How to Improve LXi Engine Cooling Performance

[davidbrady]

(11-24-2013 00:18)cmillsap Wrote:  David,

Thank you for the time you have spent on this project. It may well prove to be very beneficial to other Wanderlodge owners

My pleasure Chuck, it's been a fun project.

I can tell when my fan comes on by watching my Silverleaf VMSpc. (For those who don't know, the VMSpc sniffs the J1587 bus and looks at output from DDEC IV fast response engine sensors). Say we're enjoying a dry, windless, 65 deg F day. At full horsepower I can watch the coolant temps steadily climb. At 200 deg the temps stop climbing and quickly fall back to 190, but I'm still at full power. This is due to my fan switching to high-speed at 200 deg F. The way it works on my '02 LXi is the tstats start to open at 190. Remember the tstats are the Weir design. They're fully open at 205 deg. My fan switches to full speed at 200 deg and stays on for 180 seconds or until the coolant temp reaches 190 deg F. If I'm out on Baker Hill Nevada and the air temp is 125 deg F, then after 180s the DDEC again samples coolant temps and directs the fan to stay on for another 180s. IOWs, the fan never turns off for the duration of the climb. On a mild day the coolant temp will quickly drop to 190 within the 180s period and the fan switches off.

It's true that from the early 1990's, and probably before, Blue Bird has been building their coaches for a maximum outside air temp of 100 deg F. Take one of these coaches out to the American Southwest in the summertime and you'll likely find some conditions where you need to power down to manage heat. I recently installed an upgraded radiator core in my LXi which has 7 rows as opposed to the OEM's 6 row core. This will give me 16% more radiator volume capacity. I haven't yet driven in the extreme temps of the Southwest to test it's performance. I've never had my coolant temps go above 205 degrees, primarily because I haven't let them.

One thing I wonder is whether motorhome owners are too cautious about coolant temps - if too cautious then we power down too soon.

For the benefit of our new owners, our Wanderlodge Owners Manuals spec the Series 60 to be overheating if the coolant temperature exceeds 210 deg F and it goes on to say that if this temperature occurs at an ambient less than 100 deg F then there's a coolant system problem that needs to be fixed. If it occurs at temps above 100 deg then the operator needs to de-power. I also checked the Prevost Owners Manuals for their 1996 thru 2003 S60 equipped XL and XLII coaches; the same non-EGR engine as ours. Their manuals spec overheating to be above 215 deg F. They consider normal operating temperatures to be from 190 to 215 deg F. The Check Engine Light comes on at 217 deg and the Stop Engine light at 222 deg F.

Quantifying the improvement is difficult; frankly, the results are less dramatic than what I initially reported. This is the importance of controlled conditions back-to-back testing. I was consistent in my driving, the route, and in working quickly so outside conditions remained unchanged. As you pointed out Chuck, the tstats limit the extent of the improvement at the low end. At the high end it'd be useful to measure the ramp up/down time deltas to give us a feel for heat rejection improvements. Again, all as viewed thru my VMSpc. If pressed I'd say it's probably less than a 10% improvement. This is where the louvers come in. We know with louvers we'll only recover a portion of that 10%... This may be why Wanderlodges were never equipped with the louvered panel. Perhaps they found it too marginal of an improvement. I suppose if we want to look at the whole picture, there's also a fuel economy improvement. If we can decrease the fan duty cycle that can only save fuel. I need to grab some coffee and ponder this a bit.

[BirdPilot]

While going over my recently purchased LXi, one of the things that was added to the "fix list" was the radiator and shroud due to the amount of rust. I've been contemplating replacement of the shroud due to its design. The "orifice" style design employed on my 'Bird is about the least efficient was to design a shroud with respect to fan efficiency.

Having spent 20+ years as a heavy mobile equipment engineer, a good portion of my time was spent implementing newer engines into existing designs as the EPA emission requirements changed. Through the progression of the different Tier engines, the cooling requirement was increased on all but Tier IV. A lot of the challenge was to incorporate additional cooling into an existing envelope. One of the areas addressed was with fan efficiency. The circular plate or orifice style design does maximize available space and is the cheapest option, but as previously mentioned, is the least efficient.

David, having just changed your radiator core, it's a little late to suggest a venturi design shroud, but it can improve your cooling efficiency as much as 20%. I would also suggest exploring fan options as the technology on impeller design for efficiency and noise has progressed considerably over the past few years, at least partly from the demands of the EPA driven engine designs.

These suggestions would require more effort and $$ to follow than changes to the lower plate, but would more than likely address Baker Hill...

[cmillsap]

David,

BirdPilot made several good suggestions above. It makes me think that we may find a better solution to improve the cooling in our busses than installing the louvers. As it stands presently; our cooling systems can be described as adequate but having the ability to climb steep grades at a 10% or 15% higher road speed would be nice. I don’t like traveling in the truck lane on steep grades. That is not a good representation of the quality of a Wanderlodge but maybe I’m asking too much out of a 500 HP DDS60 to push a 50,000# behemoth up a long 6% grade at any higher speeds that it is presently capable of doing. It certainly has the power to do so if we could keep it a little cooler.

As previously mentioned, I believe the cooling system is more than adequate to allow better cooling if we could get more air cfm capacity through the radiator. I remember years ago when I owned a rear radiated Safari coach; I had the same condition. I complained to the factory and they sent me a nine bladed fan to replace my seven bladed original equipped fan. I don’t remember if the blade pitch was changed or not. I do know that it improved my ability to climb steep grades at a higher road speed.

The question now is: What is limiting the air volume (cfm) radiator throughput. Is it the static head pressure developed in the engine bay? Is it the fan’s capacity to move air against an ever increasing static head? Could it be that the slip stream effect of the air passing the side radiator limits the fan’s ability to draw from that slipstream? Or is it that the air being pulled through the radiator is limited due to its turbulence?

Several years ago there was a side radiated coach parked next to me. I noticed the owner had made a “scoop” and attached it to the trailing side of his radiator grill. He claimed it solved his overheating problem. I’m not suggesting we attach scoops to our radiator grill, just mentioning it to make a point of the slipstream’s potential effect on limiting available air for radiator throughput.

You manometer readings suggest that our present fan may not have the capacity to generate a static head of more than 0.80 in. of H2O. At its maximum head, the cfm volume becomes static also. Perhaps we should consider a fan replacement that is capable of more cfm at a higher static head. I think the fan generated air volume increase is substantial when I open the rear engine access door, especially if the fan is on override and running at maximum rpm.

Just some thoughts,

Chuck

[Hisham Amaral]

(11-24-2013 17:12)cmillsap Wrote:  David,

BirdPilot made several good suggestions above. It makes me think that we may find a better solution to improve the cooling in our busses than installing the louvers. As it stands presently; our cooling systems can be described as adequate but having the ability to climb steep grades at a 10% or 15% higher road speed would be nice. I don’t like traveling in the truck lane on steep grades. That is not a good representation of the quality of a Wanderlodge but maybe I’m asking too much out of a 500 HP DDS60 to push a 50,000# behemoth up a long 6% grade at any higher speeds that it is presently capable of doing. It certainly has the power to do so if we could keep it a little cooler.

As previously mentioned, I believe the cooling system is more than adequate to allow better cooling if we could get more air cfm capacity through the radiator. I remember years ago when I owned a rear radiated Safari coach; I had the same condition. I complained to the factory and they sent me a nine bladed fan to replace my seven bladed original equipped fan. I don’t remember if the blade pitch was changed or not. I do know that it improved my ability to climb steep grades at a higher road speed.

The question now is: What is limiting the air volume (cfm) radiator throughput. Is it the static head pressure developed in the engine bay? Is it the fan’s capacity to move air against an ever increasing static head? Could it be that the slip stream effect of the air passing the side radiator limits the fan’s ability to draw from that slipstream? Or is it that the air being pulled through the radiator is limited due to its turbulence?

Several years ago there was a side radiated coach parked next to me. I noticed the owner had made a “scoop” and attached it to the trailing side of his radiator grill. He claimed it solved his overheating problem. I’m not suggesting we attach scoops to our radiator grill, just mentioning it to make a point of the slipstream’s potential effect on limiting available air for radiator throughput.

You manometer readings suggest that our present fan may not have the capacity to generate a static head of more than 0.80 in. of H2O. At its maximum head, the cfm volume becomes static also. Perhaps we should consider a fan replacement that is capable of more cfm at a higher static head. I think the fan generated air volume increase is substantial when I open the rear engine access door, especially if the fan is on override and running at maximum rpm.

Just some thoughts,

Chuck

Chuck and David
What if you move the A/C condenser to the other side (passenger side) of the coach and install an electric fan thus reducing the restriction on the radiator and the CAC. Bob Giffen did that on his LX it is working well for him.
The other option is to stack the CAC on top of the radiator like what Prevost did on XL2. I can email you pics of my engine compartment and the Radiator. It works for Prevost why not on the BB.
Hish

[davidbrady]

(11-24-2013 13:25)BirdPilot Wrote:  While going over my recently purchased LXi, one of the things that was added to the "fix list" was the radiator and shroud due to the amount of rust. I've been contemplating replacement of the shroud due to its design. The "orifice" style design employed on my 'Bird is about the least efficient was to design a shroud with respect to fan efficiency.

Thanks BirdPilot and welcome to the forum. What year LXi did you buy? I must say, you have discerning taste! :-)

I stumbled upon the lower plate fix. I took things apart for cleaning, inspection, and tightening, went for a test drive and discovered better cooling. If there's an appreciable gain by cutting louvers into the plate then it would prove to be a cheap and easy remedy, but after a more controlled test my gut feel is that it alone won't provide the improvement Chuck's looking for on Baker Hill. An improvement of that magnitude will likely require work in several areas.

I'd like to hear about the newer fan technology. What we're running today is a Borg Warner Cooling Systems fan, PNo: 4735-41393-07. It's 32" in diameter and 9 blade. Our shroud has a 32 5/8" orifice.

The fan shroud we have in our LXi's can certainly be improved. The square corners, the lack of a ring orifice, the fan distance from the radiator, and the fan distance from the shroud could all be improved. Like Chuck, I'm inclined to believe that our limiting factor is air flow rate - I don't think we're using our radiators effectively. This is my hunch after installing an upgraded radiator core which didn't seem to provide a proportional increase in overall system cooling capacity. I wonder if the fan is primarily moving air thru the radiator in a donut shape leaving large portions of the radiator without appreciable air flow? Is there hope in pulling a more developed air flow thru the core? Also, because of the fan offset within the shroud, the air coming off the trailing fan blade tips flows straight back into the block instead of deflecting off at an angle; this also has to cut into efficiencies. It probably wouldn't take much work to come up with a new shroud to improve on these items. I have an old shroud in my garage and the South Carolina/Georgia area is the nations fiberglass capital. It'd be interesting to come up with a design and get some quotes on manufacturing.

[al perna]

what is wrong with the idea of using water ? water cools 10 to 15 times greater than air . we could put the tank in the area where the bulk oil tank is ?

[davidbrady]

Al,

My envelop scratching says that ideally you'll need 3/4ths of a gallon of water per mile but more realistically probably closer to double that amount or 1.5 gallons per mile. This assumes you want to power up the hills at 500hp but your cooling system w/o water only permits 300hp. My doubling attempts to account for the water that's splashed off or is blown off before it hits the core and for a non-uniform wetting of the core, some areas over watered some areas under watered. With 100 gallons of water you can cover 66 miles of grades. Then there's the fouling and scaling of both the radiator and the CAC core and lack of water for anything else. It's a solution, but it can consume quite a bit of water.

[al perna]

Thanks , now how did you go about the 3/4 gal @ mile ? now if we use 1 gal per mile and use it 25% of the grade s millage , how much water must we hold on a 8 mile climb at 118 degrees with a 8% Grade . ? you see I didn t even need it on a recent trip with many tough climbs this summer in Colorado . But I do think Chuck was asking for the ability to go faster , not over heat .

[BirdPilot]

My "new" LXi is an '01. Good shape as far as wear 'n tear, only 49k miles. Problem is, as far as I can tell, it's been sitting since '06. Lots of little items to find/fix as well as some higher dollar items. Just bought six coach batteries, should replace the tires. Wasn't thinking too clearly when I looked at it and almost no tire wear. Problem is date code 0706.

I've always worked with Multi-Wing on fans. They make a lot of different styles and shapes in both metal and polymers and have some very sharp engineers on board. As far as the shroud, I just find a good sheet metal house that can roll the orifice needed and weld it in. Most of the fan efficiency involves the fan blade style, inlet geometry, tip clearance to the shroud and axial placement in the shroud. I have an older article from Industrial Vehicle Technology that touches on some of these and will attempt to attach it.

As far as the radiators, a rule of thumb is not to go more than 6 rows. Not that it's necessarily detrimental, but because of diminishing returns. Don't quote me on the numbers but adding second row yields about 90-95% improvement, a third row added ups it about 35-40% and so on to where the seventh row is negligible. Another option is the radiator style. My LXi has the old "fin and tube" style radiator. Newer technology uses an extruded aluminum style that is brazed in a bath. They're not near as expensive as they used to be as the technology to fabricate them has also greatly improved. There's a company over in your neck of the woods (Mebane) that IMO produces some of the best on the market - AKG America.

I'll do some more digging on the overall cooling package and keep you posted.

[cmillsap]

David and I have been using Baker Hill as the basis for needing more cooling capacity in our LXis'. Everyone following this thread should know that Baker Hill is an extreme example to use as a basis for improving the cooling capacity in our busses. The reason it provides a challenge for most big rigs more so than other long steep western grades is that it is about 18 miles long and gets progressivly steeper from 4% to 7% as you climb it.

I was complaining to David a while back that when we were enroute to 'Vegas in last mid July heat of 112*f that I had to reduce my road speed to 35 MPH to keep my coolant temperature at or below 205*F. In the process of climbing that hill; it seemed to me that the air volume being pulled through the radiator reached a plateau prematurily about a quarter of the way up the grade and was the limiting factor to the cooling system's capacity the rest of the way up the hill.

I'm posting this because I don't want to mislead anyone into thinking there is a problem with the LXi's cooling capacity. As a general rule, given its size and weight, our Wanderlodge's cooling system is as efficient or more efficient than most coaches. Extremely steep grades and hot weather exists all over the western states and if we can improve the efficiency of our cooling system, we can navigate over those extreme grades with ease.

http://www.flickr.com/photos/oneillparke...otostream/

IIRC, Baker Grade heading east is 17 miles of 5-7% grade, starting from the town of Baker, and going all the way up to Mountain Pass. If you'r'e approaching from the Primm, NV side, the grade is ~7 miles of 7-8% grade.