My MC 96a3 with 8v92 has always had air scoops at the rear of each radiator cavity. I have always assumed that they were effective in diverting a little more air across the rads than if they were not there. However recently I have heard that due to the pattern of air flowing past the bus at those points they are in fact worthless.
Mine are currently off while I add mister systems to each radiator. Should I leave them off?
What's the consensus out there. Is there any science on this?
Thanks in advance.
Mike in GA
OH BOY Scoops and Misters --- there are a LOT of opinions --- a LOT of experience
I'm not sure what the FACTS are
Is your bus having heat problems???
Just wondering why the questions.
Melbo
Overheated once on a long grade between Kingman and Flagstaff. Probably should have been in a lower gear, higher rpms. Temps are not usually a problem.
Mike in GA
Pretty diverse opinions on this. Fred Hobie's website covers it. He seems to have put a lot of effort into improving air flow and did use them. I met a guy who had them on his 5a, when I questioned if they really worked, he told me that he was a retired airplane propeller designer and knew what he was doing. I might put some on at some point.
Mike.. When I bought my MCI from a Charter Company, I asked them the same question about the scoops. Here is what they told me. The bus came stock with an 8V71 and rarely ran hot unless pulling a very long grade. In the early 2000's the charter company installed 8V71 with a turbo and N90 injectors that they bought from the Military. The turbo'd engine would want to run hot if driven real hard or on even slight grades. It is kinda hard to NOT drive a Detroit hard. They installed the scoops right after the engine change and that seemed to have solved their problem. I've owned the bus since last August and have not seen the temps above 185 but I also haven't seen any long grades either..
Jimmy
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi783.photobucket.com%2Falbums%2Fyy114%2FHighwayYacht%2FMC-9%2FDSC01326.jpg&hash=3d69c01eaab8047389efb990200ffc8ef48d7d25)
I've seen them put electric fans in their scoops as well. Made a huge difference. School bus, but still the same principal.
You will notice that Fred Hobe's scoops on his site come further forward than what most of those purchased mickey mouse ears do.
http://users.cwnet.com/thall/fredhobe.htm (http://users.cwnet.com/thall/fredhobe.htm)
Fred was kind enough to share at a rally with a few of us that he did some preliminary work with an aeronautical engineer and tried out a set of scoops that could force in more air than the fans could inhale.
Imagine having the guts to leave the fan compartment door OPEN on an MCI, and winding it up to highway speed, watching the temp gauge climb...then head back down to normal.
But, no opportunity to recover any further development costs, so it went no further.
Keep in mind, Fred has a high HP 8V71T to keep cool.
Fix the rest of the cooling system, check Fred's pages for tips, before deciding you need band aids.
happy coaching!
buswarrior
Highway Yacht- Your MCI is a mirror of mine except I see you have ventilation openings in your rear doors, similar to Fred Hobe's. Did yours come from the P.O. that way?
Mike in GA
I wonder how a NACA duct would help. If you built a gentle ramp ahead of the intake vent leading to a large NACA duct, it seems plausible you could induce more airflow into the radiator. You could make one out of cardboard and tape it onto the side to test the idea.
A short vane sticking out at the back of the air intake might even be sufficient.
International Bus Parts in Florida will make you up custom matching panels to re-skin your engine doors with vented skins.
http://www.ibpindustries.com/ (http://www.ibpindustries.com/)
happy coaching!
buswarrior
Scoops mounted on the backside of the radiator do no good but they look good according to Richard at R & M they do help a little at very slow speeds not much but hinder the air flow at high speeds.
Very easy to do your own testing with a piece of surveyor flagging or yarn at different speeds
good luck
artvonne, Fred's initial work showed that insufficient add-ons had the potential to starve the radiators of air, compared to no modifications.
Be careful not to overheat the engine in the attempt.
The trouble is that the air curls partially into the area outside the rads, but then around and back out, not sucked in, creating a curling wave of air, which then blocks more air from getting in. The fans then have a harder time than stock to suck air through the rads.
There is a fine balance between a ram opening far enough forward to prevent the blocking curl, but then having the opening large enough to give you enough air flow.
To do this experiment properly, there's a fair bit of expensive measurement equipment needed to document the pressure and flow changes, if any, and some wind tunnel testing to get consistent comparisons, and then the issue of cross wind effects.... and of course, someone competent in this field of physics that can do the math correctly, only to come up with a solution that is easily copied by other busnuts with a tape measure instead of purchased from the developer to recoup the expense.
Busnuts are notorious at not getting the fan compartments on MCI coaches properly sealed up, there's lots of mileage of rotten rubber around each rad, and then all the way around the door.
Lots of coaches with cooling problems wouldn't, with a little work to the stock bits.
Only the hot rodders and auto transmission retrofits have a real danger of overheating and need some sort of modification.
happy coaching!
buswarrior
Quote from: Mike in GA on April 10, 2011, 09:14:20 AM
Highway Yacht- Your MCI is a mirror of mine except I see you have ventilation openings in your rear doors, similar to Fred Hobe's. Did yours come from the P.O. that way?
Mike in GA
Yes... Everything you see in the picture was done by the PO.. The picture was taken right after I got the bus home. It doesn't quite look like that now though since I have removed windows and re-skinned.
Jimmy
One thing about MCI airflow I was wondering about was whether the spaces on the sides of the engine were left open to the ground. We have put a platform in so that the space is usable, but it seems that closing those areas restricts the exhausting of the cooling air and may actually create a back pressure.
When I was in Thailand, where it's really hot and humid, I noticed the busses there had large grills on the rear engine doors to keep the hot air moving out of the engine compartment. Since Thais like to keep things presentable, some chrome parts and blue lights are often added inside the engine bay for good looks through the grille.javascript:void(0);
have used rear doors open partially on my MCI 8 which helped. also misters(wouldn't recommend for long run) as they tend to damage radiator with extended use. New radiators finally solved my problem. Bob
Instead of closed scoops, would some sort of spoiler that directed air in be better?
Quote from: Lin on April 10, 2011, 02:57:44 PM
Instead of closed scoops, would some sort of spoiler that directed air in be better?
Hmmm, I have thought about adding a 3/8" or 1/2" wickerbill to the front edge of the radiator opening? Jack
This discussion always intrigues me --- when was the last time you had heat problems at speed (ie over 55 mph) --- Even when my 8V71 was just about toast it would always run cool enough if we were rolling down the road but when I hit a hill and slowed down THEN I would need more cooling --- Everyone says the scoops don't work at speed BUT DO help when you are going more slowly --- so what to do what to do --- the misters are ALWAYS an interesting topic too --- do misters cool with water running off the rads or do they cool by evaporation???
I ALWAY like to hear (should that be read) the opinions and ideas for this --- not a problem for me with the L10 but entertaining to see what people think
Melbo
My 5C came with the scoops. 6V92/HT740, 90 injectors. It does get hot going uphill on a hot summer day. I took the scoops off, and there is NO difference. Plus it looks better without them, IMO. On my to do list is a transmission cooler.
JC
Of course, we have been leaving out another standard, which is the full length mud flap going across behind the wheels.
Quote from: Lin on April 10, 2011, 05:53:03 PM
Of course, we have been leaving out another standard, which is the full length mud flap going across behind the wheels.
It seems I read something like that once before, like on old SAAB's or something. Are you suggesting a full flap ahead of the engine would act as an air dam? That it would create more low pressure aiding air flow through the rads?
Yes, as I understand it, it was standard practice with GMC's.
Any more info on the mudflaps? That sounds interesting!
Misters are only needed on a steep climb, so they are rarely used enough to clog up the radiator. We installed some on a DL3 and they work well and are only needed on a hot climb.
Just try and use soft water in those misters. Regular water can lime it up and compound your problems in time.