Espar D4 High Altitude Pump

Pnwsquid

Member
I wanted to share some knowledge, as I spent quite a bit of time researching and had trouble finding any definite direction regarding using the high alt pump full time (even at low altitude). Several techs at Espar confirmed this does NOT cause any damage and "blow-out" will not be an issue.

The heater works fine at sea level with the high altitude pump. I actually considered the 15% reduced output a benefit, as I understand these heaters ideally run on high more often to mitigate any carbon build up. With that said, I did find the limit of this setup.

While parking at a ski resort (Red Mountain, BC) at about 3,500 feet, the heater had trouble keeping the van 70* F when it got below 15* F outside. It could get to 65* or so, but that was about the limit. After swapping the low-altitude pump back in, I could easily keep the van as warm as I wanted.

I still do think it is a good option for some people, especially if you never get into this cold of weather, but wanted to share my experience in case this comes up for anyone in the future!

After you swap the pump once, it's really a less than 5 minute job. With that, I will just keep both on board and put the high altitude pump in before the rare case of camping above 5,000 feet.
 
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avanti

2014 GWV Legend 3500 I4
Thanks for the report.

A tech at ThermoKing once told me that there exists an Espar kit that let's you wye in both pumps at the same time. That way, you can select which one to use electrically with a simple switch. This would also be useful for a setup that could be fed either from the diesel tank or a day tank containing kerosene. That way, one could use kerosene when it was available, with diesel as a backup.
 

Midwestdrifter

Engineer In Residence
Since all of these pumps have a check valve, I believe they can be plumbed in parallel. All that is needed is a SPDT switch to flip between them. It is important to use rigid fuel lines with no air pockets on the outlet side of the pump(s).

2. As an alternative Airtronic D2 and D4 heaters of any generation may be equipped with the high altitude pump kit p/n 24 0222 00 00 00. This kit contains extra pump used on high altitudes, manual switch and necessary wiring/piping parts. Can be used on altitudes of up to 3000 meters (9840’).


Here is the approximate de-rate value if using the altitude sensor. I am guessing the high altitude pump would be about ~15% lower output than the standard (same as Pnwsquid indicates).

With the optional height kit an operation of the heater in regions up from 1400m (4600’) until 3000m (9850’) are possible. After starting the heater the height sensor which is enclosed with the kit measures the atmospheric pressure and communicate it to the control unit. The control unit adjusts then the frequency of the metering pump. Because of this the heating power in height operation will be reduced by approx. 9% per 1000 m (3280’). In regions below 1400m (4600’) the heater works in normal operation with the full heating power. Example: at the Airtronic D4 (4000 watt max. heating power) the heating power will be reduced by 360 watt per 1000 metres above 1400 meters.
 

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vanski

'05 Box Snow Camper
I doubt anyone wants to wait around, but I'm in process of building a high altitude fuel compensator with an arduino board and barometric pressure sensor for d5 heaters. I'm sure the d4 is just a small adjustment to the compensation equation. I don't know how long it's going to take as I'm having to learn some new things. So far everything looks 100% possible and actually pretty straight forward. I even know which hardware components to use. I just need to write the code loop and conduct a test.
 

GoJohnGo

Road trip!
Vanski,

That sounds like a great project. Wish I'd thought of that before I bought my High Altitude Compensator!
 

vanski

'05 Box Snow Camper
Thx GJG; I've been struggling with how I'm going to test seeing as the last thing I want to do is remove my metering pump and even if I do remove it, how do I mimic the ecu of the espar???:thinking: I may have come up with a good test bed... I'm going to model and apply the compensation arithmetic to my heartbeat and monitor the output signal from the processor. We'll see. I'd like to get it done prior to a trip I have planned in February.
 

vanski

'05 Box Snow Camper
Thanks Avanti.. Wondering if an old-school AB would vary in frequency and strength (period and amplitude) like the signal from the ECU does. Or perhaps only the period changes. Need to figure that out or just build it in regardless which was what I was planning on doing but I would need to have a varying sine wave to see if everything is working properly.
 

avanti

2014 GWV Legend 3500 I4
Thanks Avanti.. Wondering if an old-school AB would vary in frequency and strength (period and amplitude) like the signal from the ECU does. Or perhaps only the period changes. Need to figure that out or just build it in regardless which was what I was planning on doing but I would need to have a varying sine wave to see if everything is working properly.
I am pretty sure that the pump is a binary device, i.e., the only thing that matters is the off-to-on transition. I don't think that the amplitude of the signal is modulated. Only the frequency matters. Could be wrong, though.
 

GoJohnGo

Road trip!
Seeing that the High Altitude Compensator is wired between the Heater Control Unit and the pump, my guess is that the Compensator is only modifying the duration of the pulse, not the frequency. It does have a little light on it that blinks every pulse. If it would be useful, I could record it in action.

Here's a link to a PDF that describes it.

It is literally a little black box.

Perhaps after you get this working, you can build an Arduino pacemaker?
 

avanti

2014 GWV Legend 3500 I4
Seeing that the High Altitude Compensator is wired between the Heater Control Unit and the pump, my guess is that the Compensator is only modifying the duration of the pulse, not the frequency.
Just the opposite, I think. At least it isn't true as it modulates on startup:

https://sprinter-source.com/forums/showthread.php?t=9070

I am pretty sure that these dosing pumps are solenoid/diaphragm type. If so, they are insensitive to pulse width. That is why they are so precise.
 

vanski

'05 Box Snow Camper
Just the opposite, I think. At least it isn't true as it modulates on startup:

https://sprinter-source.com/forums/showthread.php?t=9070

I am pretty sure that these dosing pumps are solenoid/diaphragm type. If so, they are insensitive to pulse width. That is why they are so precise.
How did I not see this post! This is going to be much easier than I thought. Just need the time between all my different projects..:bash:

And yes, a pacemaker isn't too far off but it would be an almost certain death sentence :lol:
 

TROLL

2007 Winnebago View 23H
How did I not see this post! This is going to be much easier than I thought. Just need the time between all my different projects..:bash:

And yes, a pacemaker isn't too far off but it would be an almost certain death sentence :lol:
Hey vanski -- did you ever make headway with this project? Sorry for bumping all the Espar high altitude threads, but love all the ideas floating around and curious what has risen to the surface in 2018 :).
 

CaptnALinTiverton

T1N Westfalia
I did extensive forum research years ago and conclusion was that just putting the HI-ALT pump in parallel (with e-switch) was the best solution. So I purchased the kit parts and all works fine but it was a hand-buster fitting those fuel lines together. In retrospect, since I don't travel in very cold weather, I should have just changed the pump.

AL
 

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