SVX Engine cooling "Again & Again"

[svxistentialist]

Originally Posted by TomsSVX

After seeing the minuscule volume of the inside of the manifold I can only imagine that the flow through it is limited and I would imagine the limit is right around 6500 engine RPMS and thus the high RPM engines that are experiencing the issues. Lets see what we find and work from there.

I can honestly say that impeding the flow is not going to help anything except allowing it to overheat on both sides of the engine rather than just the one restricted at this point

Tom

Originally Posted by Dessertrunner

The info that supports this argument are that the newer 6 cylinder Subarus have 2 return pipes to the radiator making me think they found the left bank wasn't getting enough cooling. Second a UK rally guy sent my buggy friend a photo of how they have moded the top pipe on the 4 cylinder so the water flows more evenly from the heads because they had been killing engines on the left bank.
Tony

Originally Posted by Dessertrunner

You may be right Tom I have not compared the amount of flow to other engines. Just the other 6clyinder Subaru which has a heap more coolent flow per min. What engine have you looked at the flow of.
Tony

I'm just going to make a general comment here about this problem, rather than a specific suggestion for a solution. I'll be watching for the success of what you are doing.

Do we all remember the development car picture with Twin Turbo on the rear corner? And we know that Subaru never supplied the SVX with a manual gearbox, stating that a manual gearbox would not handle the torque, which we long recognise was BS.

Based on the problems we are having here I'm inclined to believe that Fuji engineers were aware of the poor cooling, and the car was released without a manual to keep revs down, and without the turbos because they would add heat.

Note that instead of developing the EG 33, they next produce the EZ30 which in some ways is less advanced than the EG was. As Tony notes above though, the newer 6 cylinder has a better grasp of cooling the block.

Maybe this inhibiting problem was there and recognised by them all along, and they just moved on to a different block to get around it?

Just a thought

Joe

[SVXRide]

YT,
Have you checked to see if the modified pipe will fit under the intake? I haven't had the time to check to see what the clearance is with the stock pipe.
-Bill

[Dessertrunner]

Your point is interesting Joe, what I have noticed is that if I am driving the car at a constant speed but have it in 4th gear (6 speed box) when I should have been in 6 th gear the engine runs hotter. The moment I change to 6 th the tempreture of the engine drops. This is part of the reason that I agree with Tom on the top pipe. Somewere in the system when you increase flow the restriction in the left bank must get worse. Clearly there has to be a flow problem some were.
I am going to jump in at this point before I get every one coming out and saying this is a clear indication of cavitation of the pump. I AGREE THEY COULD BE RIGHT but it is best to stop this problem by reducing the restrictions in the pipe work and heads to enable the pump to handle higher speeds.
To explain at my work we have 3 by 500hp diesel pumps that each pump 300l of water per second. If we increase the speed on them to pump 400lps the suction pipe feeding the pump is to small and we get cavitation at the pump. This happens inspite of the suction pipe being 600mm in diameter. To solve the problem we changed the suction to 800mm and the problem went away.
Sorry to get off topic but I want to make the point we still have a lot of things to do such as increase the suction pipe from the radiator before we try to reduce the flow of the pump. It may turn out that we have to do that as well later but not now.

[TomsSVX]

Originally Posted by svxistentialist

I'm just going to make a general comment here about this problem, rather than a specific suggestion for a solution. I'll be watching for the success of what you are doing.

Do we all remember the development car picture with Twin Turbo on the rear corner? And we know that Subaru never supplied the SVX with a manual gearbox, stating that a manual gearbox would not handle the torque, which we long recognise was BS.

Based on the problems we are having here I'm inclined to believe that Fuji engineers were aware of the poor cooling, and the car was released without a manual to keep revs down, and without the turbos because they would add heat.

Note that instead of developing the EG 33, they next produce the EZ30 which in some ways is less advanced than the EG was. As Tony notes above though, the newer 6 cylinder has a better grasp of cooling the block.

Maybe this inhibiting problem was there and recognised by them all along, and they just moved on to a different block to get around it?

Just a thought

Joe

Joe I had mentioned this to Bill a while back and I think i posted it. The manual gearbox was not chosen because there was not one able to handle the torque but rather dispense it properly. Subaru did not want to put a basic 5mt into the car, they wanted an automatically controlled center differential. Since they did not have one at the time and considering their overwhelming investment in the car already, I think they planned to put it aside for a later model depending on the success/failure of sales.

The engine development was based on the GT platform which the car was being designed for. Granted I am sure they were aware of the cooling issues and this is why the RPM redline is so low. We all know now that with some better headwork the engine loves to spin

Tom

[svxistentialist]

Originally Posted by TomsSVX

Joe I had mentioned this to Bill a while back and I think i posted it. The manual gearbox was not chosen because there was not one able to handle the torque but rather dispense it properly. Subaru did not want to put a basic 5mt into the car, they wanted an automatically controlled center differential. Since they did not have one at the time and considering their overwhelming investment in the car already, I think they planned to put it aside for a later model depending on the success/failure of sales.

The engine development was based on the GT platform which the car was being designed for. Granted I am sure they were aware of the cooling issues and this is why the RPM redline is so low. We all know now that with some better headwork the engine loves to spin

Tom

Good point Tom and I accept that. I'm just not too convinced that all that's required is headwork. I do believe that fluid flow in the block is restrictive, and that this is an innate problem that you guys are currently tackling.

You have my respect and full attention.

[TomsSVX]

no I meant valve/cam work. I think the cooling issue is restricted to the X-over manifold alone. I am looking forward to proving it in the coming weeks

Tom

[svxistentialist]

Originally Posted by TomsSVX

no I meant valve/cam work. I think the cooling issue is restricted to the X-over manifold alone. I am looking forward to proving it in the coming weeks

Tom

Well I am hoping that you do, and if you do I will be

[Dessertrunner]

I have asked for price on a flow meter as I want to find a way to measure the flow of water through the block at different rev's. My guess is that the manual says two rates at two different rev but I don't beleive it. Clearly the higher revs is just double the flow of the lower rev. This doesn't make sense as friction would cause the flow to be non linear.
Tony

[oab_au]

This is an interesting problem.
There is nothing wrong with the cooling system when the car is used as it was intended. Hot days, full AC, slow traffic, never worries it, it obversely has the capacity to keep the engine cool under all conditions.

When it is run at higher engine rpms for an extended period, at has a heat problem. The problem seems to be with the left hand bank.

There is one pump, and one radiator inlet. If we look at the two systems, they are not equal. The outlets are different, the right bank has an outlet that is connected directly to the radiator inlet, the left bank passes through the crossover pipe to connect to where the right bank flow is exiting the head, so the left has to overcome the right flow, to pass to the radiator.



It would seem that at the higher engine speed, the increased pump flow causes the cooling flow to take the path of least resistance, flowing through the right bank straight to the radiator. The higher capacity from the right head prevents the left flow from overcoming its resistance so it slows down, to overheat.

Trevor touched on the problem with the older flathead V8, and Tony’s mention of the UK twin outlet 4s points to the solution, of changing the way the left blends into the right outlet, if it did not have to overcome the flow from the right side it would flow the same as the right.

Harvey.

[Trevor]

Originally Posted by Dessertrunner

Trevor,
I am to dumb to have concluded or come up with the idea its the left bank I have only comfirmed it as highly likly. The info that supports this argument are that the newer 6 cylinder Subarus have 2 return pipes to the radiator making me think they found the left bank wasn't getting enough cooling. Second a UK rally guy sent my buggy friend a photo of how they have moded the top pipe on the 4 cylinder so the water flows more evenly from the heads because they had been killing engines on the left bank.
Tony

Tony,

Be very sure that I did not consider that you are in any way "dumb", hence my words ---
"You appear to have concluded that only the left head is overheating, but it can not be concluded that this is confined to the particular area of the engine associated with the sensors."

Thankfully you have now confirmed that there can be no doubts in this area, which was in fact my reason for my comment.

All involved are now reporting with absolute certainty, that only the left side of the engine is overheating. On this basis the problem can as a first consideration, involve the split in coolant distribution.

Under no circumstances, should it be taken for granted that the design engineers were infallible.

[NiftySVX]

First let me say that I always thought the crossover pipe was a less than ideal design. I agree completely that it is possibly a restriction at higher than intended RPMs at extended periods as thought of by an engineer. We have to remember the engineering mindset. If you ask one if a cup is half full or half empty, they will tell you the cup is twice as big as it needs to be I am sure that during development testing they knew the limits of the cooling system, but since it works satisfactory with a stock setup, why make it flow more than necessary?

As for the manual transmission debate, I have always thought that the "too much torque" was a rumor, because Fuji has the capability and know how to machine stronger gears if they needed to at not much additional expense. The true reason for it that was communicated to me by a Subaru rep that was around back then told me that he remembered seeing it in writing somewhere that The SVX would not be offered in a manual transmission because it was meant to showcase the "Active" all wheel drive and they did not have a manual with an active system until the DCCD system came around.

And third, THERE IS A PICTURE OF A EG33 WITH TURBO(S) ON IT DURING DEVELOPMENT??? where???

[dynomatt]

Tom, I assume you're using the Meziere 55gpm pump? I had found the BMW one which flows 150lpm (or about 40gpm) but wondering whether the Meziere one is better.

I notice you'll be doing what I was thinking of doing...the complete remote setup with the original mechanical pump more or less gutted...to direct flow basically.

What sort of current draw are you anticipating?

[TomsSVX]

I forget what it draws to be totally honest, I knew when I purchased it. I think it is somewhere in the realm of 15-20amps

Tom

[SilverSpear]

Originally Posted by oab_au

This is an interesting problem.
There is nothing wrong with the cooling system when the car is used as it was intended. Hot days, full AC, slow traffic, never worries it, it obversely has the capacity to keep the engine cool under all conditions.

When it is run at higher engine rpms for an extended period, at has a heat problem. The problem seems to be with the left hand bank.

There is one pump, and one radiator inlet. If we look at the two systems, they are not equal. The outlets are different, the right bank has an outlet that is connected directly to the radiator inlet, the left bank passes through the crossover pipe to connect to where the right bank flow is exiting the head, so the left has to overcome the right flow, to pass to the radiator.

It would seem that at the higher engine speed, the increased pump flow causes the cooling flow to take the path of least resistance, flowing through the right bank straight to the radiator. The higher capacity from the right head prevents the left flow from overcoming its resistance so it slows down, to overheat.

Trevor touched on the problem with the older flathead V8, and Tony’s mention of the UK twin outlet 4s points to the solution, of changing the way the left blends into the right outlet, if it did not have to overcome the flow from the right side it would flow the same as the right.

Harvey.

Harv, you are completely making sense to me. I am really convinced more by what you are saying than what is currently being done. If there is a flow restriction, that restriction might be at the level of the tube leading to the rad. If you check the red box below, you will see that it is way thinner than the rest of the X-over. Here is where the right bank flows easier and the left bank is facing resistance (what you were saying above).



What Tom welded was the middle part which instead of being round or squared, subaru techs "crunched" it to make it flat for clearance purposes... but it has the same flow rate. I am not generalizing this, I am just assuming it.

Again, Harv your logic is making a lot of sense especially when comparing it to V8's (same concept, two heads) and I guess in the most ideal situation we would be having independently two pumps, two flows and two rads... but we all know that this is really hard to achieve.

[Trevor]

Originally Posted by Dessertrunner

I have asked for price on a flow meter as I want to find a way to measure the flow of water through the block at different rev's. My guess is that the manual says two rates at two different rev but I don't beleive it. Clearly the higher revs is just double the flow of the lower rev. This doesn't make sense as friction would cause the flow to be non linear.
Tony

Tony,

I agree with your thinking. It could it be that the specs. refer to the pump running free of any output constriction, a rather useless figure I agree, but likely if produced by the pump designer. Testing the flow rate left/right, as you propose, would be a bugger of a problem mechanically. All indications are such, that at this point, you can surely presume imbalance.

The placing of the sensors, would make one suspect that the designer, was aware that the left bank remained at a disadvantage, due to the hairy dual outlet arrangement. This was no doubt dictated by space restrictions, which is also a real problem involving any modification.

Any difference in restriction between the two legs of the split system will result in an imbalance in flow rate. The resistance can be anywhere within each the circuit, or at the outlets. The right has the throttle body in parallel and the left the heater. In special applications, it would be as well to close these auxiliary circuits. However the major problem to be overcome, is the unequal resistance due to the water pipe in the left leg.

The out of balance, is caused by unequal restriction which results in back pressure. The pressure difference results in a difference in flow. The unequal denominator is pressure, not as has been suggested, flow. The cart is not before the horse.

Laws dictate that an increasing common pressure, against several outputs of unequal resistance, will result in an increasing difference between the outputs. Hence the increasing problem at high RPM. Unfortunately the effect is not linear.

The easiest way to balance multiple resistive circuits, is by adding resistance rather than amplification. This is particularly so in this instance, where the problem is at the high pressure end of the system, where as a result adequate flow will exist.

It should be possible to fit a restrictive blanking plate, under the right inlet to the water pipe. A relatively soft alloy sheet and some gasket goo, a gasket or whatever could seal against the pipe, depending on the arrangement of the O-ring.

Tom has been working on distribution within the head space, and a plate could also be used to alter the flow relative to the two minor ports, if this might help.

Best of luck for all those involved in the project.

Trevor.