SVX Engine cooling "Again & Again"

[svxistentialist]

Originally Posted by BRADY

Joe,

I am about to go on tour with the band for a few months, so I will not have the time to fit it any time soon!

I intend to install the heat shield and perform a few other mods when I get back.

Cheers!

We'll hold you to that......

[Dessertrunner]

I have had the new PWR moded so the outlet pipe is in the centre of the bottom tank and finishing off the 45mm thermostate cover. My aim is to have the change in the car this weekend and give you guys some feed back as to how I got on. I will see is I can repeat a number of tests that I did in the past to get results to compare against.
Tony

[McTaff]

Originally Posted by BRADY

We're gettin' the and back together.

We're on a mission from God.

Good luck Brady!


THREAD HIJACK:
Now seeing as I am also making the switch to a manual, I'm wondering how far I would go to ensure I don't cook my SVX. I have a metal topped radiator already, and will probably hook up the tranny cooler to the 6spd, but is there any further modifications that would be worthwhile for a but of insurance (while the car has it's nose up in the air)?

[TomsSVX]

Originally Posted by Dessertrunner

I have had the new PWR moded so the outlet pipe is in the centre of the bottom tank and finishing off the 45mm thermostate cover. My aim is to have the change in the car this weekend and give you guys some feed back as to how I got on. I will see is I can repeat a number of tests that I did in the past to get results to compare against.
Tony

This plan has w1n... If you can... please run the piss out of it in the current configuration... Park it... let cool... Make the changes and do a second run under relative same conditions...

Tom

[Dessertrunner]

Matt asked a question today and I haven't discussed this point on the forum but think maybe it is time to bring it up as well.

Current PWR have a raised top tank were the return pipe enters the radiator, it is also is in the centre. The bottom outlet is to the left and the bottom tank is small in size. This leads me to beleive currently the right hand side of the radiator is not doing much of the cooling. In the ideal world the bottom tank needs to be simlar to the top so a more uniform flow to the outlet pipe can be acheived.
Tony

[Trevor]

Originally Posted by Dessertrunner

Matt asked a question today and I haven't discussed this point on the forum but think maybe it is time to bring it up as well.

Current PWR have a raised top tank were the return pipe enters the radiator, it is also is in the centre. The bottom outlet is to the left and the bottom tank is small in size. This leads me to beleive currently the right hand side of the radiator is not doing much of the cooling. In the ideal world the bottom tank needs to be simlar to the top so a more uniform flow to the outlet pipe can be acheived.
Tony

Provided that the longitudinal cross section of each tank, exceeds the cross section of every other orifice within the system, there should be no resistance at this point which could have any practical effect.

Flow into or exiting the radiator can be taken from any point along either tank, without upsetting the overall effective balance of flow through the radiator. The tanks are in fact incorporated within the system, for this very purpose. Think along the lines of a plenum distribution chamber, or a busbar within an electrical system.

[Dessertrunner]

I accept the theory of what you say and ask one question, seeing as the right side of the radiator coolant flow has twice the distance travel then the left it will either have to travel quicker or be in the radiator for a longer time.
Which is it faster or more time?

[Trevor]

Originally Posted by Dessertrunner

I accept the theory of what you say and ask one question, seeing as the right side of the radiator coolant flow has twice the distance travel then the left it will either have to travel quicker or be in the radiator for a longer time.
Which is it faster or more time?

The time taken for coolant to flow through the radiator, will in effect be averaged across the effective conducting area by the action of the tanks, this being their very purpose.

Each tank operates as a virtual storage device and holds the coolant for a certain, even though very short, degree of time. Filling also involves a mixing of the contents. As a result any element of time in respect of radiator through flow, is eliminated.

The flow in each separate channel within the radiator, comes from, and ends up, in a single common, combined place and takes the same time to get there. A fact, not a theory.

[Dessertrunner]

either the velicoty in the right side of the radiator is faster then the left or the time the coolant in the left side spends in the radiator is less then the right. In which case the left side is doing more cooling then the right. Given we need every bit of help we can get suction in the centre is important.

[Trevor]

Originally Posted by Dessertrunner

either the velicoty in the right side of the radiator is faster then the left or the time the coolant in the left side spends in the radiator is less then the right. In which case the left side is doing more cooling then the right. Given we need every bit of help we can get suction in the centre is important.

I am uncertain as to the above description, but am certain as to what it portrays and confirms.

[McTaff]

Trevor,

A picture is worth a thousand words. In this case, what Tony and I (and for that matter, those who haven't seen the interior of the radiator to understand what it looks like) aren't seeing is your portrayal of the fluid movement throughout the radiator.

If you could provide at least a 2D representation of the radiator, with the flow, and explain the speed of the flow throughout each part, it might help your description on. I've seen plenty of radiators before, but it always pays to have a very clear understanding of where the fluid is going before seeing where any flow changes are to be made.

-

At this time, I'm somewhat confused with the term "being averaged across by the tanks" as if one small portion of the radiator is slow, stagnant or otherwise due to a dead zone (for any reason), then it's not being utilised - that's what Tony is getting at.

For instance, if I have a pot and drill two holes near the edge within an inch of each other and pump a certain amount in one hole and out of the other, I'd cycle a lot of fluid in and out of the pot but the fluid over the other side would be mostly stagnant. In this case, I average the same amount of fluid in and out regardless of where the holes are, and the speed of fluid between the two holes would be quite fast but the average speed of the fluid would be the same as if the holes are at opposite sides.

Adding a barrier between the two holes that stretches almost the entire width of the pot would force the fluid to move to the other side, then around, then back to the outlet - which would have a much improved capacity to cool - and you'd still have the same average speed. Likewise, adding a complex series of baffles would spread the flow across most of the surface... creating a simple radiator, and so on.

What we want to see is that the speed in all parts of the radiator is close to that of the average speed. Car designers sometimes take shortcuts to save costs in many ways, usually to save on manufacturing costs and sometimes materials, if they deem that it "won't make a difference" - and for most drivers they will never approach the boundaries. When enthusiasts decide to start pushing the boundaries, that's where they find limits, and that's where it starts to make a (sometimes huge) difference.

-

I'm not saying anyone is wrong, or right, or anything. I'm just also hoping that there is a simple modification that will indeed improve the cooling performance of our radiators. It's regularly topping out over 110 F / 44 C here, and I don't want my 6 speed to choke while stuck in traffic.

If Tony has made a point that we can improve on, I'm all for it. If his concerns are unfounded, then at least we know. But let's thrash it out and make sure.

In my opinion, it's better to have it and not need it, rather than need it and not have it!

[Trevor]

Originally Posted by McTaff

Trevor,

A picture is worth a thousand words. In this case, what Tony and I (and for that matter, those who haven't seen the interior of the radiator to understand what it looks like) aren't seeing is your portrayal of the fluid movement throughout the radiator.

If you could provide at least a 2D representation of the radiator, with the flow, and explain the speed of the flow throughout each part, it might help your description on. I've seen plenty of radiators before, but it always pays to have a very clear understanding of where the fluid is going before seeing where any flow changes are to be made.

-

At this time, I'm somewhat confused with the term 'being averaged across by the tanks" as if one small portion of the radiator is slow, stagnant or otherwise due to a dead zone (for any reason), then it's not being utilised - that's what Tony is getting at.

For instance, if I have a pot and drill two holes near the edge within an inch of each other and pump a certain amount in one hole and out of the other, I'd cycle a lot of fluid in and out of the pot but the fluid over the other side would be mostly stagnant. In this case, I average the same amount of fluid in and out regardless of where the holes are, and the speed of fluid between the two holes would be quite fast but the average speed of the fluid would be the same as if the holes are at opposite sides.

Adding a barrier between the two holes that stretches almost the entire width of the pot would force the fluid to move to the other side, then around, then back to the outlet - which would have a much improved capacity to cool - and you'd still have the same average speed. Likewise, adding a complex series of baffles would spread the flow across most of the surface... creating a simple radiator, and so on.

What we want to see is that the speed in all parts of the radiator is close to that of the average speed. Car designers sometimes take shortcuts to save costs in many ways, usually to save on manufacturing costs and sometimes materials, if they deem that it "won't make a difference" - and for most drivers they will never approach the boundaries. When enthusiasts decide to start pushing the boundaries, that's where they find limits, and that's where it starts to make a (sometimes huge) difference.

-

I'm not saying anyone is wrong, or right, or anything. I'm just also hoping that there is a simple modification that will indeed improve the cooling performance of our radiators. It's regularly topping out over 110 F / 44 C here, and I don't want my 6 speed to choke while stuck in traffic.

If Tony has made a point that we can improve on, I'm all for it. If his concerns are unfounded, then at least we know. But let's thrash it out and make sure.

In my opinion, it's better to have it and not need it, rather than need it and not have it!

Mr Soob,

The topic currently being discussed exactly relates to, and is confined in particular to, the position of inlet and outlet in respect of the radiator tanks. My comments in reply to Tony’s post #785, have been confined to that specific subject.

You state -- “At this time, I'm somewhat confused with the term 'being averaged across by the tanks' as if one small portion of the radiator is slow, stagnant or otherwise due to a dead zone (for any reason), then it's not being utilised - that's what Tony is getting at.”
Surely it is clear that each outlet to the core has equal access to the spread of fluid available from within the tank, and that the available pressure is averaged across the multiple outlets.

If you are suggesting that a section of the core could have a resistance to flow and this requires correction, you are referring to a fault which is impossible to correct via external means, i.e. with complex baffles centre inlet or exit or whatever. To be honest, overall I do not know what you are on about.

[svxistentialist]

I see the point Tony is making about flow velocity, but it does not have an effect in this case nor should it for any radiator because the velocity of the fluid through the vertical cooling galleries is designed to be relatively constant and within the ranges of the speed the pump imparts to the coolant.

Please bear with me if the following seems simplistic; the radiator has a reservoir [tank] above and below, connected vertically by finned cooling galleries. If the coolant was able to race easily and quickly through the vertical galleries only the surface of the coolant touching the metal as it passed through would cool and heat extraction would be inefficient. To get around this the passages or galleries are designed in size to maximise turbulent flow so that the maximum heat is extracted from the coolant in its journey to the lower reservoir.

In turn this limits the speed at which coolant can pass through all galleries from the upper reservoir to the lower one feeding the pump.

If the bore cross-sections of the vertical galleries were large enough to allow the coolant to pass quickly through them, then in that instance Tony's possible scenario of selective cooling on the side nearest the extraction point might hold true. But that's not the case. The fluid velocity for all galleries will remain the same, negative pressure from the pump will provide the same pressure [suction if you like] across all exit bores of the galleries.

Take it from another perspective, that of pressure, putting fluid velocity to one side for a moment;

The fluid extraction at the lower outlet to the pump exerts a negative pressure on the fluid in the lower tank. This negative pressure will be the same over all surfaces of the lower reservoir, walls, floor, ceiling, and in the ceiling are the lower bore holes of the fluid passages.

Hot coolant pumped from the engine to the top reservoir does the same thing, it pressurises the fluid in the upper tank, this time with positive rather than negative pressure. This positive pressure is acting on all sides of the upper tank and so on to the upper bores of the vertical coolant channels.

So the cooling fluid is driven through the galleries using what in electrical terms would be called a Potential Difference, like a voltage almost. This Potential Difference is designed to be relatively constant over the speed range of the water pump, and keeps the speed of the fluid traveling through the galleries within a range that optimises heat loss to the metal of the radiator.

I hope that clarifies the fluid velocity through the cooling matrix issue. I'm sorry that was so long winded, and I'm open to correction if anything I have said is wide of the facts.

Joe

[Dessertrunner]

Well maybe the best way to answer the question is to plug a temp guage into the bottom left and right of the radiator and see what happens. Either way its an interesting debate.
Currently with the pipe at the side the bottom tank, the tank is restricting flow. At 7,500 rpm you need to pull about 250l per min through it. Thats more then in a old style 44 gallon drum. If I had a 29mm pipe into the bottom of a 44 gallon drum there is no way it will drain out in 1 minute so why do we expect the engine coolant pump to not have problems.

[svxistentialist]

Originally Posted by Dessertrunner

Well maybe the best way to answer the question is to plug a temp guage into the bottom left and right of the radiator and see what happens. Either way its an interesting debate.
Currently with the pipe at the side the bottom tank, the tank is restricting flow. At 7,500 rpm you need to pull about 250l per min through it. Thats more then in a old style 44 gallon drum. If I had a 29mm pipe into the bottom of a 44 gallon drum there is no way it will drain out in 1 minute so why do we expect the engine coolant pump to not have problems.

It is interesting all right Tony.

I think the point to keep in mind is that the radiators are designed primarily as heat exchangers, and the rate of flow through the galleries is governed [by the cross-sectional area mostly] to flow through at a speed that will lose the most heat.

The 7500 rpm you mention is outside the design range of the SVX as delivered OEM. Because they were all auto the maximum rev limit is restricted by the gearbox computer to the upper shift limit, which I think is maybe 6800, but don't quote me on that.

You are correct in your assumption that the resistance to flow could make the standard radiator a restriction in the circuit for high revs cars. What will happen in practice is the higher speed pumping will exert a higher pressure on the top tank than the radiator cap can withstand and extra fluid will be pumped to the expansion bottle.

If this was happening a lot it would indicate that a larger radiator was called for, one with more passages to let the extra fluid through [and cool it better, hopefully ]. But the coolant will still be traveling through the passages at the same speed because it must do to effectively cool the liquid. It will just be traveling through more of them to keep the pressure down below the limit where the cap releases fluid to the expansion bottle.

Joe