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Old 07-21-2021, 07:36 PM   #1
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Question Preventing Overheat thru driving technique

After two lessons with my first DP, I know, somewhat, how to avoid too-high coolant temps looking at coming up-grades, current ECT, engine load, and especially RPM > 2000 at whatever speed that brings.

The repeat trip up Yarnell grade (AZ) [OAT 100+] pulling a somewhat heavy trailer, was markedly different from last time. Granted, the retaining strap for 'doghouse' insulation previously did a slow chop-chop on the heater feed hose, but improved technique (even a blind squirrel can find a nut) delivered ECTs 30-40 lower this time.

Y'all know the huge difference above 2000 RPM {coolant circulates faster} and while not thrilled at using 3rd or 2nd gear..... Lower ECTs return much more quickly on downgrades by delaying gear select to 'D'.

It seems that engine load above 50% proportionally elevates ECT.

Lessons form longtime DPers; links or whatnot, are sought & welcome.

Thx in advance.
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Old 07-21-2021, 08:00 PM   #2
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My radiator is in the front, so I just put my foot to the floor and send it
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Old 07-24-2021, 11:11 AM   #3
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It's interesting to me to hear about the varying engine coolant temps (ECT) reported by Alpine owners. In our case, I don't manage driving technique to effect ECT. I have the same engine, but a 40' quad, probably carrying 5000# more weight, and towing a Jeep GC. In my 12 year experience with this coach, I usually just set cruise and let the system manage everything. Based upon that practice, I see a range of 179-201 degrees, depending on grade and radiator fan speed. Outside air temp doesn't seem to affect it, and I've driven in outside air temps (OAT) up into the low 100's. Now, I will manually downshift on grades, if RPM tends to hold in the 15-1600 range, but again this isn't a ECT issue.

I can only theorize that variances from coach to coach are due to radiator fan speeds, thermostats and coolant used. Depending on load, I can clearly see the fan speed changes effect on temperature. On level ground, it's pretty typical to see the temp swing from 189 back down to 183, as the fan RPM automatically ramps up and down. On heavy grades, the temp can rise to 201 and hold there as the fastest fan RPM just maintains the temp. On RARE occasions, I have seen it creep up to 202-203, but I'll usually downshift before that point.
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Old 07-25-2021, 08:35 AM   #4
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Thank you for this post. I was struggling to find info on how to drive my bus up grade. I just discovered that I can not drive the bus upgrade in Econo mode. In that mode the temp would easily climb to 212 or so. On the trip from Coeur d’Alene to Albany, I decided to take it our of EM and let the cruise do it’s thing. To my amazement, the bus did exactly what it was suppose to do. I may have saw temps around 205 on occasion, but not for long. Plus the climbs didn’t seeem as laborious on the engine.
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Old 07-25-2021, 09:07 AM   #5
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Originally Posted by Ernieo View Post
Thank you for this post. I was struggling to find info on how to drive my bus up grade. I just discovered that I can not drive the bus upgrade in Econo mode.

Actually, you CAN leave it in economy mode on grades. You then use the down arrow to select the correct climbing gear.


Been doing it that way for two decades and 3 DP's.


But, for those who choose to just leave it in "D", you are making the correct decision, though even in power mode, one needs to keep an eye on temperature and use the down arrow if coolant temperature continues to rise.



The "got ya" here is that the correct way to climb long grades is at higher engine RPM, but at less than WOT. That combination will cause the Allison to upshift, even in power mode. Hence the need to manually select the correct gear.
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Old 07-25-2021, 10:20 AM   #6
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"The "got ya" here is that the correct way to climb long grades is at higher engine RPM, but at less than WOT. That combination will cause the Allison to upshift, even in power mode. Hence the need to manually select the correct gear."


This is exactly how I have to drive to keep everything in check.

I also added a exhaust temperature gauge (egt) to the mix because I'm usually towing heavy, a little under 8k with my current setup.

By manually shifting down I can keep the engine load and fan speed down to around 75% as well as keeping the egt in check on two big hills I pull regularly. This only made me slow down a couple mph. By keeping the egt's were I'm comfortable everything else just happens automatically and I still go over the hills at 58 to 60 mph.
I might see 205 in 90 weather with the engine bay door closed, but normally only 200
I've never tried economy mod because I'm always going up or down a hill in my part of the country.
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Old 07-25-2021, 10:21 AM   #7
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Dual purpose thread

First, I'll thank all who posted helpful info. My purpose was to learn the the unknown to me and perhaps save some newer owners the difficulties and expenses we experienced.

Our radiator was removed and thoroughly cleaned, with new, correct coolant and thermostat. The coach has 90k, but I'm unaware how to view fan speed. (using VMspec). I've seen various posts on wax valves and the e-controller in our DP.

The coolest ECTs in desert (100+) is 187; up-grades now have me watching ECT closely, but 205 is not rare, IF I override to a lower gear. Dash A/C, on or off, makes no discernable difference. (fan controller increases fan speed?)

The cleanliness of the radiator fin seems okay and undamaged.

My newly adopted techniques, while requiring more attention than Cinequip's, are effective, but I'd prefer a more hands-off driving experience.

How/where is fan speed displayed?

Thanks again.
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Old 07-25-2021, 10:38 AM   #8
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Originally Posted by whalepirot View Post
How/where is fan speed displayed?

Thanks again.

To my knowledge, it is NOT.


But, by deduction, if coolant temperature does not get above 205 degrees F or so (yes, along with you driving "correctly", you can ASSUME that it is working as it should-- going to high enough fan speed to control engine coolant temperature.


Another thing you can monitor is intake manifold temperature-- from Scan Gauge D, Silverleaf, etc. With the Alpine, this is more an issue when first starting, as it is not unusual for intake manifold temperature to rise, as the fan speed is controlled by coolant temperature which rises much more slowly than intake manifold temperature. That is the gremlin with the A/C condenser in the cooling package. Until engine coolant temperature calls for fan, there is insufficient air flow over the dash A/C condenser and the high pressure switch can turn off the A/C compressor. Several have come up with good "work arounds".
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Old 07-25-2021, 10:59 AM   #9
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Originally Posted by whalepirot View Post
How/where is fan speed displayed?
If the fan is hydraulically driven, there would be no accurate way to display fan speed without having an encoder in the motor or somewhere rotational speed can be directly monitored. Fan speed on hydraulic drives is usually done through pressure control, where a wax valve that controls a relief valve that in turn allows fluid to bypass the motor to maintain some pressure at the motor inlet. Solenoid valves are also used but they’re usually binary - they’re ‘on’, forcing a lower relief pressure resulting in a slower fan speed, or ‘off’ where the relief setting is higher giving higher fan speed due to reduced bypass flow. You also get the higher fan speed if it fails, which is what you want.

Since propeller fan input power increases as the cube of the fan speed, both pressure and flow increase as the fan runs faster. And that is indirectly controlled. BUT, you could cut in a test port or tee at the motor inlet and add an electronic hydraulic pressure gauge to watch the motor inlet pressure, which is a good proxy for fan speed since small fan speed increases require relatively large pressure increases.
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Old 07-25-2021, 11:23 AM   #10
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The attached is a screenshot of my BlueFire app dash which shows the fan status as a percent. When my fan activates I've never seen anything but 100% (the screenshot is displaying sample data).
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Old 07-25-2021, 11:41 AM   #11
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Bob,

Where is your BlueFire getting the fan speed data???
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Old 07-25-2021, 11:48 AM   #12
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Quote:
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Bob,

Where is your BlueFire getting the fan speed data???
BlueFire has a Bluetooth adapter that plugs into the diagnostic port near the steering wheel column and picks up the data from, in my case, the J1939 data bus.

I believe it will also capture the fan data from a J1708 data bus.
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Old 07-25-2021, 12:10 PM   #13
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Bob,

Where is your BlueFire getting the fan speed data???
From the engine management computer, (ECM). Via the diagnostic port.
I'm not familiar with the VMspec, I don't know if it has the ability to see fan speed percentage or not.
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Old 07-25-2021, 06:13 PM   #14
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Quote:
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The attached is a screenshot of my BlueFire app dash which shows the fan status as a percent. When my fan activates I've never seen anything but 100% (the screenshot is displaying sample data).
Pretty sure the technology of the 2017 ECM is putting out a lot more data than the 2000-2008 vintage units.....the 400ISL was actually introduced in 2002 and the last Alpine was made in 2008 (Technically)..... I'm guessing this is the technology gap we are seeing here.

I personally believe that many comments are spot on but the only real way to monitor and manage your engine temps and protect it properly is to install an EGT or Pyrometer. It is the only true measure of what's driving the high temps..... The combined exhaust gas temps. This is a more timely measurement than water temps which are delayed.

I do not understand why manufacturers do not include this monitor when building the coach as they do in other machines such as airplanes.
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