SVX Engine cooling "Again & Again" - Page 80

Dessertrunner · #**1186** 09-04-2010, 05:50 PM

On the standard engine and set up the pump outlet pressure at 6,000rpm is around 30psi. The pump suction goes to -8psi then loses prime, the loss of prime happens with in less then a minute.

I have run the water pump with no engine block attached and it still goes greater then 8psi at 6,000 just due to the radiator (tried a couple of types).

So in other words 8psi max isn't going to happen would be great if it did.
Tony

TomsSVX · #**1187** 09-05-2010, 07:29 AM

Tony, have you thought about the restriction of the uper pipe causing the pressure differential? So say if the restriction was lessen by say a custom top pipe and brought the discharge pressure down to say 15-20psi, that should effectively decrease the vacuum on the inlet while increasing flow... That was the thought process when I did Dan's top pipe.

Tom

cdigerlando · #**1188** 09-05-2010, 08:19 AM

Have you thought about installing an STI water pump and modifying it to work in our engine? The impeller is different than the SVX impeller. Another option would be to shave the impeller so that it would create as much suction head.

The STi impeller may be designed to operate better at high rpms. It seems like ours will just not work at these higher rpms.

I've considered using the STi pump in the SVX, but until now could not see a reason why.

Boxersix · #**1189** 09-05-2010, 11:29 AM

Quote:

Originally Posted by cdigerlando

Have you thought about installing an STI water pump and modifying it to work in our engine? The impeller is different than the SVX impeller. Another option would be to shave the impeller so that it would create as much suction head.

The STi impeller may be designed to operate better at high rpms. It seems like ours will just not work at these higher rpms.

I've considered using the STi pump in the SVX, but until now could not see a reason why.

The sti impeller is the same. The WRX has the stamped steel impeller. I put pictures in post #1106

The WRX/Sti pump casting is ~8-10mm short and won't work on the Eg33 as It will not line up properly with the EG timing components.

SilverSpear · #**1190** 09-05-2010, 03:01 PM

Any new updates from your side Tony?

Dessertrunner · #**1191** 09-05-2010, 07:05 PM

Tom,
My personal opinion is that if you clear the back pressure to drop the pump discharge pressure you will increase the flow which will make any suction issues worse if the suction side is standard such as thermosate it. That said what you did was good because you moved the thermostate to the top of the block before the radiator which is the only way to go. Indirectly the greatest restriction you have is in that housing were it can't cause as much problem.

An important point to make is that as I understand it you guys are not holding the car at around 7,000 rpm. I feel that unless you make other changes it won't stand the high revs.

It would be good for you guys to run a test tap a hole in the thermo cover and install a vacuum guage. If I am wrong the vacuum will hold constant at 7,000 rpm, if I am right the vacuum will drop as the pump loses prime.

By the way its a waste of time changing pumps it won't fix the problem, its not the pump it's the pipe supplying it.
Tony

teksvx · #**1192** 09-07-2010, 09:14 PM

ok i found something, truck manufacturer start to put an second expension tank due to overheating issue. surge tank dont have the pressure cap on it. just a normal cap , the overflow tube is linked to the second expension tank WHO have the pressure cap. it allow the cooling system to run at 100 % coolant, no air and the second tank only for liquid expension-pressure.this second tank is also a little bit higher than the other. maybe it s will work for you... ho i forgot firts tank capacity is about 25 % system capacity.

TomsSVX · #**1193** 09-07-2010, 09:23 PM

yes, your modern trucks use a deaeration system in which the expansion tank has a spill over chamber which is what has the pressure controlled cap. To incorporate such a system is what BoxerSix has done if I am not mistaken

Tom

Boxersix · #**1194** 09-08-2010, 01:13 AM

Correct Tom, using an Sti top tank.

Still undetermined if it helps at all. I haven't had an overheat issue, but then again I've been limited to extended spirited backroad stints and an occasional RX in the car. No track sessions with this chassis yet.

cdigerlando · #**1195** 09-08-2010, 07:02 AM

Quote:

Originally Posted by Boxersix

The sti impeller is the same. The WRX has the stamped steel impeller. I put pictures in post #1106

The WRX/Sti pump casting is ~8-10mm short and won't work on the Eg33 as It will not line up properly with the EG timing components.

In some cases you are correct, but there are also some years of STi's that have different impellers. Do a search on Nasioc. Good info about the casing though. It would require a change in the impeller. Not sure how to best do that.

With that said, after further research on Nasioc, the problems we are having are also problems with both impellers on WRXs and STis.

After reviewing all of the results presented here and nasioc my suggestion would be to shave the impeller to reduce flows during high revs. Also to install a hardpipe from the motor to the radiator to prevent collaps of the suction hose, and further vacuum on the suction of the pump. With all of the research that has been done by dessertrunner, it is obvious to me that this pump is not designed to run at the continuous rpms that he is running during track conditions. Folks are also having problems with the STi with this. For us street drivers we should be OK shifting through this, but it is a bit scary

The problem with this setup may be that there will be problems at low RPMs with flow rates. This should not be a problem for a track car. You could even adjust the idle RPM up to flow more at idle, if you have not already done this for your cam set. It will also be difficult to determine how much to shave the impeller. Another option could be to reduce the diameter of the pully to reduce the pump speed. Hopefully the timing belt tensioner would take up the slack.

If you have benched the pump, and have a way to shave the impeller without removing it from the pump that would be super. Then I would just shave a bit and watch for changes in the suction head. Since we don't have impeller pump curves it would be trial and error. I'm an environmental/civil engineer. That's how we deal with these issues

Dessertrunner · #**1196** 09-08-2010, 03:22 PM

Chuck,
A couple of things you should know,
The maxium suction a pump can operate at is -14psi, weather or not it loses prime before that number is determined by the type of pump.
Our pumps lose prime at -8 to -9 psi. As Harvey has said any vacuum will lower the boiling point of the coolant. In other words the coolant will boil below 100c.
You can't reduce the pump flow to solve the problem reason being that you need all the transfer coolant aviable. To stop cavitation completely you would need to come down from 250lpm to 100lpm based on standard inlet.

I may have not made this point clear so I will make it again.
If you change the pump inlet to 50mm and remove the radiator so the coolant goes straight out of the engine and around back into the pump and this pipe is 50mm. The pump will run perfectly at 8,000rpm. You will not see 1 sign of bubbles or cavition. I would assume from this that the pump and block work perfectly and the problem exists in the standard inlet pipe and radiator.

Hope that helps.
Tony

cdigerlando · #**1197** 09-08-2010, 05:05 PM

I made one mistake. You would need to increase the size of the pulley to reduce the speed.

The point you make is a good one regarding the radiator, but I don't know how you are going to get around that since you need a radiator. You could definitely benefit from a larger suction opening, or any improvements for that matter which would reduce friction losses and thus reduce the losses through the system and the suction side of the pump. I still think shaving the impeller would be worth trying. Although you would have to be able to live with the lower flows at lower RPMs. An improved impeller design might also give you some benefit. Perhaps an impeller from a race motor designed to run at a higher RPM, and something that would fit in our water pump housing.

You speak as if your issue is resolved with the increased suction openeing. Is it?

Dessertrunner · #**1198** 09-08-2010, 05:21 PM

Chuck,
You can't change the pulley size with out screwing up the timing etc due to needing a larger belt. Also you need to keep in mind that a lot of new Subaru have higher flow pumps then the SVX.

"You speak as if your issue is resolved with the increased suction opening. Is it? "

I don't mean to sound like a smart ass but as far as I am concerned the problem is solved. You need to do the following:-

High Flow radiator.
50mm suction inlet to pump and radiator outlet.
A side tank radiator with the cap on the suction side.
The thermstate must be moved to the top of the radiator (Tom's idea).

I can assure you that if this is done any cooling issue are solved and the SVX will have no problem keeping cool.

Have a gret day.
Tony

cdigerlando · #**1199** 09-08-2010, 08:04 PM

It would be interesting to see photos of your setup and part numbers for the radiator. These seem to be issues for STi's as well. Perhaps some of these adaptations would help for them as well.

Quote:

Originally Posted by Dessertrunner

Chuck,
You can't change the pulley size with out screwing up the timing etc due to needing a larger belt. Also you need to keep in mind that a lot of new Subaru have higher flow pumps then the SVX.

"You speak as if your issue is resolved with the increased suction opening. Is it? "

I don't mean to sound like a smart ass but as far as I am concerned the problem is solved. You need to do the following:-

High Flow radiator.
50mm suction inlet to pump and radiator outlet.
A side tank radiator with the cap on the suction side.
The thermstate must be moved to the top of the radiator (Tom's idea).

I can assure you that if this is done any cooling issue are solved and the SVX will have no problem keeping cool.

Have a gret day.
Tony

Dessertrunner · #**1200** 09-15-2010, 04:00 PM

You got to wonder about the IQ of some people, I tried to start a thread about keeping Subaru engine cool on one of the other Forums. Most of the people that jumped in left a lot to be desired and one guy was on another planet. He replied "I keep my engine cool by packing it in ice".
Seems that was a waste of time.
Tony