Radiator Air Flow

[John Turney]

I'm working on a new Healey project where I'm thinking of replacing the engine-driven fan with an electric one. So this weekend I decided to measure the existing airflow through the radiator at idle. I have a Dwyer Magnehelic gauge for use with a pitot tube that reads air velocity in feet per minute.

My BN4 with 3000 engine idles at about 800 RPM, doesn't overheat and has a Texas Cooler fan.

I started by placing the pitot tube in front of the radiator and got hardly any reading. I put the pitot tube behind the fan thinking the gauge wasn't working. The readings varied from close to zero at the edge of the 14" diameter fan and at the root of the blades where they join the 5" diameter hub to a maximum reading of 3,400 feet per minute (fpm) about half way out the blade length.

This tells me that most of the air flow from the fan is coming from the side and not through the radiator. I'm surprised the engine runs as cool as it does with so little airflow through the radiator. If you are having overheating issues, a fan shroud may be something to consider.

 

[Patrick67BJ8]

I'm working on a new Healey project where I'm thinking of replacing the engine-driven fan with an electric one. So this weekend I decided to measure the existing airflow through the radiator at idle. I have a Dwyer Magnehelic gauge for use with a pitot tube that reads air velocity in feet per minute.

My BN4 with 3000 engine idles at about 800 RPM, doesn't overheat and has a Texas Cooler fan.

I started by placing the pitot tube in front of the radiator and got hardly any reading. I put the pitot tube behind the fan thinking the gauge wasn't working. The readings varied from close to zero at the edge of the 14" diameter fan and at the root of the blades where they join the 5" diameter hub to a maximum reading of 3,400 feet per minute (fpm) about half way out the blade length.

This tells me that most of the air flow from the fan is coming from the side and not through the radiator. I'm surprised the engine runs as cool as it does with so little airflow through the radiator. If you are having overheating issues, a fan shroud may be something to consider.

I took photos of some Triumphs at the British Car Show in Austin showing the shrouds they used to assist in their heating problems.

 

[TimK]

I have found the British Car Specialists Shroud behind the radiator very effective in my Healey. Interesting to see the Triumphs shrouding in front of the radiator.

 

[John Turney]

I took photos of some Triumphs at the British Car Show in Austin showing the shrouds they used to assist in their heating problems.

A bit of clarification on my terminology - The red Triumph doesn't have a "shroud" as such. The ducting in front of the radiator funnels air from the grill into the radiator and come stock on that model (although the ones you photographed are not original). The electric fans on the other two have a real shroud around the perimeter of the fan so that air isn't sucked into the fan from the side. The stainless steel flex fan supplied by British Car Specialists is what I'm referring to as a shroud.

I have aluminum ducting on the sides of my radiator funneling air from the grill into the radiator.

 

[Patrick67BJ8]

A bit of clarification on my terminology - The red Triumph doesn't have a "shroud" as such. The ducting in front of the radiator funnels air from the grill into the radiator and come stock on that model (although the ones you photographed are not original). The electric fans on the other two have a real shroud around the perimeter of the fan so that air isn't sucked into the fan from the side. The stainless steel flex fan supplied by British Car Specialists is what I'm referring to as a shroud.

I have aluminum ducting on the sides of my radiator funneling air from the grill into the radiator.

Can you post pics of your setup? The fan shroud I got from BCS has a large gap in it between the shroud and the radiator on the left side. I don’t think it’s a good fit.

 

[John Turney]

Can you post pics of your setup? The fan shroud I got from BCS has a large gap in it between the shroud and the radiator on the left side. I don’t think it’s a good fit.

The front of the car is now apart, but it's much easier to see the ducting when out anyway.



Note that I have a Texas Cooler fan, not the one from BCS.

 

[RAC68]

John,



This picture was posted on 55Modified's thread "need help with custom air deflector for BN1" and reflects what I have been considering for my BJ8. Since Steve was the only one that was able to even approach sealing the radiator bulkhead, I am intrigued by the this approach taken by Healey for the 100S and, as you are proving, is highly potential.

It is clear to me that Healey engine/compartment cooling is a matter of managing air flow. To do this, it is necessary for air to enter through the grill and exit the engine compartment without diversion. Additionally, the smoother the flow the better. To do this, a fully encompassing box (sides, bottom and top) sealed around the radiator core. This approach would eliminate the cooling inefficiency at speed as well as heated air recirculation when stopped or in slow moving traffic.

The use of a fan shroud to diminish the loss of fan efficiency as a result of air leaking off the ends of the blades is critical to creating adequate cold air flow through the radiator when stopped or at low speed as well as sufficient rearward air flow through and out of the engine compartment. Additionally, by closing the opening between the lower radiator tank and cross member and a cove over the forward 1/3 of the frame bottom (approx. 1ft in front of the pan) will greatly diminish disruptive turbulence from hampering the rearward evacuation of radiator-heated air.

Note, the presence of bonnet louvers and/or fender bents will further assist easy engine compartment flow through and diminish the need for an aggressive fan.

Adding to cabin comfort, by sealing the cold and hot air ducts to the openings on each side of the radiator air enclosure box (pictured) will eliminate any hot air from entering/recirculating into the ducts. Also, the installation of a bilge blower in the cold air duct and the heater blower with the heater turned off, will pull volumes of cooling air into the cabin to make driving and riding more enjoyable.

John, I will be considering this approach as a next project and anticipate that in a completed car, the installation of the radiator's forward located duct panels will have need to be installed through the opening of the uninstalled radiator. I believe this is necessary to mate the forward portion of the duct panels to the inside of the shroud and then anchored with the re-installation of the radiator. I would appreciate any direction you may discover during your project installation.

Thanks and good luck,
Ray(64BJ8P1)

 

[steveg]

My approach was more piecemeal. The 100S setup above (also per Randy's setup), in combination with a fan shroud in the back looks like a better way to go.

With the radiator out, one could start with the Kilmartin (BCS) shroud and figure a way to box in the entire rear of the radiator above the cross member, so the fan pulls from the whole radiator. The horns could maybe be relocated on the fender-well side of the side baffles, or moved back, BJ8 style.

John, could you change to an electric water pump, freeing up space for a puller electric fan? I'll be the Healey Factory knows about this stuff.

 

[John Turney]

...
With the radiator out, one could start with the Kilmartin (BCS) shroud and figure a way to box in the entire rear of the radiator above the cross member, so the fan pulls from the whole radiator. The horns could maybe be relocated on the fender-well side of the side baffles, or moved back, BJ8 style.

John, could you change to an electric water pump, freeing up space for a puller electric fan? I'll be the Healey Factory knows about this stuff.

I was thinking of a shroud on the back side of the radiator, but I took some measurements and the water pump sits off-center from the radiator to the left so that with the Texas Cooler fan that I have, the fan blades extend past the radiator on the left side. That complicates any boxing of the back side. That may be Patrick's issue with not getting a good fit with the BCS shroud.

I'll look into an electric water pump. There isn't enough room between the radiator and existing water pump for an electric fan without moving the radiator forward, and then I could only fit a low-profile one which doesn't move enough air.

 

[steveg]

I was thinking of a shroud on the back side of the radiator, but I took some measurements and the water pump sits off-center from the radiator to the left so that with the Texas Cooler fan that I have, the fan blades extend past the radiator on the left side. That complicates any boxing of the back side. That may be Patrick's issue with not getting a good fit with the BCS shroud.

I'll look into an electric water pump. There isn't enough room between the radiator and existing water pump for an electric fan without moving the radiator forward, and then I could only fit a low-profile one which doesn't move enough air.

You have to block off the left side of the front of the fan shroud where it extends beyond the radiator.

 

[Deleted member 21878]

How about the gap under the radiator between the frame and the bottom. would it help to close that off?

 

[RAC68]

How about the gap under the radiator between the frame and the bottom. would it help to close that off?​

I had mentioned that area in my post and have blocked that opening. I believe it has produced a positive result as air is drawn up between the cross member and radiator bottom inducing disruptive air turbulence into the exiting engine-compartment air flow. However, this turbulence means nothing when the flow is so disruptive in the first place and becomes more important when the air flow is properly managed and smoothed. The application of a fan shroud will make the effect of closing this opening and eliminating this air-exiting turbulence even more effective in developing high efficiency fan pull. However, what we have was not originally designed with modern cooling efficiency in mind and, over the years and with the implementation of such components as a Texas Cooler and a greater number of radiator core rows, we have been trying to overpower the situation.

Ray(64BJ8P1)

 

[John Turney]

All of the discussion about managing air flow into the radiator and keeping it from recirculating back to the front of the radiator is important. It controls the air flow when the car is moving, making cooling much more effective. The point of the original post is that although that has been done on my BN4, at idle the fan without a shroud doesn't pull much air through the radiator without a shroud. In spite of that, the car doesn't overheat.

What started this whole experiment was my SO saw a Healey in Monterey with AC. Since she has gone a long way toward paying the bills for my habit, I agreed to take on the project. Much of the front of the car is now disassembled (I have a couple of other projects to do while I'm at it) and I thought I might be able to recover some of the Hp lost to the AC by using an electric fan since I have to have an electric fan anyway for the AC. I can, by modifying the X-brace, install a suitable electric fan in front of the radiator/condenser, but there doesn't seem to be room to install one behind.

The question now is: can I use an electric fan in front of the radiator/condenser and remove the engine-driven fan, or leave the engine-driven fan in place, running both fans? Obviously, the heat load will increase, but the electric fan, having a shroud, will be more effective at idle. At speed, the fan would be running and airflow will be helped by the forward motion.

 

[steveg]

All of the discussion about managing air flow into the radiator and keeping it from recirculating back to the front of the radiator is important. It controls the air flow when the car is moving, making cooling much more effective. The point of the original post is that although that has been done on my BN4, at idle the fan without a shroud doesn't pull much air through the radiator without a shroud. In spite of that, the car doesn't overheat.

What started this whole experiment was my SO saw a Healey in Monterey with AC. Since she has gone a long way toward paying the bills for my habit, I agreed to take on the project. Much of the front of the car is now disassembled (I have a couple of other projects to do while I'm at it) and I thought I might be able to recover some of the Hp lost to the AC by using an electric fan since I have to have an electric fan anyway for the AC. I can, by modifying the X-brace, install a suitable electric fan in front of the radiator/condenser, but there doesn't seem to be room to install one behind.

The question now is: can I use an electric fan in front of the radiator/condenser and remove the engine-driven fan, or leave the engine-driven fan in place, running both fans? Obviously, the heat load will increase, but the electric fan, having a shroud, will be more effective at idle. At speed, the fan would be running and airflow will be helped by the forward motion.

FWIW - Cobras use a couple of electric pusher fans and, IIRC, no puller fan. My neighbor's Dino 246 uses them lower down.

 

[steveg]

An exotic setup would be to replace the water pump with a flat plate with an input from the lower hose - in combination with an electric water pump. This might give you room for an electric puller fan.

She may have seen a BJ8 - easier to install AC in than the earlier cars.

 

[John Turney]

An exotic setup would be to replace the water pump with a flat plate with an input from the lower hose - in combination with an electric water pump. This might give you room for an electric puller fan.

She may have seen a BJ8 - easier to install AC in than the earlier cars.

It was the blue BJ8 with the Canadian Maple Leaf on the doors, but with roadster doors.

 

[steveg]

Wizard has a lot of info on types of radiator/fan shroud combinations:
https://wizardcooling.com/fan-shroud-selection-chart/#Integrated

 

[steveg]

Wizard has some great looking radiators with integrated fan shrouds. Bet they could build a unit with an AC condenser in the front.

Wonder if one could remove the Healey heater and substiture an AC unit in approximately the same space.

The Healey Factory in Oz may have already figured this stuff out. Both of Ed Neumyer's Healey Factory cars have discreet AC installations.

 

[John Turney]

There are a couple of guys that have done it and published articles.
https://www.stevesaustinhealey.com/blog/9-ac-installation?showall=
Also September 2015 Healey Marque

 

[RAC68]

Hi John,

I read the paper you posted and have determined that AC is not within my Healey's future. What a job.

I appreciate your objective and the work you have put into the air deflectors to provide more air-push efficiency into the pusher fan. I had initially thought that retaining a puller fan would improve the efficiency of the forward mounted pusher fan by providing additional flow forcefully evacuate cooling air from the engine compartment. However, on thought, I am now wondering if the puller fan would do the opposite and, if not flow-matched to the pusher fan, could create a block to the air flow of the pusher fan.

I have previously posted a description of how my TR7 AC assist pusher fans were mounted. Similar to the dual fan picture posted by Bob, my TR7 has 2 thermostatically-controlled fans mounted on each end of a broad scoop that helps grab air when at speed and acts as a fan shroud when stopped of moving slowly. The fans are mounted low and on an upward facing angle to allow the created air stream to interface with the condenser/radiator cores on an angle. Since the TR7's engine compartment has a sealed radiator bulkhead along with sealed fenders and fire wall, air can only escapes through the open bottom and bonnet louvers.

The AC on the TR7 depended upon an old York unit and, when switch on, the 4-cylinder engine would significantly drained of power. To eliminate this condition, I de-installed major components (including the York) from the engine compartment and also eliminated the thermostatic engine-mounted fan. With some additional work to gain more power from the engine, I now depend only on the 2 thermostatically controlled AC fans for any engine cooling.

I bring this up because if I were to address your issue, I would favor installing a similar low mounted scoop under a few inches behind the bottom of the shroud with 2 upward facing fans. This would allow uninhibited air flow through the grill to allow cooling at speed (as apposed to many who have found the constant running of an electric pusher fan mounted on the cross braces that block grill air flow at speed).

Just my thoughts,
Ray(64BJ8P1)