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.