Improving heater output and flow
Discussion
Ha ha, its all looks worse than what it is. I’ve had the interior apart and the dash out so many times that it’s now a 20 minute job!
The heater box is quite large - Its about 32cm wide, however the blower sticks out a further 15cm or so. Its 29cm tall and has a depth of around 26cm. I’d actually like to try and retain the box if possible as I like keeping things original (ish) and with some minor mods, I think it could be improved. The 2 vents on the dashboard are quite powerful, it’s just the demister which is almost non-existent. If this could pump out a good amount of warm air, I would be happy! Figured I would try a few cheap mods first before I investigate replacing the whole thing.
I’ve been playing around with some PC fans today since I have loads of them laying around. I also checked out the RC airplane fans as suggested. However, I found this on the net:-
http://www.marinescene.co.uk/product/437/attwood-i...
For under 20 quid, it seems really cheap! There’s a 3” and 4” version, but I’m going to try the 3” first. My plan is to connect a 3” pipe to the channel that runs up through the centre of the heater box using a spigot. Cap the opening at the top off to force all the warm air through the tube, although some will still be able to make its way into the footwell vents. I’ll put a hole in the side of the heater box for the tube to exit though and connect the in-line fan to this.
I then thought about replacing the windscreen demister arrangement with 4 of these:-
https://www.europaspares.com/HEATERS_and_DEMISTERS...
I can remove the existing demister plenum from under the dash and mount the new vents in its place. I think the new vents will be more effective than the old arrangement which is just a box that fills with air before percolating through the holes cut in the top of the dash. I’m hoping that proper vents with a separate tube going to each will help channel the air and keep the speed up! I will then fabricate some kind of adapter so that the four 31mm tubes can connect to the pump. I’m picturing something like a “distributor cap” type arrangement.
I will then work on a similar arrangement to suck the air out of the car from behind the seats to try and maintain an airflow. Will give that some thought and let you know what I do.
One question though – does anyone know of a 12v speed controller that could be used to adjust the speed of my new fan? Needs to cater for about 4 amps/60 watts. I have one for a radio controlled car which I may look into, although I have no idea how to wire this up. Is there any cheap, off the shelf solution anyone is aware of, or could someone describe to me how I could make something up? I’ve seen a million different potentiometers/resisters available, but I’m no electronics expert so wouldn’t know what to buy.
Thanks,
Dan.
The heater box is quite large - Its about 32cm wide, however the blower sticks out a further 15cm or so. Its 29cm tall and has a depth of around 26cm. I’d actually like to try and retain the box if possible as I like keeping things original (ish) and with some minor mods, I think it could be improved. The 2 vents on the dashboard are quite powerful, it’s just the demister which is almost non-existent. If this could pump out a good amount of warm air, I would be happy! Figured I would try a few cheap mods first before I investigate replacing the whole thing.
I’ve been playing around with some PC fans today since I have loads of them laying around. I also checked out the RC airplane fans as suggested. However, I found this on the net:-
http://www.marinescene.co.uk/product/437/attwood-i...
For under 20 quid, it seems really cheap! There’s a 3” and 4” version, but I’m going to try the 3” first. My plan is to connect a 3” pipe to the channel that runs up through the centre of the heater box using a spigot. Cap the opening at the top off to force all the warm air through the tube, although some will still be able to make its way into the footwell vents. I’ll put a hole in the side of the heater box for the tube to exit though and connect the in-line fan to this.
I then thought about replacing the windscreen demister arrangement with 4 of these:-
https://www.europaspares.com/HEATERS_and_DEMISTERS...
I can remove the existing demister plenum from under the dash and mount the new vents in its place. I think the new vents will be more effective than the old arrangement which is just a box that fills with air before percolating through the holes cut in the top of the dash. I’m hoping that proper vents with a separate tube going to each will help channel the air and keep the speed up! I will then fabricate some kind of adapter so that the four 31mm tubes can connect to the pump. I’m picturing something like a “distributor cap” type arrangement.
I will then work on a similar arrangement to suck the air out of the car from behind the seats to try and maintain an airflow. Will give that some thought and let you know what I do.
One question though – does anyone know of a 12v speed controller that could be used to adjust the speed of my new fan? Needs to cater for about 4 amps/60 watts. I have one for a radio controlled car which I may look into, although I have no idea how to wire this up. Is there any cheap, off the shelf solution anyone is aware of, or could someone describe to me how I could make something up? I’ve seen a million different potentiometers/resisters available, but I’m no electronics expert so wouldn’t know what to buy.
Thanks,
Dan.
Some really good stuff on that site! I like the look of this:-
http://www.cbsonline.co.uk/heater-valve-kit-rotary...
I already have a valve under the bonnet which controls whether hot water can flow through the cabim heater matrix, so this could be a good way of regulating the temperature from inside the car.
I have also seen this:-
http://www.virtualvillage.co.uk/12v-15a-pwm-dc-mot...
Does anyone know whether it would be a suitable speed controller for my in-line fan? Fan is 12v and about 3amps. The speed controller says its a PWN type - does this alter the output voltage, which I'm guessing is what I need to do?
Incidently, I just found a shop near me which sells the in-line fans I posted about earlier, so I just bought one and it does pump out a lot of air! Its also not the quietest fan in the world, hence I would like to moderate the speed if possible. I'm sure with the engine running and a layer of sound proofing you wouldn't actually hear it, but I'd also like to slow it down a bit for when a full-on demister isn't needed.
Thanks,
Dan.
Edited to add: This from the maplin site seems to be what I need! http://www.maplin.co.uk/Module.aspx?moduleno=30310...
http://www.cbsonline.co.uk/heater-valve-kit-rotary...
I already have a valve under the bonnet which controls whether hot water can flow through the cabim heater matrix, so this could be a good way of regulating the temperature from inside the car.
I have also seen this:-
http://www.virtualvillage.co.uk/12v-15a-pwm-dc-mot...
Does anyone know whether it would be a suitable speed controller for my in-line fan? Fan is 12v and about 3amps. The speed controller says its a PWN type - does this alter the output voltage, which I'm guessing is what I need to do?
Incidently, I just found a shop near me which sells the in-line fans I posted about earlier, so I just bought one and it does pump out a lot of air! Its also not the quietest fan in the world, hence I would like to moderate the speed if possible. I'm sure with the engine running and a layer of sound proofing you wouldn't actually hear it, but I'd also like to slow it down a bit for when a full-on demister isn't needed.
Thanks,
Dan.
Edited to add: This from the maplin site seems to be what I need! http://www.maplin.co.uk/Module.aspx?moduleno=30310...
Edited by digga951 on Sunday 9th May 14:50
PWM keeps the voltage the same but pulses it on/off at high frequency to control the speed.
For high speed the on pulses are longer and for slow speed the off pulses are longer. The beauty is that with a bit of "elastic trickery" you can adjust the speed smoothly and it is also a very efficient method. Down side it it costs more than 2p which is why car manufacturers tend to use a multi-way switch and a bunch of Watty resistors.
HTH
For high speed the on pulses are longer and for slow speed the off pulses are longer. The beauty is that with a bit of "elastic trickery" you can adjust the speed smoothly and it is also a very efficient method. Down side it it costs more than 2p which is why car manufacturers tend to use a multi-way switch and a bunch of Watty resistors.
HTH
digga951 said:
I just ordered one of the above for use in another car. I'll let you know how I get on.
Hello,
Not too much to update on to be honest as I'm waiting for the demister vents to arrive. I need to install these first so I know what space I have remaining. However, I've just taken a few pics of some things I have been trying. It all looks really messy, but I guess thats what happens when you're trialing things and making it up as you go along...
Anyway, some of the bits I have bought. The one I'm most happy about is the rotary water pipe valve. This will allow me to control the flow of water going into the heater matrix, so I will be able to choose how hot the air is coming out of the vents. The old setup only allows for the hottest air to go to the screen which can get stuffy after a while.
Here is the heater box which I have started to modify. I've removed the old windscreen duct which ran up through the centre, made the opening bigger and bought a spigot for my bendy tubing to attach to. The idea is to run this out through the side of the box and into the blower.
This is an adapter I made from some plastic tubing and fibreglass. Still needs some smoothing and a coat of paint! Each of the small tubes will connect to a windscreen demister vent with more bendy tubing!
When joined to my blower, it looks like this.
I have removed the old air plenum from the underside of the dashboard and now there is a flat surface to mount my new vents.
With the heater box in situ, there is very little space behind the dashboard. I was originally going to put the blower on the passenger side as there was a little more space, however the tubings would have needed some serious bends to get the air going in the right direction, which in turn slowed the air speed down. I wanted the drivers side to have the shortest pipe runs, so mounting the blower here seems like the best option. I will probably need to cut the height of the heater box down slightly so that there is enough room for the demister vents and tubing.
As I say, its all work in progress at the moment but I’m sure you can see the principle of what I’m trying to achieve. Hopefully I will get the vents before the weekend so will post some more pics then.
I’m not sure that the cabin will actually be any warmer after all this - my main aim is to achieve a mist free cabin by flowing more air to the screen and extracting stale air out, however I’m sure the extra fan output will produce some extra warm air to circulate!
Dan.
Not too much to update on to be honest as I'm waiting for the demister vents to arrive. I need to install these first so I know what space I have remaining. However, I've just taken a few pics of some things I have been trying. It all looks really messy, but I guess thats what happens when you're trialing things and making it up as you go along...
Anyway, some of the bits I have bought. The one I'm most happy about is the rotary water pipe valve. This will allow me to control the flow of water going into the heater matrix, so I will be able to choose how hot the air is coming out of the vents. The old setup only allows for the hottest air to go to the screen which can get stuffy after a while.
Here is the heater box which I have started to modify. I've removed the old windscreen duct which ran up through the centre, made the opening bigger and bought a spigot for my bendy tubing to attach to. The idea is to run this out through the side of the box and into the blower.
This is an adapter I made from some plastic tubing and fibreglass. Still needs some smoothing and a coat of paint! Each of the small tubes will connect to a windscreen demister vent with more bendy tubing!
When joined to my blower, it looks like this.
I have removed the old air plenum from the underside of the dashboard and now there is a flat surface to mount my new vents.
With the heater box in situ, there is very little space behind the dashboard. I was originally going to put the blower on the passenger side as there was a little more space, however the tubings would have needed some serious bends to get the air going in the right direction, which in turn slowed the air speed down. I wanted the drivers side to have the shortest pipe runs, so mounting the blower here seems like the best option. I will probably need to cut the height of the heater box down slightly so that there is enough room for the demister vents and tubing.
As I say, its all work in progress at the moment but I’m sure you can see the principle of what I’m trying to achieve. Hopefully I will get the vents before the weekend so will post some more pics then.
I’m not sure that the cabin will actually be any warmer after all this - my main aim is to achieve a mist free cabin by flowing more air to the screen and extracting stale air out, however I’m sure the extra fan output will produce some extra warm air to circulate!
Dan.
leorest said:
digga951 said:
I just ordered one of the above for use in another car. I'll let you know how I get on.Ok, thought I would resurrect an old thread. I pretty much just finished putting my car back together following an attempt to build a window demister (in the middle of summer... I know...). My initial plans of installing a powerful fan outside of the heater box and routing this air through separate heater vents didn’t really go to plan. To start with, there simply isn’t enough room on a 350i to install the fan outside of the heater box. There also isn’t enough room to install the separate heater vents behind the dashboard due to the gauges and closeness of the windscreen.
Soooo, I compromised! I modified the heater box and installed the fan into here:-
It really was tight for space, so I literally had to build it bit by bit. I also reinstalled the original plenum under the dash, however I enlarged the outlets slightly and did away with the trims on top to maximise the air flow.
I then made a new front for the air box out of ply as the TVR effort wasn’t a tight fit. I had to cut a recess for the back of the clock, so some mastic was needed.
As the fan I installed was quite noisy, I decided to fit a variable speed controller. This came from Maplin, however I noticed that it seemed to restrict the maximium speed of the fan. So, I installed a toggle switch – up for full speed, down for variable speed. At least now I can switch to full speed when I want to clear the windscreen and then switch to a slower speed when needed. I also fitted a temperature control rotary switch to stop the flow of hot water going into the matrix. The below picture should explain all!
So there we have it, a proper windscreen demister all ready and waiting for the winter months. My next job is to install an extractor fan to suck out all the stale air from the cabin. This will most likely be installed in the boot and will suck air from where the speakers are installed behind the seats.
Will keep you updated!
Dan.
Soooo, I compromised! I modified the heater box and installed the fan into here:-
It really was tight for space, so I literally had to build it bit by bit. I also reinstalled the original plenum under the dash, however I enlarged the outlets slightly and did away with the trims on top to maximise the air flow.
I then made a new front for the air box out of ply as the TVR effort wasn’t a tight fit. I had to cut a recess for the back of the clock, so some mastic was needed.
As the fan I installed was quite noisy, I decided to fit a variable speed controller. This came from Maplin, however I noticed that it seemed to restrict the maximium speed of the fan. So, I installed a toggle switch – up for full speed, down for variable speed. At least now I can switch to full speed when I want to clear the windscreen and then switch to a slower speed when needed. I also fitted a temperature control rotary switch to stop the flow of hot water going into the matrix. The below picture should explain all!
So there we have it, a proper windscreen demister all ready and waiting for the winter months. My next job is to install an extractor fan to suck out all the stale air from the cabin. This will most likely be installed in the boot and will suck air from where the speakers are installed behind the seats.
Will keep you updated!
Dan.
Holy thread resurrection. My matrix quite spectacularly failed last summer so I'm about to remove the dashboard and rip the heater unit out. Mine used to happily demist the screen with loads of heat but wouldn't heat anything else. Given the huge size of the inefficient heater I've been looking at Car Builder options. One is the Heat 7 unit which gives over 4kw of heat, coupled to a three way diverted unit, so in theory I could have demist, dash vents and footwell positions. Has anyone actually replaced the original heater with a suitable alternative?
Thanks Adam. The car builder option looks very compact. Water connections will work and cabin floor and dash connections look straight forward. Issue will be connecting two 55mm connections up on to the windscreen vents. I'll make a start pulling it apart at the weekend. Hope all is well. Cheers
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