SVX Engine cooling "Again & Again"

[Dessertrunner]

Haven't been able to run trials yet as the outside tempreture has been to cold. The uints I got emails ore to expensive but will keep looking.

Wait till we learn some more before deciding to tap into the back of the head and installining a different radiator I feel sure that the answer is just around the corner.
Tony

[oab_au]

There is another side effect to the high pump speed increasing water output.

With the restriction at the junction of the left to right cylinder slowing the flow from the left side, it also alters the water pressure in the left side.

The water flow will take the path of least resistance and flow most of the extra flow through the right side. The left side is pushing against the high flow from the right, so not only does it slow to heat up, it also causes the pressure in the left to rise. If the right is at 14 psi the left may have risen to 16 psi. This will raise the boiling point of the water, so that bank will run at a higher temp. It may boil or it may not, but when you come off the track into the pits, the pump speed slows, the pressure drops from 16 psi to 14 psi.

The left now has water at a temperature that is over the boiling point of water at 14 psi, so it erupts into instant boiling. The temp gauge jumps between red and normal as the steam and water go by, and the overflow tank spews water out.

Sound familiar Dan?

Harvey.

[TomsSVX]

exactly my thinking at this point as well Harvey.

So, instead of piping more cool water in... How about helping it get out?

Two ports on the top of the block with adjustable ball valves to help balance the return from the engine to the radiator in combination with the modified manifold might do the trick here

Tom

[svxistentialist]

I agree with you chaps that localised boiling is part of what the circuit racers are experiencing and Harvey's pressure hypothesis has merit.

Another point touched on earlier is the fact that when bubbles are created they are not getting away or are accumulating and may be causing vapour lock in the liquid cooling circuit.

Have a look at the enclosed picture:



The SVX engine is tilted upward at the front by quite a few degrees. Yet we know that the coolant fluid connecting bar for connecting the two halves is at the back of the block.

Is it possible that bubbles when created are accumulating over time in the top highest point of the two blocks, particularly the left one? This might mean that any gas created is unable to vent to the expansion bottle and create a circulation problem.

What do you think?

Joe

[Trevor]

Originally Posted by oab_au

There is another side effect to the high pump speed increasing water output.

With the restriction at the junction of the left to right cylinder slowing the flow from the left side, it also alters the water pressure in the left side.

The water flow will take the path of least resistance and flow most of the extra flow through the right side. The left side is pushing against the high flow from the right, so not only does it slow to heat up, it also causes the pressure in the left to rise. If the right is at 14 psi the left may have risen to 16 psi. This will raise the boiling point of the water, so that bank will run at a higher temp. It may boil or it may not, but when you come off the track into the pits, the pump speed slows, the pressure drops from 16 psi to 14 psi.

The left now has water at a temperature that is over the boiling point of water at 14 psi, so it erupts into instant boiling. The temp gauge jumps between red and normal as the steam and water go by, and the overflow tank spews water out.

Sound familiar Dan?

Harvey.

The application involves a circuit supplied from one point, remote from the junction, and pressures within the circuit must at all time tend to equalise. Any flow between legs or branches within the circuit is dependant on resistance and time.

The low pressure side of any junction at a pressure lower than the input pressure to the circuit, must constitute an outlet.

In the event that one flow joins another and both are at the same pressure, but one is restricted by a resistance, the lesser flow will be assisted by the greater flow at a rate dependant on the resistance, rather than be obstructed, as has been suggested.

In the event that one flow joins another and are of unequal pressure, the lesser pressure flow will be overcome by the higher pressure flow, and that flow will be reversed at a rate dependant on the resistance presented, to a point whereby pressure is equalised.

[SVXRide]

So, if we were able to insert a restriction plate within the crossover pipe, shouldn't we be able to fine tune the overall system (have different plates, each with a different size opening)? I'm also curious about the use of a swirl tank and where we might be able to tap it into the system.
-Bill

[SilverSpear]

Originally Posted by SVXRide

So, if we were able to insert a restriction plate within the crossover pipe, shouldn't we be able to fine tune the overall system (have different plates, each with a different size opening)? I'm also curious about the use of a swirl tank and where we might be able to tap it into the system.
-Bill

I was brainstorming this issue yesterday nightime, we definitely need a Y system there with TWO TAPS. Fine tuning could be done through these taps and with a water flow meter to get the exact same flow in both engine's banks. What do you guys think?

[Dessertrunner]

More info,
On my way to work this morning I did a little trial to see what happened to the head temps. Left head was at 90 and right at about 87 traveling at 100kph outside temp 5c.
Decided to speed up and change down to 4 gear so revs went to 6,500k and speed to 140kph.
Interesting result the right head temp dropped to about 83-84 and the left head went up to 92-4. What interesting is that the outside temp was only 5c which is 5 above freezing.
I need a day were our temps get higher so I can do a proper test. I have a question.
What is the target operation temp we want the engine to run at and with the exist cooling system what temp will the coolent boil at?
Tony

[oab_au]

Boxersix and Joe raise the point of air bubbles in the system, causing trouble.

The problem of the coolant becoming aerated does happen, but not in this engine. If the system is purged when it is filled, there is no air in there and it can't get in.

If there are bubbles, they would have to be bubbles of steam or voids. Voids (bubbles of nothing) will disappear with pressure equalization. Bubbles of steam will disappear with temperature equalization.

The two outlets do come off the rear of the heads, but there appears to be a couple of bled holes forward of the outlet that would serve to remove any trapped air, when it is filled.

Harvey.

[svxistentialist]

Originally Posted by TomsSVX

exactly my thinking at this point as well Harvey.

So, instead of piping more cool water in... How about helping it get out?

Two ports on the top of the block with adjustable ball valves to help balance the return from the engine to the radiator in combination with the modified manifold might do the trick here

Tom

Originally Posted by oab_au

Boxersix and Joe raise the point of air bubbles in the system, causing trouble.

The problem of the coolant becoming aerated does happen, but not in this engine. If the system is purged when it is filled, there is no air in there and it can't get in.

If there are bubbles, they would have to be bubbles of steam or voids. Voids (bubbles of nothing) will disappear with pressure equalization. Bubbles of steam will disappear with temperature equalization.

The two outlets do come off the rear of the heads, but there appears to be a couple of bled holes forward of the outlet that would serve to remove any trapped air, when it is filled.

Harvey.

My point about bubbles, cavitation, steam, voids, whatever we call it, was in support of Tom's theory above and relating to your earlier hypothesis on pressure drop boiling, which Trevor dissed.

The whole system may be equalised by a relatively small bore interconnecting pipe at the top of the heads that would bleed any superheated gassy coolant back to the better circulating right side and vent any gas to the tank. With adjustable ball valves if they are a help.

Joe

[oab_au]

Originally Posted by Dessertrunner

More info,
On my way to work this morning I did a little trial to see what happened to the head temps. Left head was at 90 and right at about 87 traveling at 100kph outside temp 5c.
Decided to speed up and change down to 4 gear so revs went to 6,500k and speed to 140kph.
Interesting result the right head temp dropped to about 83-84 and the left head went up to 92-4. What interesting is that the outside temp was only 5c which is 5 above freezing.
I need a day were our temps get higher so I can do a proper test. I have a question.
What is the target operation temp we want the engine to run at and with the exist cooling system what temp will the coolant boil at?
Tony

Tony the thermostat opens at 90*C, and the cap pressure is 14psi, so the water will boil at about 119*C.
For efficiency, the hotter the engine runs the better, as it looses less heat energy to the cooling.

Harvey.

[Trevor]

Originally Posted by svxistentialist

My point about bubbles, cavitation, steam, voids, whatever we call it, was in support of Tom's theory above and relating to your earlier hypothesis on pressure drop boiling, which Trevor dissed.

The whole system may be equalised by a relatively small bore interconnecting pipe at the top of the heads that would bleed any superheated gassy coolant back to the better circulating right side and vent any gas to the tank. With adjustable ball valves if they are a help.

Joe

Good idea Joe,

A small bore pipe at the latest possible/practical point in the circuit, connecting each side, would equalise pressure difference between them, without any negative effect on the main flow. Only one adjustable valve would be needed for experimental purposes. In this respect, a flexible tube could be partly closed with a simple clamp during experiments. However if say a half inch tube is used, all should be in order.

As I pointed out in my last post, any difference occurs because of unequal resistance in the circuits post inlet, and a time element is involved. Your idea of a balance pipe late in the circuit close to the outlets, would balance both. Elimination of the time element, will depend on the bore/resistance of the pipe.

Cheers, Trevor.

[Dessertrunner]

My next steps on this job, (been a bit busy building a CNC mill).
- Run a more detailed test on a warm day, above 20*C in an attempt to get left bank to boil or show a clear problem. If it doesn't warm up then I will park car pull cooling fan fuses then do the rev test. Not sure it will generate enough heat with out load but I can only try. (might think about blocking the air to the radiator.
- Following this test change the top cross over pipe to the modified version to see if there is a improvement and it fixes the problem.
- If there are still issues then weld a centre pipe on the top return as we have all discussed. Aim here is to get both banks to flow the same and both guages on each head to read the same.

If all that doesn't work then "WE" will have to work out a new plan. (note the WE bit) as we are all in this together. Well team have a great day.
Tony

[yt]

I discussed it more with Dan today. Looks like we will be reinventing the wheel on the water manifold with his engine. The main discharges from the block will be relatively simple with a pair of two bolt flanges. Will drill and tap the smaller outlets in the forward portions of the block and add a third to each cylinder bank. The three outlets will join the main discharge for each side. With this each bank will be separated until they join is a Y just before the radiator inlet. This is essentially what Harvey had spoken of before. In the name of science and possibly the KISS method, we will be using the stock water pump first to see if we have actually found the issue.

At this point there are really two issues that could be causing the localized boiling.

1. Pressure differential creating a lowered boiling point.

2. Increased resistance for one bank creating a lack of flow through one side and increased flow through the other (path of least resistance)

I really cannot see anything else causing this localized boiling that we are experiencing. So lets try and decrease resistance across both cylinder banks and try to equalize them. From here we must determine if the pump's capacity is less than we need.

Tom

[Trevor]

Originally Posted by oab_au

Boxersix and Joe raise the point of air bubbles in the system, causing trouble.

The problem of the coolant becoming aerated does happen, but not in this engine. If the system is purged when it is filled, there is no air in there and it can't get in.

Air is dissolved in water at ambient temperature, to become released at about 80 deg. C or more, depending on pressure. This air remains within the closed system, unless bled out due to the cap opening to the overflow container and then not completely.

If there are bubbles, they would have to be bubbles of steam or voids. Voids (bubbles of nothing) will disappear with pressure equalization. Bubbles of steam will disappear with temperature equalization.

Bubbles of nothing?
Bubbles of water vapour/steam will form if the pressure at any point within the system, temporally exceeds the set radiator cap pressure whereby the water will boil. Such pressure hot spots can occur due to resistance to flow or blind sections, as per my previous posts. The essence of the problem with water vapour/steam, is not "temperature equalisation," which is a result, not a cause.

The two outlets do come off the rear of the heads, but there appears to be a couple of bled holes forward of the outlet that would serve to remove any trapped air, when it is filled. Harvey.

If were are such holes, the system could not hold the designed pressure. No outlets, including any at the rear of the head can bypass the radiator cap and bleed to the atmosphere. This is the very reason for careful slow filling, being required.

It must be concluded, that the only way of stopping water vapour being generated at any specific point, is to eliminate localised pressure.
P.S. As I now see yt Tom has diligently pointed out.