Block off Plate in Front Heater

[Volksaholic]

The temperature test is interesting, but it's too bad you couldn't get the water temperature flowing into the core. I assume your '84 is a 1.9L and the '91 is a 2.1L... I don't know how much that would affect the test. Different thermostats may affect the test too. Still, it's interesting to note, and when you get the '91 put back together you'll have some numbers to do a before-after comparison.

I have wondered if the baffle plate is partially to force more air to flow the long way through the heater core rather than passing straight through. If that's the case, the trade off may be higher output temperatures for less resistance to airflow. This is purely speculation on my part, though... as I stated a couple of days ago; I'm not qualified to figure out why VW included that baffle.
_________________
1988 Wolfsburg Edition, 2001 Subaru EJ251

[Wildthings]

I went out today to repeat my tests with a modified plate installed in the 91 Vanagon. The temperature at my house was the same 40°F, but the morning was clear and dry whereas when the first test was done it was overcast and quite humid. The change in humidity probably had some affect on the results, but the temperature changes for the 91 were impressive at any rate. I will try and repeat the test again. when we get another 40° overcast day. The exterior of 91 heat core was not particularly dirty, but cleaning it probably accounts for some of the change as well.

The other test conditions were as alike as I could make them.

The Feb 5 test had the stock factory block off plate installed in the '91 and in the Feb 28 test it was modified. The 84 was missing the plate in both test.


Test date----Feb 5------Feb 28

60 MPH------130°F------148°F
40MPH-------144°F------160°F

Results for 84 van with plate removed

60 MPH------138°F------144°F
40 MPH------148°F------150°f

As you can see the defroster outlet temperature went up markedly in the 91. The temperature also rose in the 84 between the two test, I assume that part of the change may have been due to the drier atmospheric conditions. I was really surprised that the defrost outlet temperatures for the 91 now exceeded the temperatures for the 84. I had expected the temps to end up about the same.

Here is a picture of the modified plate as installed in the 91 Van.

[Alan Brase]

So, are there any conclusions?
BTW, the relative humidity should not impact the results very much. Relative humidity makes warm air feel warmer and cold air feel colder to us, but only because it affects our own cooling systems. Its effect on the output temperature should be very small.
Al
_________________
Al Brase
Projects: 67 sunroof bug, 67 Porsche 912 Targa, 70 Westy
Dec 1955 Single Cab pickup WANT 15" BUS RIMS dated 8/55, thru 12/55
To New owners: 1969 doublecab, 1971 Dormobile
Vanagons:
80 P27 Westy JUL 1979, 3rd oldest known US
83 1.6TD Vanagon, 87 Wolfie Westy daily driver, swap meet home

[Wildthings]

[Alan Brase]

[ak_runner]

Does the difference between the `91's heater box and the `84's have any affect on this? I know that the design of the box changed around late `87 or `88 but I have not had the chance to examine the later style. Both of my vans are `87's and have the earlier style system.

Just curious as to anything that improves heater output as it gets cold here in the Winter. I am still working on my system that allows me to block off the outside air and use recirculating instead. So far the level of interior heat is better but I have yet to make a controlable door for the outside air intake. Right now it is just blocked off, come Spring I will install a vent door with cable control to allow me the choice of outside air, recirculated air, or a bit of both. I am also adding the late model rear side windows with vents. It was suggested to me that I look at the later style heater box as well but I have not found one to look at yet.

[Wildthings]

The main difference (that I am aware of) between the earlier WBX and later WBX front heater boxes is where the ducts for the side dash vents connect. On earlier boxes the side vents get unheated air and on later boxes they get hot air. A very good improvement, IMHO.

I wish I had done some kind of before and after test on the 84 when I had the heater box apart and subsequently removed the restrictor plate. Info from such a test would have told me a lot. It would have also been nice to do some kind of air flow test as air flow is just as important as temperature to good heater performance.

[tencentlife]

Witless Joe was describing this earlier in this thread: the free-swinging "forced air flaps" (called that in Bentley) are supposed to be slammed shut when the fan on high speed builds backpressure before the heater core. You can hear them shut when you switch the fan on high, especially when the van is parked or moving slowly. When I had my airbox apart this year I deduced that the baffle plate is there to build more backpressure to cause the flaps to close. Either the engineers miscalculated, or perhaps they changed their sourcing on cores for one that was more open to airflow later, but one or the other I believe necessitated the addition of the baffle plate.

I have proof, by the way: I left the plate out of my airbox, and now when the fan is switched on high the flaps can't be heard shutting. Because I wouldn't know what effect this would have on heating before I reassembled my dash, I added a simple mechanism that allows me to close them manually.

One thing is clear, removing the baffle plate delivers both more and hotter air. The difference in my heat delivery is like night and day.
_________________
Shop for unique Vanagon accessories at the Vanistan shop:
https://intrepidoverland.com/vanistan/

Please don't PM here, I will not reply.

Experience is kryptonite to doctrine.

[Wildthings]

Good to know, I had not thought of the back pressure angle. A spring or something would have made more sense. I will have to pay attention to if mine slam shut anymore or not, I haven't paid it any mind. I do assume they are closing, just not slamming shut hard.

WT

[VisPacem]

[tencentlife]

Tell us what you really think, there, VP.
_________________
Shop for unique Vanagon accessories at the Vanistan shop:
https://intrepidoverland.com/vanistan/

Please don't PM here, I will not reply.

Experience is kryptonite to doctrine.

[r.e.wing_fc3s]

why does the pictogram recommend speed 2 for defrost instead of 3 or hi ?

[Alan Brase]

[Volksaholic]

[Wildthings]

[vanagonjr]

I'm curious as to those who pulled the plate and have better results. Because it seems to me that no one would pull the box just for this plate - that is the heater core, flaps, or other stuff would have been done at the same time and those could have made a huge difference.

For instance, I changed out my heater core and fan, but I still need a new fan switch. At speed, even with NO fan, the heating is much improved over the old system . Not trying to pick a fight, not saying don't pull the plate but no one has data on a van where the only change was pulling the plate. I'm still not 100% sure what that plate is for. I like 10-cents idea for the manual control on the flaps after puling the plate.

John

[Wildthings]

You are welcome to do such a test yourself. For me I am satisfied I can get more air flow and heat when the plate is removed and/or drilled. I see no advantage is having a heater box that can slam the door shut hard. Slamming the door hard would indicate that there is additional back pressure against the fan and as such that there is going to be less flow. If the flap is only partially close it will hurt nothing. If the air from the air stream is at a high enough pressure to hold the door open then it will just augment the flow through the core, not decrease it. I can't visualize any circumstance even with the vehicle stopped where the flow through the heater core would be lessened by the removal of the baffle plate.

[vanagonjr]

[Alan Brase]

[Volksaholic]