement is for your bus. Some one might have changed it and put you in the trick bag. That's the nature of our hobby...there are times that some of us think we know more than the Engineers who designed these creatures we drive.

I'm going to keep track of this thread to see how you make out.

NCbob

[lostagain]

NCbob, my bus is a 5C with a 6V92/HT740. When I got it, it had a dry air filter that, although clean was showing 15" water column restriction. It was too small. I have replaced it with an Eco type disposable filter that flows 1300 cfm. It only shows 7" restriction when clean, which is fine, but I drive in dusty conditions at times, and it gets plugged up fast, because the intake is shared with the driver's side rad, which is low enough to suck up the dust kicked up by the rad blowers tornado coming out of the bottom of the engine compartment. This set up is OK, as long as the filter is clean. I made up a pre-filter with furnace filter material, oiled, that I put on the filter duct upstream of the filter when in dust. I just have to be diligent about using it when on dry dirt roads. I am still humming and hawing about building an intake duct that would suck from near the roof, but I am not crazy about running a 7 or 8" duct through the bedroom... Some of the replies on this thread have helped me realize that I really don't have a restriction problem per se, but rather just a "sucking dust problem", which buying filters more often ($$) will solve nicely...

JC